drivers/net/wireless/ath/ath9k/beacon.c - LeafOS-Devices/android_kernel_samsung_gta4xl - Gitiles

 /*
  * Copyright (c) 2008-2009 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 "ath9k.h"

 #define FUDGE 2

 /*
  *  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_hw *ah = sc->sc_ah;
 	struct ath9k_tx_queue_info qi;

 	ath9k_hw_get_txq_props(ah, sc->beacon.beaconq, &qi);
 	if (sc->sc_ah->opmode == NL80211_IFTYPE_AP) {
 		/* 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->beacon.beacon_qi.tqi_aifs;
 		qi.tqi_cwmin = 2*sc->beacon.beacon_qi.tqi_cwmin;
 		qi.tqi_cwmax = sc->beacon.beacon_qi.tqi_cwmax;
 	}

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

 /*
  *  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_vif *avp,
 			     struct ath_buf *bf)
 {
 	struct sk_buff *skb = bf->bf_mpdu;
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath_desc *ds;
 	struct ath9k_11n_rate_series series[4];
 	struct ath_rate_table *rt;
 	int flags, antenna, ctsrate = 0, ctsduration = 0;
 	u8 rate;

 	ds = bf->bf_desc;
 	flags = ATH9K_TXDESC_NOACK;

 	if (((sc->sc_ah->opmode == NL80211_IFTYPE_ADHOC) ||
 	     (sc->sc_ah->opmode == NL80211_IFTYPE_MESH_POINT)) &&
 	    (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
 		 * XXX assumes two antennae
 		 */
 		antenna = ((sc->beacon.ast_be_xmit / sc->nbcnvifs) & 1 ? 2 : 1);
 	}

 	ds->ds_data = bf->bf_buf_addr;

 	rt = sc->cur_rate_table;
 	rate = rt->info[0].ratecode;
 	if (sc->sc_flags & SC_OP_PREAMBLE_SHORT)
 		rate |= rt->info[0].short_preamble;

 	ath9k_hw_set11n_txdesc(ah, ds, skb->len + FCS_LEN,
 			       ATH9K_PKT_TYPE_BEACON,
 			       MAX_RATE_POWER,
 			       ATH9K_TXKEYIX_INVALID,
 			       ATH9K_KEY_TYPE_CLEAR,
 			       flags);

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

 	memset(series, 0, sizeof(struct ath9k_11n_rate_series) * 4);
 	series[0].Tries = 1;
 	series[0].Rate = rate;
 	series[0].ChSel = 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);
 }

 static struct ath_buf *ath_beacon_generate(struct ieee80211_hw *hw,
 					   struct ieee80211_vif *vif)
 {
 	struct ath_wiphy *aphy = hw->priv;
 	struct ath_softc *sc = aphy->sc;
 	struct ath_buf *bf;
 	struct ath_vif *avp;
 	struct sk_buff *skb;
 	struct ath_txq *cabq;
 	struct ieee80211_tx_info *info;
 	int cabq_depth;

 	if (aphy->state != ATH_WIPHY_ACTIVE)
 		return NULL;

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

 	if (avp->av_bcbuf == NULL)
 		return NULL;

 	/* Release the old beacon first */

 	bf = avp->av_bcbuf;
 	skb = bf->bf_mpdu;
 	if (skb) {
 		dma_unmap_single(sc->dev, bf->bf_dmacontext,
 				 skb->len, DMA_TO_DEVICE);
 		dev_kfree_skb_any(skb);
 	}

 	/* Get a new beacon from mac80211 */

 	skb = ieee80211_beacon_get(hw, vif);
 	bf->bf_mpdu = skb;
 	if (skb == NULL)
 		return NULL;
 	((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp =
 		avp->tsf_adjust;

 	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->tx.seq_no += 0x10;
 		hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
 		hdr->seq_ctrl |= cpu_to_le16(sc->tx.seq_no);
 	}

 	bf->bf_buf_addr = bf->bf_dmacontext =
 		dma_map_single(sc->dev, skb->data,
 			       skb->len, DMA_TO_DEVICE);
 	if (unlikely(dma_mapping_error(sc->dev, bf->bf_buf_addr))) {
 		dev_kfree_skb_any(skb);
 		bf->bf_mpdu = NULL;
 		DPRINTF(sc, ATH_DBG_FATAL, "dma_mapping_error on beaconing\n");
 		return NULL;
 	}

 	skb = ieee80211_get_buffered_bc(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 vif let the cab traffic continue.
 	 *  2) if there are more than one vif and we are using staggered
 	 *     beacons, then drain the cabq by dropping all the frames in
 	 *     the cabq so that the current vifs 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) {
 		if (sc->nvifs > 1) {
 			DPRINTF(sc, ATH_DBG_BEACON,
 				"Flushing previous cabq traffic\n");
 			ath_draintxq(sc, cabq, false);
 		}
 	}

 	ath_beacon_setup(sc, avp, bf);

 	while (skb) {
 		ath_tx_cabq(hw, skb);
 		skb = ieee80211_get_buffered_bc(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,
 				   struct ieee80211_vif *vif)
 {
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath_buf *bf;
 	struct ath_vif *avp;
 	struct sk_buff *skb;

 	avp = (void *)vif->drv_priv;

 	if (avp->av_bcbuf == NULL)
 		return;

 	bf = avp->av_bcbuf;
 	skb = bf->bf_mpdu;

 	ath_beacon_setup(sc, avp, bf);

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

 int ath_beaconq_setup(struct ath_hw *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_wiphy *aphy, struct ieee80211_vif *vif)
 {
 	struct ath_softc *sc = aphy->sc;
 	struct ath_vif *avp;
 	struct ath_buf *bf;
 	struct sk_buff *skb;
 	__le64 tstamp;

 	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->beacon.bbuf,
 						 struct ath_buf, list);
 		list_del(&avp->av_bcbuf->list);

 		if (sc->sc_ah->opmode == NL80211_IFTYPE_AP ||
 		    !(sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_VEOL)) {
 			int slot;
 			/*
 			 * Assign the vif 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->beacon.bslot[slot] == NULL) {
 					/*
 					 * XXX hack, space out slots to better
 					 * deal with misses
 					 */
 					if (slot+1 < ATH_BCBUF &&
 					    sc->beacon.bslot[slot+1] == NULL) {
 						avp->av_bslot = slot+1;
 						break;
 					}
 					avp->av_bslot = slot;
 					/* NB: keep looking for a double slot */
 				}
 			BUG_ON(sc->beacon.bslot[avp->av_bslot] != NULL);
 			sc->beacon.bslot[avp->av_bslot] = vif;
 			sc->beacon.bslot_aphy[avp->av_bslot] = aphy;
 			sc->nbcnvifs++;
 		}
 	}

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

 	/* NB: the beacon data buffer must be 32-bit aligned. */
 	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->beacon.bc_tstamp = le64_to_cpu(tstamp);
 	/* Calculate a TSF adjustment factor required for staggered beacons. */
 	if (avp->av_bslot > 0) {
 		u64 tsfadjust;
 		int intval;

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

 		/*
 		 * Calculate the TSF offset for this beacon slot, i.e., the
 		 * number of usecs that need to be added to the timestamp field
 		 * in Beacon and Probe Response frames. Beacon slot 0 is
 		 * processed at the correct offset, so it does not require TSF
 		 * adjustment. Other slots are adjusted to get the timestamp
 		 * close to the TBTT for the BSS.
 		 */
 		tsfadjust = intval * avp->av_bslot / ATH_BCBUF;
 		avp->tsf_adjust = cpu_to_le64(TU_TO_USEC(tsfadjust));

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

 		((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp =
 			avp->tsf_adjust;
 	} else
 		avp->tsf_adjust = cpu_to_le64(0);

 	bf->bf_mpdu = skb;
 	bf->bf_buf_addr = bf->bf_dmacontext =
 		dma_map_single(sc->dev, skb->data,
 			       skb->len, DMA_TO_DEVICE);
 	if (unlikely(dma_mapping_error(sc->dev, bf->bf_buf_addr))) {
 		dev_kfree_skb_any(skb);
 		bf->bf_mpdu = NULL;
 		DPRINTF(sc, ATH_DBG_FATAL,
 			"dma_mapping_error on beacon alloc\n");
 		return -ENOMEM;
 	}

 	return 0;
 }

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

 		if (avp->av_bslot != -1) {
 			sc->beacon.bslot[avp->av_bslot] = NULL;
 			sc->beacon.bslot_aphy[avp->av_bslot] = NULL;
 			sc->nbcnvifs--;
 		}

 		bf = avp->av_bcbuf;
 		if (bf->bf_mpdu != NULL) {
 			struct sk_buff *skb = bf->bf_mpdu;
 			dma_unmap_single(sc->dev, bf->bf_dmacontext,
 					 skb->len, DMA_TO_DEVICE);
 			dev_kfree_skb_any(skb);
 			bf->bf_mpdu = NULL;
 		}
 		list_add_tail(&bf->list, &sc->beacon.bbuf);

 		avp->av_bcbuf = NULL;
 	}
 }

 void ath_beacon_tasklet(unsigned long data)
 {
 	struct ath_softc *sc = (struct ath_softc *)data;
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath_buf *bf = NULL;
 	struct ieee80211_vif *vif;
 	struct ath_wiphy *aphy;
 	int slot;
 	u32 bfaddr, bc = 0, tsftu;
 	u64 tsf;
 	u16 intval;

 	/*
 	 * 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 (ath9k_hw_numtxpending(ah, sc->beacon.beaconq) != 0) {
 		sc->beacon.bmisscnt++;

 		if (sc->beacon.bmisscnt < BSTUCK_THRESH) {
 			DPRINTF(sc, ATH_DBG_BEACON,
 				"missed %u consecutive beacons\n",
 				sc->beacon.bmisscnt);
 		} else if (sc->beacon.bmisscnt >= BSTUCK_THRESH) {
 			DPRINTF(sc, ATH_DBG_BEACON,
 				"beacon is officially stuck\n");
 			ath_reset(sc, false);
 		}

 		return;
 	}

 	if (sc->beacon.bmisscnt != 0) {
 		DPRINTF(sc, ATH_DBG_BEACON,
 			"resume beacon xmit after %u misses\n",
 			sc->beacon.bmisscnt);
 		sc->beacon.bmisscnt = 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;
 	/*
 	 * Reverse the slot order to get slot 0 on the TBTT offset that does
 	 * not require TSF adjustment and other slots adding
 	 * slot/ATH_BCBUF * beacon_int to timestamp. For example, with
 	 * ATH_BCBUF = 4, we process beacon slots as follows: 3 2 1 0 3 2 1 ..
 	 * and slot 0 is at correct offset to TBTT.
 	 */
 	slot = ATH_BCBUF - slot - 1;
 	vif = sc->beacon.bslot[slot];
 	aphy = sc->beacon.bslot_aphy[slot];

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

 	bfaddr = 0;
 	if (vif) {
 		bf = ath_beacon_generate(aphy->hw, vif);
 		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.
 	 */
 	if (sc->beacon.updateslot == UPDATE) {
 		sc->beacon.updateslot = COMMIT; /* commit next beacon */
 		sc->beacon.slotupdate = slot;
 	} else if (sc->beacon.updateslot == COMMIT && sc->beacon.slotupdate == slot) {
 		ath9k_hw_setslottime(sc->sc_ah, sc->beacon.slottime);
 		sc->beacon.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->beacon.beaconq)) {
 			DPRINTF(sc, ATH_DBG_FATAL,
 				"beacon queue %u did not stop?\n", sc->beacon.beaconq);
 		}

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

 		sc->beacon.ast_be_xmit += bc;     /* XXX per-vif? */
 	}
 }

 /*
  * 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.
  */
 static void ath_beacon_config_ap(struct ath_softc *sc,
 				 struct ath_beacon_config *conf,
 				 struct ath_vif *avp)
 {
 	u32 nexttbtt, intval;

 	/* Configure the timers only when the TSF has to be reset */

 	if (!(sc->sc_flags & SC_OP_TSF_RESET))
 		return;

 	/* NB: the beacon interval is kept internally in TU's */
 	intval = conf->beacon_interval & ATH9K_BEACON_PERIOD;
 	intval /= ATH_BCBUF;    /* for staggered beacons */
 	nexttbtt = intval;
 	intval |= ATH9K_BEACON_RESET_TSF;

 	/*
 	 * In AP mode we enable the beacon timers and SWBA interrupts to
 	 * prepare beacon frames.
 	 */
 	intval |= ATH9K_BEACON_ENA;
 	sc->imask |= ATH9K_INT_SWBA;
 	ath_beaconq_config(sc);

 	/* Set the computed AP beacon timers */

 	ath9k_hw_set_interrupts(sc->sc_ah, 0);
 	ath9k_hw_beaconinit(sc->sc_ah, nexttbtt, intval);
 	sc->beacon.bmisscnt = 0;
 	ath9k_hw_set_interrupts(sc->sc_ah, sc->imask);

 	/* Clear the reset TSF flag, so that subsequent beacon updation
 	   will not reset the HW TSF. */

 	sc->sc_flags &= ~SC_OP_TSF_RESET;
 }

 /*
  * 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.
  */
 static void ath_beacon_config_sta(struct ath_softc *sc,
 				  struct ath_beacon_config *conf,
 				  struct ath_vif *avp)
 {
 	struct ath9k_beacon_state bs;
 	int dtimperiod, dtimcount, sleepduration;
 	int cfpperiod, cfpcount;
 	u32 nexttbtt = 0, intval, tsftu;
 	u64 tsf;

 	memset(&bs, 0, sizeof(bs));
 	intval = conf->beacon_interval & ATH9K_BEACON_PERIOD;

 	/*
 	 * 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;

 	/*
 	 * Pull nexttbtt forward to reflect the current
 	 * TSF and calculate dtim+cfp state for the result.
 	 */
 	tsf = ath9k_hw_gettsf64(sc->sc_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);

 	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 ensure 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;

 	/* TSF out of range threshold fixed at 1 second */
 	bs.bs_tsfoor_threshold = ATH9K_TSFOOR_THRESHOLD;

 	DPRINTF(sc, ATH_DBG_BEACON, "tsf: %llu tsftu: %u\n", tsf, tsftu);
 	DPRINTF(sc, ATH_DBG_BEACON,
 		"bmiss: %u sleep: %u cfp-period: %u maxdur: %u next: %u\n",
 		bs.bs_bmissthreshold, bs.bs_sleepduration,
 		bs.bs_cfpperiod, bs.bs_cfpmaxduration, bs.bs_cfpnext);

 	/* Set the computed STA beacon timers */

 	ath9k_hw_set_interrupts(sc->sc_ah, 0);
 	ath9k_hw_set_sta_beacon_timers(sc->sc_ah, &bs);
 	sc->imask |= ATH9K_INT_BMISS;
 	ath9k_hw_set_interrupts(sc->sc_ah, sc->imask);
 }

 static void ath_beacon_config_adhoc(struct ath_softc *sc,
 				    struct ath_beacon_config *conf,
 				    struct ath_vif *avp,
 				    struct ieee80211_vif *vif)
 {
 	u64 tsf;
 	u32 tsftu, intval, nexttbtt;

 	intval = conf->beacon_interval & ATH9K_BEACON_PERIOD;

 	/* Pull nexttbtt forward to reflect the current TSF */

 	nexttbtt = TSF_TO_TU(sc->beacon.bc_tstamp >> 32, sc->beacon.bc_tstamp);
 	if (nexttbtt == 0)
                 nexttbtt = intval;
         else if (intval)
                 nexttbtt = roundup(nexttbtt, intval);

 	tsf = ath9k_hw_gettsf64(sc->sc_ah);
 	tsftu = TSF_TO_TU((u32)(tsf>>32), (u32)tsf) + FUDGE;
 	do {
 		nexttbtt += intval;
 	} while (nexttbtt < tsftu);

 	DPRINTF(sc, ATH_DBG_BEACON,
 		"IBSS nexttbtt %u intval %u (%u)\n",
 		nexttbtt, intval, 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 (!(sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_VEOL))
 		sc->imask |= ATH9K_INT_SWBA;

 	ath_beaconq_config(sc);

 	/* Set the computed ADHOC beacon timers */

 	ath9k_hw_set_interrupts(sc->sc_ah, 0);
 	ath9k_hw_beaconinit(sc->sc_ah, nexttbtt, intval);
 	sc->beacon.bmisscnt = 0;
 	ath9k_hw_set_interrupts(sc->sc_ah, sc->imask);

 	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_VEOL)
 		ath_beacon_start_adhoc(sc, vif);
 }

 void ath_beacon_config(struct ath_softc *sc, struct ieee80211_vif *vif)
 {
 	struct ath_beacon_config conf;

 	/* Setup the beacon configuration parameters */

 	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;

 	if (vif) {
 		struct ath_vif *avp = (struct ath_vif *)vif->drv_priv;

 		switch(avp->av_opmode) {
 		case NL80211_IFTYPE_AP:
 			ath_beacon_config_ap(sc, &conf, avp);
 			break;
 		case NL80211_IFTYPE_ADHOC:
 		case NL80211_IFTYPE_MESH_POINT:
 			ath_beacon_config_adhoc(sc, &conf, avp, vif);
 			break;
 		case NL80211_IFTYPE_STATION:
 			ath_beacon_config_sta(sc, &conf, avp);
 			break;
 		default:
 			DPRINTF(sc, ATH_DBG_CONFIG,
 				"Unsupported beaconing mode\n");
 			return;
 		}

 		sc->sc_flags |= SC_OP_BEACONS;
 	}
 }
	/*
	* Copyright (c) 2008-2009 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 "ath9k.h"

	#define FUDGE 2

	/*
	* 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_hw *ah = sc->sc_ah;
	struct ath9k_tx_queue_info qi;

	ath9k_hw_get_txq_props(ah, sc->beacon.beaconq, &qi);
	if (sc->sc_ah->opmode == NL80211_IFTYPE_AP) {
	/* 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->beacon.beacon_qi.tqi_aifs;
	qi.tqi_cwmin = 2*sc->beacon.beacon_qi.tqi_cwmin;
	qi.tqi_cwmax = sc->beacon.beacon_qi.tqi_cwmax;
	}

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

	/*
	* 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_vif avp,
	struct ath_buf *bf)
	{
	struct sk_buff *skb = bf->bf_mpdu;
	struct ath_hw *ah = sc->sc_ah;
	struct ath_desc *ds;
	struct ath9k_11n_rate_series series[4];
	struct ath_rate_table *rt;
	int flags, antenna, ctsrate = 0, ctsduration = 0;
	u8 rate;

	ds = bf->bf_desc;
	flags = ATH9K_TXDESC_NOACK;

	if (((sc->sc_ah->opmode == NL80211_IFTYPE_ADHOC) \|\|
	(sc->sc_ah->opmode == NL80211_IFTYPE_MESH_POINT)) &&
	(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
	* XXX assumes two antennae
	*/
	antenna = ((sc->beacon.ast_be_xmit / sc->nbcnvifs) & 1 ? 2 : 1);
	}

	ds->ds_data = bf->bf_buf_addr;

	rt = sc->cur_rate_table;
	rate = rt->info[0].ratecode;
	if (sc->sc_flags & SC_OP_PREAMBLE_SHORT)
	rate \|= rt->info[0].short_preamble;

	ath9k_hw_set11n_txdesc(ah, ds, skb->len + FCS_LEN,
	ATH9K_PKT_TYPE_BEACON,
	MAX_RATE_POWER,
	ATH9K_TXKEYIX_INVALID,
	ATH9K_KEY_TYPE_CLEAR,
	flags);

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

	memset(series, 0, sizeof(struct ath9k_11n_rate_series) * 4);
	series[0].Tries = 1;
	series[0].Rate = rate;
	series[0].ChSel = 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);
	}

	static struct ath_buf ath_beacon_generate(struct ieee80211_hw hw,
	struct ieee80211_vif *vif)
	{
	struct ath_wiphy *aphy = hw->priv;
	struct ath_softc *sc = aphy->sc;
	struct ath_buf *bf;
	struct ath_vif *avp;
	struct sk_buff *skb;
	struct ath_txq *cabq;
	struct ieee80211_tx_info *info;
	int cabq_depth;

	if (aphy->state != ATH_WIPHY_ACTIVE)
	return NULL;

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

	if (avp->av_bcbuf == NULL)
	return NULL;

	/* Release the old beacon first */

	bf = avp->av_bcbuf;
	skb = bf->bf_mpdu;
	if (skb) {
	dma_unmap_single(sc->dev, bf->bf_dmacontext,
	skb->len, DMA_TO_DEVICE);
	dev_kfree_skb_any(skb);
	}

	/* Get a new beacon from mac80211 */

	skb = ieee80211_beacon_get(hw, vif);
	bf->bf_mpdu = skb;
	if (skb == NULL)
	return NULL;
	((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp =
	avp->tsf_adjust;

	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->tx.seq_no += 0x10;
	hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
	hdr->seq_ctrl \|= cpu_to_le16(sc->tx.seq_no);
	}

	bf->bf_buf_addr = bf->bf_dmacontext =
	dma_map_single(sc->dev, skb->data,
	skb->len, DMA_TO_DEVICE);
	if (unlikely(dma_mapping_error(sc->dev, bf->bf_buf_addr))) {
	dev_kfree_skb_any(skb);
	bf->bf_mpdu = NULL;
	DPRINTF(sc, ATH_DBG_FATAL, "dma_mapping_error on beaconing\n");
	return NULL;
	}

	skb = ieee80211_get_buffered_bc(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 vif let the cab traffic continue.
	* 2) if there are more than one vif and we are using staggered
	* beacons, then drain the cabq by dropping all the frames in
	* the cabq so that the current vifs 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) {
	if (sc->nvifs > 1) {
	DPRINTF(sc, ATH_DBG_BEACON,
	"Flushing previous cabq traffic\n");
	ath_draintxq(sc, cabq, false);
	}
	}

	ath_beacon_setup(sc, avp, bf);

	while (skb) {
	ath_tx_cabq(hw, skb);
	skb = ieee80211_get_buffered_bc(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,
	struct ieee80211_vif *vif)
	{
	struct ath_hw *ah = sc->sc_ah;
	struct ath_buf *bf;
	struct ath_vif *avp;
	struct sk_buff *skb;

	avp = (void *)vif->drv_priv;

	if (avp->av_bcbuf == NULL)
	return;

	bf = avp->av_bcbuf;
	skb = bf->bf_mpdu;

	ath_beacon_setup(sc, avp, bf);

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

	int ath_beaconq_setup(struct ath_hw *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_wiphy aphy, struct ieee80211_vif vif)
	{
	struct ath_softc *sc = aphy->sc;
	struct ath_vif *avp;
	struct ath_buf *bf;
	struct sk_buff *skb;
	__le64 tstamp;

	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->beacon.bbuf,
	struct ath_buf, list);
	list_del(&avp->av_bcbuf->list);

	if (sc->sc_ah->opmode == NL80211_IFTYPE_AP \|\|
	!(sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_VEOL)) {
	int slot;
	/*
	* Assign the vif 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->beacon.bslot[slot] == NULL) {
	/*
	* XXX hack, space out slots to better
	* deal with misses
	*/
	if (slot+1 < ATH_BCBUF &&
	sc->beacon.bslot[slot+1] == NULL) {
	avp->av_bslot = slot+1;
	break;
	}
	avp->av_bslot = slot;
	/* NB: keep looking for a double slot */
	}
	BUG_ON(sc->beacon.bslot[avp->av_bslot] != NULL);
	sc->beacon.bslot[avp->av_bslot] = vif;
	sc->beacon.bslot_aphy[avp->av_bslot] = aphy;
	sc->nbcnvifs++;
	}
	}

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

	/* NB: the beacon data buffer must be 32-bit aligned. */
	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->beacon.bc_tstamp = le64_to_cpu(tstamp);
	/* Calculate a TSF adjustment factor required for staggered beacons. */
	if (avp->av_bslot > 0) {
	u64 tsfadjust;
	int intval;

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

	/*
	* Calculate the TSF offset for this beacon slot, i.e., the
	* number of usecs that need to be added to the timestamp field
	* in Beacon and Probe Response frames. Beacon slot 0 is
	* processed at the correct offset, so it does not require TSF
	* adjustment. Other slots are adjusted to get the timestamp
	* close to the TBTT for the BSS.
	*/
	tsfadjust = intval * avp->av_bslot / ATH_BCBUF;
	avp->tsf_adjust = cpu_to_le64(TU_TO_USEC(tsfadjust));

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

	((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp =
	avp->tsf_adjust;
	} else
	avp->tsf_adjust = cpu_to_le64(0);

	bf->bf_mpdu = skb;
	bf->bf_buf_addr = bf->bf_dmacontext =
	dma_map_single(sc->dev, skb->data,
	skb->len, DMA_TO_DEVICE);
	if (unlikely(dma_mapping_error(sc->dev, bf->bf_buf_addr))) {
	dev_kfree_skb_any(skb);
	bf->bf_mpdu = NULL;
	DPRINTF(sc, ATH_DBG_FATAL,
	"dma_mapping_error on beacon alloc\n");
	return -ENOMEM;
	}

	return 0;
	}

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

	if (avp->av_bslot != -1) {
	sc->beacon.bslot[avp->av_bslot] = NULL;
	sc->beacon.bslot_aphy[avp->av_bslot] = NULL;
	sc->nbcnvifs--;
	}

	bf = avp->av_bcbuf;
	if (bf->bf_mpdu != NULL) {
	struct sk_buff *skb = bf->bf_mpdu;
	dma_unmap_single(sc->dev, bf->bf_dmacontext,
	skb->len, DMA_TO_DEVICE);
	dev_kfree_skb_any(skb);
	bf->bf_mpdu = NULL;
	}
	list_add_tail(&bf->list, &sc->beacon.bbuf);

	avp->av_bcbuf = NULL;
	}
	}

	void ath_beacon_tasklet(unsigned long data)
	{
	struct ath_softc sc = (struct ath_softc )data;
	struct ath_hw *ah = sc->sc_ah;
	struct ath_buf *bf = NULL;
	struct ieee80211_vif *vif;
	struct ath_wiphy *aphy;
	int slot;
	u32 bfaddr, bc = 0, tsftu;
	u64 tsf;
	u16 intval;

	/*
	* 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 (ath9k_hw_numtxpending(ah, sc->beacon.beaconq) != 0) {
	sc->beacon.bmisscnt++;

	if (sc->beacon.bmisscnt < BSTUCK_THRESH) {
	DPRINTF(sc, ATH_DBG_BEACON,
	"missed %u consecutive beacons\n",
	sc->beacon.bmisscnt);
	} else if (sc->beacon.bmisscnt >= BSTUCK_THRESH) {
	DPRINTF(sc, ATH_DBG_BEACON,
	"beacon is officially stuck\n");
	ath_reset(sc, false);
	}

	return;
	}

	if (sc->beacon.bmisscnt != 0) {
	DPRINTF(sc, ATH_DBG_BEACON,
	"resume beacon xmit after %u misses\n",
	sc->beacon.bmisscnt);
	sc->beacon.bmisscnt = 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;
	/*
	* Reverse the slot order to get slot 0 on the TBTT offset that does
	* not require TSF adjustment and other slots adding
	* slot/ATH_BCBUF * beacon_int to timestamp. For example, with
	* ATH_BCBUF = 4, we process beacon slots as follows: 3 2 1 0 3 2 1 ..
	* and slot 0 is at correct offset to TBTT.
	*/
	slot = ATH_BCBUF - slot - 1;
	vif = sc->beacon.bslot[slot];
	aphy = sc->beacon.bslot_aphy[slot];

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

	bfaddr = 0;
	if (vif) {
	bf = ath_beacon_generate(aphy->hw, vif);
	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.
	*/
	if (sc->beacon.updateslot == UPDATE) {
	sc->beacon.updateslot = COMMIT; /* commit next beacon */
	sc->beacon.slotupdate = slot;
	} else if (sc->beacon.updateslot == COMMIT && sc->beacon.slotupdate == slot) {
	ath9k_hw_setslottime(sc->sc_ah, sc->beacon.slottime);
	sc->beacon.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->beacon.beaconq)) {
	DPRINTF(sc, ATH_DBG_FATAL,
	"beacon queue %u did not stop?\n", sc->beacon.beaconq);
	}

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

	sc->beacon.ast_be_xmit += bc; /* XXX per-vif? */
	}
	}

	/*
	* 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.
	*/
	static void ath_beacon_config_ap(struct ath_softc *sc,
	struct ath_beacon_config *conf,
	struct ath_vif *avp)
	{
	u32 nexttbtt, intval;

	/* Configure the timers only when the TSF has to be reset */

	if (!(sc->sc_flags & SC_OP_TSF_RESET))
	return;

	/* NB: the beacon interval is kept internally in TU's */
	intval = conf->beacon_interval & ATH9K_BEACON_PERIOD;
	intval /= ATH_BCBUF; /* for staggered beacons */
	nexttbtt = intval;
	intval \|= ATH9K_BEACON_RESET_TSF;

	/*
	* In AP mode we enable the beacon timers and SWBA interrupts to
	* prepare beacon frames.
	*/
	intval \|= ATH9K_BEACON_ENA;
	sc->imask \|= ATH9K_INT_SWBA;
	ath_beaconq_config(sc);

	/* Set the computed AP beacon timers */

	ath9k_hw_set_interrupts(sc->sc_ah, 0);
	ath9k_hw_beaconinit(sc->sc_ah, nexttbtt, intval);
	sc->beacon.bmisscnt = 0;
	ath9k_hw_set_interrupts(sc->sc_ah, sc->imask);

	/* Clear the reset TSF flag, so that subsequent beacon updation
	will not reset the HW TSF. */

	sc->sc_flags &= ~SC_OP_TSF_RESET;
	}

	/*
	* 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.
	*/
	static void ath_beacon_config_sta(struct ath_softc *sc,
	struct ath_beacon_config *conf,
	struct ath_vif *avp)
	{
	struct ath9k_beacon_state bs;
	int dtimperiod, dtimcount, sleepduration;
	int cfpperiod, cfpcount;
	u32 nexttbtt = 0, intval, tsftu;
	u64 tsf;

	memset(&bs, 0, sizeof(bs));
	intval = conf->beacon_interval & ATH9K_BEACON_PERIOD;

	/*
	* 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;

	/*
	* Pull nexttbtt forward to reflect the current
	* TSF and calculate dtim+cfp state for the result.
	*/
	tsf = ath9k_hw_gettsf64(sc->sc_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);

	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 ensure 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;

	/* TSF out of range threshold fixed at 1 second */
	bs.bs_tsfoor_threshold = ATH9K_TSFOOR_THRESHOLD;

	DPRINTF(sc, ATH_DBG_BEACON, "tsf: %llu tsftu: %u\n", tsf, tsftu);
	DPRINTF(sc, ATH_DBG_BEACON,
	"bmiss: %u sleep: %u cfp-period: %u maxdur: %u next: %u\n",
	bs.bs_bmissthreshold, bs.bs_sleepduration,
	bs.bs_cfpperiod, bs.bs_cfpmaxduration, bs.bs_cfpnext);

	/* Set the computed STA beacon timers */

	ath9k_hw_set_interrupts(sc->sc_ah, 0);
	ath9k_hw_set_sta_beacon_timers(sc->sc_ah, &bs);
	sc->imask \|= ATH9K_INT_BMISS;
	ath9k_hw_set_interrupts(sc->sc_ah, sc->imask);
	}

	static void ath_beacon_config_adhoc(struct ath_softc *sc,
	struct ath_beacon_config *conf,
	struct ath_vif *avp,
	struct ieee80211_vif *vif)
	{
	u64 tsf;
	u32 tsftu, intval, nexttbtt;

	intval = conf->beacon_interval & ATH9K_BEACON_PERIOD;

	/* Pull nexttbtt forward to reflect the current TSF */

	nexttbtt = TSF_TO_TU(sc->beacon.bc_tstamp >> 32, sc->beacon.bc_tstamp);
	if (nexttbtt == 0)
	nexttbtt = intval;
	else if (intval)
	nexttbtt = roundup(nexttbtt, intval);

	tsf = ath9k_hw_gettsf64(sc->sc_ah);
	tsftu = TSF_TO_TU((u32)(tsf>>32), (u32)tsf) + FUDGE;
	do {
	nexttbtt += intval;
	} while (nexttbtt < tsftu);

	DPRINTF(sc, ATH_DBG_BEACON,
	"IBSS nexttbtt %u intval %u (%u)\n",
	nexttbtt, intval, 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 (!(sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_VEOL))
	sc->imask \|= ATH9K_INT_SWBA;

	ath_beaconq_config(sc);

	/* Set the computed ADHOC beacon timers */

	ath9k_hw_set_interrupts(sc->sc_ah, 0);
	ath9k_hw_beaconinit(sc->sc_ah, nexttbtt, intval);
	sc->beacon.bmisscnt = 0;
	ath9k_hw_set_interrupts(sc->sc_ah, sc->imask);

	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_VEOL)
	ath_beacon_start_adhoc(sc, vif);
	}

	void ath_beacon_config(struct ath_softc sc, struct ieee80211_vif vif)
	{
	struct ath_beacon_config conf;

	/* Setup the beacon configuration parameters */

	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;

	if (vif) {
	struct ath_vif avp = (struct ath_vif )vif->drv_priv;

	switch(avp->av_opmode) {
	case NL80211_IFTYPE_AP:
	ath_beacon_config_ap(sc, &conf, avp);
	break;
	case NL80211_IFTYPE_ADHOC:
	case NL80211_IFTYPE_MESH_POINT:
	ath_beacon_config_adhoc(sc, &conf, avp, vif);
	break;
	case NL80211_IFTYPE_STATION:
	ath_beacon_config_sta(sc, &conf, avp);
	break;
	default:
	DPRINTF(sc, ATH_DBG_CONFIG,
	"Unsupported beaconing mode\n");
	return;
	}

	sc->sc_flags \|= SC_OP_BEACONS;
	}
	}