[dragonfly.git] / sys / dev / netif / ath / ath / if_ath_tdma.c

/*-
 * Copyright (c) 2002-2009 Sam Leffler, Errno Consulting
 * All rights reserved.
 *
 * 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,
 *    without modification.
 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
 *    similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
 *    redistribution must be conditioned upon including a substantially
 *    similar Disclaimer requirement for further binary redistribution.
 *
 * NO WARRANTY
 * 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 NONINFRINGEMENT, MERCHANTIBILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR 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 DAMAGES.
 */

#include <sys/cdefs.h>

/*
 * Driver for the Atheros Wireless LAN controller.
 *
 * This software is derived from work of Atsushi Onoe; his contribution
 * is greatly appreciated.
 */

#include "opt_inet.h"
#include "opt_ath.h"
/*
 * This is needed for register operations which are performed
 * by the driver - eg, calls to ath_hal_gettsf32().
 *
 * It's also required for any AH_DEBUG checks in here, eg the
 * module dependencies.
 */
#include "opt_ah.h"
#include "opt_wlan.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/kernel.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/errno.h>
#include <sys/callout.h>
#include <sys/bus.h>
#include <sys/endian.h>
#include <sys/kthread.h>
#include <sys/taskqueue.h>
#include <sys/priv.h>
#include <sys/module.h>
#include <sys/ktr.h>
#include <sys/smp.h>    /* for mp_ncpus */

#include <machine/bus.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/if_media.h>
#include <net/if_types.h>
#include <net/if_arp.h>
#include <net/ethernet.h>
#include <net/if_llc.h>

#include <net80211/ieee80211_var.h>
#include <net80211/ieee80211_regdomain.h>
#ifdef IEEE80211_SUPPORT_SUPERG
#include <net80211/ieee80211_superg.h>
#endif
#ifdef IEEE80211_SUPPORT_TDMA
#include <net80211/ieee80211_tdma.h>
#endif

#include <net/bpf.h>

#ifdef INET
#include <netinet/in.h>
#include <netinet/if_ether.h>
#endif

#include <dev/ath/if_athvar.h>
#include <dev/ath/ath_hal/ah_devid.h>           /* XXX for softled */
#include <dev/ath/ath_hal/ah_diagcodes.h>

#include <dev/ath/if_ath_debug.h>
#include <dev/ath/if_ath_misc.h>
#include <dev/ath/if_ath_tsf.h>
#include <dev/ath/if_ath_tx.h>
#include <dev/ath/if_ath_sysctl.h>
#include <dev/ath/if_ath_led.h>
#include <dev/ath/if_ath_keycache.h>
#include <dev/ath/if_ath_rx.h>
#include <dev/ath/if_ath_beacon.h>
#include <dev/ath/if_athdfs.h>

#ifdef ATH_TX99_DIAG
#include <dev/ath/ath_tx99/ath_tx99.h>
#endif

#ifdef  ATH_DEBUG_ALQ
#include <dev/ath/if_ath_alq.h>
#endif

#ifdef IEEE80211_SUPPORT_TDMA
#include <dev/ath/if_ath_tdma.h>

static void     ath_tdma_settimers(struct ath_softc *sc, u_int32_t nexttbtt,
                    u_int32_t bintval);
static void     ath_tdma_bintvalsetup(struct ath_softc *sc,
                    const struct ieee80211_tdma_state *tdma);
#endif /* IEEE80211_SUPPORT_TDMA */

#ifdef IEEE80211_SUPPORT_TDMA
static void
ath_tdma_settimers(struct ath_softc *sc, u_int32_t nexttbtt, u_int32_t bintval)
{
        struct ath_hal *ah = sc->sc_ah;
        HAL_BEACON_TIMERS bt;

        bt.bt_intval = bintval | HAL_BEACON_ENA;
        bt.bt_nexttbtt = nexttbtt;
        bt.bt_nextdba = (nexttbtt<<3) - sc->sc_tdmadbaprep;
        bt.bt_nextswba = (nexttbtt<<3) - sc->sc_tdmaswbaprep;
        bt.bt_nextatim = nexttbtt+1;
        /* Enables TBTT, DBA, SWBA timers by default */
        bt.bt_flags = 0;
#if 0
        DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
            "%s: intval=%d (0x%08x) nexttbtt=%u (0x%08x), nextdba=%u (0x%08x), nextswba=%u (0x%08x),nextatim=%u (0x%08x)\n",
            __func__,
            bt.bt_intval,
            bt.bt_intval,
            bt.bt_nexttbtt,
            bt.bt_nexttbtt,
            bt.bt_nextdba,
            bt.bt_nextdba,
            bt.bt_nextswba,
            bt.bt_nextswba,
            bt.bt_nextatim,
            bt.bt_nextatim);
#endif

#ifdef  ATH_DEBUG_ALQ
        if (if_ath_alq_checkdebug(&sc->sc_alq, ATH_ALQ_TDMA_TIMER_SET)) {
                struct if_ath_alq_tdma_timer_set t;
                t.bt_intval = htobe32(bt.bt_intval);
                t.bt_nexttbtt = htobe32(bt.bt_nexttbtt);
                t.bt_nextdba = htobe32(bt.bt_nextdba);
                t.bt_nextswba = htobe32(bt.bt_nextswba);
                t.bt_nextatim = htobe32(bt.bt_nextatim);
                t.bt_flags = htobe32(bt.bt_flags);
                t.sc_tdmadbaprep = htobe32(sc->sc_tdmadbaprep);
                t.sc_tdmaswbaprep = htobe32(sc->sc_tdmaswbaprep);
                if_ath_alq_post(&sc->sc_alq, ATH_ALQ_TDMA_TIMER_SET,
                    sizeof(t), (char *) &t);
        }
#endif

        DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
            "%s: nexttbtt=%u (0x%08x), nexttbtt tsf=%lld (0x%08llx)\n",
            __func__,
            bt.bt_nexttbtt,
            bt.bt_nexttbtt,
            (long long) ( ((u_int64_t) (bt.bt_nexttbtt)) << 10),
            (long long) ( ((u_int64_t) (bt.bt_nexttbtt)) << 10));
        ath_hal_beaconsettimers(ah, &bt);
}

/*
 * Calculate the beacon interval.  This is periodic in the
 * superframe for the bss.  We assume each station is configured
 * identically wrt transmit rate so the guard time we calculate
 * above will be the same on all stations.  Note we need to
 * factor in the xmit time because the hardware will schedule
 * a frame for transmit if the start of the frame is within
 * the burst time.  When we get hardware that properly kills
 * frames in the PCU we can reduce/eliminate the guard time.
 *
 * Roundup to 1024 is so we have 1 TU buffer in the guard time
 * to deal with the granularity of the nexttbtt timer.  11n MAC's
 * with 1us timer granularity should allow us to reduce/eliminate
 * this.
 */
static void
ath_tdma_bintvalsetup(struct ath_softc *sc,
        const struct ieee80211_tdma_state *tdma)
{
        /* copy from vap state (XXX check all vaps have same value?) */
        sc->sc_tdmaslotlen = tdma->tdma_slotlen;

        sc->sc_tdmabintval = roundup((sc->sc_tdmaslotlen+sc->sc_tdmaguard) *
                tdma->tdma_slotcnt, 1024);
        sc->sc_tdmabintval >>= 10;              /* TSF -> TU */
        if (sc->sc_tdmabintval & 1)
                sc->sc_tdmabintval++;

        if (tdma->tdma_slot == 0) {
                /*
                 * Only slot 0 beacons; other slots respond.
                 */
                sc->sc_imask |= HAL_INT_SWBA;
                sc->sc_tdmaswba = 0;            /* beacon immediately */
        } else {
                /* XXX all vaps must be slot 0 or slot !0 */
                sc->sc_imask &= ~HAL_INT_SWBA;
        }
}

/*
 * Max 802.11 overhead.  This assumes no 4-address frames and
 * the encapsulation done by ieee80211_encap (llc).  We also
 * include potential crypto overhead.
 */
#define IEEE80211_MAXOVERHEAD \
        (sizeof(struct ieee80211_qosframe) \
         + sizeof(struct llc) \
         + IEEE80211_ADDR_LEN \
         + IEEE80211_WEP_IVLEN \
         + IEEE80211_WEP_KIDLEN \
         + IEEE80211_WEP_CRCLEN \
         + IEEE80211_WEP_MICLEN \
         + IEEE80211_CRC_LEN)

/*
 * Setup initially for tdma operation.  Start the beacon
 * timers and enable SWBA if we are slot 0.  Otherwise
 * we wait for slot 0 to arrive so we can sync up before
 * starting to transmit.
 */
void
ath_tdma_config(struct ath_softc *sc, struct ieee80211vap *vap)
{
        struct ath_hal *ah = sc->sc_ah;
        struct ifnet *ifp = sc->sc_ifp;
        struct ieee80211com *ic = ifp->if_l2com;
        const struct ieee80211_txparam *tp;
        const struct ieee80211_tdma_state *tdma = NULL;
        int rix;

        if (vap == NULL) {
                vap = TAILQ_FIRST(&ic->ic_vaps);   /* XXX */
                if (vap == NULL) {
                        if_printf(ifp, "%s: no vaps?\n", __func__);
                        return;
                }
        }
        /* XXX should take a locked ref to iv_bss */
        tp = vap->iv_bss->ni_txparms;
        /*
         * Calculate the guard time for each slot.  This is the
         * time to send a maximal-size frame according to the
         * fixed/lowest transmit rate.  Note that the interface
         * mtu does not include the 802.11 overhead so we must
         * tack that on (ath_hal_computetxtime includes the
         * preamble and plcp in it's calculation).
         */
        tdma = vap->iv_tdma;
        if (tp->ucastrate != IEEE80211_FIXED_RATE_NONE)
                rix = ath_tx_findrix(sc, tp->ucastrate);
        else
                rix = ath_tx_findrix(sc, tp->mcastrate);

        /*
         * If the chip supports enforcing TxOP on transmission,
         * we can just delete the guard window.  It isn't at all required.
         */
        if (sc->sc_hasenforcetxop) {
                sc->sc_tdmaguard = 0;
        } else {
                /* XXX short preamble assumed */
                /* XXX non-11n rate assumed */
                sc->sc_tdmaguard = ath_hal_computetxtime(ah, sc->sc_currates,
                        ifp->if_mtu + IEEE80211_MAXOVERHEAD, rix, AH_TRUE);
        }

        ath_hal_intrset(ah, 0);

        ath_beaconq_config(sc);                 /* setup h/w beacon q */
        if (sc->sc_setcca)
                ath_hal_setcca(ah, AH_FALSE);   /* disable CCA */
        ath_tdma_bintvalsetup(sc, tdma);        /* calculate beacon interval */
        ath_tdma_settimers(sc, sc->sc_tdmabintval,
                sc->sc_tdmabintval | HAL_BEACON_RESET_TSF);
        sc->sc_syncbeacon = 0;

        sc->sc_avgtsfdeltap = TDMA_DUMMY_MARKER;
        sc->sc_avgtsfdeltam = TDMA_DUMMY_MARKER;

        ath_hal_intrset(ah, sc->sc_imask);

        DPRINTF(sc, ATH_DEBUG_TDMA, "%s: slot %u len %uus cnt %u "
            "bsched %u guard %uus bintval %u TU dba prep %u\n", __func__,
            tdma->tdma_slot, tdma->tdma_slotlen, tdma->tdma_slotcnt,
            tdma->tdma_bintval, sc->sc_tdmaguard, sc->sc_tdmabintval,
            sc->sc_tdmadbaprep);

#ifdef  ATH_DEBUG_ALQ
        if (if_ath_alq_checkdebug(&sc->sc_alq, ATH_ALQ_TDMA_TIMER_CONFIG)) {
                struct if_ath_alq_tdma_timer_config t;

                t.tdma_slot = htobe32(tdma->tdma_slot);
                t.tdma_slotlen = htobe32(tdma->tdma_slotlen);
                t.tdma_slotcnt = htobe32(tdma->tdma_slotcnt);
                t.tdma_bintval = htobe32(tdma->tdma_bintval);
                t.tdma_guard = htobe32(sc->sc_tdmaguard);
                t.tdma_scbintval = htobe32(sc->sc_tdmabintval);
                t.tdma_dbaprep = htobe32(sc->sc_tdmadbaprep);

                if_ath_alq_post(&sc->sc_alq, ATH_ALQ_TDMA_TIMER_CONFIG,
                    sizeof(t), (char *) &t);
        }
#endif  /* ATH_DEBUG_ALQ */
}

/*
 * Update tdma operation.  Called from the 802.11 layer
 * when a beacon is received from the TDMA station operating
 * in the slot immediately preceding us in the bss.  Use
 * the rx timestamp for the beacon frame to update our
 * beacon timers so we follow their schedule.  Note that
 * by using the rx timestamp we implicitly include the
 * propagation delay in our schedule.
 *
 * XXX TODO: since the changes for the AR5416 and later chips
 * involved changing the TSF/TU calculations, we need to make
 * sure that various calculations wrap consistently.
 *
 * A lot of the problems stemmed from the calculations wrapping
 * at 65,535 TU.  Since a lot of the math is still being done in
 * TU, please audit it to ensure that when the TU values programmed
 * into the timers wrap at (2^31)-1 TSF, all the various terms
 * wrap consistently.
 */
void
ath_tdma_update(struct ieee80211_node *ni,
        const struct ieee80211_tdma_param *tdma, int changed)
{
#define TSF_TO_TU(_h,_l) \
        ((((u_int32_t)(_h)) << 22) | (((u_int32_t)(_l)) >> 10))
#define TU_TO_TSF(_tu)  (((u_int64_t)(_tu)) << 10)
        struct ieee80211vap *vap = ni->ni_vap;
        struct ieee80211com *ic = ni->ni_ic;
        struct ath_softc *sc = ic->ic_ifp->if_softc;
        struct ath_hal *ah = sc->sc_ah;
        const HAL_RATE_TABLE *rt = sc->sc_currates;
        u_int64_t tsf, rstamp, nextslot, nexttbtt, nexttbtt_full;
        u_int32_t txtime, nextslottu;
        int32_t tudelta, tsfdelta;
        const struct ath_rx_status *rs;
        int rix;

        sc->sc_stats.ast_tdma_update++;

        /*
         * Check for and adopt configuration changes.
         */
        if (changed != 0) {
                const struct ieee80211_tdma_state *ts = vap->iv_tdma;

                ath_tdma_bintvalsetup(sc, ts);
                if (changed & TDMA_UPDATE_SLOTLEN)
                        ath_wme_update(ic);

                DPRINTF(sc, ATH_DEBUG_TDMA,
                    "%s: adopt slot %u slotcnt %u slotlen %u us "
                    "bintval %u TU\n", __func__,
                    ts->tdma_slot, ts->tdma_slotcnt, ts->tdma_slotlen,
                    sc->sc_tdmabintval);

                /* XXX right? */
                ath_hal_intrset(ah, sc->sc_imask);
                /* NB: beacon timers programmed below */
        }

        /* extend rx timestamp to 64 bits */
        rs = sc->sc_lastrs;
        tsf = ath_hal_gettsf64(ah);
        rstamp = ath_extend_tsf(sc, rs->rs_tstamp, tsf);
        /*
         * The rx timestamp is set by the hardware on completing
         * reception (at the point where the rx descriptor is DMA'd
         * to the host).  To find the start of our next slot we
         * must adjust this time by the time required to send
         * the packet just received.
         */
        rix = rt->rateCodeToIndex[rs->rs_rate];

        /*
         * To calculate the packet duration for legacy rates, we
         * only need the rix and preamble.
         *
         * For 11n non-aggregate frames, we also need the channel
         * width and short/long guard interval.
         *
         * For 11n aggregate frames, the required hacks are a little
         * more subtle.  You need to figure out the frame duration
         * for each frame, including the delimiters.  However, when
         * a frame isn't received successfully, we won't hear it
         * (unless you enable reception of CRC errored frames), so
         * your duration calculation is going to be off.
         *
         * However, we can assume that the beacon frames won't be
         * transmitted as aggregate frames, so we should be okay.
         * Just add a check to ensure that we aren't handed something
         * bad.
         *
         * For ath_hal_pkt_txtime() - for 11n rates, shortPreamble is
         * actually short guard interval. For legacy rates,
         * it's short preamble.
         */
        txtime = ath_hal_pkt_txtime(ah, rt, rs->rs_datalen,
            rix,
            !! (rs->rs_flags & HAL_RX_2040),
            (rix & 0x80) ?
              (! (rs->rs_flags & HAL_RX_GI)) : rt->info[rix].shortPreamble);
        /* NB: << 9 is to cvt to TU and /2 */
        nextslot = (rstamp - txtime) + (sc->sc_tdmabintval << 9);

        /*
         * For 802.11n chips: nextslottu needs to be the full TSF space,
         * not just 0..65535 TU.
         */
        nextslottu = TSF_TO_TU(nextslot>>32, nextslot);
        /*
         * Retrieve the hardware NextTBTT in usecs
         * and calculate the difference between what the
         * other station thinks and what we have programmed.  This
         * lets us figure how to adjust our timers to match.  The
         * adjustments are done by pulling the TSF forward and possibly
         * rewriting the beacon timers.
         */
        /*
         * The logic here assumes the nexttbtt counter is in TSF
         * but the prr-11n NICs are in TU.  The HAL shifts them
         * to TSF but there's two important differences:
         *
         * + The TU->TSF values have 0's for the low 9 bits, and
         * + The counter wraps at TU_TO_TSF(HAL_BEACON_PERIOD + 1) for
         *   the pre-11n NICs, but not for the 11n NICs.
         *
         * So for now, just make sure the nexttbtt value we get
         * matches the second issue or once nexttbtt exceeds this
         * value, tsfdelta ends up becoming very negative and all
         * of the adjustments get very messed up.
         */

        /*
         * We need to track the full nexttbtt rather than having it
         * truncated at HAL_BEACON_PERIOD, as programming the
         * nexttbtt (and related) registers for the 11n chips is
         * actually going to take the full 32 bit space, rather than
         * just 0..65535 TU.
         */
        nexttbtt_full = ath_hal_getnexttbtt(ah);
        nexttbtt = nexttbtt_full % (TU_TO_TSF(HAL_BEACON_PERIOD + 1));
        tsfdelta = (int32_t)((nextslot % TU_TO_TSF(HAL_BEACON_PERIOD + 1)) - nexttbtt);

        DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
            "rs->rstamp %llu rstamp %llu tsf %llu txtime %d, nextslot %llu, "
            "nextslottu %d, nextslottume %d\n",
            (unsigned long long) rs->rs_tstamp, rstamp, tsf, txtime,
            nextslot, nextslottu, TSF_TO_TU(nextslot >> 32, nextslot));
        DPRINTF(sc, ATH_DEBUG_TDMA,
            "  beacon tstamp: %llu (0x%016llx)\n",
            le64toh(ni->ni_tstamp.tsf),
            le64toh(ni->ni_tstamp.tsf));

        DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
            "nexttbtt %llu (0x%08llx) tsfdelta %d avg +%d/-%d\n",
            nexttbtt,
            (long long) nexttbtt,
            tsfdelta,
            TDMA_AVG(sc->sc_avgtsfdeltap), TDMA_AVG(sc->sc_avgtsfdeltam));

        if (tsfdelta < 0) {
                TDMA_SAMPLE(sc->sc_avgtsfdeltap, 0);
                TDMA_SAMPLE(sc->sc_avgtsfdeltam, -tsfdelta);
                tsfdelta = -tsfdelta % 1024;
                nextslottu++;
        } else if (tsfdelta > 0) {
                TDMA_SAMPLE(sc->sc_avgtsfdeltap, tsfdelta);
                TDMA_SAMPLE(sc->sc_avgtsfdeltam, 0);
                tsfdelta = 1024 - (tsfdelta % 1024);
                nextslottu++;
        } else {
                TDMA_SAMPLE(sc->sc_avgtsfdeltap, 0);
                TDMA_SAMPLE(sc->sc_avgtsfdeltam, 0);
        }
        tudelta = nextslottu - TSF_TO_TU(nexttbtt_full >> 32, nexttbtt_full);

#ifdef  ATH_DEBUG_ALQ
        if (if_ath_alq_checkdebug(&sc->sc_alq, ATH_ALQ_TDMA_BEACON_STATE)) {
                struct if_ath_alq_tdma_beacon_state t;
                t.rx_tsf = htobe64(rstamp);
                t.beacon_tsf = htobe64(le64toh(ni->ni_tstamp.tsf));
                t.tsf64 = htobe64(tsf);
                t.nextslot_tsf = htobe64(nextslot);
                t.nextslot_tu = htobe32(nextslottu);
                t.txtime = htobe32(txtime);
                if_ath_alq_post(&sc->sc_alq, ATH_ALQ_TDMA_BEACON_STATE,
                    sizeof(t), (char *) &t);
        }

        if (if_ath_alq_checkdebug(&sc->sc_alq, ATH_ALQ_TDMA_SLOT_CALC)) {
                struct if_ath_alq_tdma_slot_calc t;

                t.nexttbtt = htobe64(nexttbtt_full);
                t.next_slot = htobe64(nextslot);
                t.tsfdelta = htobe32(tsfdelta);
                t.avg_plus = htobe32(TDMA_AVG(sc->sc_avgtsfdeltap));
                t.avg_minus = htobe32(TDMA_AVG(sc->sc_avgtsfdeltam));

                if_ath_alq_post(&sc->sc_alq, ATH_ALQ_TDMA_SLOT_CALC,
                    sizeof(t), (char *) &t);
        }
#endif

        /*
         * Copy sender's timetstamp into tdma ie so they can
         * calculate roundtrip time.  We submit a beacon frame
         * below after any timer adjustment.  The frame goes out
         * at the next TBTT so the sender can calculate the
         * roundtrip by inspecting the tdma ie in our beacon frame.
         *
         * NB: This tstamp is subtlely preserved when
         *     IEEE80211_BEACON_TDMA is marked (e.g. when the
         *     slot position changes) because ieee80211_add_tdma
         *     skips over the data.
         */
        memcpy(ATH_VAP(vap)->av_boff.bo_tdma +
                __offsetof(struct ieee80211_tdma_param, tdma_tstamp),
                &ni->ni_tstamp.data, 8);
#if 0
        DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
            "tsf %llu nextslot %llu (%d, %d) nextslottu %u nexttbtt %llu (%d)\n",
            (unsigned long long) tsf, (unsigned long long) nextslot,
            (int)(nextslot - tsf), tsfdelta, nextslottu, nexttbtt, tudelta);
#endif
        /*
         * Adjust the beacon timers only when pulling them forward
         * or when going back by less than the beacon interval.
         * Negative jumps larger than the beacon interval seem to
         * cause the timers to stop and generally cause instability.
         * This basically filters out jumps due to missed beacons.
         */
        if (tudelta != 0 && (tudelta > 0 || -tudelta < sc->sc_tdmabintval)) {
                DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
                    "%s: calling ath_tdma_settimers; nextslottu=%d, bintval=%d\n",
                    __func__,
                    nextslottu,
                    sc->sc_tdmabintval);
                ath_tdma_settimers(sc, nextslottu, sc->sc_tdmabintval);
                sc->sc_stats.ast_tdma_timers++;
        }
        if (tsfdelta > 0) {
                uint64_t tsf;

                /* XXX should just teach ath_hal_adjusttsf() to do this */
                tsf = ath_hal_gettsf64(ah);
                ath_hal_settsf64(ah, tsf + tsfdelta);
                DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
                    "%s: calling ath_hal_adjusttsf: TSF=%llu, tsfdelta=%d\n",
                    __func__,
                    tsf,
                    tsfdelta);

#ifdef  ATH_DEBUG_ALQ
                if (if_ath_alq_checkdebug(&sc->sc_alq,
                    ATH_ALQ_TDMA_TSF_ADJUST)) {
                        struct if_ath_alq_tdma_tsf_adjust t;

                        t.tsfdelta = htobe32(tsfdelta);
                        t.tsf64_old = htobe64(tsf);
                        t.tsf64_new = htobe64(tsf + tsfdelta);
                        if_ath_alq_post(&sc->sc_alq, ATH_ALQ_TDMA_TSF_ADJUST,
                            sizeof(t), (char *) &t);
                }
#endif  /* ATH_DEBUG_ALQ */
                sc->sc_stats.ast_tdma_tsf++;
        }
        ath_tdma_beacon_send(sc, vap);          /* prepare response */
#undef TU_TO_TSF
#undef TSF_TO_TU
}

/*
 * Transmit a beacon frame at SWBA.  Dynamic updates
 * to the frame contents are done as needed.
 */
void
ath_tdma_beacon_send(struct ath_softc *sc, struct ieee80211vap *vap)
{
        struct ath_hal *ah = sc->sc_ah;
        struct ath_buf *bf;
        int otherant;

        /*
         * Check if the previous beacon has gone out.  If
         * not don't try to post another, skip this period
         * and wait for the next.  Missed beacons indicate
         * a problem and should not occur.  If we miss too
         * many consecutive beacons reset the device.
         */
        if (ath_hal_numtxpending(ah, sc->sc_bhalq) != 0) {
                sc->sc_bmisscount++;
                DPRINTF(sc, ATH_DEBUG_BEACON,
                        "%s: missed %u consecutive beacons\n",
                        __func__, sc->sc_bmisscount);
                if (sc->sc_bmisscount >= ath_bstuck_threshold)
                        taskqueue_enqueue(sc->sc_tq, &sc->sc_bstucktask);
                return;
        }
        if (sc->sc_bmisscount != 0) {
                DPRINTF(sc, ATH_DEBUG_BEACON,
                        "%s: resume beacon xmit after %u misses\n",
                        __func__, sc->sc_bmisscount);
                sc->sc_bmisscount = 0;
        }

        /*
         * Check recent per-antenna transmit statistics and flip
         * the default antenna if noticeably more frames went out
         * on the non-default antenna.
         * XXX assumes 2 anntenae
         */
        if (!sc->sc_diversity) {
                otherant = sc->sc_defant & 1 ? 2 : 1;
                if (sc->sc_ant_tx[otherant] > sc->sc_ant_tx[sc->sc_defant] + 2)
                        ath_setdefantenna(sc, otherant);
                sc->sc_ant_tx[1] = sc->sc_ant_tx[2] = 0;
        }

        bf = ath_beacon_generate(sc, vap);
        /* XXX We don't do cabq traffic, but just for completeness .. */
        ATH_TXQ_LOCK(sc->sc_cabq);
        ath_beacon_cabq_start(sc);
        ATH_TXQ_UNLOCK(sc->sc_cabq);

        if (bf != NULL) {
                /*
                 * Stop any current dma and put the new frame on the queue.
                 * This should never fail since we check above that no frames
                 * are still pending on the queue.
                 */
                if ((! sc->sc_isedma) &&
                    (! ath_hal_stoptxdma(ah, sc->sc_bhalq))) {
                        DPRINTF(sc, ATH_DEBUG_ANY,
                                "%s: beacon queue %u did not stop?\n",
                                __func__, sc->sc_bhalq);
                        /* NB: the HAL still stops DMA, so proceed */
                }
                ath_hal_puttxbuf(ah, sc->sc_bhalq, bf->bf_daddr);
                ath_hal_txstart(ah, sc->sc_bhalq);

                sc->sc_stats.ast_be_xmit++;             /* XXX per-vap? */

                /*
                 * Record local TSF for our last send for use
                 * in arbitrating slot collisions.
                 */
                /* XXX should take a locked ref to iv_bss */
                vap->iv_bss->ni_tstamp.tsf = ath_hal_gettsf64(ah);
        }
}
#endif /* IEEE80211_SUPPORT_TDMA */