ath9k: Add a debugfs file for dumping DMA status

[linux-2.6/verdex.git] / drivers / net / wireless / ath9k / beacon.c

/*
 * Copyright (c) 2008 Atheros Communications Inc.
 *
 * Permission to use, copy, modify, and/or 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.
 */

#include "core.h"

/*
 *  This function will modify certain transmit queue properties depending on
 *  the operating mode of the station (AP or AdHoc).  Parameters are AIFS
 *  settings and channel width min/max
*/
static int ath_beaconq_config(struct ath_softc *sc)
{
        struct ath_hal *ah = sc->sc_ah;
        struct ath9k_tx_queue_info qi;

        ath9k_hw_get_txq_props(ah, sc->sc_bhalq, &qi);
        if (sc->sc_ah->ah_opmode == ATH9K_M_HOSTAP) {
                /* Always burst out beacon and CAB traffic. */
                qi.tqi_aifs = 1;
                qi.tqi_cwmin = 0;
                qi.tqi_cwmax = 0;
        } else {
                /* Adhoc mode; important thing is to use 2x cwmin. */
                qi.tqi_aifs = sc->sc_beacon_qi.tqi_aifs;
                qi.tqi_cwmin = 2*sc->sc_beacon_qi.tqi_cwmin;
                qi.tqi_cwmax = sc->sc_beacon_qi.tqi_cwmax;
        }

        if (!ath9k_hw_set_txq_props(ah, sc->sc_bhalq, &qi)) {
                DPRINTF(sc, ATH_DBG_FATAL,
                        "unable to update h/w beacon queue parameters\n");
                return 0;
        } else {
                ath9k_hw_resettxqueue(ah, sc->sc_bhalq); /* push to h/w */
                return 1;
        }
}

static void ath_bstuck_process(struct ath_softc *sc)
{
        DPRINTF(sc, ATH_DBG_BEACON,
                "stuck beacon; resetting (bmiss count %u)\n",
                sc->sc_bmisscount);
        ath_reset(sc, false);
}

/*
 *  Associates the beacon frame buffer with a transmit descriptor.  Will set
 *  up all required antenna switch parameters, rate codes, and channel flags.
 *  Beacons are always sent out at the lowest rate, and are not retried.
*/
static void ath_beacon_setup(struct ath_softc *sc,
                             struct ath_vap *avp, struct ath_buf *bf)
{
        struct sk_buff *skb = (struct sk_buff *)bf->bf_mpdu;
        struct ath_hal *ah = sc->sc_ah;
        struct ath_desc *ds;
        struct ath9k_11n_rate_series series[4];
        struct ath_rate_table *rt;
        int flags, antenna;
        u8 rix, rate;
        int ctsrate = 0;
        int ctsduration = 0;

        DPRINTF(sc, ATH_DBG_BEACON, "m %p len %u\n", skb, skb->len);

        /* setup descriptors */
        ds = bf->bf_desc;

        flags = ATH9K_TXDESC_NOACK;

        if (sc->sc_ah->ah_opmode == ATH9K_M_IBSS &&
            (ah->ah_caps.hw_caps & ATH9K_HW_CAP_VEOL)) {
                ds->ds_link = bf->bf_daddr; /* self-linked */
                flags |= ATH9K_TXDESC_VEOL;
                /* Let hardware handle antenna switching. */
                antenna = 0;
        } else {
                ds->ds_link = 0;
                /*
                 * Switch antenna every beacon.
                 * Should only switch every beacon period, not for every
                 * SWBA's
                 * XXX assumes two antenna
                 */
                antenna = ((sc->ast_be_xmit / sc->sc_nbcnvaps) & 1 ? 2 : 1);
        }

        ds->ds_data = bf->bf_buf_addr;

        /*
         * Calculate rate code.
         * XXX everything at min xmit rate
         */
        rix = 0;
        rt = sc->hw_rate_table[sc->sc_curmode];
        rate = rt->info[rix].ratecode;
        if (sc->sc_flags & SC_OP_PREAMBLE_SHORT)
                rate |= rt->info[rix].short_preamble;

        ath9k_hw_set11n_txdesc(ah, ds,
                               skb->len + FCS_LEN,     /* frame length */
                               ATH9K_PKT_TYPE_BEACON,  /* Atheros packet type */
                               MAX_RATE_POWER,         /* FIXME */
                               ATH9K_TXKEYIX_INVALID,  /* no encryption */
                               ATH9K_KEY_TYPE_CLEAR,   /* no encryption */
                               flags                   /* no ack,
                                                          veol for beacons */
                );

        /* NB: beacon's BufLen must be a multiple of 4 bytes */
        ath9k_hw_filltxdesc(ah, ds,
                            roundup(skb->len, 4), /* buffer length */
                            true,                 /* first segment */
                            true,                 /* last segment */
                            ds                    /* first descriptor */
                );

        memset(series, 0, sizeof(struct ath9k_11n_rate_series) * 4);
        series[0].Tries = 1;
        series[0].Rate = rate;
        series[0].ChSel = sc->sc_tx_chainmask;
        series[0].RateFlags = (ctsrate) ? ATH9K_RATESERIES_RTS_CTS : 0;
        ath9k_hw_set11n_ratescenario(ah, ds, ds, 0,
                ctsrate, ctsduration, series, 4, 0);
}

/* Generate beacon frame and queue cab data for a vap */
static struct ath_buf *ath_beacon_generate(struct ath_softc *sc, int if_id)
{
        struct ath_buf *bf;
        struct ath_vap *avp;
        struct sk_buff *skb;
        struct ath_txq *cabq;
        struct ieee80211_vif *vif;
        struct ieee80211_tx_info *info;
        int cabq_depth;

        vif = sc->sc_vaps[if_id];
        ASSERT(vif);

        avp = (void *)vif->drv_priv;
        cabq = sc->sc_cabq;

        if (avp->av_bcbuf == NULL) {
                DPRINTF(sc, ATH_DBG_BEACON, "avp=%p av_bcbuf=%p\n",
                        avp, avp->av_bcbuf);
                return NULL;
        }

        bf = avp->av_bcbuf;
        skb = (struct sk_buff *)bf->bf_mpdu;
        if (skb) {
                pci_unmap_single(sc->pdev, bf->bf_dmacontext,
                                 skb->len,
                                 PCI_DMA_TODEVICE);
        }

        skb = ieee80211_beacon_get(sc->hw, vif);
        bf->bf_mpdu = skb;
        if (skb == NULL)
                return NULL;

        info = IEEE80211_SKB_CB(skb);
        if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
                /*
                 * TODO: make sure the seq# gets assigned properly (vs. other
                 * TX frames)
                 */
                struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
                sc->seq_no += 0x10;
                hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
                hdr->seq_ctrl |= cpu_to_le16(sc->seq_no);
        }

        bf->bf_buf_addr = bf->bf_dmacontext =
                pci_map_single(sc->pdev, skb->data,
                               skb->len,
                               PCI_DMA_TODEVICE);

        skb = ieee80211_get_buffered_bc(sc->hw, vif);

        /*
         * if the CABQ traffic from previous DTIM is pending and the current
         *  beacon is also a DTIM.
         *  1) if there is only one vap let the cab traffic continue.
         *  2) if there are more than one vap and we are using staggered
         *     beacons, then drain the cabq by dropping all the frames in
         *     the cabq so that the current vaps cab traffic can be scheduled.
         */
        spin_lock_bh(&cabq->axq_lock);
        cabq_depth = cabq->axq_depth;
        spin_unlock_bh(&cabq->axq_lock);

        if (skb && cabq_depth) {
                /*
                 * Unlock the cabq lock as ath_tx_draintxq acquires
                 * the lock again which is a common function and that
                 * acquires txq lock inside.
                 */
                if (sc->sc_nvaps > 1) {
                        ath_tx_draintxq(sc, cabq, false);
                        DPRINTF(sc, ATH_DBG_BEACON,
                                "flush previous cabq traffic\n");
                }
        }

        /* Construct tx descriptor. */
        ath_beacon_setup(sc, avp, bf);

        /*
         * Enable the CAB queue before the beacon queue to
         * insure cab frames are triggered by this beacon.
         */
        while (skb) {
                ath_tx_cabq(sc, skb);
                skb = ieee80211_get_buffered_bc(sc->hw, vif);
        }

        return bf;
}

/*
 * Startup beacon transmission for adhoc mode when they are sent entirely
 * by the hardware using the self-linked descriptor + veol trick.
*/
static void ath_beacon_start_adhoc(struct ath_softc *sc, int if_id)
{
        struct ieee80211_vif *vif;
        struct ath_hal *ah = sc->sc_ah;
        struct ath_buf *bf;
        struct ath_vap *avp;
        struct sk_buff *skb;

        vif = sc->sc_vaps[if_id];
        ASSERT(vif);

        avp = (void *)vif->drv_priv;

        if (avp->av_bcbuf == NULL) {
                DPRINTF(sc, ATH_DBG_BEACON, "avp=%p av_bcbuf=%p\n",
                        avp, avp != NULL ? avp->av_bcbuf : NULL);
                return;
        }
        bf = avp->av_bcbuf;
        skb = (struct sk_buff *) bf->bf_mpdu;

        /* Construct tx descriptor. */
        ath_beacon_setup(sc, avp, bf);

        /* NB: caller is known to have already stopped tx dma */
        ath9k_hw_puttxbuf(ah, sc->sc_bhalq, bf->bf_daddr);
        ath9k_hw_txstart(ah, sc->sc_bhalq);
        DPRINTF(sc, ATH_DBG_BEACON, "TXDP%u = %llx (%p)\n",
                sc->sc_bhalq, ito64(bf->bf_daddr), bf->bf_desc);
}

int ath_beaconq_setup(struct ath_hal *ah)
{
        struct ath9k_tx_queue_info qi;

        memset(&qi, 0, sizeof(qi));
        qi.tqi_aifs = 1;
        qi.tqi_cwmin = 0;
        qi.tqi_cwmax = 0;
        /* NB: don't enable any interrupts */
        return ath9k_hw_setuptxqueue(ah, ATH9K_TX_QUEUE_BEACON, &qi);
}

int ath_beacon_alloc(struct ath_softc *sc, int if_id)
{
        struct ieee80211_vif *vif;
        struct ath_vap *avp;
        struct ieee80211_hdr *hdr;
        struct ath_buf *bf;
        struct sk_buff *skb;
        __le64 tstamp;

        vif = sc->sc_vaps[if_id];
        ASSERT(vif);

        avp = (void *)vif->drv_priv;

        /* Allocate a beacon descriptor if we haven't done so. */
        if (!avp->av_bcbuf) {
                /* Allocate beacon state for hostap/ibss.  We know
                 * a buffer is available. */
                avp->av_bcbuf = list_first_entry(&sc->sc_bbuf,
                                                 struct ath_buf, list);
                list_del(&avp->av_bcbuf->list);

                if (sc->sc_ah->ah_opmode == ATH9K_M_HOSTAP ||
                    !(sc->sc_ah->ah_caps.hw_caps & ATH9K_HW_CAP_VEOL)) {
                        int slot;
                        /*
                         * Assign the vap to a beacon xmit slot. As
                         * above, this cannot fail to find one.
                         */
                        avp->av_bslot = 0;
                        for (slot = 0; slot < ATH_BCBUF; slot++)
                                if (sc->sc_bslot[slot] == ATH_IF_ID_ANY) {
                                        /*
                                         * XXX hack, space out slots to better
                                         * deal with misses
                                         */
                                        if (slot+1 < ATH_BCBUF &&
                                            sc->sc_bslot[slot+1] ==
                                                ATH_IF_ID_ANY) {
                                                avp->av_bslot = slot+1;
                                                break;
                                        }
                                        avp->av_bslot = slot;
                                        /* NB: keep looking for a double slot */
                                }
                        BUG_ON(sc->sc_bslot[avp->av_bslot] != ATH_IF_ID_ANY);
                        sc->sc_bslot[avp->av_bslot] = if_id;
                        sc->sc_nbcnvaps++;
                }
        }

        /* release the previous beacon frame , if it already exists. */
        bf = avp->av_bcbuf;
        if (bf->bf_mpdu != NULL) {
                skb = (struct sk_buff *)bf->bf_mpdu;
                pci_unmap_single(sc->pdev, bf->bf_dmacontext,
                                 skb->len,
                                 PCI_DMA_TODEVICE);
                dev_kfree_skb_any(skb);
                bf->bf_mpdu = NULL;
        }

        /*
         * NB: the beacon data buffer must be 32-bit aligned.
         * FIXME: Fill avp->av_btxctl.txpower and
         * avp->av_btxctl.shortPreamble
         */
        skb = ieee80211_beacon_get(sc->hw, vif);
        if (skb == NULL) {
                DPRINTF(sc, ATH_DBG_BEACON, "cannot get skb\n");
                return -ENOMEM;
        }

        tstamp = ((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp;
        sc->bc_tstamp = le64_to_cpu(tstamp);

        /*
         * Calculate a TSF adjustment factor required for
         * staggered beacons.  Note that we assume the format
         * of the beacon frame leaves the tstamp field immediately
         * following the header.
         */
        if (avp->av_bslot > 0) {
                u64 tsfadjust;
                __le64 val;
                int intval;

                intval = sc->hw->conf.beacon_int ?
                        sc->hw->conf.beacon_int : ATH_DEFAULT_BINTVAL;

                /*
                 * The beacon interval is in TU's; the TSF in usecs.
                 * We figure out how many TU's to add to align the
                 * timestamp then convert to TSF units and handle
                 * byte swapping before writing it in the frame.
                 * The hardware will then add this each time a beacon
                 * frame is sent.  Note that we align vap's 1..N
                 * and leave vap 0 untouched.  This means vap 0
                 * has a timestamp in one beacon interval while the
                 * others get a timestamp aligned to the next interval.
                 */
                tsfadjust = (intval * (ATH_BCBUF - avp->av_bslot)) / ATH_BCBUF;
                val = cpu_to_le64(tsfadjust << 10);     /* TU->TSF */

                DPRINTF(sc, ATH_DBG_BEACON,
                        "stagger beacons, bslot %d intval %u tsfadjust %llu\n",
                        avp->av_bslot, intval, (unsigned long long)tsfadjust);

                hdr = (struct ieee80211_hdr *)skb->data;
                memcpy(&hdr[1], &val, sizeof(val));
        }

        bf->bf_buf_addr = bf->bf_dmacontext =
                pci_map_single(sc->pdev, skb->data,
                               skb->len,
                               PCI_DMA_TODEVICE);
        bf->bf_mpdu = skb;

        return 0;
}

void ath_beacon_return(struct ath_softc *sc, struct ath_vap *avp)
{
        if (avp->av_bcbuf != NULL) {
                struct ath_buf *bf;

                if (avp->av_bslot != -1) {
                        sc->sc_bslot[avp->av_bslot] = ATH_IF_ID_ANY;
                        sc->sc_nbcnvaps--;
                }

                bf = avp->av_bcbuf;
                if (bf->bf_mpdu != NULL) {
                        struct sk_buff *skb = (struct sk_buff *)bf->bf_mpdu;
                        pci_unmap_single(sc->pdev, bf->bf_dmacontext,
                                         skb->len,
                                         PCI_DMA_TODEVICE);
                        dev_kfree_skb_any(skb);
                        bf->bf_mpdu = NULL;
                }
                list_add_tail(&bf->list, &sc->sc_bbuf);

                avp->av_bcbuf = NULL;
        }
}

void ath9k_beacon_tasklet(unsigned long data)
{
        struct ath_softc *sc = (struct ath_softc *)data;
        struct ath_hal *ah = sc->sc_ah;
        struct ath_buf *bf = NULL;
        int slot, if_id;
        u32 bfaddr;
        u32 rx_clear = 0, rx_frame = 0, tx_frame = 0;
        u32 show_cycles = 0;
        u32 bc = 0; /* beacon count */
        u64 tsf;
        u32 tsftu;
        u16 intval;

        if (sc->sc_flags & SC_OP_NO_RESET) {
                show_cycles = ath9k_hw_GetMibCycleCountsPct(ah,
                                            &rx_clear, &rx_frame, &tx_frame);
        }

        /*
         * 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.
         *
         * FIXME: Clean up this mess !!
         */
        if (ath9k_hw_numtxpending(ah, sc->sc_bhalq) != 0) {
                sc->sc_bmisscount++;
                /* XXX: doth needs the chanchange IE countdown decremented.
                 *      We should consider adding a mac80211 call to indicate
                 *      a beacon miss so appropriate action could be taken
                 *      (in that layer).
                 */
                if (sc->sc_bmisscount < BSTUCK_THRESH) {
                        if (sc->sc_flags & SC_OP_NO_RESET) {
                                DPRINTF(sc, ATH_DBG_BEACON,
                                        "missed %u consecutive beacons\n",
                                        sc->sc_bmisscount);
                                if (show_cycles) {
                                        /*
                                         * Display cycle counter stats from HW
                                         * to aide in debug of stickiness.
                                         */
                                        DPRINTF(sc, ATH_DBG_BEACON,
                                                "busy times: rx_clear=%d, "
                                                "rx_frame=%d, tx_frame=%d\n",
                                                rx_clear, rx_frame,
                                                tx_frame);
                                } else {
                                        DPRINTF(sc, ATH_DBG_BEACON,
                                                "unable to obtain "
                                                "busy times\n");
                                }
                        } else {
                                DPRINTF(sc, ATH_DBG_BEACON,
                                        "missed %u consecutive beacons\n",
                                        sc->sc_bmisscount);
                        }
                } else if (sc->sc_bmisscount >= BSTUCK_THRESH) {
                        if (sc->sc_flags & SC_OP_NO_RESET) {
                                if (sc->sc_bmisscount == BSTUCK_THRESH) {
                                        DPRINTF(sc, ATH_DBG_BEACON,
                                                "beacon is officially "
                                                "stuck\n");
                                }
                        } else {
                                DPRINTF(sc, ATH_DBG_BEACON,
                                        "beacon is officially stuck\n");
                                ath_bstuck_process(sc);
                        }
                }
                return;
        }

        if (sc->sc_bmisscount != 0) {
                if (sc->sc_flags & SC_OP_NO_RESET) {
                        DPRINTF(sc, ATH_DBG_BEACON,
                                "resume beacon xmit after %u misses\n",
                                sc->sc_bmisscount);
                } else {
                        DPRINTF(sc, ATH_DBG_BEACON,
                                "resume beacon xmit after %u misses\n",
                                sc->sc_bmisscount);
                }
                sc->sc_bmisscount = 0;
        }

        /*
         * Generate beacon frames. we are sending frames
         * staggered so calculate the slot for this frame based
         * on the tsf to safeguard against missing an swba.
         */

        intval = sc->hw->conf.beacon_int ?
                sc->hw->conf.beacon_int : ATH_DEFAULT_BINTVAL;

        tsf = ath9k_hw_gettsf64(ah);
        tsftu = TSF_TO_TU(tsf>>32, tsf);
        slot = ((tsftu % intval) * ATH_BCBUF) / intval;
        if_id = sc->sc_bslot[(slot + 1) % ATH_BCBUF];

        DPRINTF(sc, ATH_DBG_BEACON,
                "slot %d [tsf %llu tsftu %u intval %u] if_id %d\n",
                slot, (unsigned long long)tsf, tsftu,
                intval, if_id);

        bfaddr = 0;
        if (if_id != ATH_IF_ID_ANY) {
                bf = ath_beacon_generate(sc, if_id);
                if (bf != NULL) {
                        bfaddr = bf->bf_daddr;
                        bc = 1;
                }
        }
        /*
         * Handle slot time change when a non-ERP station joins/leaves
         * an 11g network.  The 802.11 layer notifies us via callback,
         * we mark updateslot, then wait one beacon before effecting
         * the change.  This gives associated stations at least one
         * beacon interval to note the state change.
         *
         * NB: The slot time change state machine is clocked according
         *     to whether we are bursting or staggering beacons.  We
         *     recognize the request to update and record the current
         *     slot then don't transition until that slot is reached
         *     again.  If we miss a beacon for that slot then we'll be
         *     slow to transition but we'll be sure at least one beacon
         *     interval has passed.  When bursting slot is always left
         *     set to ATH_BCBUF so this check is a noop.
         */
        /* XXX locking */
        if (sc->sc_updateslot == UPDATE) {
                sc->sc_updateslot = COMMIT; /* commit next beacon */
                sc->sc_slotupdate = slot;
        } else if (sc->sc_updateslot == COMMIT && sc->sc_slotupdate == slot) {
                ath9k_hw_setslottime(sc->sc_ah, sc->sc_slottime);
                sc->sc_updateslot = OK;
        }
        if (bfaddr != 0) {
                /*
                 * Stop any current dma and put the new frame(s) on the queue.
                 * This should never fail since we check above that no frames
                 * are still pending on the queue.
                 */
                if (!ath9k_hw_stoptxdma(ah, sc->sc_bhalq)) {
                        DPRINTF(sc, ATH_DBG_FATAL,
                                "beacon queue %u did not stop?\n", sc->sc_bhalq);
                        /* NB: the HAL still stops DMA, so proceed */
                }

                /* NB: cabq traffic should already be queued and primed */
                ath9k_hw_puttxbuf(ah, sc->sc_bhalq, bfaddr);
                ath9k_hw_txstart(ah, sc->sc_bhalq);

                sc->ast_be_xmit += bc;     /* XXX per-vap? */
        }
}

/*
 * Configure the beacon and sleep timers.
 *
 * When operating as an AP this resets the TSF and sets
 * up the hardware to notify us when we need to issue beacons.
 *
 * When operating in station mode this sets up the beacon
 * timers according to the timestamp of the last received
 * beacon and the current TSF, configures PCF and DTIM
 * handling, programs the sleep registers so the hardware
 * will wakeup in time to receive beacons, and configures
 * the beacon miss handling so we'll receive a BMISS
 * interrupt when we stop seeing beacons from the AP
 * we've associated with.
 */
void ath_beacon_config(struct ath_softc *sc, int if_id)
{
        struct ieee80211_vif *vif;
        struct ath_hal *ah = sc->sc_ah;
        struct ath_beacon_config conf;
        struct ath_vap *avp;
        enum ath9k_opmode av_opmode;
        u32 nexttbtt, intval;

        if (if_id != ATH_IF_ID_ANY) {
                vif = sc->sc_vaps[if_id];
                ASSERT(vif);
                avp = (void *)vif->drv_priv;
                av_opmode = avp->av_opmode;
        } else {
                av_opmode = sc->sc_ah->ah_opmode;
        }

        memset(&conf, 0, sizeof(struct ath_beacon_config));

        conf.beacon_interval = sc->hw->conf.beacon_int ?
                sc->hw->conf.beacon_int : ATH_DEFAULT_BINTVAL;
        conf.listen_interval = 1;
        conf.dtim_period = conf.beacon_interval;
        conf.dtim_count = 1;
        conf.bmiss_timeout = ATH_DEFAULT_BMISS_LIMIT * conf.beacon_interval;

        /* extract tstamp from last beacon and convert to TU */
        nexttbtt = TSF_TO_TU(sc->bc_tstamp >> 32, sc->bc_tstamp);

        /* XXX conditionalize multi-bss support? */
        if (sc->sc_ah->ah_opmode == ATH9K_M_HOSTAP) {
                /*
                 * For multi-bss ap support beacons are either staggered
                 * evenly over N slots or burst together.  For the former
                 * arrange for the SWBA to be delivered for each slot.
                 * Slots that are not occupied will generate nothing.
                 */
                /* NB: the beacon interval is kept internally in TU's */
                intval = conf.beacon_interval & ATH9K_BEACON_PERIOD;
                intval /= ATH_BCBUF;    /* for staggered beacons */
        } else {
                intval = conf.beacon_interval & ATH9K_BEACON_PERIOD;
        }

        if (nexttbtt == 0)      /* e.g. for ap mode */
                nexttbtt = intval;
        else if (intval)        /* NB: can be 0 for monitor mode */
                nexttbtt = roundup(nexttbtt, intval);

        DPRINTF(sc, ATH_DBG_BEACON, "nexttbtt %u intval %u (%u)\n",
                nexttbtt, intval, conf.beacon_interval);

        /* Check for ATH9K_M_HOSTAP and sc_nostabeacons for WDS client */
        if (sc->sc_ah->ah_opmode == ATH9K_M_STA) {
                struct ath9k_beacon_state bs;
                u64 tsf;
                u32 tsftu;
                int dtimperiod, dtimcount, sleepduration;
                int cfpperiod, cfpcount;

                /*
                 * Setup dtim and cfp parameters according to
                 * last beacon we received (which may be none).
                 */
                dtimperiod = conf.dtim_period;
                if (dtimperiod <= 0)            /* NB: 0 if not known */
                        dtimperiod = 1;
                dtimcount = conf.dtim_count;
                if (dtimcount >= dtimperiod)    /* NB: sanity check */
                        dtimcount = 0;
                cfpperiod = 1;                  /* NB: no PCF support yet */
                cfpcount = 0;

                sleepduration = conf.listen_interval * intval;
                if (sleepduration <= 0)
                        sleepduration = intval;

#define FUDGE 2
                /*
                 * Pull nexttbtt forward to reflect the current
                 * TSF and calculate dtim+cfp state for the result.
                 */
                tsf = ath9k_hw_gettsf64(ah);
                tsftu = TSF_TO_TU(tsf>>32, tsf) + FUDGE;
                do {
                        nexttbtt += intval;
                        if (--dtimcount < 0) {
                                dtimcount = dtimperiod - 1;
                                if (--cfpcount < 0)
                                        cfpcount = cfpperiod - 1;
                        }
                } while (nexttbtt < tsftu);
#undef FUDGE
                memset(&bs, 0, sizeof(bs));
                bs.bs_intval = intval;
                bs.bs_nexttbtt = nexttbtt;
                bs.bs_dtimperiod = dtimperiod*intval;
                bs.bs_nextdtim = bs.bs_nexttbtt + dtimcount*intval;
                bs.bs_cfpperiod = cfpperiod*bs.bs_dtimperiod;
                bs.bs_cfpnext = bs.bs_nextdtim + cfpcount*bs.bs_dtimperiod;
                bs.bs_cfpmaxduration = 0;

                /*
                 * Calculate the number of consecutive beacons to miss
                 * before taking a BMISS interrupt.  The configuration
                 * is specified in TU so we only need calculate based
                 * on the beacon interval.  Note that we clamp the
                 * result to at most 15 beacons.
                 */
                if (sleepduration > intval) {
                        bs.bs_bmissthreshold = conf.listen_interval *
                                ATH_DEFAULT_BMISS_LIMIT / 2;
                } else {
                        bs.bs_bmissthreshold =
                                DIV_ROUND_UP(conf.bmiss_timeout, intval);
                        if (bs.bs_bmissthreshold > 15)
                                bs.bs_bmissthreshold = 15;
                        else if (bs.bs_bmissthreshold <= 0)
                                bs.bs_bmissthreshold = 1;
                }

                /*
                 * Calculate sleep duration.  The configuration is
                 * given in ms.  We insure a multiple of the beacon
                 * period is used.  Also, if the sleep duration is
                 * greater than the DTIM period then it makes senses
                 * to make it a multiple of that.
                 *
                 * XXX fixed at 100ms
                 */

                bs.bs_sleepduration = roundup(IEEE80211_MS_TO_TU(100),
                                              sleepduration);
                if (bs.bs_sleepduration > bs.bs_dtimperiod)
                        bs.bs_sleepduration = bs.bs_dtimperiod;

                DPRINTF(sc, ATH_DBG_BEACON,
                        "tsf %llu "
                        "tsf:tu %u "
                        "intval %u "
                        "nexttbtt %u "
                        "dtim %u "
                        "nextdtim %u "
                        "bmiss %u "
                        "sleep %u "
                        "cfp:period %u "
                        "maxdur %u "
                        "next %u "
                        "timoffset %u\n",
                        (unsigned long long)tsf, tsftu,
                        bs.bs_intval,
                        bs.bs_nexttbtt,
                        bs.bs_dtimperiod,
                        bs.bs_nextdtim,
                        bs.bs_bmissthreshold,
                        bs.bs_sleepduration,
                        bs.bs_cfpperiod,
                        bs.bs_cfpmaxduration,
                        bs.bs_cfpnext,
                        bs.bs_timoffset
                        );

                ath9k_hw_set_interrupts(ah, 0);
                ath9k_hw_set_sta_beacon_timers(ah, &bs);
                sc->sc_imask |= ATH9K_INT_BMISS;
                ath9k_hw_set_interrupts(ah, sc->sc_imask);
        } else {
                u64 tsf;
                u32 tsftu;
                ath9k_hw_set_interrupts(ah, 0);
                if (nexttbtt == intval)
                        intval |= ATH9K_BEACON_RESET_TSF;
                if (sc->sc_ah->ah_opmode == ATH9K_M_IBSS) {
                        /*
                         * Pull nexttbtt forward to reflect the current
                         * TSF
                         */
#define FUDGE 2
                        if (!(intval & ATH9K_BEACON_RESET_TSF)) {
                                tsf = ath9k_hw_gettsf64(ah);
                                tsftu = TSF_TO_TU((u32)(tsf>>32),
                                        (u32)tsf) + FUDGE;
                                do {
                                        nexttbtt += intval;
                                } while (nexttbtt < tsftu);
                        }
#undef FUDGE
                        DPRINTF(sc, ATH_DBG_BEACON,
                                "IBSS nexttbtt %u intval %u (%u)\n",
                                nexttbtt,
                                intval & ~ATH9K_BEACON_RESET_TSF,
                                conf.beacon_interval);

                        /*
                         * In IBSS mode enable the beacon timers but only
                         * enable SWBA interrupts if we need to manually
                         * prepare beacon frames.  Otherwise we use a
                         * self-linked tx descriptor and let the hardware
                         * deal with things.
                         */
                        intval |= ATH9K_BEACON_ENA;
                        if (!(ah->ah_caps.hw_caps & ATH9K_HW_CAP_VEOL))
                                sc->sc_imask |= ATH9K_INT_SWBA;
                        ath_beaconq_config(sc);
                } else if (sc->sc_ah->ah_opmode == ATH9K_M_HOSTAP) {
                        /*
                         * In AP mode we enable the beacon timers and
                         * SWBA interrupts to prepare beacon frames.
                         */
                        intval |= ATH9K_BEACON_ENA;
                        sc->sc_imask |= ATH9K_INT_SWBA;   /* beacon prepare */
                        ath_beaconq_config(sc);
                }
                ath9k_hw_beaconinit(ah, nexttbtt, intval);
                sc->sc_bmisscount = 0;
                ath9k_hw_set_interrupts(ah, sc->sc_imask);
                /*
                 * When using a self-linked beacon descriptor in
                 * ibss mode load it once here.
                 */
                if (sc->sc_ah->ah_opmode == ATH9K_M_IBSS &&
                    (ah->ah_caps.hw_caps & ATH9K_HW_CAP_VEOL))
                        ath_beacon_start_adhoc(sc, 0);
        }
}

void ath_beacon_sync(struct ath_softc *sc, int if_id)
{
        /*
         * Resync beacon timers using the tsf of the
         * beacon frame we just received.
         */
        ath_beacon_config(sc, if_id);
        sc->sc_flags |= SC_OP_BEACONS;
}