kernel - Change ccb state with lock held

[dragonfly.git] / sys / dev / disk / ahci / ahci.c

/*
 * (MPSAFE)
 *
 * Copyright (c) 2006 David Gwynne <dlg@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 *
 * Copyright (c) 2009 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $OpenBSD: ahci.c,v 1.147 2009/02/16 21:19:07 miod Exp $
 */

#include "ahci.h"

void    ahci_port_interrupt_enable(struct ahci_port *ap);

int     ahci_load_prdt(struct ahci_ccb *);
void    ahci_unload_prdt(struct ahci_ccb *);
static void ahci_load_prdt_callback(void *info, bus_dma_segment_t *segs,
                                    int nsegs, int error);
void    ahci_start(struct ahci_ccb *);
int     ahci_port_softreset(struct ahci_port *ap);
int     ahci_port_hardreset(struct ahci_port *ap, int hard);
void    ahci_port_hardstop(struct ahci_port *ap);

static void ahci_ata_cmd_timeout_unserialized(void *);
void    ahci_check_active_timeouts(struct ahci_port *ap);

void    ahci_beg_exclusive_access(struct ahci_port *ap, struct ata_port *at);
void    ahci_end_exclusive_access(struct ahci_port *ap, struct ata_port *at);
void    ahci_issue_pending_commands(struct ahci_port *ap, struct ahci_ccb *ccb);
void    ahci_issue_saved_commands(struct ahci_port *ap, u_int32_t mask);

int     ahci_port_read_ncq_error(struct ahci_port *, int);

struct ahci_dmamem *ahci_dmamem_alloc(struct ahci_softc *, bus_dma_tag_t tag);
void    ahci_dmamem_free(struct ahci_softc *, struct ahci_dmamem *);
static void ahci_dmamem_saveseg(void *info, bus_dma_segment_t *segs, int nsegs, int error);

static void ahci_dummy_done(struct ata_xfer *xa);
static void ahci_empty_done(struct ahci_ccb *ccb);
static void ahci_ata_cmd_done(struct ahci_ccb *ccb);
static u_int32_t ahci_pactive(struct ahci_port *ap);

/*
 * Initialize the global AHCI hardware.  This code does not set up any of
 * its ports.
 */
int
ahci_init(struct ahci_softc *sc)
{
        u_int32_t       cap, pi, pleft;
        int             i;
        struct ahci_port *ap;

        DPRINTF(AHCI_D_VERBOSE, " GHC 0x%b",
                ahci_read(sc, AHCI_REG_GHC), AHCI_FMT_GHC);

        /*
         * save BIOS initialised parameters, enable staggered spin up
         */
        cap = ahci_read(sc, AHCI_REG_CAP);
        cap &= AHCI_REG_CAP_SMPS;
        cap |= AHCI_REG_CAP_SSS;
        pi = ahci_read(sc, AHCI_REG_PI);

        /*
         * Unconditionally reset the controller, do not conditionalize on
         * trying to figure it if it was previously active or not.
         *
         * NOTE: On AE before HR.  The AHCI-1.1 spec has a note in section
         *       5.2.2.1 regarding this.  HR should be set to 1 only after
         *       AE is set to 1.  The reset sequence will clear HR when
         *       it completes, and will also clear AE if SAM is 0.  AE must
         *       then be set again.  When SAM is 1 the AE bit typically reads
         *       as 1 (and is read-only).
         *
         * NOTE: Avoid PCI[e] transaction burst by issuing dummy reads,
         *       otherwise the writes will only be separated by a few
         *       nanoseconds.
         *
         * NOTE BRICKS (1)
         *
         *      If you have a port multiplier and it does not have a device
         *      in target 0, and it probes normally, but a later operation
         *      mis-probes a target behind that PM, it is possible for the
         *      port to brick such that only (a) a power cycle of the host
         *      or (b) placing a device in target 0 will fix the problem.
         *      Power cycling the PM has no effect (it works fine on another
         *      host port).  This issue is unrelated to CLO.
         */
        /*
         * Wait for any prior reset sequence to complete
         */
        if (ahci_wait_ne(sc, AHCI_REG_GHC,
                         AHCI_REG_GHC_HR, AHCI_REG_GHC_HR) != 0) {
                device_printf(sc->sc_dev, "Controller is stuck in reset\n");
                return (1);
        }
        ahci_write(sc, AHCI_REG_GHC, AHCI_REG_GHC_AE);
        ahci_os_sleep(500);
        ahci_read(sc, AHCI_REG_GHC);            /* flush */
        ahci_write(sc, AHCI_REG_GHC, AHCI_REG_GHC_AE | AHCI_REG_GHC_HR);
        ahci_os_sleep(500);
        ahci_read(sc, AHCI_REG_GHC);            /* flush */
        if (ahci_wait_ne(sc, AHCI_REG_GHC,
                         AHCI_REG_GHC_HR, AHCI_REG_GHC_HR) != 0) {
                device_printf(sc->sc_dev, "unable to reset controller\n");
                return (1);
        }
        if (ahci_read(sc, AHCI_REG_GHC) & AHCI_REG_GHC_AE) {
                device_printf(sc->sc_dev, "AE did not auto-clear!\n");
                ahci_write(sc, AHCI_REG_GHC, 0);
                ahci_os_sleep(500);
        }

        /*
         * Enable ahci (global interrupts disabled)
         *
         * Restore saved parameters.  Avoid pci transaction burst write
         * by issuing dummy reads.
         */
        ahci_os_sleep(500);
        ahci_write(sc, AHCI_REG_GHC, AHCI_REG_GHC_AE);
        ahci_os_sleep(500);

        ahci_read(sc, AHCI_REG_GHC);            /* flush */
        ahci_write(sc, AHCI_REG_CAP, cap);
        ahci_write(sc, AHCI_REG_PI, pi);
        ahci_read(sc, AHCI_REG_GHC);            /* flush */

        /*
         * Intel hocus pocus in case the BIOS has not set the chip up
         * properly for AHCI operation.
         */
        if (pci_get_vendor(sc->sc_dev) == PCI_VENDOR_INTEL) {
                if ((pci_read_config(sc->sc_dev, 0x92, 2) & 0x0F) != 0x0F)
                        device_printf(sc->sc_dev, "Intel hocus pocus\n");
                pci_write_config(sc->sc_dev, 0x92,
                             pci_read_config(sc->sc_dev, 0x92, 2) | 0x0F, 2);
        }

        /*
         * This is a hack that currently does not appear to have
         * a significant effect, but I noticed the port registers
         * do not appear to be completely cleared after the host
         * controller is reset.
         *
         * Use a temporary ap structure so we can call ahci_pwrite().
         *
         * We must be sure to stop the port
         */
        ap = kmalloc(sizeof(*ap), M_DEVBUF, M_WAITOK | M_ZERO);
        ap->ap_sc = sc;
        pleft = pi;
        for (i = 0; i < AHCI_MAX_PORTS; ++i) {
                if (pleft == 0)
                        break;
                if ((pi & (1 << i)) == 0)
                        continue;
                if (bus_space_subregion(sc->sc_iot, sc->sc_ioh,
                    AHCI_PORT_REGION(i), AHCI_PORT_SIZE, &ap->ap_ioh) != 0) {
                        device_printf(sc->sc_dev, "can't map port\n");
                        return (1);
                }
                /*
                 * NOTE!  Setting AHCI_PREG_SCTL_DET_DISABLE on AHCI1.0 or
                 *        AHCI1.1 can brick the chipset.  Not only brick it,
                 *        but also crash the PC.  The bit seems unreliable
                 *        on AHCI1.2 as well.
                 */
                ahci_port_stop(ap, 1);
                ahci_pwrite(ap, AHCI_PREG_SCTL, AHCI_PREG_SCTL_IPM_DISABLED);
                ahci_pwrite(ap, AHCI_PREG_SERR, -1);
                ahci_pwrite(ap, AHCI_PREG_IE, 0);
                ahci_write(ap->ap_sc, AHCI_REG_IS, 1 << i);
                ahci_pwrite(ap, AHCI_PREG_CMD, 0);
                ahci_pwrite(ap, AHCI_PREG_IS, -1);
                sc->sc_portmask |= (1 << i);
                pleft &= ~(1 << i);
        }
        sc->sc_numports = i;
        kfree(ap, M_DEVBUF);

        return (0);
}

/*
 * Allocate and initialize an AHCI port.
 */
int
ahci_port_alloc(struct ahci_softc *sc, u_int port)
{
        struct ahci_port        *ap;
        struct ata_port         *at;
        struct ahci_ccb         *ccb;
        u_int64_t               dva;
        u_int32_t               cmd;
        u_int32_t               data;
        struct ahci_cmd_hdr     *hdr;
        struct ahci_cmd_table   *table;
        int     rc = ENOMEM;
        int     error;
        int     i;

        ap = kmalloc(sizeof(*ap), M_DEVBUF, M_WAITOK | M_ZERO);
        ap->ap_err_scratch = kmalloc(512, M_DEVBUF, M_WAITOK | M_ZERO);

        ksnprintf(ap->ap_name, sizeof(ap->ap_name), "%s%d.%d",
                  device_get_name(sc->sc_dev),
                  device_get_unit(sc->sc_dev),
                  port);
        sc->sc_ports[port] = ap;

        /*
         * Allocate enough so we never have to reallocate, it makes
         * it easier.
         *
         * ap_pmcount will be reduced by the scan if we encounter the
         * port multiplier port prior to target 15.
         *
         * kmalloc power-of-2 allocations are guaranteed not to cross
         * a page boundary.  Make sure the identify sub-structure in the
         * at structure does not cross a page boundary, just in case the
         * part is AHCI-1.1 and can't handle multiple DRQ blocks.
         */
        if (ap->ap_ata[0] == NULL) {
                int pw2;

                for (pw2 = 1; pw2 < sizeof(*at); pw2 <<= 1)
                        ;
                for (i = 0; i < AHCI_MAX_PMPORTS; ++i) {
                        at = kmalloc(pw2, M_DEVBUF, M_INTWAIT | M_ZERO);
                        ap->ap_ata[i] = at;
                        at->at_ahci_port = ap;
                        at->at_target = i;
                        at->at_probe = ATA_PROBE_NEED_INIT;
                        at->at_features |= ATA_PORT_F_RESCAN;
                        ksnprintf(at->at_name, sizeof(at->at_name),
                                  "%s.%d", ap->ap_name, i);
                }
        }
        if (bus_space_subregion(sc->sc_iot, sc->sc_ioh,
            AHCI_PORT_REGION(port), AHCI_PORT_SIZE, &ap->ap_ioh) != 0) {
                device_printf(sc->sc_dev,
                              "unable to create register window for port %d\n",
                              port);
                goto freeport;
        }

        ap->ap_sc = sc;
        ap->ap_num = port;
        ap->ap_probe = ATA_PROBE_NEED_INIT;
        ap->link_pwr_mgmt = AHCI_LINK_PWR_MGMT_NONE;
        ap->sysctl_tree = NULL;
        TAILQ_INIT(&ap->ap_ccb_free);
        TAILQ_INIT(&ap->ap_ccb_pending);
        lockinit(&ap->ap_ccb_lock, "ahcipo", 0, 0);

        /* Disable port interrupts */
        ahci_pwrite(ap, AHCI_PREG_IE, 0);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);

        /*
         * Sec 10.1.2 - deinitialise port if it is already running
         */
        cmd = ahci_pread(ap, AHCI_PREG_CMD);
        kprintf("%s: Caps %b\n", PORTNAME(ap), cmd, AHCI_PFMT_CMD);

        if ((cmd & (AHCI_PREG_CMD_ST | AHCI_PREG_CMD_CR |
                    AHCI_PREG_CMD_FRE | AHCI_PREG_CMD_FR)) ||
            (ahci_pread(ap, AHCI_PREG_SCTL) & AHCI_PREG_SCTL_DET)) {
                int r;

                r = ahci_port_stop(ap, 1);
                if (r) {
                        device_printf(sc->sc_dev,
                                  "unable to disable %s, ignoring port %d\n",
                                  ((r == 2) ? "CR" : "FR"), port);
                        rc = ENXIO;
                        goto freeport;
                }

                /* Write DET to zero */
                ahci_pwrite(ap, AHCI_PREG_SCTL, AHCI_PREG_SCTL_IPM_DISABLED);
        }

        /* Allocate RFIS */
        ap->ap_dmamem_rfis = ahci_dmamem_alloc(sc, sc->sc_tag_rfis);
        if (ap->ap_dmamem_rfis == NULL) {
                kprintf("%s: NORFIS\n", PORTNAME(ap));
                goto nomem;
        }

        /* Setup RFIS base address */
        ap->ap_rfis = (struct ahci_rfis *) AHCI_DMA_KVA(ap->ap_dmamem_rfis);
        dva = AHCI_DMA_DVA(ap->ap_dmamem_rfis);
        ahci_pwrite(ap, AHCI_PREG_FBU, (u_int32_t)(dva >> 32));
        ahci_pwrite(ap, AHCI_PREG_FB, (u_int32_t)dva);

        /* Clear SERR before starting FIS reception or ST or anything */
        ahci_flush_tfd(ap);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);

        /* Enable FIS reception and activate port. */
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        cmd &= ~(AHCI_PREG_CMD_CLO | AHCI_PREG_CMD_PMA);
        cmd |= AHCI_PREG_CMD_FRE | AHCI_PREG_CMD_POD | AHCI_PREG_CMD_SUD;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd | AHCI_PREG_CMD_ICC_ACTIVE);

        /* Check whether port activated.  Skip it if not. */
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        if ((cmd & AHCI_PREG_CMD_FRE) == 0) {
                kprintf("%s: NOT-ACTIVATED\n", PORTNAME(ap));
                rc = ENXIO;
                goto freeport;
        }

        /* Allocate a CCB for each command slot */
        ap->ap_ccbs = kmalloc(sizeof(struct ahci_ccb) * sc->sc_ncmds, M_DEVBUF,
                              M_WAITOK | M_ZERO);
        if (ap->ap_ccbs == NULL) {
                device_printf(sc->sc_dev,
                              "unable to allocate command list for port %d\n",
                              port);
                goto freeport;
        }

        /* Command List Structures and Command Tables */
        ap->ap_dmamem_cmd_list = ahci_dmamem_alloc(sc, sc->sc_tag_cmdh);
        ap->ap_dmamem_cmd_table = ahci_dmamem_alloc(sc, sc->sc_tag_cmdt);
        if (ap->ap_dmamem_cmd_table == NULL ||
            ap->ap_dmamem_cmd_list == NULL) {
nomem:
                device_printf(sc->sc_dev,
                              "unable to allocate DMA memory for port %d\n",
                              port);
                goto freeport;
        }

        /* Setup command list base address */
        dva = AHCI_DMA_DVA(ap->ap_dmamem_cmd_list);
        ahci_pwrite(ap, AHCI_PREG_CLBU, (u_int32_t)(dva >> 32));
        ahci_pwrite(ap, AHCI_PREG_CLB, (u_int32_t)dva);

        /* Split CCB allocation into CCBs and assign to command header/table */
        hdr = AHCI_DMA_KVA(ap->ap_dmamem_cmd_list);
        table = AHCI_DMA_KVA(ap->ap_dmamem_cmd_table);
        for (i = 0; i < sc->sc_ncmds; i++) {
                ccb = &ap->ap_ccbs[i];

                error = bus_dmamap_create(sc->sc_tag_data, BUS_DMA_ALLOCNOW,
                                          &ccb->ccb_dmamap);
                if (error) {
                        device_printf(sc->sc_dev,
                                      "unable to create dmamap for port %d "
                                      "ccb %d\n", port, i);
                        goto freeport;
                }

                callout_init(&ccb->ccb_timeout);
                ccb->ccb_slot = i;
                ccb->ccb_port = ap;
                ccb->ccb_cmd_hdr = &hdr[i];
                ccb->ccb_cmd_table = &table[i];
                dva = AHCI_DMA_DVA(ap->ap_dmamem_cmd_table) +
                    ccb->ccb_slot * sizeof(struct ahci_cmd_table);
                ccb->ccb_cmd_hdr->ctba_hi = htole32((u_int32_t)(dva >> 32));
                ccb->ccb_cmd_hdr->ctba_lo = htole32((u_int32_t)dva);

                ccb->ccb_xa.fis =
                    (struct ata_fis_h2d *)ccb->ccb_cmd_table->cfis;
                ccb->ccb_xa.packetcmd = ccb->ccb_cmd_table->acmd;
                ccb->ccb_xa.tag = i;

                ccb->ccb_xa.state = ATA_S_COMPLETE;

                /*
                 * CCB[1] is the error CCB and is not get or put.  It is
                 * also used for probing.  Numerous HBAs only load the
                 * signature from CCB[1] so it MUST be used for the second
                 * FIS.
                 */
                if (i == 1)
                        ap->ap_err_ccb = ccb;
                else
                        ahci_put_ccb(ccb);
        }

        /*
         * Wait for ICC change to complete
         */
        ahci_pwait_clr(ap, AHCI_PREG_CMD, AHCI_PREG_CMD_ICC);

        /*
         * Calculate the interrupt mask
         */
        data = AHCI_PREG_IE_TFEE | AHCI_PREG_IE_HBFE |
               AHCI_PREG_IE_IFE | AHCI_PREG_IE_OFE |
               AHCI_PREG_IE_DPE | AHCI_PREG_IE_UFE |
               AHCI_PREG_IE_PCE | AHCI_PREG_IE_PRCE |
               AHCI_PREG_IE_DHRE | AHCI_PREG_IE_SDBE;
        if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SSNTF)
                data |= AHCI_PREG_IE_IPME;
#ifdef AHCI_COALESCE
        if (sc->sc_ccc_ports & (1 << port)
                data &= ~(AHCI_PREG_IE_SDBE | AHCI_PREG_IE_DHRE);
#endif
        ap->ap_intmask = data;

        /*
         * Start the port helper thread.  The helper thread will call
         * ahci_port_init() so the ports can all be started in parallel.
         * A failure by ahci_port_init() does not deallocate the port
         * since we still want hot-plug events.
         */
        ahci_os_start_port(ap);
        return(0);
freeport:
        ahci_port_free(sc, port);
        return (rc);
}

/*
 * [re]initialize an idle port.  No CCBs should be active.  (from port thread)
 *
 * This function is called during the initial port allocation sequence
 * and is also called on hot-plug insertion.  We take no chances and
 * use a portreset instead of a softreset.
 *
 * This function is the only way to move a failed port back to active
 * status.
 *
 * Returns 0 if a device is successfully detected.
 */
int
ahci_port_init(struct ahci_port *ap)
{
        u_int32_t cmd;

        /*
         * Register [re]initialization
         *
         * Flush the TFD and SERR and make sure the port is stopped before
         * enabling its interrupt.  We no longer cycle the port start as
         * the port should not be started unless a device is present.
         *
         * XXX should we enable FIS reception? (FRE)?
         */
        ahci_pwrite(ap, AHCI_PREG_IE, 0);
        ahci_port_stop(ap, 0);
        if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SSNTF)
                ahci_pwrite(ap, AHCI_PREG_SNTF, -1);
        ahci_flush_tfd(ap);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);

        /*
         * If we are being harsh try to kill the port completely.  Normally
         * we would want to hold on to some of the state the BIOS may have
         * set, such as SUD (spin up device).
         *
         * AP_F_HARSH_REINIT is cleared in the hard reset state
         */
        if (ap->ap_flags & AP_F_HARSH_REINIT) {
                ahci_pwrite(ap, AHCI_PREG_SCTL, AHCI_PREG_SCTL_IPM_DISABLED);
                ahci_pwrite(ap, AHCI_PREG_CMD, 0);

                ahci_os_sleep(1000);

                cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
                cmd &= ~(AHCI_PREG_CMD_CLO | AHCI_PREG_CMD_PMA);
                cmd |= AHCI_PREG_CMD_FRE | AHCI_PREG_CMD_POD |
                       AHCI_PREG_CMD_SUD;
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd | AHCI_PREG_CMD_ICC_ACTIVE);
                cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
                if ((cmd & AHCI_PREG_CMD_FRE) == 0) {
                        kprintf("%s: Warning: FRE did not come up during "
                                "harsh reinitialization\n",
                                PORTNAME(ap));
                }
                ahci_os_sleep(1000);
        }

        /*
         * Clear any pending garbage and re-enable the interrupt before
         * going to the next stage.
         */
        ap->ap_probe = ATA_PROBE_NEED_HARD_RESET;
        ap->ap_pmcount = 0;

        if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SSNTF)
                ahci_pwrite(ap, AHCI_PREG_SNTF, -1);
        ahci_flush_tfd(ap);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);
        ahci_pwrite(ap, AHCI_PREG_IS, -1);

        ahci_port_interrupt_enable(ap);

        return (0);
}

/*
 * Enable or re-enable interrupts on a port.
 *
 * This routine is called from the port initialization code or from the
 * helper thread as the real interrupt may be forced to turn off certain
 * interrupt sources.
 */
void
ahci_port_interrupt_enable(struct ahci_port *ap)
{
        ahci_pwrite(ap, AHCI_PREG_IE, ap->ap_intmask);
}

/*
 * Manage the agressive link power management capability.
 */
void
ahci_port_link_pwr_mgmt(struct ahci_port *ap, int link_pwr_mgmt)
{
        u_int32_t cmd, sctl;

        if (link_pwr_mgmt == ap->link_pwr_mgmt)
                return;

        if ((ap->ap_sc->sc_cap & AHCI_REG_CAP_SALP) == 0) {
                kprintf("%s: link power management not supported.\n",
                        PORTNAME(ap));
                return;
        }

        ahci_os_lock_port(ap);

        if (link_pwr_mgmt == AHCI_LINK_PWR_MGMT_AGGR &&
            (ap->ap_sc->sc_cap & AHCI_REG_CAP_SSC)) {
                kprintf("%s: enabling aggressive link power management.\n",
                        PORTNAME(ap));

                ap->link_pwr_mgmt = link_pwr_mgmt;

                ap->ap_intmask &= ~AHCI_PREG_IE_PRCE;
                ahci_port_interrupt_enable(ap);

                sctl = ahci_pread(ap, AHCI_PREG_SCTL);
                sctl &= ~(AHCI_PREG_SCTL_IPM_DISABLED);
                ahci_pwrite(ap, AHCI_PREG_SCTL, sctl);

                /*
                 * Enable device initiated link power management for
                 * directly attached devices that support it.
                 */
                if (ap->ap_type != ATA_PORT_T_PM &&
                    ap->ap_ata[0]->at_identify.satafsup & (1 << 3)) {
                        if (ahci_set_feature(ap, NULL, ATA_SATAFT_DEVIPS, 1))
                                kprintf("%s: Could not enable device initiated "
                                    "link power management.\n",
                                    PORTNAME(ap));
                }

                cmd = ahci_pread(ap, AHCI_PREG_CMD);
                cmd |= AHCI_PREG_CMD_ASP;
                cmd |= AHCI_PREG_CMD_ALPE;
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd);

        } else if (link_pwr_mgmt == AHCI_LINK_PWR_MGMT_MEDIUM &&
                   (ap->ap_sc->sc_cap & AHCI_REG_CAP_PSC)) {
                kprintf("%s: enabling medium link power management.\n",
                        PORTNAME(ap));

                ap->link_pwr_mgmt = link_pwr_mgmt;

                ap->ap_intmask &= ~AHCI_PREG_IE_PRCE;
                ahci_port_interrupt_enable(ap);

                sctl = ahci_pread(ap, AHCI_PREG_SCTL);
                sctl |= AHCI_PREG_SCTL_IPM_DISABLED;
                sctl &= ~AHCI_PREG_SCTL_IPM_NOPARTIAL;
                ahci_pwrite(ap, AHCI_PREG_SCTL, sctl);

                cmd = ahci_pread(ap, AHCI_PREG_CMD);
                cmd &= ~AHCI_PREG_CMD_ASP;
                cmd |= AHCI_PREG_CMD_ALPE;
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd);

        } else if (link_pwr_mgmt == AHCI_LINK_PWR_MGMT_NONE) {
                kprintf("%s: disabling link power management.\n",
                        PORTNAME(ap));

                /* Disable device initiated link power management */
                if (ap->ap_type != ATA_PORT_T_PM &&
                    ap->ap_ata[0]->at_identify.satafsup & (1 << 3))
                        ahci_set_feature(ap, NULL, ATA_SATAFT_DEVIPS, 0);

                cmd = ahci_pread(ap, AHCI_PREG_CMD);
                cmd &= ~(AHCI_PREG_CMD_ALPE | AHCI_PREG_CMD_ASP);
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd);

                sctl = ahci_pread(ap, AHCI_PREG_SCTL);
                sctl |= AHCI_PREG_SCTL_IPM_DISABLED;
                ahci_pwrite(ap, AHCI_PREG_SCTL, sctl);

                /* let the drive come back to avoid PRCS interrupts later */
                ahci_os_unlock_port(ap);
                ahci_os_sleep(1000);
                ahci_os_lock_port(ap);

                ahci_pwrite(ap, AHCI_PREG_SERR,
                            AHCI_PREG_SERR_DIAG_N | AHCI_PREG_SERR_DIAG_W);
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_PRCS);

                ap->ap_intmask |= AHCI_PREG_IE_PRCE;
                ahci_port_interrupt_enable(ap);

                ap->link_pwr_mgmt = link_pwr_mgmt;
        } else {
                kprintf("%s: unsupported link power management state %d.\n",
                        PORTNAME(ap), link_pwr_mgmt);
        }

        ahci_os_unlock_port(ap);
}

/*
 * Return current link power state.
 */
int
ahci_port_link_pwr_state(struct ahci_port *ap)
{
        uint32_t r;

        r = ahci_pread(ap, AHCI_PREG_SSTS);
        switch (r & SATA_PM_SSTS_IPM) {
        case SATA_PM_SSTS_IPM_ACTIVE:
                return 1;
        case SATA_PM_SSTS_IPM_PARTIAL:
                return 2;
        case SATA_PM_SSTS_IPM_SLUMBER:
                return 3;
        default:
                return 0;
        }
}

/*
 * Run the port / target state machine from a main context.
 *
 * The state machine for the port is always run.
 *
 * If atx is non-NULL run the state machine for a particular target.
 * If atx is NULL run the state machine for all targets.
 */
void
ahci_port_state_machine(struct ahci_port *ap, int initial)
{
        struct ata_port *at;
        u_int32_t data;
        int target;
        int didsleep;
        int loop;

        /*
         * State machine for port.  Note that CAM is not yet associated
         * during the initial parallel probe and the port's probe state
         * will not get past ATA_PROBE_NEED_IDENT.
         */
        {
                if (initial == 0 && ap->ap_probe <= ATA_PROBE_NEED_HARD_RESET) {
                        kprintf("%s: Waiting 10 seconds on insertion\n",
                                PORTNAME(ap));
                        ahci_os_sleep(10000);
                        initial = 1;
                }
                if (ap->ap_probe == ATA_PROBE_NEED_INIT)
                        ahci_port_init(ap);
                if (ap->ap_probe == ATA_PROBE_NEED_HARD_RESET)
                        ahci_port_reset(ap, NULL, 1);
                if (ap->ap_probe == ATA_PROBE_NEED_SOFT_RESET)
                        ahci_port_reset(ap, NULL, 0);
                if (ap->ap_probe == ATA_PROBE_NEED_IDENT)
                        ahci_cam_probe(ap, NULL);
        }
        if (ap->ap_type != ATA_PORT_T_PM) {
                if (ap->ap_probe == ATA_PROBE_FAILED) {
                        ahci_cam_changed(ap, NULL, 0);
                } else if (ap->ap_probe >= ATA_PROBE_NEED_IDENT) {
                        ahci_cam_changed(ap, NULL, 1);
                }
                return;
        }

        /*
         * Port Multiplier state machine.
         *
         * Get a mask of changed targets and combine with any runnable
         * states already present.
         */
        for (loop = 0; ;++loop) {
                if (ahci_pm_read(ap, 15, SATA_PMREG_EINFO, &data)) {
                        kprintf("%s: PM unable to read hot-plug bitmap\n",
                                PORTNAME(ap));
                        break;
                }

                /*
                 * Do at least one loop, then stop if no more state changes
                 * have occured.  The PM might not generate a new
                 * notification until we clear the entire bitmap.
                 */
                if (loop && data == 0)
                        break;

                /*
                 * New devices showing up in the bitmap require some spin-up
                 * time before we start probing them.  Reset didsleep.  The
                 * first new device we detect will sleep before probing.
                 *
                 * This only applies to devices whos change bit is set in
                 * the data, and does not apply to the initial boot-time
                 * probe.
                 */
                didsleep = 0;

                for (target = 0; target < ap->ap_pmcount; ++target) {
                        at = ap->ap_ata[target];

                        /*
                         * Check the target state for targets behind the PM
                         * which have changed state.  This will adjust
                         * at_probe and set ATA_PORT_F_RESCAN
                         *
                         * We want to wait at least 10 seconds before probing
                         * a newly inserted device.  If the check status
                         * indicates a device is present and in need of a
                         * hard reset, we make sure we have slept before
                         * continuing.
                         *
                         * We also need to wait at least 1 second for the
                         * PHY state to change after insertion, if we
                         * haven't already waited the 10 seconds.
                         *
                         * NOTE: When pm_check_good finds a good port it
                         *       typically starts us in probe state
                         *       NEED_HARD_RESET rather than INIT.
                         */
                        if (data & (1 << target)) {
                                if (initial == 0 && didsleep == 0)
                                        ahci_os_sleep(1000);
                                ahci_pm_check_good(ap, target);
                                if (initial == 0 && didsleep == 0 &&
                                    at->at_probe <= ATA_PROBE_NEED_HARD_RESET
                                ) {
                                        didsleep = 1;
                                        kprintf("%s: Waiting 10 seconds on insertion\n", PORTNAME(ap));
                                        ahci_os_sleep(10000);
                                }
                        }

                        /*
                         * Report hot-plug events before the probe state
                         * really gets hot.  Only actual events are reported
                         * here to reduce spew.
                         */
                        if (data & (1 << target)) {
                                kprintf("%s: HOTPLUG (PM) - ", ATANAME(ap, at));
                                switch(at->at_probe) {
                                case ATA_PROBE_NEED_INIT:
                                case ATA_PROBE_NEED_HARD_RESET:
                                        kprintf("Device inserted\n");
                                        break;
                                case ATA_PROBE_FAILED:
                                        kprintf("Device removed\n");
                                        break;
                                default:
                                        kprintf("Device probe in progress\n");
                                        break;
                                }
                        }

                        /*
                         * Run through the state machine as necessary if
                         * the port is not marked failed.
                         *
                         * The state machine may stop at NEED_IDENT if
                         * CAM is not yet attached.
                         *
                         * Acquire exclusive access to the port while we
                         * are doing this.  This prevents command-completion
                         * from queueing commands for non-polled targets
                         * inbetween our probe steps.  We need to do this
                         * because the reset probes can generate severe PHY
                         * and protocol errors and soft-brick the port.
                         */
                        if (at->at_probe != ATA_PROBE_FAILED &&
                            at->at_probe != ATA_PROBE_GOOD) {
                                ahci_beg_exclusive_access(ap, at);
                                if (at->at_probe == ATA_PROBE_NEED_INIT)
                                        ahci_pm_port_init(ap, at);
                                if (at->at_probe == ATA_PROBE_NEED_HARD_RESET)
                                        ahci_port_reset(ap, at, 1);
                                if (at->at_probe == ATA_PROBE_NEED_SOFT_RESET)
                                        ahci_port_reset(ap, at, 0);
                                if (at->at_probe == ATA_PROBE_NEED_IDENT)
                                        ahci_cam_probe(ap, at);
                                ahci_end_exclusive_access(ap, at);
                        }

                        /*
                         * Add or remove from CAM
                         */
                        if (at->at_features & ATA_PORT_F_RESCAN) {
                                at->at_features &= ~ATA_PORT_F_RESCAN;
                                if (at->at_probe == ATA_PROBE_FAILED) {
                                        ahci_cam_changed(ap, at, 0);
                                } else if (at->at_probe >= ATA_PROBE_NEED_IDENT) {
                                        ahci_cam_changed(ap, at, 1);
                                }
                        }
                        data &= ~(1 << target);
                }
                if (data) {
                        kprintf("%s: WARNING (PM): extra bits set in "
                                "EINFO: %08x\n", PORTNAME(ap), data);
                        while (target < AHCI_MAX_PMPORTS) {
                                ahci_pm_check_good(ap, target);
                                ++target;
                        }
                }
        }
}


/*
 * De-initialize and detach a port.
 */
void
ahci_port_free(struct ahci_softc *sc, u_int port)
{
        struct ahci_port        *ap = sc->sc_ports[port];
        struct ahci_ccb         *ccb;
        int i;

        /*
         * Ensure port is disabled and its interrupts are all flushed.
         */
        if (ap->ap_sc) {
                ahci_port_stop(ap, 1);
                ahci_os_stop_port(ap);
                ahci_pwrite(ap, AHCI_PREG_CMD, 0);
                ahci_pwrite(ap, AHCI_PREG_IE, 0);
                ahci_pwrite(ap, AHCI_PREG_IS, ahci_pread(ap, AHCI_PREG_IS));
                ahci_write(sc, AHCI_REG_IS, 1 << port);
        }

        if (ap->ap_ccbs) {
                while ((ccb = ahci_get_ccb(ap)) != NULL) {
                        if (ccb->ccb_dmamap) {
                                bus_dmamap_destroy(sc->sc_tag_data,
                                                   ccb->ccb_dmamap);
                                ccb->ccb_dmamap = NULL;
                        }
                }
                if ((ccb = ap->ap_err_ccb) != NULL) {
                        if (ccb->ccb_dmamap) {
                                bus_dmamap_destroy(sc->sc_tag_data,
                                                   ccb->ccb_dmamap);
                                ccb->ccb_dmamap = NULL;
                        }
                        ap->ap_err_ccb = NULL;
                }
                kfree(ap->ap_ccbs, M_DEVBUF);
                ap->ap_ccbs = NULL;
        }

        if (ap->ap_dmamem_cmd_list) {
                ahci_dmamem_free(sc, ap->ap_dmamem_cmd_list);
                ap->ap_dmamem_cmd_list = NULL;
        }
        if (ap->ap_dmamem_rfis) {
                ahci_dmamem_free(sc, ap->ap_dmamem_rfis);
                ap->ap_dmamem_rfis = NULL;
        }
        if (ap->ap_dmamem_cmd_table) {
                ahci_dmamem_free(sc, ap->ap_dmamem_cmd_table);
                ap->ap_dmamem_cmd_table = NULL;
        }
        if (ap->ap_ata) {
                for (i = 0; i < AHCI_MAX_PMPORTS; ++i) {
                        if (ap->ap_ata[i]) {
                                kfree(ap->ap_ata[i], M_DEVBUF);
                                ap->ap_ata[i] = NULL;
                        }
                }
        }
        if (ap->ap_err_scratch) {
                kfree(ap->ap_err_scratch, M_DEVBUF);
                ap->ap_err_scratch = NULL;
        }

        /* bus_space(9) says we dont free the subregions handle */

        kfree(ap, M_DEVBUF);
        sc->sc_ports[port] = NULL;
}

static
u_int32_t
ahci_pactive(struct ahci_port *ap)
{
        u_int32_t mask;

        mask = ahci_pread(ap, AHCI_PREG_CI);
        if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SNCQ)
                mask |= ahci_pread(ap, AHCI_PREG_SACT);
        return(mask);
}

/*
 * Start high-level command processing on the port
 */
int
ahci_port_start(struct ahci_port *ap)
{
        u_int32_t       r, s, is, tfd;

        /*
         * FRE must be turned on before ST.  Wait for FR to go active
         * before turning on ST.  The spec doesn't seem to think this
         * is necessary but waiting here avoids an on-off race in the
         * ahci_port_stop() code.
         */
        r = ahci_pread(ap, AHCI_PREG_CMD);
        if ((r & AHCI_PREG_CMD_FRE) == 0) {
                r |= AHCI_PREG_CMD_FRE;
                ahci_pwrite(ap, AHCI_PREG_CMD, r);
        }
        if ((ap->ap_sc->sc_flags & AHCI_F_IGN_FR) == 0) {
                if (ahci_pwait_set(ap, AHCI_PREG_CMD, AHCI_PREG_CMD_FR)) {
                        kprintf("%s: Cannot start FIS reception\n",
                                PORTNAME(ap));
                        return (2);
                }
        } else {
                ahci_os_sleep(10);
        }

        /*
         * Turn on ST, wait for CR to come up.
         */
        r |= AHCI_PREG_CMD_ST;
        ahci_pwrite(ap, AHCI_PREG_CMD, r);
        if (ahci_pwait_set_to(ap, 2000, AHCI_PREG_CMD, AHCI_PREG_CMD_CR)) {
                s = ahci_pread(ap, AHCI_PREG_SERR);
                is = ahci_pread(ap, AHCI_PREG_IS);
                tfd = ahci_pread(ap, AHCI_PREG_TFD);
                kprintf("%s: Cannot start command DMA\n"
                        "NCMP=%b NSERR=%b\n"
                        "NEWIS=%b\n"
                        "NEWTFD=%b\n",
                        PORTNAME(ap),
                        r, AHCI_PFMT_CMD, s, AHCI_PFMT_SERR,
                        is, AHCI_PFMT_IS,
                        tfd, AHCI_PFMT_TFD_STS);
                return (1);
        }

#ifdef AHCI_COALESCE
        /*
         * (Re-)enable coalescing on the port.
         */
        if (ap->ap_sc->sc_ccc_ports & (1 << ap->ap_num)) {
                ap->ap_sc->sc_ccc_ports_cur |= (1 << ap->ap_num);
                ahci_write(ap->ap_sc, AHCI_REG_CCC_PORTS,
                    ap->ap_sc->sc_ccc_ports_cur);
        }
#endif

        return (0);
}

/*
 * Stop high-level command processing on a port
 *
 * WARNING!  If the port is stopped while CR is still active our saved
 *           CI/SACT will race any commands completed by the command
 *           processor prior to being able to stop.  Thus we never call
 *           this function unless we intend to dispose of any remaining
 *           active commands.  In particular, this complicates the timeout
 *           code.
 */
int
ahci_port_stop(struct ahci_port *ap, int stop_fis_rx)
{
        u_int32_t       r;

#ifdef AHCI_COALESCE
        /*
         * Disable coalescing on the port while it is stopped.
         */
        if (ap->ap_sc->sc_ccc_ports & (1 << ap->ap_num)) {
                ap->ap_sc->sc_ccc_ports_cur &= ~(1 << ap->ap_num);
                ahci_write(ap->ap_sc, AHCI_REG_CCC_PORTS,
                    ap->ap_sc->sc_ccc_ports_cur);
        }
#endif

        /*
         * Turn off ST, then wait for CR to go off.
         */
        r = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        r &= ~AHCI_PREG_CMD_ST;
        ahci_pwrite(ap, AHCI_PREG_CMD, r);

        if (ahci_pwait_clr(ap, AHCI_PREG_CMD, AHCI_PREG_CMD_CR)) {
                kprintf("%s: Port bricked, unable to stop (ST)\n",
                        PORTNAME(ap));
                return (1);
        }

#if 0
        /*
         * Turn off FRE, then wait for FR to go off.  FRE cannot
         * be turned off until CR transitions to 0.
         */
        if ((r & AHCI_PREG_CMD_FR) == 0) {
                kprintf("%s: FR stopped, clear FRE for next start\n",
                        PORTNAME(ap));
                stop_fis_rx = 2;
        }
#endif
        if (stop_fis_rx) {
                r &= ~AHCI_PREG_CMD_FRE;
                ahci_pwrite(ap, AHCI_PREG_CMD, r);
                if (ahci_pwait_clr(ap, AHCI_PREG_CMD, AHCI_PREG_CMD_FR)) {
                        kprintf("%s: Port bricked, unable to stop (FRE)\n",
                                PORTNAME(ap));
                        return (2);
                }
        }

        return (0);
}

/*
 * AHCI command list override -> forcibly clear TFD.STS.{BSY,DRQ}
 */
int
ahci_port_clo(struct ahci_port *ap)
{
        struct ahci_softc               *sc = ap->ap_sc;
        u_int32_t                       cmd;

        /* Only attempt CLO if supported by controller */
        if ((ahci_read(sc, AHCI_REG_CAP) & AHCI_REG_CAP_SCLO) == 0)
                return (1);

        /* Issue CLO */
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd | AHCI_PREG_CMD_CLO);

        /* Wait for completion */
        if (ahci_pwait_clr(ap, AHCI_PREG_CMD, AHCI_PREG_CMD_CLO)) {
                kprintf("%s: CLO did not complete\n", PORTNAME(ap));
                return (1);
        }

        return (0);
}

/*
 * Reset a port.
 *
 * If hard is 0 perform a softreset of the port.
 * If hard is 1 perform a hard reset of the port.
 *
 * If at is non-NULL an indirect port via a port-multiplier is being
 * reset, otherwise a direct port is being reset.
 *
 * NOTE: Indirect ports can only be soft-reset.
 */
int
ahci_port_reset(struct ahci_port *ap, struct ata_port *at, int hard)
{
        int rc;

        if (hard) {
                if (at)
                        rc = ahci_pm_hardreset(ap, at->at_target, hard);
                else
                        rc = ahci_port_hardreset(ap, hard);
        } else {
                if (at)
                        rc = ahci_pm_softreset(ap, at->at_target);
                else
                        rc = ahci_port_softreset(ap);
        }
        return(rc);
}

/*
 * AHCI soft reset, Section 10.4.1
 *
 * (at) will be NULL when soft-resetting a directly-attached device, and
 * non-NULL when soft-resetting a device through a port multiplier.
 *
 * This function keeps port communications intact and attempts to generate
 * a reset to the connected device using device commands.
 */
int
ahci_port_softreset(struct ahci_port *ap)
{
        struct ahci_ccb         *ccb = NULL;
        struct ahci_cmd_hdr     *cmd_slot;
        u_int8_t                *fis;
        int                     error;

        error = EIO;

        if (bootverbose) {
                kprintf("%s: START SOFTRESET %b\n", PORTNAME(ap),
                        ahci_pread(ap, AHCI_PREG_CMD), AHCI_PFMT_CMD);
        }

        DPRINTF(AHCI_D_VERBOSE, "%s: soft reset\n", PORTNAME(ap));

        crit_enter();
        ap->ap_flags |= AP_F_IN_RESET;
        ap->ap_state = AP_S_NORMAL;

        /*
         * Remember port state in cmd (main to restore start/stop)
         *
         * Idle port.
         */
        if (ahci_port_stop(ap, 0)) {
                kprintf("%s: failed to stop port, cannot softreset\n",
                        PORTNAME(ap));
                goto err;
        }

        /*
         * Request CLO if device appears hung.
         */
        if (ahci_pread(ap, AHCI_PREG_TFD) &
                   (AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                ahci_port_clo(ap);
        }

        /*
         * This is an attempt to clear errors so a new signature will
         * be latched.  It isn't working properly.  XXX
         */
        ahci_flush_tfd(ap);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);

        /* Restart port */
        if (ahci_port_start(ap)) {
                kprintf("%s: failed to start port, cannot softreset\n",
                        PORTNAME(ap));
                goto err;
        }

        /* Check whether CLO worked */
        if (ahci_pwait_clr(ap, AHCI_PREG_TFD,
                               AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                kprintf("%s: CLO %s, need port reset\n",
                        PORTNAME(ap),
                        (ahci_read(ap->ap_sc, AHCI_REG_CAP) & AHCI_REG_CAP_SCLO)
                        ? "failed" : "unsupported");
                error = EBUSY;
                goto err;
        }

        /*
         * Prep first D2H command with SRST feature & clear busy/reset flags
         *
         * It is unclear which other fields in the FIS are used.  Just zero
         * everything.
         *
         * NOTE!  This CCB is used for both the first and second commands.
         *        The second command must use CCB slot 1 to properly load
         *        the signature.
         */
        ccb = ahci_get_err_ccb(ap);
        ccb->ccb_xa.complete = ahci_dummy_done;
        ccb->ccb_xa.flags = ATA_F_POLL | ATA_F_EXCLUSIVE;
        KKASSERT(ccb->ccb_slot == 1);
        ccb->ccb_xa.at = NULL;
        cmd_slot = ccb->ccb_cmd_hdr;

        fis = ccb->ccb_cmd_table->cfis;
        bzero(fis, sizeof(ccb->ccb_cmd_table->cfis));
        fis[0] = ATA_FIS_TYPE_H2D;
        fis[15] = ATA_FIS_CONTROL_SRST|ATA_FIS_CONTROL_4BIT;

        cmd_slot->prdtl = 0;
        cmd_slot->flags = htole16(5);   /* FIS length: 5 DWORDS */
        cmd_slot->flags |= htole16(AHCI_CMD_LIST_FLAG_C); /* Clear busy on OK */
        cmd_slot->flags |= htole16(AHCI_CMD_LIST_FLAG_R); /* Reset */

        ccb->ccb_xa.state = ATA_S_PENDING;

        if (ahci_poll(ccb, 1000, ahci_quick_timeout) != ATA_S_COMPLETE) {
                kprintf("%s: First FIS failed\n", PORTNAME(ap));
                goto err;
        }

        /*
         * WARNING!     TIME SENSITIVE SPACE!   WARNING!
         *
         * The two FISes are supposed to be back to back.  Don't issue other
         * commands or even delay if we can help it.
         */

        /*
         * Prep second D2H command to read status and complete reset sequence
         * AHCI 10.4.1 and "Serial ATA Revision 2.6".  I can't find the ATA
         * Rev 2.6 and it is unclear how the second FIS should be set up
         * from the AHCI document.
         *
         * It is unclear which other fields in the FIS are used.  Just zero
         * everything.
         */
        ccb->ccb_xa.flags = ATA_F_POLL | ATA_F_AUTOSENSE | ATA_F_EXCLUSIVE;

        bzero(fis, sizeof(ccb->ccb_cmd_table->cfis));
        fis[0] = ATA_FIS_TYPE_H2D;
        fis[15] = ATA_FIS_CONTROL_4BIT;

        cmd_slot->prdtl = 0;
        cmd_slot->flags = htole16(5);   /* FIS length: 5 DWORDS */

        ccb->ccb_xa.state = ATA_S_PENDING;
        if (ahci_poll(ccb, 1000, ahci_quick_timeout) != ATA_S_COMPLETE) {
                kprintf("%s: Second FIS failed\n", PORTNAME(ap));
                goto err;
        }

        if (ahci_pwait_clr(ap, AHCI_PREG_TFD,
                            AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                kprintf("%s: device didn't come ready after reset, TFD: 0x%b\n",
                        PORTNAME(ap),
                        ahci_pread(ap, AHCI_PREG_TFD), AHCI_PFMT_TFD_STS);
                error = EBUSY;
                goto err;
        }

        /*
         * If the softreset is trying to clear a BSY condition after a
         * normal portreset we assign the port type.
         *
         * If the softreset is being run first as part of the ccb error
         * processing code then report if the device signature changed
         * unexpectedly.
         */
        ahci_os_sleep(100);
        if (ap->ap_type == ATA_PORT_T_NONE) {
                ap->ap_type = ahci_port_signature_detect(ap, NULL);
        } else {
                if (ahci_port_signature_detect(ap, NULL) != ap->ap_type) {
                        kprintf("%s: device signature unexpectedly "
                                "changed\n", PORTNAME(ap));
                        error = EBUSY; /* XXX */
                }
        }
        error = 0;

        ahci_os_sleep(3);
err:
        if (ccb != NULL) {
                ahci_put_err_ccb(ccb);

                /*
                 * If the target is busy use CLO to clear the busy
                 * condition.  The BSY should be cleared on the next
                 * start.
                 */
                if (ahci_pread(ap, AHCI_PREG_TFD) &
                    (AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                        ahci_port_clo(ap);
                }
        }

        /*
         * If we failed to softreset make the port quiescent, otherwise
         * make sure the port's start/stop state matches what it was on
         * entry.
         *
         * Don't kill the port if the softreset is on a port multiplier
         * target, that would kill all the targets!
         */
        if (error) {
                ahci_port_hardstop(ap);
                /* ap_probe set to failed */
        } else {
                ap->ap_probe = ATA_PROBE_NEED_IDENT;
                ap->ap_pmcount = 1;
                ahci_port_start(ap);
        }
        ap->ap_flags &= ~AP_F_IN_RESET;
        crit_exit();

        if (bootverbose)
                kprintf("%s: END SOFTRESET\n", PORTNAME(ap));

        return (error);
}

/*
 * Issue just do the core COMRESET and basic device detection on a port.
 *
 * NOTE: Only called by ahci_port_hardreset().
 */
static int
ahci_comreset(struct ahci_port *ap, int *pmdetectp)
{
        u_int32_t cmd;
        u_int32_t r;
        int error;
        int loop;

        /*
         * Idle the port,
         */
        *pmdetectp = 0;
        ahci_port_stop(ap, 0);
        ap->ap_state = AP_S_NORMAL;
        ahci_os_sleep(10);

        /*
         * The port may have been quiescent with its SUD bit cleared, so
         * set the SUD (spin up device).
         *
         * NOTE: I do not know if SUD is a hardware pin/low-level signal
         *       or if it is messaged.
         */
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;

        cmd |= AHCI_PREG_CMD_SUD | AHCI_PREG_CMD_POD;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
        ahci_os_sleep(10);

        /*
         * Make sure that all power management is disabled.
         *
         * NOTE!  AHCI_PREG_SCTL_DET_DISABLE seems to be highly unreliable
         *        on multiple chipsets and can brick the chipset or even
         *        the whole PC.  Never use it.
         */
        ap->ap_type = ATA_PORT_T_NONE;

        r = AHCI_PREG_SCTL_IPM_DISABLED |
            AHCI_PREG_SCTL_SPM_DISABLED;
        ahci_pwrite(ap, AHCI_PREG_SCTL, r);
        ahci_os_sleep(10);

        /*
         * Start transmitting COMRESET.  The spec says that COMRESET must
         * be sent for at least 1ms but in actual fact numerous devices
         * appear to take much longer.  Delay a whole second here.
         *
         * In addition, SATA-3 ports can take longer to train, so even
         * SATA-2 devices which would normally detect very quickly may
         * take longer when plugged into a SATA-3 port.
         */
        r |= AHCI_PREG_SCTL_DET_INIT;
        switch(AhciForceGen) {
        case 0:
                r |= AHCI_PREG_SCTL_SPD_ANY;
                break;
        case 1:
                r |= AHCI_PREG_SCTL_SPD_GEN1;
                break;
        case 2:
                r |= AHCI_PREG_SCTL_SPD_GEN2;
                break;
        case 3:
                r |= AHCI_PREG_SCTL_SPD_GEN3;
                break;
        default:
                r |= AHCI_PREG_SCTL_SPD_GEN3;
                break;
        }
        ahci_pwrite(ap, AHCI_PREG_SCTL, r);
        ahci_os_sleep(1000);
        r &= ~AHCI_PREG_SCTL_SPD;

        ap->ap_flags &= ~AP_F_HARSH_REINIT;

        /*
         * Only SERR_DIAG_X needs to be cleared for TFD updates, but
         * since we are hard-resetting the port we might as well clear
         * the whole enchillada.
         *
         * Wait 1 whole second after clearing INIT before checking
         * the device detection bits in an attempt to work around chipsets
         * which do not properly mask PCS/PRCS during low level init.
         */
        ahci_flush_tfd(ap);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);
        ahci_os_sleep(10);

        r &= ~AHCI_PREG_SCTL_DET_INIT;
        r |= AHCI_PREG_SCTL_DET_NONE;
        ahci_pwrite(ap, AHCI_PREG_SCTL, r);
        ahci_os_sleep(1000);

        /*
         * Try to determine if there is a device on the port.
         *
         * Give the device 3/10 second to at least be detected.
         * If we fail clear PRCS (phy detect) since we may cycled
         * the phy and probably caused another PRCS interrupt.
         */
        loop = 300;
        while (loop > 0) {
                r = ahci_pread(ap, AHCI_PREG_SSTS);
                if (r & AHCI_PREG_SSTS_DET)
                        break;
                loop -= ahci_os_softsleep();
        }
        if (loop == 0) {
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_PRCS);
                if (bootverbose) {
                        kprintf("%s: Port appears to be unplugged\n",
                                PORTNAME(ap));
                }
                error = ENODEV;
                goto done;
        }

        /*
         * There is something on the port.  Regardless of what happens
         * after this tell the caller to try to detect a port multiplier.
         *
         * Give the device 3 seconds to fully negotiate.
         */
        *pmdetectp = 1;

        if (ahci_pwait_eq(ap, 3000, AHCI_PREG_SSTS,
                          AHCI_PREG_SSTS_DET, AHCI_PREG_SSTS_DET_DEV)) {
                if (bootverbose) {
                        kprintf("%s: Device may be powered down\n",
                                PORTNAME(ap));
                }
                error = ENODEV;
                goto done;
        }

        /*
         * We got something that definitely looks like a device.  Give
         * the device time to send us its first D2H FIS.  Waiting for
         * BSY to clear accomplishes this.
         *
         * NOTE: A port multiplier may or may not clear BSY here,
         *       depending on what is sitting in target 0 behind it.
         */
        ahci_flush_tfd(ap);
        if (ahci_pwait_clr_to(ap, 3000, AHCI_PREG_TFD,
                            AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                error = EBUSY;
        } else {
                error = 0;
        }

done:
        ahci_flush_tfd(ap);
        return error;
}


/*
 * AHCI port reset, Section 10.4.2
 *
 * This function does a hard reset of the port.  Note that the device
 * connected to the port could still end-up hung.
 */
int
ahci_port_hardreset(struct ahci_port *ap, int hard)
{
        u_int32_t data;
        int     error;
        int     pmdetect;

        if (bootverbose)
                kprintf("%s: START HARDRESET\n", PORTNAME(ap));
        ap->ap_flags |= AP_F_IN_RESET;

        error = ahci_comreset(ap, &pmdetect);

        /*
         * We may be asked to perform a port multiplier check even if the
         * comreset failed.  This typically occurs when the PM has nothing
         * in slot 0, which can cause BSY to remain set.
         *
         * If the PM detection is successful it will override (error),
         * otherwise (error) is retained.  If an error does occur it
         * is possible that a normal device has blown up on us DUE to
         * the PM detection code, so re-run the comreset and assume
         * a normal device.
         */
        if (pmdetect) {
                if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SPM) {
                        error = ahci_pm_port_probe(ap, error);
                        if (error) {
                                error = ahci_comreset(ap, &pmdetect);
                        }
                }
        }

        /*
         * Finish up.
         */
        ahci_os_sleep(500);

        switch(error) {
        case 0:
                /*
                 * All good, make sure the port is running and set the
                 * probe state.  Ignore the signature junk (it's unreliable)
                 * until we get to the softreset code.
                 */
                if (ahci_port_start(ap)) {
                        kprintf("%s: failed to start command DMA on port, "
                                "disabling\n", PORTNAME(ap));
                        error = EBUSY;
                        break;
                }
                if (ap->ap_type == ATA_PORT_T_PM)
                        ap->ap_probe = ATA_PROBE_GOOD;
                else
                        ap->ap_probe = ATA_PROBE_NEED_SOFT_RESET;
                break;
        case ENODEV:
                /*
                 * Normal device probe failure
                 */
                data = ahci_pread(ap, AHCI_PREG_SSTS);

                switch(data & AHCI_PREG_SSTS_DET) {
                case AHCI_PREG_SSTS_DET_DEV_NE:
                        kprintf("%s: Device not communicating\n",
                                PORTNAME(ap));
                        break;
                case AHCI_PREG_SSTS_DET_PHYOFFLINE:
                        kprintf("%s: PHY offline\n",
                                PORTNAME(ap));
                        break;
                default:
                        kprintf("%s: No device detected\n",
                                PORTNAME(ap));
                        break;
                }
                ahci_port_hardstop(ap);
                break;
        default:
                /*
                 * Abnormal probe (EBUSY)
                 */
                kprintf("%s: Device on port is bricked\n",
                        PORTNAME(ap));
                ahci_port_hardstop(ap);
#if 0
                rc = ahci_port_reset(ap, atx, 0);
                if (rc) {
                        kprintf("%s: Unable unbrick device\n",
                                PORTNAME(ap));
                } else {
                        kprintf("%s: Successfully unbricked\n",
                                PORTNAME(ap));
                }
#endif
                break;
        }

        /*
         * Clean up
         */
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);
        ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS);

        ap->ap_flags &= ~AP_F_IN_RESET;

        if (bootverbose)
                kprintf("%s: END HARDRESET %d\n", PORTNAME(ap), error);
        return (error);
}

/*
 * Hard-stop on hot-swap device removal.  See 10.10.1
 *
 * Place the port in a mode that will allow it to detect hot-swap insertions.
 * This is a bit imprecise because just setting-up SCTL to DET_INIT doesn't
 * seem to do the job.
 *
 * FIS reception is left enabled but command processing is disabled.
 * Cycling FIS reception (FRE) can brick ports.
 */
void
ahci_port_hardstop(struct ahci_port *ap)
{
        struct ahci_ccb *ccb;
        struct ata_port *at;
        u_int32_t r;
        u_int32_t cmd;
        int slot;
        int i;

        /*
         * Stop the port.  We can't modify things like SUD if the port
         * is running.
         */
        ap->ap_state = AP_S_FATAL_ERROR;
        ap->ap_probe = ATA_PROBE_FAILED;
        ap->ap_type = ATA_PORT_T_NONE;
        ahci_port_stop(ap, 0);
        cmd = ahci_pread(ap, AHCI_PREG_CMD);
        cmd &= ~(AHCI_PREG_CMD_CLO | AHCI_PREG_CMD_PMA | AHCI_PREG_CMD_ICC);
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);

        /*
         * Clean up AT sub-ports on SATA port.
         */
        for (i = 0; ap->ap_ata && i < AHCI_MAX_PMPORTS; ++i) {
                at = ap->ap_ata[i];
                at->at_type = ATA_PORT_T_NONE;
                at->at_probe = ATA_PROBE_FAILED;
        }

        /*
         * Make sure FRE is active.  There isn't anything we can do if it
         * fails so just ignore errors.
         */
        if ((cmd & AHCI_PREG_CMD_FRE) == 0) {
                cmd |= AHCI_PREG_CMD_FRE;
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
                if ((ap->ap_sc->sc_flags & AHCI_F_IGN_FR) == 0)
                        ahci_pwait_set(ap, AHCI_PREG_CMD, AHCI_PREG_CMD_FR);
        }

        /*
         * 10.10.1 place us in the Listen state.
         *
         * 10.10.3 DET must be set to 0 and found to be 0 before
         * setting SUD to 0.
         *
         * Deactivating SUD only applies if the controller supports SUD, it
         * is a bit unclear what happens w/regards to detecting hotplug
         * if it doesn't.
         */
        r = AHCI_PREG_SCTL_IPM_DISABLED |
            AHCI_PREG_SCTL_SPM_DISABLED;
        ahci_pwrite(ap, AHCI_PREG_SCTL, r);
        ahci_os_sleep(10);
        cmd &= ~AHCI_PREG_CMD_SUD;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
        ahci_os_sleep(10);

        /*
         * 10.10.1
         *
         * Transition su to the spin-up state.  HBA shall send COMRESET and
         * begin initialization sequence (whatever that means).  Presumably
         * this is edge-triggered.  Following the spin-up state the HBA
         * will automatically transition to the Normal state.
         *
         * This only applies if the controller supports SUD.
         * NEVER use AHCI_PREG_DET_DISABLE.
         */
        cmd |= AHCI_PREG_CMD_POD |
               AHCI_PREG_CMD_SUD |
               AHCI_PREG_CMD_ICC_ACTIVE;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
        ahci_os_sleep(10);

        /*
         * Flush SERR_DIAG_X so the TFD can update.
         */
        ahci_flush_tfd(ap);

        /*
         * Clean out pending ccbs
         */
        while (ap->ap_active) {
                slot = ffs(ap->ap_active) - 1;
                ap->ap_active &= ~(1 << slot);
                ap->ap_expired &= ~(1 << slot);
                --ap->ap_active_cnt;
                ccb = &ap->ap_ccbs[slot];
                if (ccb->ccb_xa.flags & ATA_F_TIMEOUT_RUNNING) {
                        callout_stop(&ccb->ccb_timeout);
                        ccb->ccb_xa.flags &= ~ATA_F_TIMEOUT_RUNNING;
                }
                ccb->ccb_xa.flags &= ~(ATA_F_TIMEOUT_DESIRED |
                                       ATA_F_TIMEOUT_EXPIRED);
                ccb->ccb_xa.state = ATA_S_TIMEOUT;
                ccb->ccb_done(ccb);
                ccb->ccb_xa.complete(&ccb->ccb_xa);
        }
        while (ap->ap_sactive) {
                slot = ffs(ap->ap_sactive) - 1;
                ap->ap_sactive &= ~(1 << slot);
                ap->ap_expired &= ~(1 << slot);
                ccb = &ap->ap_ccbs[slot];
                if (ccb->ccb_xa.flags & ATA_F_TIMEOUT_RUNNING) {
                        callout_stop(&ccb->ccb_timeout);
                        ccb->ccb_xa.flags &= ~ATA_F_TIMEOUT_RUNNING;
                }
                ccb->ccb_xa.flags &= ~(ATA_F_TIMEOUT_DESIRED |
                                       ATA_F_TIMEOUT_EXPIRED);
                ccb->ccb_xa.state = ATA_S_TIMEOUT;
                ccb->ccb_done(ccb);
                ccb->ccb_xa.complete(&ccb->ccb_xa);
        }
        KKASSERT(ap->ap_active_cnt == 0);

        while ((ccb = TAILQ_FIRST(&ap->ap_ccb_pending)) != NULL) {
                TAILQ_REMOVE(&ap->ap_ccb_pending, ccb, ccb_entry);
                ccb->ccb_xa.state = ATA_S_TIMEOUT;
                ccb->ccb_xa.flags &= ~ATA_F_TIMEOUT_DESIRED;
                ccb->ccb_done(ccb);
                ccb->ccb_xa.complete(&ccb->ccb_xa);
        }

        /*
         * Hot-plug device detection should work at this point.  e.g. on
         * AMD chipsets Spin-Up/Normal state is sufficient for hot-plug
         * detection and entering RESET (continuous COMRESET by setting INIT)
         * will actually prevent hot-plug detection from working properly.
         *
         * There may be cases where this will fail to work, I have some
         * additional code to place the HBA in RESET (send continuous
         * COMRESET) and hopefully get DIAG.X or other events when something
         * is plugged in.  Unfortunately this isn't universal and can
         * also prevent events from generating interrupts.
         */

#if 0
        /*
         * Transition us to the Reset state.  Theoretically we send a
         * continuous stream of COMRESETs in this state.
         */
        r |= AHCI_PREG_SCTL_DET_INIT;
        if (AhciForceGen1 & (1 << ap->ap_num)) {
                kprintf("%s: Force 1.5Gbits\n", PORTNAME(ap));
                r |= AHCI_PREG_SCTL_SPD_GEN1;
        } else {
                r |= AHCI_PREG_SCTL_SPD_ANY;
        }
        ahci_pwrite(ap, AHCI_PREG_SCTL, r);
        ahci_os_sleep(10);

        /*
         * Flush SERR_DIAG_X so the TFD can update.
         */
        ahci_flush_tfd(ap);
#endif
        /* NOP */
}

/*
 * We can't loop on the X bit, a continuous COMINIT received will make
 * it loop forever.  Just assume one event has built up and clear X
 * so the task file descriptor can update.
 */
void
ahci_flush_tfd(struct ahci_port *ap)
{
        u_int32_t r;

        r = ahci_pread(ap, AHCI_PREG_SERR);
        if (r & AHCI_PREG_SERR_DIAG_X)
                ahci_pwrite(ap, AHCI_PREG_SERR, AHCI_PREG_SERR_DIAG_X);
}

/*
 * Figure out what type of device is connected to the port, ATAPI or
 * DISK.
 */
int
ahci_port_signature_detect(struct ahci_port *ap, struct ata_port *at)
{
        u_int32_t sig;

        sig = ahci_pread(ap, AHCI_PREG_SIG);
        if (bootverbose)
                kprintf("%s: sig %08x\n", ATANAME(ap, at), sig);
        if ((sig & 0xffff0000) == (SATA_SIGNATURE_ATAPI & 0xffff0000)) {
                return(ATA_PORT_T_ATAPI);
        } else if ((sig & 0xffff0000) ==
                 (SATA_SIGNATURE_PORT_MULTIPLIER & 0xffff0000)) {
                return(ATA_PORT_T_PM);
        } else {
                return(ATA_PORT_T_DISK);
        }
}

/*
 * Load the DMA descriptor table for a CCB's buffer.
 */
int
ahci_load_prdt(struct ahci_ccb *ccb)
{
        struct ahci_port                *ap = ccb->ccb_port;
        struct ahci_softc               *sc = ap->ap_sc;
        struct ata_xfer                 *xa = &ccb->ccb_xa;
        struct ahci_prdt                *prdt = ccb->ccb_cmd_table->prdt;
        bus_dmamap_t                    dmap = ccb->ccb_dmamap;
        struct ahci_cmd_hdr             *cmd_slot = ccb->ccb_cmd_hdr;
        int                             error;

        if (xa->datalen == 0) {
                ccb->ccb_cmd_hdr->prdtl = 0;
                return (0);
        }

        error = bus_dmamap_load(sc->sc_tag_data, dmap,
                                xa->data, xa->datalen,
                                ahci_load_prdt_callback,
                                &prdt,
                                ((xa->flags & ATA_F_NOWAIT) ?
                                    BUS_DMA_NOWAIT : BUS_DMA_WAITOK));
        if (error != 0) {
                kprintf("%s: error %d loading dmamap\n", PORTNAME(ap), error);
                return (1);
        }
#if 0
        if (xa->flags & ATA_F_PIO)
                prdt->flags |= htole32(AHCI_PRDT_FLAG_INTR);
#endif

        cmd_slot->prdtl = htole16(prdt - ccb->ccb_cmd_table->prdt + 1);

        if (xa->flags & ATA_F_READ)
                bus_dmamap_sync(sc->sc_tag_data, dmap, BUS_DMASYNC_PREREAD);
        if (xa->flags & ATA_F_WRITE)
                bus_dmamap_sync(sc->sc_tag_data, dmap, BUS_DMASYNC_PREWRITE);

        return (0);
}

/*
 * Callback from BUSDMA system to load the segment list.  The passed segment
 * list is a temporary structure.
 */
static
void
ahci_load_prdt_callback(void *info, bus_dma_segment_t *segs, int nsegs,
                        int error)
{
        struct ahci_prdt *prd = *(void **)info;
        u_int64_t addr;

        KKASSERT(nsegs <= AHCI_MAX_PRDT);

        while (nsegs) {
                addr = segs->ds_addr;
                prd->dba_hi = htole32((u_int32_t)(addr >> 32));
                prd->dba_lo = htole32((u_int32_t)addr);
                prd->flags = htole32(segs->ds_len - 1);
                --nsegs;
                if (nsegs)
                        ++prd;
                ++segs;
        }
        *(void **)info = prd;   /* return last valid segment */
}

void
ahci_unload_prdt(struct ahci_ccb *ccb)
{
        struct ahci_port                *ap = ccb->ccb_port;
        struct ahci_softc               *sc = ap->ap_sc;
        struct ata_xfer                 *xa = &ccb->ccb_xa;
        bus_dmamap_t                    dmap = ccb->ccb_dmamap;

        if (xa->datalen != 0) {
                if (xa->flags & ATA_F_READ) {
                        bus_dmamap_sync(sc->sc_tag_data, dmap,
                                        BUS_DMASYNC_POSTREAD);
                }
                if (xa->flags & ATA_F_WRITE) {
                        bus_dmamap_sync(sc->sc_tag_data, dmap,
                                        BUS_DMASYNC_POSTWRITE);
                }
                bus_dmamap_unload(sc->sc_tag_data, dmap);

                /*
                 * prdbc is only updated by hardware for non-NCQ commands.
                 */
                if (ccb->ccb_xa.flags & ATA_F_NCQ) {
                        xa->resid = 0;
                } else {
                        if (ccb->ccb_cmd_hdr->prdbc == 0 &&
                            ccb->ccb_xa.state == ATA_S_COMPLETE) {
                                kprintf("%s: WARNING!  Unload prdbc resid "
                                        "was zero! tag=%d\n",
                                        ATANAME(ap, xa->at), ccb->ccb_slot);
                        }
                        xa->resid = xa->datalen -
                            le32toh(ccb->ccb_cmd_hdr->prdbc);
                }
        }
}

/*
 * Start a command and poll for completion.
 *
 * timeout is in ms and only counts once the command gets on-chip.
 *
 * Returns ATA_S_* state, compare against ATA_S_COMPLETE to determine
 * that no error occured.
 *
 * NOTE: If the caller specifies a NULL timeout function the caller is
 *       responsible for clearing hardware state on failure, but we will
 *       deal with removing the ccb from any pending queue.
 *
 * NOTE: NCQ should never be used with this function.
 *
 * NOTE: If the port is in a failed state and stopped we do not try
 *       to activate the ccb.
 */
int
ahci_poll(struct ahci_ccb *ccb, int timeout,
          void (*timeout_fn)(struct ahci_ccb *))
{
        struct ahci_port *ap = ccb->ccb_port;

        if (ccb->ccb_port->ap_state == AP_S_FATAL_ERROR) {
                ccb->ccb_xa.state = ATA_S_ERROR;
                return(ccb->ccb_xa.state);
        }
        crit_enter();
#if 0
        kprintf("%s: Start command %02x tag=%d\n",
                ATANAME(ccb->ccb_port, ccb->ccb_xa.at),
                ccb->ccb_xa.fis->command, ccb->ccb_slot);
#endif
        ahci_start(ccb);

        do {
                ahci_port_intr(ap, 1);
                switch(ccb->ccb_xa.state) {
                case ATA_S_ONCHIP:
                        timeout -= ahci_os_softsleep();
                        break;
                case ATA_S_PENDING:
                        ahci_os_softsleep();
                        ahci_check_active_timeouts(ap);
                        break;
                default:
                        crit_exit();
                        return (ccb->ccb_xa.state);
                }
        } while (timeout > 0);

        if ((ccb->ccb_xa.flags & ATA_F_SILENT) == 0) {
                kprintf("%s: Poll timeout slot %d CMD: %b TFD: 0x%b SERR: %b\n",
                        ATANAME(ap, ccb->ccb_xa.at), ccb->ccb_slot,
                        ahci_pread(ap, AHCI_PREG_CMD), AHCI_PFMT_CMD,
                        ahci_pread(ap, AHCI_PREG_TFD), AHCI_PFMT_TFD_STS,
                        ahci_pread(ap, AHCI_PREG_SERR), AHCI_PFMT_SERR);
        }

        timeout_fn(ccb);

        crit_exit();

        return(ccb->ccb_xa.state);
}

/*
 * When polling we have to check if the currently active CCB(s)
 * have timed out as the callout will be deadlocked while we
 * hold the port lock.
 */
void
ahci_check_active_timeouts(struct ahci_port *ap)
{
        struct ahci_ccb *ccb;
        u_int32_t mask;
        int tag;

        mask = ap->ap_active | ap->ap_sactive;
        while (mask) {
                tag = ffs(mask) - 1;
                mask &= ~(1 << tag);
                ccb = &ap->ap_ccbs[tag];
                if (ccb->ccb_xa.flags & ATA_F_TIMEOUT_EXPIRED) {
                        ahci_ata_cmd_timeout(ccb);
                }
        }
}

static
__inline
void
ahci_start_timeout(struct ahci_ccb *ccb)
{
        if (ccb->ccb_xa.flags & ATA_F_TIMEOUT_DESIRED) {
                ccb->ccb_xa.flags |= ATA_F_TIMEOUT_RUNNING;
                callout_reset(&ccb->ccb_timeout,
                              (ccb->ccb_xa.timeout * hz + 999) / 1000,
                              ahci_ata_cmd_timeout_unserialized, ccb);
        }
}

void
ahci_start(struct ahci_ccb *ccb)
{
        struct ahci_port                *ap = ccb->ccb_port;
        struct ahci_softc               *sc = ap->ap_sc;

        KKASSERT(ccb->ccb_xa.state == ATA_S_PENDING);

        /* Zero transferred byte count before transfer */
        ccb->ccb_cmd_hdr->prdbc = 0;

        /* Sync command list entry and corresponding command table entry */
        bus_dmamap_sync(sc->sc_tag_cmdh,
                        AHCI_DMA_MAP(ap->ap_dmamem_cmd_list),
                        BUS_DMASYNC_PREWRITE);
        bus_dmamap_sync(sc->sc_tag_cmdt,
                        AHCI_DMA_MAP(ap->ap_dmamem_cmd_table),
                        BUS_DMASYNC_PREWRITE);

        /* Prepare RFIS area for write by controller */
        bus_dmamap_sync(sc->sc_tag_rfis,
                        AHCI_DMA_MAP(ap->ap_dmamem_rfis),
                        BUS_DMASYNC_PREREAD);

        /*
         * There's no point trying to optimize this, it only shaves a few
         * nanoseconds so just queue the command and call our generic issue.
         */
        ahci_issue_pending_commands(ap, ccb);
}

/*
 * While holding the port lock acquire exclusive access to the port.
 *
 * This is used when running the state machine to initialize and identify
 * targets over a port multiplier.  Setting exclusive access prevents
 * ahci_port_intr() from activating any requests sitting on the pending
 * queue.
 */
void
ahci_beg_exclusive_access(struct ahci_port *ap, struct ata_port *at)
{
        KKASSERT((ap->ap_flags & AP_F_EXCLUSIVE_ACCESS) == 0);
        ap->ap_flags |= AP_F_EXCLUSIVE_ACCESS;
        while (ap->ap_active || ap->ap_sactive) {
                ahci_port_intr(ap, 1);
                ahci_os_softsleep();
        }
}

void
ahci_end_exclusive_access(struct ahci_port *ap, struct ata_port *at)
{
        KKASSERT((ap->ap_flags & AP_F_EXCLUSIVE_ACCESS) != 0);
        ap->ap_flags &= ~AP_F_EXCLUSIVE_ACCESS;
        ahci_issue_pending_commands(ap, NULL);
}

#if 0

static void
fubar(struct ahci_ccb *ccb)
{
        struct ahci_port *ap = ccb->ccb_port;
        struct ahci_cmd_hdr     *cmd;
        struct ahci_cmd_table   *tab;
        struct ahci_prdt        *prdt;
        int i;

        kprintf("%s: ISSUE %02x\n",
                ATANAME(ap, ccb->ccb_xa.at),
                ccb->ccb_xa.fis->command);
        cmd = ccb->ccb_cmd_hdr;
        tab = ccb->ccb_cmd_table;
        prdt = ccb->ccb_cmd_table->prdt;
        kprintf("cmd flags=%04x prdtl=%d prdbc=%d ctba=%08x%08x\n",
                cmd->flags, cmd->prdtl, cmd->prdbc,
                cmd->ctba_hi, cmd->ctba_lo);
        for (i = 0; i < cmd->prdtl; ++i) {
                kprintf("\t%d dba=%08x%08x res=%08x flags=%08x\n",
                        i, prdt->dba_hi, prdt->dba_lo, prdt->reserved,
                        prdt->flags);
        }
        kprintf("tab\n");
}

#endif

/*
 * If ccb is not NULL enqueue and/or issue it.
 *
 * If ccb is NULL issue whatever we can from the queue.  However, nothing
 * new is issued if the exclusive access flag is set or expired ccb's are
 * present.
 *
 * If existing commands are still active (ap_active/ap_sactive) we can only
 * issue matching new commands.
 */
void
ahci_issue_pending_commands(struct ahci_port *ap, struct ahci_ccb *ccb)
{
        u_int32_t               mask;
        int                     limit;

        /*
         * Enqueue the ccb.
         *
         * If just running the queue and in exclusive access mode we
         * just return.  Also in this case if there are any expired ccb's
         * we want to clear the queue so the port can be safely stopped.
         */
        if (ccb) {
                TAILQ_INSERT_TAIL(&ap->ap_ccb_pending, ccb, ccb_entry);
        } else if ((ap->ap_flags & AP_F_EXCLUSIVE_ACCESS) || ap->ap_expired) {
                return;
        }

        /*
         * Pull the next ccb off the queue and run it if possible.
         */
        if ((ccb = TAILQ_FIRST(&ap->ap_ccb_pending)) == NULL)
                return;

        /*
         * Handle exclusivity requirements.
         *
         * ATA_F_EXCLUSIVE is used when we want to be the only command
         * running.
         *
         * ATA_F_AUTOSENSE is used when we want the D2H rfis loaded
         * back into the ccb on a normal (non-errored) command completion.
         * For example, for PM requests to target 15.  Because the AHCI
         * spec does not stop the command processor and has only one rfis
         * area (for non-FBSS anyway), AUTOSENSE currently implies EXCLUSIVE.
         * Otherwise multiple completions can destroy the rfis data before
         * we have a chance to copy it.
         */
        if (ap->ap_active & ~ap->ap_expired) {
                /*
                 * There may be multiple ccb's already running,
                 * if any are running and ap_run_flags sets
                 * one of these flags then we know only one is
                 * running.
                 *
                 * XXX Current AUTOSENSE code forces exclusivity
                 *     to simplify the code.
                 */
                if (ap->ap_run_flags &
                    (ATA_F_EXCLUSIVE | ATA_F_AUTOSENSE)) {
                        return;
                }

                if (ccb->ccb_xa.flags &
                    (ATA_F_EXCLUSIVE | ATA_F_AUTOSENSE)) {
                        return;
                }
        }

        if (ccb->ccb_xa.flags & ATA_F_NCQ) {
                /*
                 * The next command is a NCQ command and can be issued as
                 * long as currently active commands are not standard.
                 */
                if (ap->ap_active) {
                        KKASSERT(ap->ap_active_cnt > 0);
                        return;
                }
                KKASSERT(ap->ap_active_cnt == 0);

                mask = 0;
                do {
                        TAILQ_REMOVE(&ap->ap_ccb_pending, ccb, ccb_entry);
                        mask |= 1 << ccb->ccb_slot;
                        ccb->ccb_xa.state = ATA_S_ONCHIP;
                        ahci_start_timeout(ccb);
                        ap->ap_run_flags = ccb->ccb_xa.flags;
                        ccb = TAILQ_FIRST(&ap->ap_ccb_pending);
                } while (ccb && (ccb->ccb_xa.flags & ATA_F_NCQ) &&
                         (ap->ap_run_flags &
                             (ATA_F_EXCLUSIVE | ATA_F_AUTOSENSE)) == 0);

                ap->ap_sactive |= mask;
                ahci_pwrite(ap, AHCI_PREG_SACT, mask);
                ahci_pwrite(ap, AHCI_PREG_CI, mask);
        } else {
                /*
                 * The next command is a standard command and can be issued
                 * as long as currently active commands are not NCQ.
                 *
                 * We limit ourself to 1 command if we have a port multiplier,
                 * (at least without FBSS support), otherwise timeouts on
                 * one port can race completions on other ports (see
                 * ahci_ata_cmd_timeout() for more information).
                 *
                 * If not on a port multiplier generally allow up to 4
                 * standard commands to be enqueued.  Remember that the
                 * command processor will still process them sequentially.
                 */
                if (ap->ap_sactive)
                        return;
                if (ap->ap_type == ATA_PORT_T_PM)
                        limit = 1;
                else if (ap->ap_sc->sc_ncmds > 4)
                        limit = 4;
                else
                        limit = 2;

                while (ap->ap_active_cnt < limit && ccb &&
                       (ccb->ccb_xa.flags & ATA_F_NCQ) == 0) {
                        TAILQ_REMOVE(&ap->ap_ccb_pending, ccb, ccb_entry);
#if 0
                        fubar(ccb);
#endif
                        ap->ap_active |= 1 << ccb->ccb_slot;
                        ap->ap_active_cnt++;
                        ap->ap_run_flags = ccb->ccb_xa.flags;
                        ccb->ccb_xa.state = ATA_S_ONCHIP;
                        ahci_pwrite(ap, AHCI_PREG_CI, 1 << ccb->ccb_slot);
                        ahci_start_timeout(ccb);
                        if ((ap->ap_run_flags &
                            (ATA_F_EXCLUSIVE | ATA_F_AUTOSENSE)) == 0) {
                                break;
                        }
                        ccb = TAILQ_FIRST(&ap->ap_ccb_pending);
                        if (ccb && (ccb->ccb_xa.flags &
                                    (ATA_F_EXCLUSIVE | ATA_F_AUTOSENSE))) {
                                break;
                        }
                }
        }
}

void
ahci_intr(void *arg)
{
        struct ahci_softc       *sc = arg;
        struct ahci_port        *ap;
        u_int32_t               is;
        u_int32_t               ack;
        int                     port;

        /*
         * Check if the master enable is up, and whether any interrupts are
         * pending.
         */
        if ((sc->sc_flags & AHCI_F_INT_GOOD) == 0)
                return;
        is = ahci_read(sc, AHCI_REG_IS);
        if (is == 0 || is == 0xffffffff) {
                return;
        }
        is &= sc->sc_portmask;

#ifdef AHCI_COALESCE
        /* Check coalescing interrupt first */
        if (is & sc->sc_ccc_mask) {
                DPRINTF(AHCI_D_INTR, "%s: command coalescing interrupt\n",
                    DEVNAME(sc));
                is &= ~sc->sc_ccc_mask;
                is |= sc->sc_ccc_ports_cur;
        }
#endif

        /*
         * Process interrupts for each port in a non-blocking fashion.
         *
         * The global IS bit is forced on if any unmasked port interrupts
         * are pending, even if we clear.
         */
        for (ack = 0; is; is &= ~(1 << port)) {
                port = ffs(is) - 1;
                ack |= 1 << port;

                ap = sc->sc_ports[port];
                if (ap == NULL)
                        continue;

                if (ahci_os_lock_port_nb(ap) == 0) {
                        ahci_port_intr(ap, 0);
                        ahci_os_unlock_port(ap);
                } else {
                        ahci_pwrite(ap, AHCI_PREG_IE, 0);
                        ahci_os_signal_port_thread(ap, AP_SIGF_PORTINT);
                }
        }
        ahci_write(sc, AHCI_REG_IS, ack);
}

/*
 * Core called from helper thread.
 */
void
ahci_port_thread_core(struct ahci_port *ap, int mask)
{
        /*
         * Process any expired timedouts.
         */
        ahci_os_lock_port(ap);
        if (mask & AP_SIGF_TIMEOUT) {
                ahci_check_active_timeouts(ap);
        }

        /*
         * Process port interrupts which require a higher level of
         * intervention.
         */
        if (mask & AP_SIGF_PORTINT) {
                ahci_port_intr(ap, 1);
                ahci_port_interrupt_enable(ap);
                ahci_os_unlock_port(ap);
        } else if (ap->ap_probe != ATA_PROBE_FAILED) {
                ahci_port_intr(ap, 1);
                ahci_port_interrupt_enable(ap);
                ahci_os_unlock_port(ap);
        } else {
                ahci_os_unlock_port(ap);
        }
}

/*
 * Core per-port interrupt handler.
 *
 * If blockable is 0 we cannot call ahci_os_sleep() at all and we can only
 * deal with normal command completions which do not require blocking.
 */
void
ahci_port_intr(struct ahci_port *ap, int blockable)
{
        struct ahci_softc       *sc = ap->ap_sc;
        u_int32_t               is, ci_saved, ci_masked;
        int                     slot;
        int                     stopped = 0;
        struct ahci_ccb         *ccb = NULL;
        struct ata_port         *ccb_at = NULL;
        volatile u_int32_t      *active;
        const u_int32_t         blockable_mask = AHCI_PREG_IS_TFES |
                                                 AHCI_PREG_IS_IFS |
                                                 AHCI_PREG_IS_PCS |
                                                 AHCI_PREG_IS_PRCS |
                                                 AHCI_PREG_IS_HBFS |
                                                 AHCI_PREG_IS_OFS |
                                                 AHCI_PREG_IS_UFS;

        enum { NEED_NOTHING, NEED_REINIT, NEED_RESTART,
               NEED_HOTPLUG_INSERT, NEED_HOTPLUG_REMOVE } need = NEED_NOTHING;

        /*
         * All basic command completions are always processed.
         */
        is = ahci_pread(ap, AHCI_PREG_IS);
        if (is & AHCI_PREG_IS_DPS)
                ahci_pwrite(ap, AHCI_PREG_IS, is & AHCI_PREG_IS_DPS);

        /*
         * If we can't block then we can't handle these here.  Disable
         * the interrupts in question so we don't live-lock, the helper
         * thread will re-enable them.
         *
         * If the port is in a completely failed state we do not want
         * to drop through to failed-command-processing if blockable is 0,
         * just let the thread deal with it all.
         *
         * Otherwise we fall through and still handle DHRS and any commands
         * which completed normally.  Even if we are errored we haven't
         * stopped the port yet so CI/SACT are still good.
         */
        if (blockable == 0) {
                if (ap->ap_state == AP_S_FATAL_ERROR) {
                        ahci_pwrite(ap, AHCI_PREG_IE, 0);
                        ahci_os_signal_port_thread(ap, AP_SIGF_PORTINT);
                        return;
                }
                if (is & blockable_mask) {
                        ahci_pwrite(ap, AHCI_PREG_IE, 0);
                        ahci_os_signal_port_thread(ap, AP_SIGF_PORTINT);
                        return;
                }
        }

        /*
         * Either NCQ or non-NCQ commands will be active, never both.
         */
        if (ap->ap_sactive) {
                KKASSERT(ap->ap_active == 0);
                KKASSERT(ap->ap_active_cnt == 0);
                ci_saved = ahci_pread(ap, AHCI_PREG_SACT);
                active = &ap->ap_sactive;
        } else {
                ci_saved = ahci_pread(ap, AHCI_PREG_CI);
                active = &ap->ap_active;
        }
        KKASSERT(!(ap->ap_sactive && ap->ap_active));
#if 0
        kprintf("CHECK act=%08x/%08x sact=%08x/%08x\n",
                ap->ap_active, ahci_pread(ap, AHCI_PREG_CI),
                ap->ap_sactive, ahci_pread(ap, AHCI_PREG_SACT));
#endif

        /*
         * Ignore AHCI_PREG_IS_PRCS when link power management is on
         */
        if (ap->link_pwr_mgmt != AHCI_LINK_PWR_MGMT_NONE) {
                is &= ~AHCI_PREG_IS_PRCS;
                ahci_pwrite(ap, AHCI_PREG_SERR,
                    AHCI_PREG_SERR_DIAG_N | AHCI_PREG_SERR_DIAG_W);
        }

        /*
         * Command failed (blockable).
         *
         * See AHCI 1.1 spec 6.2.2.1 and 6.2.2.2.
         *
         * This stops command processing.
         */
        if (is & AHCI_PREG_IS_TFES) {
                u_int32_t tfd, serr;
                int     err_slot;

process_error:
                tfd = ahci_pread(ap, AHCI_PREG_TFD);
                serr = ahci_pread(ap, AHCI_PREG_SERR);

                /*
                 * Load the error slot and restart command processing.
                 * CLO if we need to.  The error slot may not be valid.
                 * MUST BE DONE BEFORE CLEARING ST!
                 *
                 * Cycle ST.
                 *
                 * It is unclear but we may have to clear SERR to reenable
                 * error processing.
                 */
                err_slot = AHCI_PREG_CMD_CCS(ahci_pread(ap, AHCI_PREG_CMD));
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_TFES |
                                              AHCI_PREG_IS_PSS |
                                              AHCI_PREG_IS_DHRS |
                                              AHCI_PREG_IS_SDBS);
                is &= ~(AHCI_PREG_IS_TFES | AHCI_PREG_IS_PSS |
                        AHCI_PREG_IS_DHRS | AHCI_PREG_IS_SDBS);
                ahci_pwrite(ap, AHCI_PREG_SERR, serr);
                ahci_port_stop(ap, 0);
                ahci_os_hardsleep(10);
                if (tfd & (AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                        kprintf("%s: Issuing CLO\n", PORTNAME(ap));
                        ahci_port_clo(ap);
                }

                /*
                 * We are now stopped and need a restart.  If we have to
                 * process a NCQ error we will temporarily start and then
                 * stop the port again, so this condition holds.
                 */
                stopped = 1;
                need = NEED_RESTART;

                /*
                 * ATAPI errors are fairly common from probing, just
                 * report disk errors or if bootverbose is on.
                 */
                if (bootverbose || ap->ap_type != ATA_PORT_T_ATAPI) {
                        kprintf("%s: TFES slot %d ci_saved = %08x\n",
                                PORTNAME(ap), err_slot, ci_saved);
                }

                /*
                 * If we got an error on an error CCB just complete it
                 * with an error.  ci_saved has the mask to restart
                 * (the err_ccb will be removed from it by finish_error).
                 */
                if (ap->ap_flags & AP_F_ERR_CCB_RESERVED) {
                        err_slot = ap->ap_err_ccb->ccb_slot;
                        goto finish_error;
                }

                /*
                 * If NCQ commands were active get the error slot from
                 * the log page.  NCQ is not supported for PM's so this
                 * is a direct-attached target.
                 *
                 * Otherwise if no commands were active we have a problem.
                 *
                 * Otherwise if the error slot is bad we have a problem.
                 *
                 * Otherwise process the error for the slot.
                 */
                if (ap->ap_sactive) {
                        ahci_port_start(ap);
                        err_slot = ahci_port_read_ncq_error(ap, 0);
                        ahci_port_stop(ap, 0);
                } else if (ap->ap_active == 0) {
                        kprintf("%s: TFES with no commands pending\n",
                                PORTNAME(ap));
                        err_slot = -1;
                } else if (err_slot < 0 || err_slot >= ap->ap_sc->sc_ncmds) {
                        kprintf("%s: bad error slot %d\n",
                                PORTNAME(ap), err_slot);
                        err_slot = -1;
                } else {
                        ccb = &ap->ap_ccbs[err_slot];

                        /*
                         * Validate the errored ccb.  Note that ccb_at can
                         * be NULL for direct-attached ccb's.
                         *
                         * Copy received taskfile data from the RFIS.
                         */
                        if (ccb->ccb_xa.state == ATA_S_ONCHIP) {
                                ccb_at = ccb->ccb_xa.at;
                                memcpy(&ccb->ccb_xa.rfis, ap->ap_rfis->rfis,
                                       sizeof(struct ata_fis_d2h));
                                if (bootverbose) {
                                        kprintf("%s: Copying rfis slot %d\n",
                                                ATANAME(ap, ccb_at), err_slot);
                                }
                        } else {
                                kprintf("%s: Cannot copy rfis, CCB slot "
                                        "%d is not on-chip (state=%d)\n",
                                        ATANAME(ap, ccb->ccb_xa.at),
                                        err_slot, ccb->ccb_xa.state);
                                err_slot = -1;
                        }
                }

                /*
                 * If we could not determine the errored slot then
                 * reset the port.
                 */
                if (err_slot < 0) {
                        kprintf("%s: TFES: Unable to determine errored slot\n",
                                PORTNAME(ap));
                        if (ap->ap_flags & AP_F_IN_RESET)
                                goto fatal;
                        goto failall;
                }

                /*
                 * Finish error on slot.  We will restart ci_saved
                 * commands except the errored slot which we generate
                 * a failure for.
                 */
finish_error:
                ccb = &ap->ap_ccbs[err_slot];
                ci_saved &= ~(1 << err_slot);
                KKASSERT(ccb->ccb_xa.state == ATA_S_ONCHIP);
                ccb->ccb_xa.state = ATA_S_ERROR;
        } else if (is & AHCI_PREG_IS_DHRS) {
                /*
                 * Command posted D2H register FIS to the rfis (non-blocking).
                 *
                 * A normal completion with an error may set DHRS instead
                 * of TFES.  The CCS bits are only valid if ERR was set.
                 * If ERR is set command processing was probably stopped.
                 *
                 * If ERR was not set we can only copy-back data for
                 * exclusive-mode commands because otherwise we won't know
                 * which tag the rfis belonged to.
                 *
                 * err_slot must be read from the CCS before any other port
                 * action, such as stopping the port.
                 *
                 * WARNING!     This is not well documented in the AHCI spec.
                 *              It can be found in the state machine tables
                 *              but not in the explanations.
                 */
                u_int32_t tfd;
                u_int32_t cmd;
                int err_slot;

                tfd = ahci_pread(ap, AHCI_PREG_TFD);
                cmd = ahci_pread(ap, AHCI_PREG_CMD);

                if ((tfd & AHCI_PREG_TFD_STS_ERR) &&
                    (cmd & AHCI_PREG_CMD_CR) == 0) {
                        err_slot = AHCI_PREG_CMD_CCS(
                                                ahci_pread(ap, AHCI_PREG_CMD));
                        ccb = &ap->ap_ccbs[err_slot];
                        kprintf("%s: DHRS tfd=%b err_slot=%d cmd=%02x\n",
                                PORTNAME(ap),
                                tfd, AHCI_PFMT_TFD_STS,
                                err_slot, ccb->ccb_xa.fis->command);
                        goto process_error;
                }
                /*
                 * NO ELSE... copy back is in the normal command completion
                 * code and only if no error occured and ATA_F_AUTOSENSE
                 * was set.
                 */
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_DHRS);
        }

        /*
         * Device notification to us (non-blocking)
         *
         * NOTE!  On some parts notification bits can cause an IPMS
         *        interrupt instead of a SDBS interrupt.
         *
         * NOTE!  On some parts (e.g. VBOX, probably intel ICHx),
         *        SDBS notifies us of the completion of a NCQ command
         *        and DBS does not.
         */
        if (is & (AHCI_PREG_IS_SDBS | AHCI_PREG_IS_IPMS)) {
                u_int32_t data;

                ahci_pwrite(ap, AHCI_PREG_IS,
                                AHCI_PREG_IS_SDBS | AHCI_PREG_IS_IPMS);
                if (sc->sc_cap & AHCI_REG_CAP_SSNTF) {
                        data = ahci_pread(ap, AHCI_PREG_SNTF);
                        if (data) {
                                ahci_pwrite(ap, AHCI_PREG_IS,
                                                AHCI_PREG_IS_SDBS);
                                kprintf("%s: NOTIFY %08x\n",
                                        PORTNAME(ap), data);
                                ahci_pwrite(ap, AHCI_PREG_SERR,
                                                AHCI_PREG_SERR_DIAG_N);
                                ahci_pwrite(ap, AHCI_PREG_SNTF, data);
                                ahci_cam_changed(ap, NULL, -1);
                        }
                }
                is &= ~(AHCI_PREG_IS_SDBS | AHCI_PREG_IS_IPMS);
        }

        /*
         * Spurious IFS errors (blockable) - when AP_F_IGNORE_IFS is set.
         *
         * Spurious IFS errors can occur while we are doing a reset
         * sequence through a PM, probably due to an unexpected FIS
         * being received during the PM target reset sequence.  Chipsets
         * are supposed to mask these events but some do not.
         *
         * Try to recover from the condition.
         */
        if ((is & AHCI_PREG_IS_IFS) && (ap->ap_flags & AP_F_IGNORE_IFS)) {
                u_int32_t serr = ahci_pread(ap, AHCI_PREG_SERR);
                if ((ap->ap_flags & AP_F_IFS_IGNORED) == 0) {
                        kprintf("%s: IFS during PM probe (ignored) "
                                "IS=%b, SERR=%b\n",
                                PORTNAME(ap),
                                is, AHCI_PFMT_IS,
                                serr, AHCI_PFMT_SERR);
                        ap->ap_flags |= AP_F_IFS_IGNORED;
                }

                /*
                 * Try to clear the error condition.  The IFS error killed
                 * the port so stop it so we can restart it.
                 */
                ahci_pwrite(ap, AHCI_PREG_SERR, -1);
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_IFS);
                is &= ~AHCI_PREG_IS_IFS;
                need = NEED_RESTART;
                goto failall;
        }

        /*
         * Port change (hot-plug) (blockable).
         *
         * A PRCS interrupt can occur:
         *      (1) On hot-unplug / normal-unplug (phy lost)
         *      (2) Sometimes on hot-plug too.
         *
         * A PCS interrupt can occur in a number of situations:
         *      (1) On hot-plug once communication is established
         *      (2) On hot-unplug sometimes.
         *      (3) For chipsets with badly written firmware it can occur
         *          during INIT/RESET sequences due to the device reset.
         *      (4) For chipsets with badly written firmware it can occur
         *          when it thinks an unsolicited COMRESET is received
         *          during a INIT/RESET sequence, even though we actually
         *          did request it.
         *
         * XXX We can then check the CPS (Cold Presence State) bit, if
         * supported, to determine if a device is plugged in or not and do
         * the right thing.
         *
         * PCS interrupts are cleared by clearing DIAG_X.  If this occurs
         * command processing is automatically stopped (CR goes inactive)
         * and the port must be stopped and restarted.
         *
         * WARNING: AMD parts (e.g. 880G chipset, probably others) can
         *          generate PCS on initialization even when device is
         *          already connected up.  It is unclear why this happens.
         *          Depending on the state of the device detect this can
         *          cause us to go into harsh reinit or hot-plug insertion
         *          mode.
         *
         * WARNING: PCS errors can be repetitive (e.g. unsolicited COMRESET
         *          continues to flow in from the device), we must clear the
         *          interrupt in all cases and enforce a delay to prevent
         *          a livelock and give the port time to settle down.
         *          Only print something if we aren't in INIT/HARD-RESET.
         */
        if (is & (AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS)) {
                /*
                 * Try to clear the error.  Because of the repetitiveness
                 * of this interrupt avoid any harsh action if the port is
                 * already in the init or hard-reset probe state.
                 */
                ahci_pwrite(ap, AHCI_PREG_SERR, -1);
                /* (AHCI_PREG_SERR_DIAG_N | AHCI_PREG_SERR_DIAG_X) */
                ahci_pwrite(ap, AHCI_PREG_IS,
                            is & (AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS));

                /*
                 * Ignore PCS/PRCS errors during probes (but still clear the
                 * interrupt to avoid a livelock).  The AMD 880/890/SB850
                 * chipsets do not mask PCS/PRCS internally during reset
                 * sequences.
                 */
                if (ap->ap_flags & AP_F_IN_RESET)
                        goto skip_pcs;

                if (ap->ap_probe == ATA_PROBE_NEED_INIT ||
                    ap->ap_probe == ATA_PROBE_NEED_HARD_RESET) {
                        is &= ~(AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS);
                        need = NEED_NOTHING;
                        ahci_os_sleep(1000);
                        goto failall;
                }
                kprintf("%s: Transient Errors: %b (%d)\n",
                        PORTNAME(ap), is, AHCI_PFMT_IS, ap->ap_probe);
                is &= ~(AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS);
                ahci_os_sleep(200);

                /*
                 * Stop the port and figure out what to do next.
                 */
                ahci_port_stop(ap, 0);
                stopped = 1;

                switch (ahci_pread(ap, AHCI_PREG_SSTS) & AHCI_PREG_SSTS_DET) {
                case AHCI_PREG_SSTS_DET_DEV:
                        /*
                         * Device detect
                         */
                        if (ap->ap_probe == ATA_PROBE_FAILED) {
                                need = NEED_HOTPLUG_INSERT;
                                goto fatal;
                        }
                        need = NEED_RESTART;
                        break;
                case AHCI_PREG_SSTS_DET_DEV_NE:
                        /*
                         * Device not communicating.  AMD parts seem to
                         * like to throw this error on initialization
                         * for no reason that I can fathom.
                         */
                        kprintf("%s: Device present but not communicating, "
                                "attempting port restart\n",
                                PORTNAME(ap));
                        need = NEED_REINIT;
                        goto fatal;
                default:
                        if (ap->ap_probe != ATA_PROBE_FAILED) {
                                need = NEED_HOTPLUG_REMOVE;
                                goto fatal;
                        }
                        need = NEED_RESTART;
                        break;
                }
skip_pcs:
                ;
        }

        /*
         * Check for remaining errors - they are fatal. (blockable)
         */
        if (is & (AHCI_PREG_IS_TFES | AHCI_PREG_IS_HBFS | AHCI_PREG_IS_IFS |
                  AHCI_PREG_IS_OFS | AHCI_PREG_IS_UFS)) {
                u_int32_t serr;

                ahci_pwrite(ap, AHCI_PREG_IS,
                            is & (AHCI_PREG_IS_TFES | AHCI_PREG_IS_HBFS |
                                  AHCI_PREG_IS_IFS | AHCI_PREG_IS_OFS |
                                  AHCI_PREG_IS_UFS));
                serr = ahci_pread(ap, AHCI_PREG_SERR);
                kprintf("%s: Unrecoverable errors (IS: %b, SERR: %b), "
                        "disabling port.\n",
                        PORTNAME(ap),
                        is, AHCI_PFMT_IS,
                        serr, AHCI_PFMT_SERR
                );
                is &= ~(AHCI_PREG_IS_TFES | AHCI_PREG_IS_HBFS |
                        AHCI_PREG_IS_IFS | AHCI_PREG_IS_OFS |
                        AHCI_PREG_IS_UFS);

                /*
                 * Fail all commands but then what?  For now try to
                 * reinitialize the port.
                 */
                need = NEED_REINIT;
                goto fatal;
        }

        /*
         * Fail all outstanding commands if we know the port won't recover.
         *
         * We may have a ccb_at if the failed command is known and was
         * being sent to a device over a port multiplier (PM).  In this
         * case if the port itself has not completely failed we fail just
         * the commands related to that target.
         *
         * ci_saved contains the mask of active commands as of when the
         * error occured, prior to any port stops.
         */
        if (ap->ap_state == AP_S_FATAL_ERROR) {
fatal:
                ap->ap_state = AP_S_FATAL_ERROR;
failall:
                ahci_port_stop(ap, 0);
                stopped = 1;

                /*
                 * Error all the active slots not already errored.
                 */
                ci_masked = ci_saved & *active & ~ap->ap_expired;
                if (ci_masked) {
                        kprintf("%s: Failing all commands: %08x\n",
                                PORTNAME(ap), ci_masked);
                }

                while (ci_masked) {
                        slot = ffs(ci_masked) - 1;
                        ccb = &ap->ap_ccbs[slot];
                        ccb->ccb_xa.state = ATA_S_TIMEOUT;
                        ap->ap_expired |= 1 << slot;
                        ci_saved &= ~(1 << slot);
                        ci_masked &= ~(1 << slot);
                }

                /*
                 * Clear bits in ci_saved (cause completions to be run)
                 * for all slots which are not active.
                 */
                ci_saved &= ~*active;

                /*
                 * Don't restart the port if our problems were deemed fatal.
                 *
                 * Also acknowlege all fatal interrupt sources to prevent
                 * a livelock.
                 */
                if (ap->ap_state == AP_S_FATAL_ERROR) {
                        if (need == NEED_RESTART)
                                need = NEED_NOTHING;
                        ahci_pwrite(ap, AHCI_PREG_IS,
                                    AHCI_PREG_IS_TFES | AHCI_PREG_IS_HBFS |
                                    AHCI_PREG_IS_IFS | AHCI_PREG_IS_OFS |
                                    AHCI_PREG_IS_UFS);
                }
        }

        /*
         * If we are stopped the AHCI chipset is supposed to have cleared
         * CI and SACT.  Did it?  If it didn't we try very hard to clear
         * the fields otherwise we may end up completing CCBs which are
         * actually still active.
         *
         * IFS errors on (at least) AMD chipsets create this confusion.
         */
        if (stopped) {
                u_int32_t mask;
                if ((mask = ahci_pactive(ap)) != 0) {
                        kprintf("%s: chipset failed to clear "
                                "active cmds %08x\n",
                                PORTNAME(ap), mask);
                        ahci_port_start(ap);
                        ahci_port_stop(ap, 0);
                        if ((mask = ahci_pactive(ap)) != 0) {
                                kprintf("%s: unable to prod the chip into "
                                        "clearing active cmds %08x\n",
                                        PORTNAME(ap), mask);
                                /* what do we do now? */
                        }
                }
        }

        /*
         * CCB completion (non blocking).
         *
         * CCB completion is detected by noticing its slot's bit in CI has
         * changed to zero some time after we activated it.
         * If we are polling, we may only be interested in particular slot(s).
         *
         * Any active bits not saved are completed within the restrictions
         * imposed by the caller.
         */
        ci_masked = ~ci_saved & *active;
        while (ci_masked) {
                slot = ffs(ci_masked) - 1;
                ccb = &ap->ap_ccbs[slot];
                ci_masked &= ~(1 << slot);

                DPRINTF(AHCI_D_INTR, "%s: slot %d is complete%s\n",
                    PORTNAME(ap), slot, ccb->ccb_xa.state == ATA_S_ERROR ?
                    " (error)" : "");

                bus_dmamap_sync(sc->sc_tag_cmdh,
                                AHCI_DMA_MAP(ap->ap_dmamem_cmd_list),
                                BUS_DMASYNC_POSTWRITE);

                bus_dmamap_sync(sc->sc_tag_cmdt,
                                AHCI_DMA_MAP(ap->ap_dmamem_cmd_table),
                                BUS_DMASYNC_POSTWRITE);

                bus_dmamap_sync(sc->sc_tag_rfis,
                                AHCI_DMA_MAP(ap->ap_dmamem_rfis),
                                BUS_DMASYNC_POSTREAD);

                *active &= ~(1 << ccb->ccb_slot);
                if (active == &ap->ap_active) {
                        KKASSERT(ap->ap_active_cnt > 0);
                        --ap->ap_active_cnt;
                }

                /*
                 * Complete the ccb.  If the ccb was marked expired it
                 * was probably already removed from the command processor,
                 * so don't take the clear ci_saved bit as meaning the
                 * command actually succeeded, it didn't.
                 */
                if (ap->ap_expired & (1 << ccb->ccb_slot)) {
                        ap->ap_expired &= ~(1 << ccb->ccb_slot);
                        ccb->ccb_xa.state = ATA_S_TIMEOUT;
                        ccb->ccb_done(ccb);
                        ccb->ccb_xa.complete(&ccb->ccb_xa);
                } else {
                        if (ccb->ccb_xa.state == ATA_S_ONCHIP) {
                                ccb->ccb_xa.state = ATA_S_COMPLETE;
                                if (ccb->ccb_xa.flags & ATA_F_AUTOSENSE) {
                                        memcpy(&ccb->ccb_xa.rfis,
                                            ap->ap_rfis->rfis,
                                            sizeof(struct ata_fis_d2h));
                                        if (ccb->ccb_xa.state == ATA_S_TIMEOUT)
                                                ccb->ccb_xa.state = ATA_S_ERROR;
                                }
                        }
                        ccb->ccb_done(ccb);
                }
        }

        /*
         * Cleanup.  Will not be set if non-blocking.
         */
        switch(need) {
        case NEED_NOTHING:
                /*
                 * If operating normally and not stopped the interrupt was
                 * probably just a normal completion and we may be able to
                 * issue more commands.
                 */
                if (stopped == 0 && ap->ap_state != AP_S_FATAL_ERROR)
                        ahci_issue_pending_commands(ap, NULL);
                break;
        case NEED_RESTART:
                /*
                 * A recoverable error occured and we can restart outstanding
                 * commands on the port.
                 */
                ci_saved &= ~ap->ap_expired;
                if (ci_saved) {
                        kprintf("%s: Restart %08x\n", PORTNAME(ap), ci_saved);
                        ahci_issue_saved_commands(ap, ci_saved);
                }

                /*
                 * Potentially issue new commands if not in a failed
                 * state.
                 */
                if (ap->ap_state != AP_S_FATAL_ERROR) {
                        ahci_port_start(ap);
                        ahci_issue_pending_commands(ap, NULL);
                }
                break;
        case NEED_REINIT:
                /*
                 * Something horrible happened to the port and we
                 * need to reinitialize it.
                 */
                kprintf("%s: REINIT - Attempting to reinitialize the port "
                        "after it had a horrible accident\n",
                        PORTNAME(ap));
                ap->ap_flags |= AP_F_IN_RESET;
                ap->ap_flags |= AP_F_HARSH_REINIT;
                ap->ap_probe = ATA_PROBE_NEED_INIT;
                ahci_cam_changed(ap, NULL, -1);
                break;
        case NEED_HOTPLUG_INSERT:
                /*
                 * A hot-plug insertion event has occured and all
                 * outstanding commands have already been revoked.
                 *
                 * Don't recurse if this occurs while we are
                 * resetting the port.
                 */
                if ((ap->ap_flags & AP_F_IN_RESET) == 0) {
                        kprintf("%s: HOTPLUG - Device inserted\n",
                                PORTNAME(ap));
                        ap->ap_probe = ATA_PROBE_NEED_INIT;
                        ahci_cam_changed(ap, NULL, -1);
                }
                break;
        case NEED_HOTPLUG_REMOVE:
                /*
                 * A hot-plug removal event has occured and all
                 * outstanding commands have already been revoked.
                 *
                 * Don't recurse if this occurs while we are
                 * resetting the port.
                 */
                if ((ap->ap_flags & AP_F_IN_RESET) == 0) {
                        kprintf("%s: HOTPLUG - Device removed\n",
                                PORTNAME(ap));
                        ahci_port_hardstop(ap);
                        /* ap_probe set to failed */
                        ahci_cam_changed(ap, NULL, -1);
                }
                break;
        default:
                break;
        }
}

struct ahci_ccb *
ahci_get_ccb(struct ahci_port *ap)
{
        struct ahci_ccb                 *ccb;

        lockmgr(&ap->ap_ccb_lock, LK_EXCLUSIVE);
        ccb = TAILQ_FIRST(&ap->ap_ccb_free);
        if (ccb != NULL) {
                KKASSERT(ccb->ccb_xa.state == ATA_S_PUT);
                TAILQ_REMOVE(&ap->ap_ccb_free, ccb, ccb_entry);
                ccb->ccb_xa.state = ATA_S_SETUP;
                ccb->ccb_xa.flags = 0;
                ccb->ccb_xa.at = NULL;
        }
        lockmgr(&ap->ap_ccb_lock, LK_RELEASE);

        return (ccb);
}

void
ahci_put_ccb(struct ahci_ccb *ccb)
{
        struct ahci_port                *ap = ccb->ccb_port;

        lockmgr(&ap->ap_ccb_lock, LK_EXCLUSIVE);
        ccb->ccb_xa.state = ATA_S_PUT;
        TAILQ_INSERT_TAIL(&ap->ap_ccb_free, ccb, ccb_entry);
        lockmgr(&ap->ap_ccb_lock, LK_RELEASE);
}

struct ahci_ccb *
ahci_get_err_ccb(struct ahci_port *ap)
{
        struct ahci_ccb *err_ccb;
        u_int32_t sact;
        u_int32_t ci;

        /* No commands may be active on the chip. */

        if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SNCQ) {
                sact = ahci_pread(ap, AHCI_PREG_SACT);
                if (sact != 0) {
                        kprintf("%s: ahci_get_err_ccb but SACT %08x != 0?\n",
                                PORTNAME(ap), sact);
                }
        }
        ci = ahci_pread(ap, AHCI_PREG_CI);
        if (ci) {
                kprintf("%s: ahci_get_err_ccb: ci not 0 (%08x)\n",
                        ap->ap_name, ci);
        }
        KKASSERT(ci == 0);
        KKASSERT((ap->ap_flags & AP_F_ERR_CCB_RESERVED) == 0);
        ap->ap_flags |= AP_F_ERR_CCB_RESERVED;

        /* Save outstanding command state. */
        ap->ap_err_saved_active = ap->ap_active;
        ap->ap_err_saved_active_cnt = ap->ap_active_cnt;
        ap->ap_err_saved_sactive = ap->ap_sactive;

        /*
         * Pretend we have no commands outstanding, so that completions won't
         * run prematurely.
         */
        ap->ap_active = ap->ap_active_cnt = ap->ap_sactive = 0;

        /*
         * Grab a CCB to use for error recovery.  This should never fail, as
         * we ask atascsi to reserve one for us at init time.
         */
        err_ccb = ap->ap_err_ccb;
        KKASSERT(err_ccb != NULL);
        err_ccb->ccb_xa.flags = 0;
        err_ccb->ccb_done = ahci_empty_done;

        return err_ccb;
}

void
ahci_put_err_ccb(struct ahci_ccb *ccb)
{
        struct ahci_port *ap = ccb->ccb_port;
        u_int32_t sact;
        u_int32_t ci;

        KKASSERT((ap->ap_flags & AP_F_ERR_CCB_RESERVED) != 0);

        /*
         * No commands may be active on the chip
         */
        if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SNCQ) {
                sact = ahci_pread(ap, AHCI_PREG_SACT);
                if (sact) {
                        panic("ahci_port_err_ccb(%d) but SACT %08x != 0\n",
                              ccb->ccb_slot, sact);
                }
        }
        ci = ahci_pread(ap, AHCI_PREG_CI);
        if (ci) {
                panic("ahci_put_err_ccb(%d) but CI %08x != 0 "
                      "(act=%08x sact=%08x)\n",
                      ccb->ccb_slot, ci,
                      ap->ap_active, ap->ap_sactive);
        }

        KKASSERT(ccb == ap->ap_err_ccb);

        /* Restore outstanding command state */
        ap->ap_sactive = ap->ap_err_saved_sactive;
        ap->ap_active_cnt = ap->ap_err_saved_active_cnt;
        ap->ap_active = ap->ap_err_saved_active;

        ap->ap_flags &= ~AP_F_ERR_CCB_RESERVED;
}

/*
 * Read log page to get NCQ error.
 *
 * NOTE: NCQ not currently supported on port multipliers. XXX
 */
int
ahci_port_read_ncq_error(struct ahci_port *ap, int target)
{
        struct ata_log_page_10h *log;
        struct ahci_ccb         *ccb;
        struct ahci_ccb         *ccb2;
        struct ahci_cmd_hdr     *cmd_slot;
        struct ata_fis_h2d      *fis;
        int                     err_slot;

        if (bootverbose) {
                kprintf("%s: READ LOG PAGE target %d\n", PORTNAME(ap),
                        target);
        }

        /*
         * Prep error CCB for READ LOG EXT, page 10h, 1 sector.
         *
         * Getting err_ccb clears active/sactive/active_cnt, putting
         * it back restores the fields.
         */
        ccb = ahci_get_err_ccb(ap);
        ccb->ccb_xa.flags = ATA_F_READ | ATA_F_POLL;
        ccb->ccb_xa.data = ap->ap_err_scratch;
        ccb->ccb_xa.datalen = 512;
        ccb->ccb_xa.complete = ahci_dummy_done;
        ccb->ccb_xa.at = ap->ap_ata[target];

        fis = (struct ata_fis_h2d *)ccb->ccb_cmd_table->cfis;
        bzero(fis, sizeof(*fis));
        fis->type = ATA_FIS_TYPE_H2D;
        fis->flags = ATA_H2D_FLAGS_CMD | target;
        fis->command = ATA_C_READ_LOG_EXT;
        fis->lba_low = 0x10;            /* queued error log page (10h) */
        fis->sector_count = 1;          /* number of sectors (1) */
        fis->sector_count_exp = 0;
        fis->lba_mid = 0;               /* starting offset */
        fis->lba_mid_exp = 0;
        fis->device = 0;

        cmd_slot = ccb->ccb_cmd_hdr;
        cmd_slot->flags = htole16(5);   /* FIS length: 5 DWORDS */

        if (ahci_load_prdt(ccb) != 0) {
                err_slot = -1;
                goto err;
        }

        ccb->ccb_xa.state = ATA_S_PENDING;
        if (ahci_poll(ccb, 1000, ahci_quick_timeout) != ATA_S_COMPLETE) {
                err_slot = -1;
                ahci_unload_prdt(ccb);
                goto err;
        }
        ahci_unload_prdt(ccb);

        /*
         * Success, extract failed register set and tags from the scratch
         * space.
         */
        log = (struct ata_log_page_10h *)ap->ap_err_scratch;
        if (log->err_regs.type & ATA_LOG_10H_TYPE_NOTQUEUED) {
                /* Not queued bit was set - wasn't an NCQ error? */
                kprintf("%s: read NCQ error page, but not an NCQ error?\n",
                        PORTNAME(ap));
                err_slot = -1;
        } else {
                /* Copy back the log record as a D2H register FIS. */
                err_slot = log->err_regs.type & ATA_LOG_10H_TYPE_TAG_MASK;

                ccb2 = &ap->ap_ccbs[err_slot];
                if (ccb2->ccb_xa.state == ATA_S_ONCHIP) {
                        kprintf("%s: read NCQ error page slot=%d\n",
                                ATANAME(ap, ccb2->ccb_xa.at),
                                err_slot);
                        memcpy(&ccb2->ccb_xa.rfis, &log->err_regs,
                                sizeof(struct ata_fis_d2h));
                        ccb2->ccb_xa.rfis.type = ATA_FIS_TYPE_D2H;
                        ccb2->ccb_xa.rfis.flags = 0;
                } else {
                        kprintf("%s: read NCQ error page slot=%d, "
                                "slot does not match any cmds\n",
                                ATANAME(ccb2->ccb_port, ccb2->ccb_xa.at),
                                err_slot);
                        err_slot = -1;
                }
        }
err:
        ahci_put_err_ccb(ccb);
        kprintf("%s: DONE log page target %d err_slot=%d\n",
                PORTNAME(ap), target, err_slot);
        return (err_slot);
}

/*
 * Allocate memory for various structures DMAd by hardware.  The maximum
 * number of segments for these tags is 1 so the DMA memory will have a
 * single physical base address.
 */
struct ahci_dmamem *
ahci_dmamem_alloc(struct ahci_softc *sc, bus_dma_tag_t tag)
{
        struct ahci_dmamem *adm;
        int     error;

        adm = kmalloc(sizeof(*adm), M_DEVBUF, M_INTWAIT | M_ZERO);

        error = bus_dmamem_alloc(tag, (void **)&adm->adm_kva,
                                 BUS_DMA_ZERO, &adm->adm_map);
        if (error == 0) {
                adm->adm_tag = tag;
                error = bus_dmamap_load(tag, adm->adm_map,
                                        adm->adm_kva,
                                        bus_dma_tag_getmaxsize(tag),
                                        ahci_dmamem_saveseg, &adm->adm_busaddr,
                                        0);
        }
        if (error) {
                if (adm->adm_map) {
                        bus_dmamap_destroy(tag, adm->adm_map);
                        adm->adm_map = NULL;
                        adm->adm_tag = NULL;
                        adm->adm_kva = NULL;
                }
                kfree(adm, M_DEVBUF);
                adm = NULL;
        }
        return (adm);
}

static
void
ahci_dmamem_saveseg(void *info, bus_dma_segment_t *segs, int nsegs, int error)
{
        KKASSERT(error == 0);
        KKASSERT(nsegs == 1);
        *(bus_addr_t *)info = segs->ds_addr;
}


void
ahci_dmamem_free(struct ahci_softc *sc, struct ahci_dmamem *adm)
{
        if (adm->adm_map) {
                bus_dmamap_unload(adm->adm_tag, adm->adm_map);
                bus_dmamap_destroy(adm->adm_tag, adm->adm_map);
                adm->adm_map = NULL;
                adm->adm_tag = NULL;
                adm->adm_kva = NULL;
        }
        kfree(adm, M_DEVBUF);
}

u_int32_t
ahci_read(struct ahci_softc *sc, bus_size_t r)
{
        bus_space_barrier(sc->sc_iot, sc->sc_ioh, r, 4,
                          BUS_SPACE_BARRIER_READ);
        return (bus_space_read_4(sc->sc_iot, sc->sc_ioh, r));
}

void
ahci_write(struct ahci_softc *sc, bus_size_t r, u_int32_t v)
{
        bus_space_write_4(sc->sc_iot, sc->sc_ioh, r, v);
        bus_space_barrier(sc->sc_iot, sc->sc_ioh, r, 4,
                          BUS_SPACE_BARRIER_WRITE);
}

u_int32_t
ahci_pread(struct ahci_port *ap, bus_size_t r)
{
        bus_space_barrier(ap->ap_sc->sc_iot, ap->ap_ioh, r, 4,
                          BUS_SPACE_BARRIER_READ);
        return (bus_space_read_4(ap->ap_sc->sc_iot, ap->ap_ioh, r));
}

void
ahci_pwrite(struct ahci_port *ap, bus_size_t r, u_int32_t v)
{
        bus_space_write_4(ap->ap_sc->sc_iot, ap->ap_ioh, r, v);
        bus_space_barrier(ap->ap_sc->sc_iot, ap->ap_ioh, r, 4,
                          BUS_SPACE_BARRIER_WRITE);
}

/*
 * Wait up to (timeout) milliseconds for the masked port register to
 * match the target.
 *
 * Timeout is in milliseconds.
 */
int
ahci_pwait_eq(struct ahci_port *ap, int timeout,
              bus_size_t r, u_int32_t mask, u_int32_t target)
{
        int     t;

        /*
         * Loop hard up to 100uS
         */
        for (t = 0; t < 100; ++t) {
                if ((ahci_pread(ap, r) & mask) == target)
                        return (0);
                ahci_os_hardsleep(1);   /* us */
        }

        do {
                timeout -= ahci_os_softsleep();
                if ((ahci_pread(ap, r) & mask) == target)
                        return (0);
        } while (timeout > 0);
        return (1);
}

int
ahci_wait_ne(struct ahci_softc *sc, bus_size_t r, u_int32_t mask,
             u_int32_t target)
{
        int     t;

        /*
         * Loop hard up to 100uS
         */
        for (t = 0; t < 100; ++t) {
                if ((ahci_read(sc, r) & mask) != target)
                        return (0);
                ahci_os_hardsleep(1);   /* us */
        }

        /*
         * And one millisecond the slow way
         */
        t = 1000;
        do {
                t -= ahci_os_softsleep();
                if ((ahci_read(sc, r) & mask) != target)
                        return (0);
        } while (t > 0);

        return (1);
}


/*
 * Acquire an ata transfer.
 *
 * Pass a NULL at for direct-attached transfers, and a non-NULL at for
 * targets that go through the port multiplier.
 */
struct ata_xfer *
ahci_ata_get_xfer(struct ahci_port *ap, struct ata_port *at)
{
        struct ahci_ccb         *ccb;

        ccb = ahci_get_ccb(ap);
        if (ccb == NULL) {
                DPRINTF(AHCI_D_XFER, "%s: ahci_ata_get_xfer: NULL ccb\n",
                    PORTNAME(ap));
                return (NULL);
        }

        DPRINTF(AHCI_D_XFER, "%s: ahci_ata_get_xfer got slot %d\n",
            PORTNAME(ap), ccb->ccb_slot);

        bzero(ccb->ccb_xa.fis, sizeof(*ccb->ccb_xa.fis));
        ccb->ccb_xa.at = at;
        ccb->ccb_xa.fis->type = ATA_FIS_TYPE_H2D;

        return (&ccb->ccb_xa);
}

void
ahci_ata_put_xfer(struct ata_xfer *xa)
{
        struct ahci_ccb                 *ccb = (struct ahci_ccb *)xa;

        DPRINTF(AHCI_D_XFER, "ahci_ata_put_xfer slot %d\n", ccb->ccb_slot);

        ahci_put_ccb(ccb);
}

int
ahci_ata_cmd(struct ata_xfer *xa)
{
        struct ahci_ccb                 *ccb = (struct ahci_ccb *)xa;
        struct ahci_cmd_hdr             *cmd_slot;

        KKASSERT(xa->state == ATA_S_SETUP);

        if (ccb->ccb_port->ap_state == AP_S_FATAL_ERROR)
                goto failcmd;
        ccb->ccb_done = ahci_ata_cmd_done;

        cmd_slot = ccb->ccb_cmd_hdr;
        cmd_slot->flags = htole16(5); /* FIS length (in DWORDs) */
        if (ccb->ccb_xa.at) {
                cmd_slot->flags |= htole16(ccb->ccb_xa.at->at_target <<
                                           AHCI_CMD_LIST_FLAG_PMP_SHIFT);
        }

        if (xa->flags & ATA_F_WRITE)
                cmd_slot->flags |= htole16(AHCI_CMD_LIST_FLAG_W);

        if (xa->flags & ATA_F_PACKET)
                cmd_slot->flags |= htole16(AHCI_CMD_LIST_FLAG_A);

        if (ahci_load_prdt(ccb) != 0)
                goto failcmd;

        xa->state = ATA_S_PENDING;

        if (xa->flags & ATA_F_POLL)
                return (ahci_poll(ccb, xa->timeout, ahci_ata_cmd_timeout));

        crit_enter();
        KKASSERT((xa->flags & ATA_F_TIMEOUT_EXPIRED) == 0);
        xa->flags |= ATA_F_TIMEOUT_DESIRED;
        ahci_start(ccb);
        crit_exit();
        return (xa->state);

failcmd:
        crit_enter();
        xa->state = ATA_S_ERROR;
        xa->complete(xa);
        crit_exit();
        return (ATA_S_ERROR);
}

void
ahci_ata_cmd_done(struct ahci_ccb *ccb)
{
        struct ata_xfer                 *xa = &ccb->ccb_xa;

        /*
         * NOTE: callout does not lock port and may race us modifying
         * the flags, so make sure its stopped.
         */
        if (xa->flags & ATA_F_TIMEOUT_RUNNING) {
                callout_stop(&ccb->ccb_timeout);
                xa->flags &= ~ATA_F_TIMEOUT_RUNNING;
        }
        xa->flags &= ~(ATA_F_TIMEOUT_DESIRED | ATA_F_TIMEOUT_EXPIRED);

        KKASSERT(xa->state != ATA_S_ONCHIP);
        ahci_unload_prdt(ccb);

        if (xa->state != ATA_S_TIMEOUT)
                xa->complete(xa);
}

/*
 * Timeout from callout, MPSAFE - nothing can mess with the CCB's flags
 * while the callout is runing.
 *
 * We can't safely get the port lock here or delay, we could block
 * the callout thread.
 */
static void
ahci_ata_cmd_timeout_unserialized(void *arg)
{
        struct ahci_ccb         *ccb = arg;
        struct ahci_port        *ap = ccb->ccb_port;

        ccb->ccb_xa.flags &= ~ATA_F_TIMEOUT_RUNNING;
        ccb->ccb_xa.flags |= ATA_F_TIMEOUT_EXPIRED;
        ahci_os_signal_port_thread(ap, AP_SIGF_TIMEOUT);
}

/*
 * Timeout code, typically called when the port command processor is running.
 *
 * We have to be very very careful here.  We cannot stop the port unless
 * CR is already clear or the only active commands remaining are timed-out
 * ones.  Otherwise stopping the port will race the command processor and
 * we can lose events.  While we can theoretically just restart everything
 * that could result in a double-issue which will not work for ATAPI commands.
 */
void
ahci_ata_cmd_timeout(struct ahci_ccb *ccb)
{
        struct ata_xfer         *xa = &ccb->ccb_xa;
        struct ahci_port        *ap = ccb->ccb_port;
        struct ata_port         *at;
        u_int32_t               ci_saved;
        u_int32_t               mask;
        int                     slot;

        at = ccb->ccb_xa.at;

        kprintf("%s: CMD TIMEOUT state=%d slot=%d\n"
                "\tcmd-reg 0x%b\n"
                "\tsactive=%08x active=%08x expired=%08x\n"
                "\t   sact=%08x     ci=%08x\n"
                "\t    STS=%b\n",
                ATANAME(ap, at),
                ccb->ccb_xa.state, ccb->ccb_slot,
                ahci_pread(ap, AHCI_PREG_CMD), AHCI_PFMT_CMD,
                ap->ap_sactive, ap->ap_active, ap->ap_expired,
                ahci_pread(ap, AHCI_PREG_SACT),
                ahci_pread(ap, AHCI_PREG_CI),
                ahci_pread(ap, AHCI_PREG_TFD), AHCI_PFMT_TFD_STS
        );


        /*
         * NOTE: Timeout will not be running if the command was polled.
         *       If we got here at least one of these flags should be set.
         */
        KKASSERT(xa->flags & (ATA_F_POLL | ATA_F_TIMEOUT_DESIRED |
                              ATA_F_TIMEOUT_RUNNING));
        xa->flags &= ~(ATA_F_TIMEOUT_RUNNING | ATA_F_TIMEOUT_EXPIRED);

        if (ccb->ccb_xa.state == ATA_S_PENDING) {
                TAILQ_REMOVE(&ap->ap_ccb_pending, ccb, ccb_entry);
                ccb->ccb_xa.state = ATA_S_TIMEOUT;
                ccb->ccb_done(ccb);
                xa->complete(xa);
                ahci_issue_pending_commands(ap, NULL);
                return;
        }
        if (ccb->ccb_xa.state != ATA_S_ONCHIP) {
                kprintf("%s: Unexpected state during timeout: %d\n",
                        ATANAME(ap, at), ccb->ccb_xa.state);
                return;
        }

        /*
         * Ok, we can only get this command off the chip if CR is inactive
         * or if the only commands running on the chip are all expired.
         * Otherwise we have to wait until the port is in a safe state.
         *
         * Do not set state here, it will cause polls to return when the
         * ccb is not yet off the chip.
         */
        ap->ap_expired |= 1 << ccb->ccb_slot;

        if ((ahci_pread(ap, AHCI_PREG_CMD) & AHCI_PREG_CMD_CR) &&
            (ap->ap_active | ap->ap_sactive) != ap->ap_expired) {
                /*
                 * If using FBSS or NCQ we can't safely stop the port
                 * right now.
                 */
                kprintf("%s: Deferred timeout until its safe, slot %d\n",
                        ATANAME(ap, at), ccb->ccb_slot);
                return;
        }

        /*
         * We can safely stop the port and process all expired ccb's,
         * which will include our current ccb.
         */
        ci_saved = (ap->ap_sactive) ? ahci_pread(ap, AHCI_PREG_SACT) :
                                      ahci_pread(ap, AHCI_PREG_CI);
        ahci_port_stop(ap, 0);

        while (ap->ap_expired) {
                slot = ffs(ap->ap_expired) - 1;
                ap->ap_expired &= ~(1 << slot);
                ci_saved &= ~(1 << slot);
                ccb = &ap->ap_ccbs[slot];
                ccb->ccb_xa.state = ATA_S_TIMEOUT;
                if (ccb->ccb_xa.flags & ATA_F_NCQ) {
                        KKASSERT(ap->ap_sactive & (1 << slot));
                        ap->ap_sactive &= ~(1 << slot);
                } else {
                        KKASSERT(ap->ap_active & (1 << slot));
                        ap->ap_active &= ~(1 << slot);
                        --ap->ap_active_cnt;
                }
                ccb->ccb_done(ccb);
                ccb->ccb_xa.complete(&ccb->ccb_xa);
        }
        /* ccb invalid now */

        /*
         * We can safely CLO the port to clear any BSY/DRQ, a case which
         * can occur with port multipliers.  This will unbrick the port
         * and allow commands to other targets behind the PM continue.
         * (FBSS).
         *
         * Finally, once the port has been restarted we can issue any
         * previously saved pending commands, and run the port interrupt
         * code to handle any completions which may have occured when
         * we saved CI.
         */
        if (ahci_pread(ap, AHCI_PREG_TFD) &
                   (AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                kprintf("%s: Warning, issuing CLO after timeout\n",
                        ATANAME(ap, at));
                ahci_port_clo(ap);
        }
        ahci_port_start(ap);

        /*
         * We absolutely must make sure the chipset cleared activity on
         * all slots.  This sometimes might not happen due to races with
         * a chipset interrupt which stops the port before we can manage
         * to.  For some reason some chipsets don't clear the active
         * commands when we turn off CMD_ST after the chip has stopped
         * operations itself.
         */
        if (ahci_pactive(ap) != 0) {
                ahci_port_stop(ap, 0);
                ahci_port_start(ap);
                if ((mask = ahci_pactive(ap)) != 0) {
                        kprintf("%s: quick-timeout: chipset failed "
                                "to clear active cmds %08x\n",
                                PORTNAME(ap), mask);
                }
        }
        ahci_issue_saved_commands(ap, ci_saved & ~ap->ap_expired);
        ahci_issue_pending_commands(ap, NULL);
        ahci_port_intr(ap, 0);
}

/*
 * Issue a previously saved set of commands
 */
void
ahci_issue_saved_commands(struct ahci_port *ap, u_int32_t ci_saved)
{
        if (ci_saved) {
                KKASSERT(!((ap->ap_active & ci_saved) &&
                           (ap->ap_sactive & ci_saved)));
                KKASSERT((ci_saved & ap->ap_expired) == 0);
                if (ap->ap_sactive & ci_saved)
                        ahci_pwrite(ap, AHCI_PREG_SACT, ci_saved);
                ahci_pwrite(ap, AHCI_PREG_CI, ci_saved);
        }
}

/*
 * Used by the softreset, pmprobe, and read_ncq_error only, in very
 * specialized, controlled circumstances.
 *
 * Only one command may be pending.
 */
void
ahci_quick_timeout(struct ahci_ccb *ccb)
{
        struct ahci_port *ap = ccb->ccb_port;
        u_int32_t mask;

        switch (ccb->ccb_xa.state) {
        case ATA_S_PENDING:
                TAILQ_REMOVE(&ap->ap_ccb_pending, ccb, ccb_entry);
                ccb->ccb_xa.state = ATA_S_TIMEOUT;
                break;
        case ATA_S_ONCHIP:
                /*
                 * We have to clear the command on-chip.
                 */
                KKASSERT(ap->ap_active == (1 << ccb->ccb_slot) &&
                         ap->ap_sactive == 0);
                ahci_port_stop(ap, 0);
                ahci_port_start(ap);
                if (ahci_pactive(ap) != 0) {
                        ahci_port_stop(ap, 0);
                        ahci_port_start(ap);
                        if ((mask = ahci_pactive(ap)) != 0) {
                                kprintf("%s: quick-timeout: chipset failed "
                                        "to clear active cmds %08x\n",
                                        PORTNAME(ap), mask);
                        }
                }

                ccb->ccb_xa.state = ATA_S_TIMEOUT;
                ap->ap_active &= ~(1 << ccb->ccb_slot);
                KKASSERT(ap->ap_active_cnt > 0);
                --ap->ap_active_cnt;
                break;
        default:
                panic("%s: ahci_quick_timeout: ccb in bad state %d",
                      ATANAME(ap, ccb->ccb_xa.at), ccb->ccb_xa.state);
        }
}

static void
ahci_dummy_done(struct ata_xfer *xa)
{
}

static void
ahci_empty_done(struct ahci_ccb *ccb)
{
}

int
ahci_set_feature(struct ahci_port *ap, struct ata_port *atx,
                 int feature, int enable)
{
        struct ata_port *at;
        struct ata_xfer *xa;
        int error;

        at = atx ? atx : ap->ap_ata[0];

        xa = ahci_ata_get_xfer(ap, atx);

        xa->fis->type = ATA_FIS_TYPE_H2D;
        xa->fis->flags = ATA_H2D_FLAGS_CMD | at->at_target;
        xa->fis->command = ATA_C_SET_FEATURES;
        xa->fis->features = enable ? ATA_C_SATA_FEATURE_ENA :
                                     ATA_C_SATA_FEATURE_DIS;
        xa->fis->sector_count = feature;
        xa->fis->control = ATA_FIS_CONTROL_4BIT;

        xa->complete = ahci_dummy_done;
        xa->datalen = 0;
        xa->flags = ATA_F_POLL;
        xa->timeout = 1000;

        if (ahci_ata_cmd(xa) == ATA_S_COMPLETE)
                error = 0;
        else
                error = EIO;
        ahci_ata_put_xfer(xa);
        return(error);
}