AHCI - Fix CAM reentrancy problem, work-around HW async notification issue.

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

/*
 * 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"

int     ahci_port_init(struct ahci_port *ap, struct ata_port *at);
int     ahci_port_start(struct ahci_port *);
int     ahci_port_stop(struct ahci_port *, int);
int     ahci_port_clo(struct ahci_port *);

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_pmprobe(struct ahci_port *ap);
int     ahci_port_hardreset(struct ahci_port *ap, int hard);
void    ahci_port_hardstop(struct ahci_port *ap);
void    ahci_flush_tfd(struct ahci_port *ap);

static void ahci_ata_cmd_timeout_unserialized(void *arg);

void    ahci_issue_pending_ncq_commands(struct ahci_port *);
void    ahci_issue_pending_commands(struct ahci_port *, int);

struct ahci_ccb *ahci_get_err_ccb(struct ahci_port *);
void    ahci_put_err_ccb(struct ahci_ccb *);

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);

void    ahci_empty_done(struct ahci_ccb *ccb);
void    ahci_ata_cmd_done(struct ahci_ccb *ccb);

/* Wait for all bits in _b to be cleared */
#define ahci_pwait_clr(_ap, _r, _b) \
        ahci_pwait_eq((_ap), AHCI_PWAIT_TIMEOUT, (_r), (_b), 0)
#define ahci_pwait_clr_to(_ap, _to,  _r, _b) \
        ahci_pwait_eq((_ap), _to, (_r), (_b), 0)

/* Wait for all bits in _b to be set */
#define ahci_pwait_set(_ap, _r, _b) \
        ahci_pwait_eq((_ap), AHCI_PWAIT_TIMEOUT, (_r), (_b), (_b))
#define ahci_pwait_set_to(_ap, _to, _r, _b) \
        ahci_pwait_eq((_ap), _to, (_r), (_b), (_b))

#define AHCI_PWAIT_TIMEOUT      1000

/*
 * 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;

        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.
         */
        ahci_write(sc, AHCI_REG_GHC, AHCI_REG_GHC_HR);
        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);
        }

        /* enable ahci (global interrupts disabled) */
        ahci_write(sc, AHCI_REG_GHC, AHCI_REG_GHC_AE);

        /* restore parameters */
        ahci_write(sc, AHCI_REG_CAP, cap);
        ahci_write(sc, AHCI_REG_PI, pi);

        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;
        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);
        if (ap == NULL) {
                device_printf(sc->sc_dev,
                              "unable to allocate memory for port %d\n",
                              port);
                goto reterr;
        }

        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.
         */
        if (ap->ap_ata == NULL) {
                ap->ap_ata = kmalloc(sizeof(*ap->ap_ata) * AHCI_MAX_PMPORTS,
                                     M_DEVBUF, M_INTWAIT | M_ZERO);
                for (i = 0; i < AHCI_MAX_PMPORTS; ++i) {
                        at = &ap->ap_ata[i];
                        at->at_ahci_port = ap;
                        at->at_target = i;
                        at->at_probe = ATA_PROBE_NEED_INIT;
                        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;
        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);

        /*
         * Sec 10.1.2 - deinitialise port if it is already running
         */
        cmd = ahci_pread(ap, AHCI_PREG_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);

        /* 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;
                ahci_put_ccb(ccb);
        }

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

        /*
         * Do device-related port initialization.  A failure here does not
         * cause the port to be deallocated as we want to receive future
         * hot-plug events.
         */
        ahci_port_init(ap, NULL);
        return(0);
freeport:
        ahci_port_free(sc, port);
reterr:
        return (rc);
}

/*
 * [re]initialize an idle port.  No CCBs should be active.
 *
 * If at is NULL we are initializing a directly connected port, otherwise
 * we are indirectly initializing a port multiplier port.
 *
 * 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, struct ata_port *at)
{
        u_int32_t data;
        int rc;

        /*
         * Clear all notification bits
         */
        if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SSNTF)
                ahci_pwrite(ap, AHCI_PREG_SNTF, -1);

        /*
         * Hard-reset the port.  If a device is detected but it is busy
         * we try a second time, this time cycling the phy as well.
         */
        ap->ap_probe = ATA_PROBE_NEED_HARD_RESET;
        rc = ahci_port_reset(ap, at, 1);
        if (rc == EBUSY) {
                rc = ahci_port_reset(ap, at, 2);
        }

        switch (rc) {
        case ENODEV:
                /*
                 * We had problems talking to the device on the port.
                 */
                switch (ahci_pread(ap, AHCI_PREG_SSTS) & 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;
                }
                break;

        case EBUSY:
                /*
                 * The device on the port is still telling us its busy,
                 * which means that it is not properly handling a SATA
                 * port COMRESET.
                 *
                 * It may be possible to softreset the device using CLO
                 * and a device reset command.
                 */
                kprintf("%s: Device on port is bricked, trying softreset\n",
                        PORTNAME(ap));

                rc = ahci_port_reset(ap, at, 0);
                if (rc) {
                        kprintf("%s: Unable unbrick device\n",
                                PORTNAME(ap));
                } else {
                        kprintf("%s: Successfully unbricked\n",
                                PORTNAME(ap));
                }
                break;

        default:
                break;
        }

        /*
         * Command transfers can only be enabled if a device was successfully
         * detected.
         *
         * Allocate or deallocate the ap_ata array here too.
         */
        switch(ap->ap_type) {
        case ATA_PORT_T_NONE:
                ap->ap_pmcount = 0;
                break;
        case ATA_PORT_T_PM:
                /* already set */
                break;
        default:
                ap->ap_pmcount = 1;
                break;
        }

        /*
         * Start the port if we succeeded.
         *
         * There's nothing to start for devices behind a port multiplier.
         */
        if (rc == 0 && at == NULL) {
                if (ahci_port_start(ap)) {
                        kprintf("%s: failed to start command DMA on port, "
                                "disabling\n", PORTNAME(ap));
                        rc = ENXIO;     /* couldn't start port */
                }
        }

        /*
         * Flush interrupts on the port. XXX
         *
         * Enable interrupts on the port whether a device is sitting on
         * it or not, to handle hot-plug events.
         */
        if (at == NULL) {
                ahci_pwrite(ap, AHCI_PREG_IS, ahci_pread(ap, AHCI_PREG_IS));
                ahci_write(ap->ap_sc, AHCI_REG_IS, 1 << ap->ap_num);

                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;
                if (ap->ap_sc->sc_cap & AHCI_REG_CAP_SSNTF)
                        data |= AHCI_PREG_IE_SDBE;
#ifdef AHCI_COALESCE
                if (sc->sc_ccc_ports & (1 << port)
                        data &= ~(AHCI_PREG_IE_SDBE | AHCI_PREG_IE_DHRE);
#endif
                ahci_pwrite(ap, AHCI_PREG_IE, data);
        }
        return(rc);
}

/*
 * 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)
{
        struct ata_port *at;
        u_int32_t data;
        int target;
        int didsleep;

        if (ap->ap_type == ATA_PORT_T_NONE) {
                if (ap->ap_probe == ATA_PROBE_NEED_INIT) {
                        for (target = 0; target < AHCI_MAX_PMPORTS; ++target) {
                                at = &ap->ap_ata[target];
                                at->at_probe = ATA_PROBE_NEED_INIT;
                        }
                        ahci_port_init(ap, NULL);
                }
                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_GOOD) {
                        ahci_cam_changed(ap, NULL, 1);
                }
                return;
        }

        for (;;) {
                if (ahci_pm_read(ap, 15, AHCI_PMREG_EINFO, &data)) {
                        kprintf("%s: PM unable to read hot-plug bitmap\n",
                                PORTNAME(ap));
                        break;
                }
                data &= (1 << ap->ap_pmcount) - 1;

                /*
                 * Stop if no ports on the target have indicated a state
                 * change.
                 */
                if (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.
                 */
                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 4 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.
                         */
                        if (data & (1 << target)) {
                                ahci_pm_check_good(ap, target);
                                if (at->at_probe == ATA_PROBE_NEED_HARD_RESET) {
                                        if (didsleep == 0) {
                                                didsleep = 1;
                                                ahci_os_sleep(4000);
                                        }
                                }
                        }

                        /*
                         * Run through the state machine as necessary.
                         */
                        if (at->at_type == ATA_PORT_T_NONE &&
                            at->at_probe != ATA_PROBE_FAILED) {
                                if (at->at_probe == ATA_PROBE_NEED_INIT)
                                        ahci_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);
                        }

                        if (data & (1 << target)) {
                                kprintf("%s: HOTPLUG event, ",
                                        ATANAME(ap, at));
                                if (at->at_probe == ATA_PROBE_GOOD)
                                        kprintf("device inserted\n");
                                else
                                        kprintf("device removed\n");
                        }

                        /*
                         * Initial conditions set automatic add/rem
                         */
                        if (at->at_probe <= ATA_PROBE_NEED_HARD_RESET)
                                at->at_features |= ATA_PORT_F_RESCAN;

                        /*
                         * 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_GOOD) {
                                        ahci_cam_changed(ap, at, 1);
                                }
                        }
                }
        }
}


/*
 * 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;

        /*
         * Ensure port is disabled and its interrupts are all flushed.
         */
        if (ap->ap_sc) {
                ahci_port_stop(ap, 1);
                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;
                        }
                }
                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) {
                kfree(ap->ap_ata, M_DEVBUF);
                ap->ap_ata = NULL;
        }

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

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

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

        /*
         * 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.
         */
         /* XXX REMOVE ME */
        olds = ahci_pread(ap, AHCI_PREG_SERR);
        oldis= ahci_pread(ap, AHCI_PREG_IS);
        oldtfd = ahci_pread(ap, AHCI_PREG_TFD);
        oldr = r = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        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);
                }
        }

        /*
         * 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(ap, 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"
                        "OCMD=%b OSERR=%b\n"
                        "NCMP=%b NSERR=%b\n"
                        "OLDIS=%b\nNEWIS=%b\n"
                        "OLDTFD=%b\nNEWTFD=%b\n",
                        PORTNAME(ap),
                        oldr, AHCI_PFMT_CMD, olds, AHCI_PFMT_SERR,
                        r, AHCI_PFMT_CMD, s, AHCI_PFMT_SERR,
                        oldis, AHCI_PFMT_IS, is, AHCI_PFMT_IS,
                        oldtfd, AHCI_PFMT_TFD_STS, 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
 */
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;
#ifdef DIAGNOSTIC
        if (cmd & AHCI_PREG_CMD_ST) {
                kprintf("%s: CLO requested while port running\n",
                        PORTNAME(ap));
        }
#endif
        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 hard is 2 perform a hard reset of the port and cycle the phy.
 *
 * 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);
#if 0
                if (rc && at == NULL)
                        rc = ahci_port_hardreset(ap, hard);
#endif
        }
        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;
        u_int32_t               cmd;

        error = EIO;

        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.
         */
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        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.
         */
        ccb = ahci_get_err_ccb(ap);
        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;
        ccb->ccb_xa.flags = 0;
        if (ahci_poll(ccb, 1000, NULL) != 0 ||
            ccb->ccb_xa.state != ATA_S_COMPLETE) {
                kprintf("%s: First FIS failed\n", PORTNAME(ap));
                goto err;
        }

        /*
         * The device may muff the PHY up.
         */
        ahci_os_sleep(10);      /* 3ms min, use 10 */

        /*
         * 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.
         *
         * Give the device 3ms before sending the second FIS.
         *
         * It is unclear which other fields in the FIS are used.  Just zero
         * everything.
         */
        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;
        ccb->ccb_xa.flags = 0;
        if (ahci_poll(ccb, 1000, NULL) != 0 ||
            ccb->ccb_xa.state != 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;
        }
        ahci_os_sleep(10);

        /*
         * 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.
         */
        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) {
                /*
                 * Abort our command, if it failed, by stopping command DMA.
                 */
                if (error && (ap->ap_active & (1 << ccb->ccb_slot))) {
                        kprintf("%s: stopping the port, softreset slot "
                                "%d was still active.\n",
                                PORTNAME(ap),
                                ccb->ccb_slot);
                        ahci_port_stop(ap, 0);
                }
                ccb->ccb_xa.state = ATA_S_ERROR;
                fis[15] = 0;
                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 if (cmd & AHCI_PREG_CMD_ST) {
                ap->ap_probe = ATA_PROBE_NEED_IDENT;
                kprintf("%s: STARTING PORT\n", PORTNAME(ap));
                ahci_port_start(ap);
        } else {
                ap->ap_probe = ATA_PROBE_NEED_IDENT;
                kprintf("%s: STOPPING PORT\n", PORTNAME(ap));
                ahci_port_stop(ap, !(cmd & AHCI_PREG_CMD_FRE));
        }
        ap->ap_flags &= ~AP_F_IN_RESET;
        crit_exit();

        kprintf("%s: END SOFTRESET\n", PORTNAME(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 cmd, r;
        int     error;
        int     loop;
        int     type;

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

        ap->ap_flags |= AP_F_IN_RESET;

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

        /*
         * The port may have been quiescent with its SUD bit cleared, so
         * set the SUD (spin up device).
         */
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        cmd |= AHCI_PREG_CMD_SUD;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);

        /*
         * Perform device detection.  Cycle the PHY off, wait 10ms.
         * This simulates the SATA cable being physically unplugged.
         */
        ap->ap_type = ATA_PORT_T_NONE;

        r = AHCI_PREG_SCTL_IPM_DISABLED;
        if (hard == 2)
                r |= AHCI_PREG_SCTL_DET_DISABLE;
        ahci_pwrite(ap, AHCI_PREG_SCTL, r);
        ahci_os_sleep(10);

        /*
         * Start transmitting COMRESET.  COMRESET must be sent for at
         * least 1ms.
         */
        r = AHCI_PREG_SCTL_IPM_DISABLED | 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(1);

        /*
         * 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
         */
        ahci_flush_tfd(ap);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);
        r &= ~AHCI_PREG_SCTL_DET_INIT;
        r |= AHCI_PREG_SCTL_DET_NONE;
        ahci_pwrite(ap, AHCI_PREG_SCTL, r);

        /*
         * 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.
         */
        for (loop = 30; loop; --loop) {
                r = ahci_pread(ap, AHCI_PREG_SSTS);
                if (r & AHCI_PREG_SSTS_DET)
                        break;
                ahci_os_sleep(10);
        }
        if (loop == 0) {
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_PRCS);
                kprintf("%s: Port appears to be unplugged\n",
                        PORTNAME(ap));
                error = ENODEV;
        }

        /*
         * There is something on the port.  Give the device 3 seconds
         * to fully negotiate.
         */
        if (error == 0 &&
            ahci_pwait_eq(ap, 3000, AHCI_PREG_SSTS,
                          AHCI_PREG_SSTS_DET, AHCI_PREG_SSTS_DET_DEV)) {
                kprintf("%s: Device may be powered down\n",
                        PORTNAME(ap));
                error = ENODEV;
        }

        /*
         * Wait for the device to become ready.
         *
         * This can take more then a second, give it 3 seconds.  If we
         * succeed give the device another 3ms after that.
         *
         * NOTE: Port multipliers can do two things here.  First they can
         *       return device-ready if a device is on target 0 and also
         *       return the signature for that device.  If there is no
         *       device on target 0 then BSY/DRQ is never cleared and
         *       it never comes ready.
         */
        if (error == 0 &&
            ahci_pwait_clr_to(ap, 3000, AHCI_PREG_TFD,
                            AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                /*
                 * The device is bricked or its a port multiplier and will
                 * not unbusy until we do the pmprobe CLO softreset sequence.
                 */
                error = ahci_port_pmprobe(ap);
                if (error) {
                        kprintf("%s: Device will not come ready 0x%b\n",
                                PORTNAME(ap),
                                ahci_pread(ap, AHCI_PREG_TFD),
                                AHCI_PFMT_TFD_STS);
                } else {
                        ap->ap_type = ATA_PORT_T_PM;
                }
        } else if (error == 0) {
                /*
                 * We generally will not get a port multiplier signature in
                 * this case even if this is a port multiplier, because of
                 * Intel's stupidity.  We almost certainly got target 0
                 * behind the PM, if there is a PM.
                 *
                 * Save the signature and probe for a PM.  If we do not
                 * find a PM then use the saved signature and return
                 * success.
                 */
                type = ahci_port_signature_detect(ap, NULL);
                error = ahci_port_pmprobe(ap);
                if (error) {
                        ap->ap_type = type;
                        ap->ap_probe = ATA_PROBE_NEED_SOFT_RESET;
                        error = 0;
                } else {
                        ap->ap_type = ATA_PORT_T_PM;
                        kprintf("%s: Port multiplier detected\n",
                                PORTNAME(ap));
                }
        }

        /*
         * hard-stop the port if we failed.  This will set ap_probe
         * to FAILED.
         */
        ap->ap_flags &= ~AP_F_IN_RESET;
        if (error) {
                ahci_port_hardstop(ap);
                /* ap_probe set to failed */
        } else {
                ap->ap_probe = (ap->ap_type == ATA_PORT_T_PM) ?
                                ATA_PROBE_GOOD : ATA_PROBE_NEED_SOFT_RESET;
        }
        return (error);
}

/*
 * AHCI port multiplier probe.  This routine is run by the hardreset code
 * if it gets past the device detect, whether or not BSY is found to be
 * stuck.
 *
 * We MUST use CLO to properly probe whether the port multiplier exists
 * or not.
 *
 * Return 0 on success, non-zero on failure.
 */
int
ahci_port_pmprobe(struct ahci_port *ap)
{
        struct ahci_cmd_hdr *cmd_slot;
        struct ahci_ccb *ccb = NULL;
        u_int8_t        *fis = NULL;
        int             rc = EIO;
        u_int32_t       cmd;
        int             count;

        /*
         * If we don't support port multipliers don't try to detect one.
         */
        if ((ap->ap_sc->sc_cap & AHCI_REG_CAP_SPM) == 0)
                return (ENODEV);

        count = 2;
#if 0
        kprintf("%s: START PMPROBE\n", PORTNAME(ap));
#endif
retry:
        /*
         * This code is only called from hardreset, which does not
         * high level command processing.  The port should be stopped.
         *
         * Set PMA mode while the port is stopped.
         *
         * NOTE: On retry the port might be running, stopped, or failed.
         */
        ahci_port_stop(ap, 0);
        ap->ap_state = AP_S_NORMAL;
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
        cmd |= AHCI_PREG_CMD_PMA;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);

        /*
         * Flush any errors and request CLO unconditionally, then start
         * the port.
         */
        ahci_flush_tfd(ap);
        ahci_port_clo(ap);
        if (ahci_port_start(ap)) {
                kprintf("%s: PMPROBE 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: PMPROBE CLO %s, need port reset\n",
                        PORTNAME(ap),
                        (ahci_read(ap->ap_sc, AHCI_REG_CAP) & AHCI_REG_CAP_SCLO)
                        ? "failed" : "unsupported");
                rc = EBUSY;
                goto err;
        }

        /*
         * Prep the first H2D command with SRST feature & clear busy/reset
         * flags.
         */
        ccb = ahci_get_err_ccb(ap);
        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[1] = 0x0F;                  /* Target 15 */
        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 */
        cmd_slot->flags |= htole16(AHCI_CMD_LIST_FLAG_PMP); /* port 0xF */

        ccb->ccb_xa.state = ATA_S_PENDING;
        ccb->ccb_xa.flags = 0;

        if (ahci_poll(ccb, 1000, NULL) != 0 ||
            ccb->ccb_xa.state != ATA_S_COMPLETE) {
                kprintf("%s: PMPROBE First FIS failed\n", PORTNAME(ap));
                if (--count) {
                        fis[15] = 0;
                        ahci_put_err_ccb(ccb);
                        goto retry;
                }
                goto err;
        }
        if (ahci_pwait_clr(ap, AHCI_PREG_TFD,
                               AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                kprintf("%s: PMPROBE Busy after first FIS\n", PORTNAME(ap));
        }

        /*
         * The device may have muffed up the PHY when it reset.
         */
        ahci_os_sleep(10);
        ahci_flush_tfd(ap);
        ahci_pwrite(ap, AHCI_PREG_SERR, -1);
        /* ahci_pm_phy_status(ap, 15, &cmd); */

        /*
         * 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.
         *
         * Give the device 3ms before sending the second FIS.
         *
         * It is unclear which other fields in the FIS are used.  Just zero
         * everything.
         */
        bzero(fis, sizeof(ccb->ccb_cmd_table->cfis));
        fis[0] = ATA_FIS_TYPE_H2D;
        fis[1] = 0x0F;
        fis[15] = 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_PMP); /* port 0xF */

        ccb->ccb_xa.state = ATA_S_PENDING;
        ccb->ccb_xa.flags = 0;

        if (ahci_poll(ccb, 1000, NULL) != 0 ||
            ccb->ccb_xa.state != ATA_S_COMPLETE) {
                kprintf("%s: PMPROBE Second FIS failed\n", PORTNAME(ap));
                if (--count) {
                        fis[15] = 0;
                        ahci_put_err_ccb(ccb);
                        goto retry;
                }
                goto err;
        }

        /*
         * What? We succeeded?  Yup, but for some reason the signature
         * is still latched from the original detect (that saw target 0
         * behind the PM), and I don't know how to clear the condition
         * other then by retrying the whole reset sequence.
         */
        if (--count) {
                fis[15] = 0;
                ahci_put_err_ccb(ccb);
                goto retry;
        }

        /*
         * Get the signature.  The caller sets the ap fields.
         */
        if (ahci_port_signature_detect(ap, NULL) == ATA_PORT_T_PM) {
                ap->ap_ata[15].at_probe = ATA_PROBE_GOOD;
                rc = 0;
        } else {
                rc = EBUSY;
        }

        /*
         * Fall through / clean up the CCB and perform error processing.
         */
err:
        if (ccb != NULL) {
                /*
                 * Abort our command, if it failed, by stopping command DMA.
                 */
#if 0
                kprintf("rc=%d active=%08x sactive=%08x slot=%d\n",
                        rc, ap->ap_active, ap->ap_sactive, ccb->ccb_slot);
#endif
                if (rc && (ap->ap_active & (1 << ccb->ccb_slot))) {
                        kprintf("%s: PMP stopping the port, softreset slot "
                                "%d was still active.\n",
                                PORTNAME(ap),
                                ccb->ccb_slot);
                        ahci_port_stop(ap, 0);
                }
                ccb->ccb_xa.state = ATA_S_ERROR;
                fis[15] = 0;
                ahci_put_err_ccb(ccb);
        }

        if (rc == 0 && ahci_pm_identify(ap)) {
                kprintf("%s: PM - cannot identify port multiplier\n",
                        PORTNAME(ap));
                rc = EBUSY;
        }
#if 0
        if (rc == 0 && ahci_pm_set_feature(ap, ATA_SATAFT_ASYNCNOTIFY, 1)) {
                kprintf("%s: PM - Warning, cannot enable async notify\n",
                        PORTNAME(ap));
                /* ignore error */
        }
        if (rc == 0) {
                u_int32_t data;
                if (ahci_pm_read(ap, 2, 4, &data))
                        kprintf("Cannot read snotify\n");
                else
                        kprintf("Read snotify %08x\n", data);
        }
#endif

        /*
         * If we failed turn off PMA, otherwise identify the port multiplier.
         * CAM will iterate the devices.
         */
        if (rc) {
                ahci_port_stop(ap, 0);
                cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;
                cmd &= ~AHCI_PREG_CMD_PMA;
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
        }
        ahci_port_stop(ap, 0);

#if 0
        kprintf("%s: END PMPROBE\n", PORTNAME(ap));
#endif

        return(rc);
}


/*
 * 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.
 */
void
ahci_port_hardstop(struct ahci_port *ap)
{
        struct ata_port *at;
        u_int32_t r;
        u_int32_t cmd;
        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);

        /*
         * 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;
        }

        /*
         * Turn off port-multiplier control bit
         */
        if (cmd & AHCI_PREG_CMD_PMA) {
                cmd &= ~AHCI_PREG_CMD_PMA;
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
        }

        /*
         * 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);
        }

        /*
         * 10.10.3 DET must be set to 0 before setting SUD to 0.
         * 10.10.1 place us in the Listen state.
         *
         * Deactivating SUD only applies if the controller supports SUD.
         */
        ahci_pwrite(ap, AHCI_PREG_SCTL, AHCI_PREG_SCTL_IPM_DISABLED);
        ahci_os_sleep(1);
        if (cmd & AHCI_PREG_CMD_SUD) {
                cmd &= ~AHCI_PREG_CMD_SUD;
                ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
        }
        ahci_os_sleep(1);

        /*
         * Transition su to the spin-up state.  HVA shall send COMRESET and
         * begin initialization sequence (whatever that means).
         *
         * This only applies if the controller supports SUD.
         */
        cmd |= AHCI_PREG_CMD_SUD;
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);
        ahci_os_sleep(1);

        /*
         * Transition us to the Reset state.  Theoretically we send a
         * continuous stream of COMRESETs in this state.
         */
        r = AHCI_PREG_SCTL_IPM_DISABLED | 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(1);

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

        /*
         * Leave us in COMRESET (both SUD and INIT active), the HBA should
         * hopefully send us a DIAG_X-related interrupt if it receives
         * a COMINIT, and if not that then at least a Phy transition
         * interrupt.
         *
         * If we transition INIT from 1->0 to begin the initalization
         * sequence it is unclear if that sequence will remain active
         * until the next device insertion.
         *
         * If we go back to the listen state it is unclear if the
         * device will actually send us a COMINIT, since we aren't
         * sending any COMRESET's
         */
        /* NOP */
}

/*
 * Multiple events may have built up in the TFD.  The spec is not very
 * clear on this but it does seem to serialize events so clearing DIAG_X
 * just once might not do the job during a reset sequence.
 */
void
ahci_flush_tfd(struct ahci_port *ap)
{
        u_int32_t r;

        r = ahci_pread(ap, AHCI_PREG_SERR);
        while (r & AHCI_PREG_SERR_DIAG_X) {
                ahci_pwrite(ap, AHCI_PREG_SERR, AHCI_PREG_SERR_DIAG_X);
                ahci_os_sleep(1);
                r = ahci_pread(ap, AHCI_PREG_SERR);
        }
}

/*
 * 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);
        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 (xa->flags & ATA_F_PIO)
                prdt->flags |= htole32(AHCI_PRDT_FLAG_INTR);

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

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

        return (0);

#ifdef DIAGNOSTIC
diagerr:
        bus_dmamap_unload(sc->sc_tag_data, dmap);
        return (1);
#endif
}

/*
 * 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);
#ifdef DIAGNOSTIC
                KKASSERT((addr & 1) == 0);
                KKASSERT((segs->ds_len & 1) == 0);
#endif
                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) {
                bus_dmamap_sync(sc->sc_tag_data, dmap,
                                (xa->flags & ATA_F_READ) ?
                                BUS_DMASYNC_POSTREAD : BUS_DMASYNC_POSTWRITE);

                bus_dmamap_unload(sc->sc_tag_data, dmap);

                if (ccb->ccb_xa.flags & ATA_F_NCQ)
                        xa->resid = 0;
                else
                        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.
 *
 * 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)(void *))
{
        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(1);
        }
        crit_enter();
        ahci_start(ccb);

        do {
                ahci_port_intr(ap);
                if (ccb->ccb_xa.state != ATA_S_ONCHIP &&
                    ccb->ccb_xa.state != ATA_S_PENDING) {
                        crit_exit();
                        return (0);
                }
                ahci_os_sleep(100);
                if (ccb->ccb_xa.state == ATA_S_ONCHIP)
                        timeout -= 100;
        } while (timeout > 0);

        kprintf("%s: Poll timed-out for slot %d state %d\n",
                ATANAME(ap, ccb->ccb_xa.at), ccb->ccb_slot, ccb->ccb_xa.state);

        if (timeout_fn != NULL) {
                timeout_fn(ccb);
        } else {
                if (ccb->ccb_xa.state == ATA_S_PENDING)
                        TAILQ_REMOVE(&ap->ap_ccb_pending, ccb, ccb_entry);
                ccb->ccb_xa.state = ATA_S_TIMEOUT;
        }
        crit_exit();

        return (1);
}

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);

        if (ccb->ccb_xa.flags & ATA_F_NCQ) {
                /*
                 * Issue NCQ commands only when there are no outstanding
                 * standard commands.
                 */
                if (ap->ap_active || TAILQ_FIRST(&ap->ap_ccb_pending)) {
                        TAILQ_INSERT_TAIL(&ap->ap_ccb_pending, ccb, ccb_entry);
                } else {
                        ahci_start_timeout(ccb);
                        KKASSERT(ap->ap_active_cnt == 0);
                        ap->ap_sactive |= (1 << ccb->ccb_slot);
                        ccb->ccb_xa.state = ATA_S_ONCHIP;
                        ahci_pwrite(ap, AHCI_PREG_SACT, 1 << ccb->ccb_slot);
                        ahci_pwrite(ap, AHCI_PREG_CI, 1 << ccb->ccb_slot);
                }
        } else {
                /*
                 * Wait for all NCQ commands to finish before issuing standard
                 * command.  Allow up to <limit> non-NCQ commands to be active.
                 *
                 * XXX If ap is a port multiplier only allow 1.  At least the
                 *     NVidia-MCP77 part seems to barf if more then one
                 *     command is activated, even though it isn't NCQ.
                 *
                 *     If I set up more then one I get phy errors and the
                 *     port fails.
                 */
                int limit = (ap->ap_type == ATA_PORT_T_PM) ? 1 : 2;
                if (ap->ap_sactive || ap->ap_active_cnt >= limit) {
                        TAILQ_INSERT_TAIL(&ap->ap_ccb_pending, ccb, ccb_entry);
                } else {
                        ahci_start_timeout(ccb);
                        ap->ap_active |= 1 << ccb->ccb_slot;
                        ccb->ccb_xa.state = ATA_S_ONCHIP;
                        ahci_pwrite(ap, AHCI_PREG_CI, 1 << ccb->ccb_slot);
                        ap->ap_active_cnt++;
                }
        }
}

void
ahci_issue_pending_ncq_commands(struct ahci_port *ap)
{
        struct ahci_ccb                 *nextccb;
        u_int32_t                       sact_change = 0;

        KKASSERT(ap->ap_active_cnt == 0);

        nextccb = TAILQ_FIRST(&ap->ap_ccb_pending);
        if (nextccb == NULL || !(nextccb->ccb_xa.flags & ATA_F_NCQ))
                return;

        /* Start all the NCQ commands at the head of the pending list. */
        do {
                TAILQ_REMOVE(&ap->ap_ccb_pending, nextccb, ccb_entry);
                ahci_start_timeout(nextccb);
                sact_change |= 1 << nextccb->ccb_slot;
                nextccb->ccb_xa.state = ATA_S_ONCHIP;
                nextccb = TAILQ_FIRST(&ap->ap_ccb_pending);
        } while (nextccb && (nextccb->ccb_xa.flags & ATA_F_NCQ));

        ap->ap_sactive |= sact_change;
        ahci_pwrite(ap, AHCI_PREG_SACT, sact_change);
        ahci_pwrite(ap, AHCI_PREG_CI, sact_change);

        return;
}

void
ahci_issue_pending_commands(struct ahci_port *ap, int last_was_ncq)
{
        struct ahci_ccb                 *nextccb;

        nextccb = TAILQ_FIRST(&ap->ap_ccb_pending);
        if (nextccb && (nextccb->ccb_xa.flags & ATA_F_NCQ)) {
                KKASSERT(last_was_ncq == 0);    /* otherwise it should have
                                                 * been started already. */

                /*
                 * Issue NCQ commands only when there are no outstanding
                 * standard commands.
                 */
                if (ap->ap_active == 0)
                        ahci_issue_pending_ncq_commands(ap);
                else
                        KKASSERT(ap->ap_active_cnt > 0);
        } else if (nextccb) {
                if (ap->ap_sactive || last_was_ncq)
                        KKASSERT(ap->ap_active_cnt == 0);

                /*
                 * Wait for all NCQ commands to finish before issuing standard
                 * command.  Then keep up to 2 standard commands on-chip at
                 * a time.
                 */
                if (ap->ap_sactive)
                        return;

                while (ap->ap_active_cnt < 2 &&
                       nextccb && (nextccb->ccb_xa.flags & ATA_F_NCQ) == 0) {
                        TAILQ_REMOVE(&ap->ap_ccb_pending, nextccb, ccb_entry);
                        ahci_start_timeout(nextccb);
                        ap->ap_active |= 1 << nextccb->ccb_slot;
                        nextccb->ccb_xa.state = ATA_S_ONCHIP;
                        ahci_pwrite(ap, AHCI_PREG_CI, 1 << nextccb->ccb_slot);
                        ap->ap_active_cnt++;
                        nextccb = TAILQ_FIRST(&ap->ap_ccb_pending);
                }
        }
}

void
ahci_intr(void *arg)
{
        struct ahci_softc               *sc = arg;
        u_int32_t                       is, ack = 0;
        int                             port;

        /* Read global interrupt status */
        is = ahci_read(sc, AHCI_REG_IS);
        if (is == 0 || is == 0xffffffff)
                return;
        ack = is;

#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 */
        while (is) {
                port = ffs(is) - 1;
                if (sc->sc_ports[port])
                        ahci_port_intr(sc->sc_ports[port]);
                is &= ~(1 << port);
        }

        /* Finally, acknowledge global interrupt */
        ahci_write(sc, AHCI_REG_IS, ack);
}

void
ahci_port_intr(struct ahci_port *ap)
{
        struct ahci_softc               *sc = ap->ap_sc;
        u_int32_t                       is, ci_saved, ci_masked;
        int                             slot;
        struct ahci_ccb                 *ccb = NULL;
        struct ata_port                 *ccb_at = NULL;
        volatile u_int32_t              *active;
#ifdef DIAGNOSTIC
        u_int32_t                       tmp;
#endif
        enum { NEED_NOTHING, NEED_RESTART, NEED_HOTPLUG_INSERT,
               NEED_HOTPLUG_REMOVE } need = NEED_NOTHING;

        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 0
        kprintf("%s: INTERRUPT %b\n", PORTNAME(ap),
                is, AHCI_PFMT_IS);
#endif

        /*
         * Ack the port interrupt
         */
        if (ap->ap_sactive) {
                /* Active NCQ commands - use SActive instead of CI */
                KKASSERT(ap->ap_active == 0);
                KKASSERT(ap->ap_active_cnt == 0);
                ci_saved = ahci_pread(ap, AHCI_PREG_SACT);
                active = &ap->ap_sactive;
        } else {
                /* Save CI */
                ci_saved = ahci_pread(ap, AHCI_PREG_CI);
                active = &ap->ap_active;
        }

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

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

                /*
                 * If no NCQ commands are active the error slot is easily
                 * determined, otherwise we have to extract the error
                 * from the log page.
                 */
                if (ap->ap_sactive == 0) {
                        err_slot = AHCI_PREG_CMD_CCS(
                                        ahci_pread(ap, AHCI_PREG_CMD));
                        ccb = &ap->ap_ccbs[err_slot];
                        ccb_at = ccb->ccb_xa.at;        /* can be NULL */

                        /* Preserve received taskfile data from the RFIS. */
                        memcpy(&ccb->ccb_xa.rfis, ap->ap_rfis->rfis,
                               sizeof(struct ata_fis_d2h));
                } else {
                        err_slot = -1;
                }

                DPRINTF(AHCI_D_VERBOSE, "%s: errd slot %d, TFD: %b, SERR: %b\n",
                        PORTNAME(ap), err_slot,
                        tfd, AHCI_PFMT_TFD_STS,
                        serr, AHCI_PFMT_SERR);

                /* Stopping the port clears CI and SACT */
                ahci_port_stop(ap, 0);
                need = NEED_RESTART;

                /*
                 * Clear SERR (primarily DIAG_X) to enable capturing of the
                 * next error.
                 */
                ahci_pwrite(ap, AHCI_PREG_SERR, serr);

                /* Acknowledge the interrupts we can recover from. */
                ahci_pwrite(ap, AHCI_PREG_IS,
                            is & (AHCI_PREG_IS_TFES | AHCI_PREG_IS_IFS));
                is &= ~(AHCI_PREG_IS_TFES | AHCI_PREG_IS_IFS);

                /* If device hasn't cleared its busy status, try to idle it. */
                if (tfd & (AHCI_PREG_TFD_STS_BSY | AHCI_PREG_TFD_STS_DRQ)) {
                        kprintf("%s: Attempting to idle device ccb=%p\n",
                                PORTNAME(ap), ccb_at);
                        if (ap->ap_flags & AP_F_IN_RESET)
                                goto fatal;
                        /*
                         * XXX how do we unbrick a PM target (ccb_at != NULL).
                         *
                         * For now fail the target and use CLO to clear the
                         * busy condition and make the ahci port usable for
                         * the remaining devices.
                         */
                        if (ccb_at) {
                                ccb_at->at_probe = ATA_PROBE_FAILED;
                                ahci_port_clo(ap);
                        } else if (ahci_port_reset(ap, ccb_at, 0)) {
                                kprintf("%s: Unable to idle device, port "
                                        "bricked on us\n",
                                        PORTNAME(ap));
                                goto fatal;
                        }

                        /* Had to reset device, can't gather extended info. */
                } else if (ap->ap_sactive) {
                        /*
                         * Recover the NCQ error from log page 10h.
                         *
                         * XXX NCQ currently not supported with port
                         *     multiplier.
                         */
                        ahci_port_read_ncq_error(ap, &err_slot);
                        kprintf("recover from NCQ error err_slot %d\n",
                                err_slot);
                        if (err_slot < 0)
                                goto failall;

                        DPRINTF(AHCI_D_VERBOSE, "%s: NCQ errored slot %d\n",
                                PORTNAME(ap), err_slot);

                        ccb = &ap->ap_ccbs[err_slot];
                } else {
                        /* Didn't reset, could gather extended info from log. */
                        kprintf("%s: didn't reset err_slot %d "
                                "sact=%08x act=%08x\n",
                                PORTNAME(ap),
                                err_slot, ap->ap_sactive, ap->ap_active);
                }

                /*
                 * If we couldn't determine the errored slot, reset the port
                 * and fail all the active slots.
                 */
                if (err_slot == -1) {
                        if (ap->ap_flags & AP_F_IN_RESET)
                                goto fatal;
                        /*
                         * XXX how do we unbrick a PM target (ccb_at != NULL).
                         *
                         * For now fail the target and use CLO to clear the
                         * busy condition and make the ahci port usable for
                         * the remaining devices.
                         */
                        if (ccb_at) {
                                ccb_at->at_probe = ATA_PROBE_FAILED;
                                ahci_port_clo(ap);
                        } else if (ahci_port_reset(ap, ccb_at, 0)) {
                                kprintf("%s: Unable to idle device after "
                                        "NCQ error, port bricked on us\n",
                                        PORTNAME(ap));
                                goto fatal;
                        }
                        kprintf("%s: couldn't recover NCQ error, failing "
                                "all outstanding commands.\n",
                                PORTNAME(ap));
                        goto failall;
                }

                /* Clear the failed command in saved CI so completion runs. */
                ci_saved &= ~(1 << err_slot);

                /* Note the error in the ata_xfer. */
                KKASSERT(ccb->ccb_xa.state == ATA_S_ONCHIP);
                ccb->ccb_xa.state = ATA_S_ERROR;

#ifdef DIAGNOSTIC
                /* There may only be one outstanding standard command now. */
                if (ap->ap_sactive == 0) {
                        tmp = ci_saved;
                        if (tmp) {
                                slot = ffs(tmp) - 1;
                                tmp &= ~(1 << slot);
                                KKASSERT(tmp == 0);
                        }
                }
#endif
        } else if (is & AHCI_PREG_IS_DHRS) {
                /*
                 * Command posted D2H register FIS to the rfis.  This
                 * does NOT stop command processing and it is unclear
                 * how we are supposed to deal with it other then using
                 * only a queue of 1.
                 *
                 * We must copy the port rfis to the ccb and restart
                 * command processing.  ahci_pm_read() does not function
                 * without this support.
                 */
                int     err_slot;

                if (ap->ap_sactive == 0) {
                        err_slot = AHCI_PREG_CMD_CCS(
                                        ahci_pread(ap, AHCI_PREG_CMD));
                        ccb = &ap->ap_ccbs[err_slot];
                        ccb_at = ccb->ccb_xa.at;        /* can be NULL */

                        memcpy(&ccb->ccb_xa.rfis, ap->ap_rfis->rfis,
                               sizeof(struct ata_fis_d2h));
                } else {
                        kprintf("%s: Unexpected DHRS posted while "
                                "NCQ running\n", PORTNAME(ap));
                        err_slot = -1;
                }
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_DHRS);
                is &= ~AHCI_PREG_IS_DHRS;
        }

        /*
         * Device notification to us.
         *
         * NOTE!  On some parts notification bits can get set without
         *        generating an interrupt.  It is unclear whether this is
         *        a bug in the PM (sending a DTOH device setbits with 'N' set
         *        and 'I' not set), or a bug in the host controller.
         *
         *        It only seems to occur under load.
         */
        if (/*(is & AHCI_PREG_IS_SDBS) &&*/ (sc->sc_cap & AHCI_REG_CAP_SSNTF)) {
                u_int32_t data;
                const char *xstr;

                data = ahci_pread(ap, AHCI_PREG_SNTF);
                if (is & AHCI_PREG_IS_SDBS) {
                        ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_SDBS);
                        is &= ~AHCI_PREG_IS_SDBS;
                        xstr = " (no SDBS!)";
                } else {
                        xstr = "";
                }
                if (data) {
                        ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_SDBS);

                        kprintf("%s: NOTIFY %08x%s\n",
                                PORTNAME(ap), data, xstr);
                        ahci_pwrite(ap, AHCI_PREG_SERR, AHCI_PREG_SERR_DIAG_N);
                        ahci_pwrite(ap, AHCI_PREG_SNTF, data);
                        ahci_cam_changed(ap, NULL, -1);
                }
        }

        /*
         * Spurious IFS errors can occur while we are doing a reset
         * sequence through a PM.  Try to recover if we are being asked
         * to ignore IFS errors during these periods.
         */
        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: Ignoring IFS (XXX) (IS: %b, SERR: %b)\n",
                                PORTNAME(ap),
                                is, AHCI_PFMT_IS,
                                serr, AHCI_PFMT_SERR);
                        ap->ap_flags |= AP_F_IFS_IGNORED;
                }
                ap->ap_flags |= AP_F_IFS_OCCURED;
                ahci_pwrite(ap, AHCI_PREG_SERR, -1);
                ahci_pwrite(ap, AHCI_PREG_IS, AHCI_PREG_IS_IFS);
                is &= ~AHCI_PREG_IS_IFS;
                ahci_port_stop(ap, 0);
                ahci_port_start(ap);
                need = NEED_RESTART;
        }

        /*
         * Port change (hot-plug).
         *
         * A PCS interrupt will occur on hot-plug once communication is
         * established.
         *
         * A PRCS interrupt will occur on hot-unplug (and possibly also
         * on hot-plug).
         *
         * 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.
         *
         * WARNING:  A PCS interrupt is cleared by clearing DIAG_X, and
         *           can also occur if an unsolicited COMINIT is received.
         *           If this occurs command processing is automatically
         *           stopped (CR goes inactive) and the port must be stopped
         *           and restarted.
         */
        if (is & (AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS)) {
                ahci_pwrite(ap, AHCI_PREG_IS,
                            is & (AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS));
                is &= ~(AHCI_PREG_IS_PCS | AHCI_PREG_IS_PRCS);
                ahci_pwrite(ap, AHCI_PREG_SERR,
                        (AHCI_PREG_SERR_DIAG_N | AHCI_PREG_SERR_DIAG_X));
                ahci_port_stop(ap, 0);
                switch (ahci_pread(ap, AHCI_PREG_SSTS) & AHCI_PREG_SSTS_DET) {
                case AHCI_PREG_SSTS_DET_DEV:
                        if (ap->ap_type == ATA_PORT_T_NONE) {
                                need = NEED_HOTPLUG_INSERT;
                                goto fatal;
                        }
                        need = NEED_RESTART;
                        break;
                default:
                        if (ap->ap_type != ATA_PORT_T_NONE) {
                                need = NEED_HOTPLUG_REMOVE;
                                goto fatal;
                        }
                        need = NEED_RESTART;
                        break;
                }
        }

        /*
         * Check for remaining errors - they are fatal.
         */
        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));
                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
                );
                /* XXX try recovery first */
                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.
         */
        if (ap->ap_state == AP_S_FATAL_ERROR) {
fatal:
                ap->ap_state = AP_S_FATAL_ERROR;
failall:

                /* Stopping the port clears CI/SACT */
                ahci_port_stop(ap, 0);

                /*
                 * Error all the active slots.  If running across a PM
                 * try to error out just the slots related to the target.
                 */
                ci_masked = ci_saved & *active;
                while (ci_masked) {
                        slot = ffs(ci_masked) - 1;
                        ccb = &ap->ap_ccbs[slot];
                        if (ccb_at == ccb->ccb_xa.at ||
                            ap->ap_state == AP_S_FATAL_ERROR) {
                                ci_masked &= ~(1 << slot);
                                ccb->ccb_xa.state = ATA_S_ERROR;
                        }
                }

                /* Run completion for all active slots. */
                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);
                }
        }

        /*
         * 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;
                }
                ccb->ccb_done(ccb);
        }

        switch(need) {
        case NEED_RESTART:
                /*
                 * A recoverable error occured and we can restart outstanding
                 * commands on the port.
                 */
                ahci_port_start(ap);

                if (ci_saved) {
#ifdef DIAGNOSTIC
                        tmp = ci_saved;
                        while (tmp) {
                                slot = ffs(tmp) - 1;
                                tmp &= ~(1 << slot);
                                ccb = &ap->ap_ccbs[slot];
                                KKASSERT(ccb->ccb_xa.state == ATA_S_ONCHIP);
                                KKASSERT((!!(ccb->ccb_xa.flags & ATA_F_NCQ)) ==
                                    (!!ap->ap_sactive));
                        }
#endif
                        DPRINTF(AHCI_D_VERBOSE, "%s: ahci_port_intr "
                            "re-enabling%s slots %08x\n", PORTNAME(ap),
                            ap->ap_sactive ? " NCQ" : "", ci_saved);

                        if (ap->ap_sactive)
                                ahci_pwrite(ap, AHCI_PREG_SACT, ci_saved);
                        ahci_pwrite(ap, AHCI_PREG_CI, ci_saved);
                }
                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.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;

#ifdef DIAGNOSTIC
        if (ccb->ccb_xa.state != ATA_S_COMPLETE &&
            ccb->ccb_xa.state != ATA_S_TIMEOUT &&
            ccb->ccb_xa.state != ATA_S_ERROR) {
                kprintf("%s: invalid ata_xfer state %02x in ahci_put_ccb, "
                        "slot %d\n",
                        PORTNAME(ccb->ccb_port), ccb->ccb_xa.state,
                        ccb->ccb_slot);
        }
#endif

        ccb->ccb_xa.state = ATA_S_PUT;
        lockmgr(&ap->ap_ccb_lock, LK_EXCLUSIVE);
        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;

        /* No commands may be active on the chip. */
        sact = ahci_pread(ap, AHCI_PREG_SACT);
        if (sact != 0)
                kprintf("ahci_get_err_ccb but SACT %08x != 0?\n", sact);
        KKASSERT(ahci_pread(ap, AHCI_PREG_CI) == 0);

#ifdef DIAGNOSTIC
        KKASSERT(ap->ap_err_busy == 0);
        ap->ap_err_busy = 1;
#endif
        /* 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 = ahci_get_ccb(ap);
        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;

#ifdef DIAGNOSTIC
        KKASSERT(ap->ap_err_busy);
#endif
        /*
         * No commands may be active on the chip
         */
        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);
        }

        /* Done with the CCB */
        ahci_put_ccb(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;

#ifdef DIAGNOSTIC
        ap->ap_err_busy = 0;
#endif
}

/*
 * 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 *err_slotp)
{
        struct ahci_ccb                 *ccb;
        struct ahci_cmd_hdr             *cmd_slot;
        u_int32_t                       cmd;
        struct ata_fis_h2d              *fis;
        int                             rc = EIO;

        DPRINTF(AHCI_D_VERBOSE, "%s: read log page\n", PORTNAME(ap));

        /* Save command register state. */
        cmd = ahci_pread(ap, AHCI_PREG_CMD) & ~AHCI_PREG_CMD_ICC;

        /* Port should have been idled already.  Start it. */
        KKASSERT((cmd & AHCI_PREG_CMD_CR) == 0);
        ahci_port_start(ap);

        /* Prep error CCB for READ LOG EXT, page 10h, 1 sector. */
        ccb = ahci_get_err_ccb(ap);
        ccb->ccb_xa.flags = ATA_F_NOWAIT | ATA_F_READ | ATA_F_POLL;
        ccb->ccb_xa.data = ap->ap_err_scratch;
        ccb->ccb_xa.datalen = 512;
        cmd_slot = ccb->ccb_cmd_hdr;
        bzero(ccb->ccb_cmd_table, sizeof(struct ahci_cmd_table));

        fis = (struct ata_fis_h2d *)ccb->ccb_cmd_table->cfis;
        fis->type = ATA_FIS_TYPE_H2D;
        fis->flags = ATA_H2D_FLAGS_CMD;
        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->flags = htole16(5);   /* FIS length: 5 DWORDS */

        if (ahci_load_prdt(ccb) != 0) {
                rc = ENOMEM;    /* XXX caller must abort all commands */
                goto err;
        }

        ccb->ccb_xa.state = ATA_S_PENDING;
        if (ahci_poll(ccb, 1000, NULL) != 0)
                goto err;

        rc = 0;
err:
        /* Abort our command, if it failed, by stopping command DMA. */
        if (rc && (ap->ap_active & (1 << ccb->ccb_slot))) {
                kprintf("%s: log page read failed, slot %d was still active.\n",
                        PORTNAME(ap), ccb->ccb_slot);
                ahci_port_stop(ap, 0);
        }

        /* Done with the error CCB now. */
        ahci_unload_prdt(ccb);
        ahci_put_err_ccb(ccb);

        /* Extract failed register set and tags from the scratch space. */
        if (rc == 0) {
                struct ata_log_page_10h         *log;
                int                             err_slot;

                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));
                        rc = ESRCH;
                } else {
                        /* Copy back the log record as a D2H register FIS. */
                        *err_slotp = err_slot = log->err_regs.type &
                            ATA_LOG_10H_TYPE_TAG_MASK;

                        ccb = &ap->ap_ccbs[err_slot];
                        memcpy(&ccb->ccb_xa.rfis, &log->err_regs,
                            sizeof(struct ata_fis_d2h));
                        ccb->ccb_xa.rfis.type = ATA_FIS_TYPE_D2H;
                        ccb->ccb_xa.rfis.flags = 0;
                }
        }

        /* Restore saved CMD register state */
        ahci_pwrite(ap, AHCI_PREG_CMD, cmd);

        return (rc);
}

/*
 * 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);
}

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

        for (i = 0; i < 1000; i++) {
                if ((ahci_read(sc, r) & mask) != target)
                        return (0);
                ahci_os_sleep(1);
        }

        return (1);
}

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);
}

int
ahci_pwait_eq(struct ahci_port *ap, int timeout,
              bus_size_t r, u_int32_t mask, u_int32_t target)
{
        int                             i;

        for (i = 0; i < timeout; i++) {
                if ((ahci_pread(ap, r) & mask) == target)
                        return (0);
                ahci_os_sleep(1);
        }

        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);

        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;
#if 0
        kprintf("%s: started std command %b ccb %d ccb_at %p %d\n",
                ATANAME(ccb->ccb_port, ccb->ccb_xa.at),
                ahci_pread(ccb->ccb_port, AHCI_PREG_CMD), AHCI_PFMT_CMD,
                ccb->ccb_slot,
                ccb->ccb_xa.at,
                ccb->ccb_xa.at ? ccb->ccb_xa.at->at_target : -1);
#endif

        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) {
                ahci_poll(ccb, xa->timeout, ahci_ata_cmd_timeout);
                return (ATA_COMPLETE);
        }

        crit_enter();
        xa->flags |= ATA_F_TIMEOUT_DESIRED;
        ahci_start(ccb);
        crit_exit();
        return (ATA_QUEUED);

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

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

        if (xa->flags & ATA_F_TIMEOUT_RUNNING) {
                xa->flags &= ~ATA_F_TIMEOUT_RUNNING;
                callout_stop(&ccb->ccb_timeout);
        }
        xa->flags &= ~ATA_F_TIMEOUT_DESIRED;

        if (xa->state == ATA_S_ONCHIP || xa->state == ATA_S_ERROR)
                ahci_issue_pending_commands(ccb->ccb_port,
                    xa->flags & ATA_F_NCQ);

        ahci_unload_prdt(ccb);

        if (xa->state == ATA_S_ONCHIP)
                xa->state = ATA_S_COMPLETE;
#ifdef DIAGNOSTIC
        else if (xa->state != ATA_S_ERROR && xa->state != ATA_S_TIMEOUT)
                kprintf("%s: invalid ata_xfer state %02x in ahci_ata_cmd_done, "
                        "slot %d\n",
                        PORTNAME(ccb->ccb_port), xa->state, ccb->ccb_slot);
#endif
        if (xa->state != ATA_S_TIMEOUT)
                xa->complete(xa);
}

static void
ahci_ata_cmd_timeout_unserialized(void *arg)
{
        struct ahci_ccb         *ccb = arg;
        struct ahci_port        *ap = ccb->ccb_port;

        lwkt_serialize_enter(&ap->ap_sc->sc_serializer);
        ahci_ata_cmd_timeout(arg);
        lwkt_serialize_exit(&ap->ap_sc->sc_serializer);
}

void
ahci_ata_cmd_timeout(void *arg)
{
        struct ahci_ccb         *ccb = arg;
        struct ata_xfer         *xa = &ccb->ccb_xa;
        struct ahci_port        *ap = ccb->ccb_port;
        volatile u_int32_t      *active;
        int                     ccb_was_started, ncq_cmd;
        int                     status;

        crit_enter();
        kprintf("%s: CMD TIMEOUT cmd-reg 0x%b\n"
                "\tsactive=%08x active=%08x\n"
                "\t   sact=%08x     ci=%08x\n",
                ATANAME(ap, ccb->ccb_xa.at),
                ahci_pread(ap, AHCI_PREG_CMD), AHCI_PFMT_CMD,
                ap->ap_sactive, ap->ap_active,
                ahci_pread(ap, AHCI_PREG_SACT),
                ahci_pread(ap, AHCI_PREG_CI));

        /*
         * 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;
        ncq_cmd = (xa->flags & ATA_F_NCQ);
        active = ncq_cmd ? &ap->ap_sactive : &ap->ap_active;

        if (ccb->ccb_xa.state == ATA_S_PENDING) {
                DPRINTF(AHCI_D_TIMEOUT, "%s: command for slot %d timed out "
                    "before it got on chip\n", PORTNAME(ap), ccb->ccb_slot);
                TAILQ_REMOVE(&ap->ap_ccb_pending, ccb, ccb_entry);
                ccb_was_started = 0;
        } else if (ccb->ccb_xa.state != ATA_S_ONCHIP) {
                DPRINTF(AHCI_D_TIMEOUT, "%s: command slot %d already "
                    "handled%s\n", PORTNAME(ap), ccb->ccb_slot,
                    (*active & (1 << ccb->ccb_slot)) ?
                    " but slot is still active?" : ".");
                goto ret;
        } else if ((ahci_pread(ap, ncq_cmd ? AHCI_PREG_SACT : AHCI_PREG_CI) &
                    (1 << ccb->ccb_slot)) == 0 &&
                   (*active & (1 << ccb->ccb_slot))) {
                DPRINTF(AHCI_D_TIMEOUT, "%s: command slot %d completed but "
                    "IRQ handler didn't detect it.  Why?\n", PORTNAME(ap),
                    ccb->ccb_slot);
                *active &= ~(1 << ccb->ccb_slot);
                if (ncq_cmd == 0) {
                        KKASSERT(ap->ap_active_cnt > 0);
                        --ap->ap_active_cnt;
                }
                ccb->ccb_done(ccb);
                goto ret;
        } else {
                ccb_was_started = 1;
        }

        /* Complete the slot with a timeout error. */
        ccb->ccb_xa.state = ATA_S_TIMEOUT;
        *active &= ~(1 << ccb->ccb_slot);
        if (ncq_cmd == 0) {
                KKASSERT(ap->ap_active_cnt > 0);
                --ap->ap_active_cnt;
        }
        DPRINTF(AHCI_D_TIMEOUT, "%s: run completion (1)\n", PORTNAME(ap));
        ccb->ccb_done(ccb);     /* This won't issue pending commands or run the
                                   atascsi completion. */

        /* Reset port to abort running command. */
        if (ccb_was_started) {
                DPRINTF(AHCI_D_TIMEOUT, "%s: resetting port to abort%s command "
                    "in slot %d, active %08x\n", PORTNAME(ap), ncq_cmd ? " NCQ"
                    : "", ccb->ccb_slot, *active);
                /* XXX */
                if (ccb->ccb_xa.at && ap->ap_type == ATA_PORT_T_PM) {
                        /* XXX how do we unbrick a PM target? */
                        kprintf("%s: PM target bricked and timed-out, "
                                "disabling PM target but trying to "
                                "leave the port intact\n",
                                ATANAME(ap, ccb->ccb_xa.at));
                        ccb->ccb_xa.at->at_probe = ATA_PROBE_FAILED;
                        ahci_port_intr(ap);
                        ahci_port_stop(ap, 0);
                        ahci_port_clo(ap);
                        ahci_port_start(ap);
                        status = 0;
                } else if (ahci_port_reset(ap, ccb->ccb_xa.at, 0)) {
                        /*
                         * If the softreset failed place the port in a
                         * failed state and use ahci_port_intr() to cancel
                         * any remaining commands.
                         */
                        kprintf("%s: Unable to reset during timeout, port "
                                "bricked on us\n",
                                PORTNAME(ap));
                        ap->ap_state = AP_S_FATAL_ERROR;
                        ahci_port_intr(ap);
                        status = 1;
                } else {
                        status = 0;
                }
                if (status == 0) {
                        /*
                         * Restart any other commands that were aborted
                         * by the reset.
                         */
                        if (*active) {
                                DPRINTF(AHCI_D_TIMEOUT, "%s: re-enabling%s slots "
                                    "%08x\n", PORTNAME(ap), ncq_cmd ? " NCQ" : "",
                                    *active);
                                if (ncq_cmd)
                                        ahci_pwrite(ap, AHCI_PREG_SACT, *active);
                                ahci_pwrite(ap, AHCI_PREG_CI, *active);
                        }
                }
        }

        /* Issue any pending commands now. */
        DPRINTF(AHCI_D_TIMEOUT, "%s: issue pending\n", PORTNAME(ap));
        if (ccb_was_started)
                ahci_issue_pending_commands(ap, ncq_cmd);
        else if (ap->ap_active == 0)
                ahci_issue_pending_ncq_commands(ap);

        /* Complete the timed out ata_xfer I/O (may generate new I/O). */
        DPRINTF(AHCI_D_TIMEOUT, "%s: run completion (2)\n", PORTNAME(ap));
        xa->complete(xa);

        DPRINTF(AHCI_D_TIMEOUT, "%s: splx\n", PORTNAME(ap));
ret:
        crit_exit();
}

void
ahci_empty_done(struct ahci_ccb *ccb)
{
        ccb->ccb_xa.state = ATA_S_COMPLETE;
}