ath9k: Add new Atheros IEEE 802.11n driver

This adds the new mac80211 11n ath9k Atheros driver. Only STA support
is currently enabled and tested.

Signed-off-by: Senthil Balasubramanian <senthilkumar@atheros.com>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Jack Howarth <howarth@bromo.msbb.uc.edu>
Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: Sujith Manoharan <Sujith.Manoharan@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 2870 insertions, 0 deletions

diff --git a/drivers/net/wireless/ath9k/xmit.c b/drivers/net/wireless/ath9k/xmit.c
new file mode 100644
index 000000000000..f0297ee5d053
--- /dev/null
+++ b/drivers/net/wireless/ath9k/xmit.c
@@ -0,0 +1,2870 @@
+/*
+ * 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.
+ */
+
+/*
+ * Implementation of transmit path.
+ */
+
+#include "core.h"
+
+#define BITS_PER_BYTE           8
+#define OFDM_PLCP_BITS          22
+#define HT_RC_2_MCS(_rc)        ((_rc) & 0x0f)
+#define HT_RC_2_STREAMS(_rc)    ((((_rc) & 0x78) >> 3) + 1)
+#define L_STF                   8
+#define L_LTF                   8
+#define L_SIG                   4
+#define HT_SIG                  8
+#define HT_STF                  4
+#define HT_LTF(_ns)             (4 * (_ns))
+#define SYMBOL_TIME(_ns)        ((_ns) << 2) /* ns * 4 us */
+#define SYMBOL_TIME_HALFGI(_ns) (((_ns) * 18 + 4) / 5)  /* ns * 3.6 us */
+#define NUM_SYMBOLS_PER_USEC(_usec) (_usec >> 2)
+#define NUM_SYMBOLS_PER_USEC_HALFGI(_usec) (((_usec*5)-4)/18)
+
+#define OFDM_SIFS_TIME    	    16
+
+static u32 bits_per_symbol[][2] = {
+	/* 20MHz 40MHz */
+	{    26,   54 },     /*  0: BPSK */
+	{    52,  108 },     /*  1: QPSK 1/2 */
+	{    78,  162 },     /*  2: QPSK 3/4 */
+	{   104,  216 },     /*  3: 16-QAM 1/2 */
+	{   156,  324 },     /*  4: 16-QAM 3/4 */
+	{   208,  432 },     /*  5: 64-QAM 2/3 */
+	{   234,  486 },     /*  6: 64-QAM 3/4 */
+	{   260,  540 },     /*  7: 64-QAM 5/6 */
+	{    52,  108 },     /*  8: BPSK */
+	{   104,  216 },     /*  9: QPSK 1/2 */
+	{   156,  324 },     /* 10: QPSK 3/4 */
+	{   208,  432 },     /* 11: 16-QAM 1/2 */
+	{   312,  648 },     /* 12: 16-QAM 3/4 */
+	{   416,  864 },     /* 13: 64-QAM 2/3 */
+	{   468,  972 },     /* 14: 64-QAM 3/4 */
+	{   520, 1080 },     /* 15: 64-QAM 5/6 */
+};
+
+#define IS_HT_RATE(_rate)     ((_rate) & 0x80)
+
+/*
+ * Insert a chain of ath_buf (descriptors) on a multicast txq
+ * but do NOT start tx DMA on this queue.
+ * NB: must be called with txq lock held
+ */
+
+static void ath_tx_mcastqaddbuf(struct ath_softc *sc,
+				struct ath_txq *txq,
+				struct list_head *head)
+{
+	struct ath_hal *ah = sc->sc_ah;
+	struct ath_buf *bf;
+
+	if (list_empty(head))
+		return;
+
+	/*
+	 * Insert the frame on the outbound list and
+	 * pass it on to the hardware.
+	 */
+	bf = list_first_entry(head, struct ath_buf, list);
+
+	/*
+	 * The CAB queue is started from the SWBA handler since
+	 * frames only go out on DTIM and to avoid possible races.
+	 */
+	ath9k_hw_set_interrupts(ah, 0);
+
+	/*
+	 * If there is anything in the mcastq, we want to set
+	 * the "more data" bit in the last item in the queue to
+	 * indicate that there is "more data". It makes sense to add
+	 * it here since you are *always* going to have
+	 * more data when adding to this queue, no matter where
+	 * you call from.
+	 */
+
+	if (txq->axq_depth) {
+		struct ath_buf *lbf;
+		struct ieee80211_hdr *hdr;
+
+		/*
+		 * Add the "more data flag" to the last frame
+		 */
+
+		lbf = list_entry(txq->axq_q.prev, struct ath_buf, list);
+		hdr = (struct ieee80211_hdr *)
+			((struct sk_buff *)(lbf->bf_mpdu))->data;
+		hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREDATA);
+	}
+
+	/*
+	 * Now, concat the frame onto the queue
+	 */
+	list_splice_tail_init(head, &txq->axq_q);
+	txq->axq_depth++;
+	txq->axq_totalqueued++;
+	txq->axq_linkbuf = list_entry(txq->axq_q.prev, struct ath_buf, list);
+
+	DPRINTF(sc, ATH_DBG_QUEUE,
+		"%s: txq depth = %d\n", __func__, txq->axq_depth);
+	if (txq->axq_link != NULL) {
+		*txq->axq_link = bf->bf_daddr;
+		DPRINTF(sc, ATH_DBG_XMIT,
+			"%s: link[%u](%p)=%llx (%p)\n",
+			__func__,
+			txq->axq_qnum, txq->axq_link,
+			ito64(bf->bf_daddr), bf->bf_desc);
+	}
+	txq->axq_link = &(bf->bf_lastbf->bf_desc->ds_link);
+	ath9k_hw_set_interrupts(ah, sc->sc_imask);
+}
+
+/*
+ * Insert a chain of ath_buf (descriptors) on a txq and
+ * assume the descriptors are already chained together by caller.
+ * NB: must be called with txq lock held
+ */
+
+static void ath_tx_txqaddbuf(struct ath_softc *sc,
+		struct ath_txq *txq, struct list_head *head)
+{
+	struct ath_hal *ah = sc->sc_ah;
+	struct ath_buf *bf;
+	/*
+	 * Insert the frame on the outbound list and
+	 * pass it on to the hardware.
+	 */
+
+	if (list_empty(head))
+		return;
+
+	bf = list_first_entry(head, struct ath_buf, list);
+
+	list_splice_tail_init(head, &txq->axq_q);
+	txq->axq_depth++;
+	txq->axq_totalqueued++;
+	txq->axq_linkbuf = list_entry(txq->axq_q.prev, struct ath_buf, list);
+
+	DPRINTF(sc, ATH_DBG_QUEUE,
+		"%s: txq depth = %d\n", __func__, txq->axq_depth);
+
+	if (txq->axq_link == NULL) {
+		ath9k_hw_puttxbuf(ah, txq->axq_qnum, bf->bf_daddr);
+		DPRINTF(sc, ATH_DBG_XMIT,
+			"%s: TXDP[%u] = %llx (%p)\n",
+			__func__, txq->axq_qnum,
+			ito64(bf->bf_daddr), bf->bf_desc);
+	} else {
+		*txq->axq_link = bf->bf_daddr;
+		DPRINTF(sc, ATH_DBG_XMIT, "%s: link[%u] (%p)=%llx (%p)\n",
+			__func__,
+			txq->axq_qnum, txq->axq_link,
+			ito64(bf->bf_daddr), bf->bf_desc);
+	}
+	txq->axq_link = &(bf->bf_lastbf->bf_desc->ds_link);
+	ath9k_hw_txstart(ah, txq->axq_qnum);
+}
+
+/* Get transmit rate index using rate in Kbps */
+
+static int ath_tx_findindex(const struct ath9k_rate_table *rt, int rate)
+{
+	int i;
+	int ndx = 0;
+
+	for (i = 0; i < rt->rateCount; i++) {
+		if (rt->info[i].rateKbps == rate) {
+			ndx = i;
+			break;
+		}
+	}
+
+	return ndx;
+}
+
+/* Check if it's okay to send out aggregates */
+
+static int ath_aggr_query(struct ath_softc *sc,
+	struct ath_node *an, u8 tidno)
+{
+	struct ath_atx_tid *tid;
+	tid = ATH_AN_2_TID(an, tidno);
+
+	if (tid->addba_exchangecomplete || tid->addba_exchangeinprogress)
+		return 1;
+	else
+		return 0;
+}
+
+static enum ath9k_pkt_type get_hal_packet_type(struct ieee80211_hdr *hdr)
+{
+	enum ath9k_pkt_type htype;
+	__le16 fc;
+
+	fc = hdr->frame_control;
+
+	/* Calculate Atheros packet type from IEEE80211 packet header */
+
+	if (ieee80211_is_beacon(fc))
+		htype = ATH9K_PKT_TYPE_BEACON;
+	else if (ieee80211_is_probe_resp(fc))
+		htype = ATH9K_PKT_TYPE_PROBE_RESP;
+	else if (ieee80211_is_atim(fc))
+		htype = ATH9K_PKT_TYPE_ATIM;
+	else if (ieee80211_is_pspoll(fc))
+		htype = ATH9K_PKT_TYPE_PSPOLL;
+	else
+		htype = ATH9K_PKT_TYPE_NORMAL;
+
+	return htype;
+}
+
+static void fill_min_rates(struct sk_buff *skb, struct ath_tx_control *txctl)
+{
+	struct ieee80211_hdr *hdr;
+	struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
+	struct ath_tx_info_priv *tx_info_priv;
+	__le16 fc;
+
+	hdr = (struct ieee80211_hdr *)skb->data;
+	fc = hdr->frame_control;
+	tx_info_priv = (struct ath_tx_info_priv *)tx_info->driver_data[0];
+
+	if (ieee80211_is_mgmt(fc) || ieee80211_is_ctl(fc)) {
+		txctl->use_minrate = 1;
+		txctl->min_rate = tx_info_priv->min_rate;
+	} else if (ieee80211_is_data(fc)) {
+		if (ieee80211_is_nullfunc(fc) ||
+			/* Port Access Entity (IEEE 802.1X) */
+			(skb->protocol == cpu_to_be16(0x888E))) {
+			txctl->use_minrate = 1;
+			txctl->min_rate = tx_info_priv->min_rate;
+		}
+		if (is_multicast_ether_addr(hdr->addr1))
+			txctl->mcast_rate = tx_info_priv->min_rate;
+	}
+
+}
+
+/* This function will setup additional txctl information, mostly rate stuff */
+/* FIXME: seqno, ps */
+static int ath_tx_prepare(struct ath_softc *sc,
+			  struct sk_buff *skb,
+			  struct ath_tx_control *txctl)
+{
+	struct ieee80211_hw *hw = sc->hw;
+	struct ieee80211_hdr *hdr;
+	struct ath_rc_series *rcs;
+	struct ath_txq *txq = NULL;
+	const struct ath9k_rate_table *rt;
+	struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
+	struct ath_tx_info_priv *tx_info_priv;
+	int hdrlen;
+	u8 rix, antenna;
+	__le16 fc;
+	u8 *qc;
+
+	memset(txctl, 0, sizeof(struct ath_tx_control));
+
+	txctl->dev = sc;
+	hdr = (struct ieee80211_hdr *)skb->data;
+	hdrlen = ieee80211_get_hdrlen_from_skb(skb);
+	fc = hdr->frame_control;
+
+	rt = sc->sc_currates;
+	BUG_ON(!rt);
+
+	/* Fill misc fields */
+
+	spin_lock_bh(&sc->node_lock);
+	txctl->an = ath_node_get(sc, hdr->addr1);
+	/* create a temp node, if the node is not there already */
+	if (!txctl->an)
+		txctl->an = ath_node_attach(sc, hdr->addr1, 0);
+	spin_unlock_bh(&sc->node_lock);
+
+	if (ieee80211_is_data_qos(fc)) {
+		qc = ieee80211_get_qos_ctl(hdr);
+		txctl->tidno = qc[0] & 0xf;
+	}
+
+	txctl->if_id = 0;
+	txctl->nextfraglen = 0;
+	txctl->frmlen = skb->len + FCS_LEN - (hdrlen & 3);
+	txctl->txpower = MAX_RATE_POWER; /* FIXME */
+
+	/* Fill Key related fields */
+
+	txctl->keytype = ATH9K_KEY_TYPE_CLEAR;
+	txctl->keyix = ATH9K_TXKEYIX_INVALID;
+
+	if (tx_info->control.hw_key) {
+		txctl->keyix = tx_info->control.hw_key->hw_key_idx;
+		txctl->frmlen += tx_info->control.icv_len;
+
+		if (sc->sc_keytype == ATH9K_CIPHER_WEP)
+			txctl->keytype = ATH9K_KEY_TYPE_WEP;
+		else if (sc->sc_keytype == ATH9K_CIPHER_TKIP)
+			txctl->keytype = ATH9K_KEY_TYPE_TKIP;
+		else if (sc->sc_keytype == ATH9K_CIPHER_AES_CCM)
+			txctl->keytype = ATH9K_KEY_TYPE_AES;
+	}
+
+	/* Fill packet type */
+
+	txctl->atype = get_hal_packet_type(hdr);
+
+	/* Fill qnum */
+
+	txctl->qnum = ath_get_hal_qnum(skb_get_queue_mapping(skb), sc);
+	txq = &sc->sc_txq[txctl->qnum];
+	spin_lock_bh(&txq->axq_lock);
+
+	/* Try to avoid running out of descriptors */
+	if (txq->axq_depth >= (ATH_TXBUF - 20)) {
+		DPRINTF(sc, ATH_DBG_FATAL,
+			"%s: TX queue: %d is full, depth: %d\n",
+			__func__,
+			txctl->qnum,
+			txq->axq_depth);
+		ieee80211_stop_queue(hw, skb_get_queue_mapping(skb));
+		txq->stopped = 1;
+		spin_unlock_bh(&txq->axq_lock);
+		return -1;
+	}
+
+	spin_unlock_bh(&txq->axq_lock);
+
+	/* Fill rate */
+
+	fill_min_rates(skb, txctl);
+
+	/* Fill flags */
+
+	txctl->flags = ATH9K_TXDESC_CLRDMASK;    /* needed for crypto errors */
+
+	if (tx_info->flags & IEEE80211_TX_CTL_NO_ACK)
+		tx_info->flags |= ATH9K_TXDESC_NOACK;
+	if (tx_info->flags & IEEE80211_TX_CTL_USE_RTS_CTS)
+		tx_info->flags |= ATH9K_TXDESC_RTSENA;
+
+	/*
+	 * Setup for rate calculations.
+	 */
+	tx_info_priv = (struct ath_tx_info_priv *)tx_info->driver_data[0];
+	rcs = tx_info_priv->rcs;
+
+	if (ieee80211_is_data(fc) && !txctl->use_minrate) {
+
+		/* Enable HT only for DATA frames and not for EAPOL */
+		txctl->ht = (hw->conf.ht_conf.ht_supported &&
+			    (tx_info->flags & IEEE80211_TX_CTL_AMPDU));
+
+		if (is_multicast_ether_addr(hdr->addr1)) {
+			rcs[0].rix = (u8)
+				ath_tx_findindex(rt, txctl->mcast_rate);
+
+			/*
+			 * mcast packets are not re-tried.
+			 */
+			rcs[0].tries = 1;
+		}
+		/* For HT capable stations, we save tidno for later use.
+		 * We also override seqno set by upper layer with the one
+		 * in tx aggregation state.
+		 *
+		 * First, the fragmentation stat is determined.
+		 * If fragmentation is on, the sequence number is
+		 * not overridden, since it has been
+		 * incremented by the fragmentation routine.
+		 */
+		if (likely(!(txctl->flags & ATH9K_TXDESC_FRAG_IS_ON)) &&
+			txctl->ht && sc->sc_txaggr) {
+			struct ath_atx_tid *tid;
+
+			tid = ATH_AN_2_TID(txctl->an, txctl->tidno);
+
+			hdr->seq_ctrl = cpu_to_le16(tid->seq_next <<
+				IEEE80211_SEQ_SEQ_SHIFT);
+			txctl->seqno = tid->seq_next;
+			INCR(tid->seq_next, IEEE80211_SEQ_MAX);
+		}
+	} else {
+		/* for management and control frames,
+		 * or for NULL and EAPOL frames */
+		if (txctl->min_rate)
+			rcs[0].rix = ath_rate_findrateix(sc, txctl->min_rate);
+		else
+			rcs[0].rix = sc->sc_minrateix;
+		rcs[0].tries = ATH_MGT_TXMAXTRY;
+	}
+	rix = rcs[0].rix;
+
+	/*
+	 * Calculate duration.  This logically belongs in the 802.11
+	 * layer but it lacks sufficient information to calculate it.
+	 */
+	if ((txctl->flags & ATH9K_TXDESC_NOACK) == 0 && !ieee80211_is_ctl(fc)) {
+		u16 dur;
+		/*
+		 * XXX not right with fragmentation.
+		 */
+		if (sc->sc_flags & ATH_PREAMBLE_SHORT)
+			dur = rt->info[rix].spAckDuration;
+		else
+			dur = rt->info[rix].lpAckDuration;
+
+		if (le16_to_cpu(hdr->frame_control) &
+				IEEE80211_FCTL_MOREFRAGS) {
+			dur += dur;  /* Add additional 'SIFS + ACK' */
+
+			/*
+			** Compute size of next fragment in order to compute
+			** durations needed to update NAV.
+			** The last fragment uses the ACK duration only.
+			** Add time for next fragment.
+			*/
+			dur += ath9k_hw_computetxtime(sc->sc_ah, rt,
+					txctl->nextfraglen,
+					rix, sc->sc_flags & ATH_PREAMBLE_SHORT);
+		}
+
+		if (ieee80211_has_morefrags(fc) ||
+		     (le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG)) {
+			/*
+			**  Force hardware to use computed duration for next
+			**  fragment by disabling multi-rate retry, which
+			**  updates duration based on the multi-rate
+			**  duration table.
+			*/
+			rcs[1].tries = rcs[2].tries = rcs[3].tries = 0;
+			rcs[1].rix = rcs[2].rix = rcs[3].rix = 0;
+			/* reset tries but keep rate index */
+			rcs[0].tries = ATH_TXMAXTRY;
+		}
+
+		hdr->duration_id = cpu_to_le16(dur);
+	}
+
+	/*
+	 * Determine if a tx interrupt should be generated for
+	 * this descriptor.  We take a tx interrupt to reap
+	 * descriptors when the h/w hits an EOL condition or
+	 * when the descriptor is specifically marked to generate
+	 * an interrupt.  We periodically mark descriptors in this
+	 * way to insure timely replenishing of the supply needed
+	 * for sending frames.  Defering interrupts reduces system
+	 * load and potentially allows more concurrent work to be
+	 * done but if done to aggressively can cause senders to
+	 * backup.
+	 *
+	 * NB: use >= to deal with sc_txintrperiod changing
+	 *     dynamically through sysctl.
+	 */
+	spin_lock_bh(&txq->axq_lock);
+	if ((++txq->axq_intrcnt >= sc->sc_txintrperiod)) {
+		txctl->flags |= ATH9K_TXDESC_INTREQ;
+		txq->axq_intrcnt = 0;
+	}
+	spin_unlock_bh(&txq->axq_lock);
+
+	if (is_multicast_ether_addr(hdr->addr1)) {
+		antenna = sc->sc_mcastantenna + 1;
+		sc->sc_mcastantenna = (sc->sc_mcastantenna + 1) & 0x1;
+	} else
+		antenna = sc->sc_txantenna;
+
+#ifdef USE_LEGACY_HAL
+	txctl->antenna = antenna;
+#endif
+	return 0;
+}
+
+/* To complete a chain of buffers associated a frame */
+
+static void ath_tx_complete_buf(struct ath_softc *sc,
+				struct ath_buf *bf,
+				struct list_head *bf_q,
+				int txok, int sendbar)
+{
+	struct sk_buff *skb = bf->bf_mpdu;
+	struct ath_xmit_status tx_status;
+	dma_addr_t *pa;
+
+	/*
+	 * Set retry information.
+	 * NB: Don't use the information in the descriptor, because the frame
+	 * could be software retried.
+	 */
+	tx_status.retries = bf->bf_retries;
+	tx_status.flags = 0;
+
+	if (sendbar)
+		tx_status.flags = ATH_TX_BAR;
+
+	if (!txok) {
+		tx_status.flags |= ATH_TX_ERROR;
+
+		if (bf->bf_isxretried)
+			tx_status.flags |= ATH_TX_XRETRY;
+	}
+	/* Unmap this frame */
+	pa = get_dma_mem_context(bf, bf_dmacontext);
+	pci_unmap_single(sc->pdev,
+			 *pa,
+			 skb->len,
+			 PCI_DMA_TODEVICE);
+	/* complete this frame */
+	ath_tx_complete(sc, skb, &tx_status, bf->bf_node);
+
+	/*
+	 * Return the list of ath_buf of this mpdu to free queue
+	 */
+	spin_lock_bh(&sc->sc_txbuflock);
+	list_splice_tail_init(bf_q, &sc->sc_txbuf);
+	spin_unlock_bh(&sc->sc_txbuflock);
+}
+
+/*
+ * queue up a dest/ac pair for tx scheduling
+ * NB: must be called with txq lock held
+ */
+
+static void ath_tx_queue_tid(struct ath_txq *txq, struct ath_atx_tid *tid)
+{
+	struct ath_atx_ac *ac = tid->ac;
+
+	/*
+	 * if tid is paused, hold off
+	 */
+	if (tid->paused)
+		return;
+
+	/*
+	 * add tid to ac atmost once
+	 */
+	if (tid->sched)
+		return;
+
+	tid->sched = true;
+	list_add_tail(&tid->list, &ac->tid_q);
+
+	/*
+	 * add node ac to txq atmost once
+	 */
+	if (ac->sched)
+		return;
+
+	ac->sched = true;
+	list_add_tail(&ac->list, &txq->axq_acq);
+}
+
+/* pause a tid */
+
+static void ath_tx_pause_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
+{
+	struct ath_txq *txq = &sc->sc_txq[tid->ac->qnum];
+
+	spin_lock_bh(&txq->axq_lock);
+
+	tid->paused++;
+
+	spin_unlock_bh(&txq->axq_lock);
+}
+
+/* resume a tid and schedule aggregate */
+
+void ath_tx_resume_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
+{
+	struct ath_txq *txq = &sc->sc_txq[tid->ac->qnum];
+
+	ASSERT(tid->paused > 0);
+	spin_lock_bh(&txq->axq_lock);
+
+	tid->paused--;
+
+	if (tid->paused > 0)
+		goto unlock;
+
+	if (list_empty(&tid->buf_q))
+		goto unlock;
+
+	/*
+	 * Add this TID to scheduler and try to send out aggregates
+	 */
+	ath_tx_queue_tid(txq, tid);
+	ath_txq_schedule(sc, txq);
+unlock:
+	spin_unlock_bh(&txq->axq_lock);
+}
+
+/* Compute the number of bad frames */
+
+static int ath_tx_num_badfrms(struct ath_softc *sc,
+	struct ath_buf *bf, int txok)
+{
+	struct ath_node *an = bf->bf_node;
+	int isnodegone = (an->an_flags & ATH_NODE_CLEAN);
+	struct ath_buf *bf_last = bf->bf_lastbf;
+	struct ath_desc *ds = bf_last->bf_desc;
+	u16 seq_st = 0;
+	u32 ba[WME_BA_BMP_SIZE >> 5];
+	int ba_index;
+	int nbad = 0;
+	int isaggr = 0;
+
+	if (isnodegone || ds->ds_txstat.ts_flags == ATH9K_TX_SW_ABORTED)
+		return 0;
+
+	isaggr = bf->bf_isaggr;
+	if (isaggr) {
+		seq_st = ATH_DS_BA_SEQ(ds);
+		memcpy(ba, ATH_DS_BA_BITMAP(ds), WME_BA_BMP_SIZE >> 3);
+	}
+
+	while (bf) {
+		ba_index = ATH_BA_INDEX(seq_st, bf->bf_seqno);
+		if (!txok || (isaggr && !ATH_BA_ISSET(ba, ba_index)))
+			nbad++;
+
+		bf = bf->bf_next;
+	}
+
+	return nbad;
+}
+
+static void ath_tx_set_retry(struct ath_softc *sc, struct ath_buf *bf)
+{
+	struct sk_buff *skb;
+	struct ieee80211_hdr *hdr;
+
+	bf->bf_isretried = 1;
+	bf->bf_retries++;
+
+	skb = bf->bf_mpdu;
+	hdr = (struct ieee80211_hdr *)skb->data;
+	hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_RETRY);
+}
+
+/* Update block ack window */
+
+static void ath_tx_update_baw(struct ath_softc *sc,
+	struct ath_atx_tid *tid, int seqno)
+{
+	int index, cindex;
+
+	index  = ATH_BA_INDEX(tid->seq_start, seqno);
+	cindex = (tid->baw_head + index) & (ATH_TID_MAX_BUFS - 1);
+
+	tid->tx_buf[cindex] = NULL;
+
+	while (tid->baw_head != tid->baw_tail && !tid->tx_buf[tid->baw_head]) {
+		INCR(tid->seq_start, IEEE80211_SEQ_MAX);
+		INCR(tid->baw_head, ATH_TID_MAX_BUFS);
+	}
+}
+
+/*
+ * ath_pkt_dur - compute packet duration (NB: not NAV)
+ *
+ * rix - rate index
+ * pktlen - total bytes (delims + data + fcs + pads + pad delims)
+ * width  - 0 for 20 MHz, 1 for 40 MHz
+ * half_gi - to use 4us v/s 3.6 us for symbol time
+ */
+
+static u32 ath_pkt_duration(struct ath_softc *sc,
+				  u8 rix,
+				  struct ath_buf *bf,
+				  int width,
+				  int half_gi,
+				  bool shortPreamble)
+{
+	const struct ath9k_rate_table *rt = sc->sc_currates;
+	u32 nbits, nsymbits, duration, nsymbols;
+	u8 rc;
+	int streams, pktlen;
+
+	pktlen = bf->bf_isaggr ? bf->bf_al : bf->bf_frmlen;
+	rc = rt->info[rix].rateCode;
+
+	/*
+	 * for legacy rates, use old function to compute packet duration
+	 */
+	if (!IS_HT_RATE(rc))
+		return ath9k_hw_computetxtime(sc->sc_ah,
+					     rt,
+					     pktlen,
+					     rix,
+					     shortPreamble);
+	/*
+	 * find number of symbols: PLCP + data
+	 */
+	nbits = (pktlen << 3) + OFDM_PLCP_BITS;
+	nsymbits = bits_per_symbol[HT_RC_2_MCS(rc)][width];
+	nsymbols = (nbits + nsymbits - 1) / nsymbits;
+
+	if (!half_gi)
+		duration = SYMBOL_TIME(nsymbols);
+	else
+		duration = SYMBOL_TIME_HALFGI(nsymbols);
+
+	/*
+	 * addup duration for legacy/ht training and signal fields
+	 */
+	streams = HT_RC_2_STREAMS(rc);
+	duration += L_STF + L_LTF + L_SIG + HT_SIG + HT_STF + HT_LTF(streams);
+	return duration;
+}
+
+/* Rate module function to set rate related fields in tx descriptor */
+
+static void ath_buf_set_rate(struct ath_softc *sc, struct ath_buf *bf)
+{
+	struct ath_hal *ah = sc->sc_ah;
+	const struct ath9k_rate_table *rt;
+	struct ath_desc *ds = bf->bf_desc;
+	struct ath_desc *lastds = bf->bf_lastbf->bf_desc;
+	struct ath9k_11n_rate_series series[4];
+	int i, flags, rtsctsena = 0, dynamic_mimops = 0;
+	u32 ctsduration = 0;
+	u8 rix = 0, cix, ctsrate = 0;
+	u32 aggr_limit_with_rts = sc->sc_rtsaggrlimit;
+	struct ath_node *an = (struct ath_node *) bf->bf_node;
+
+	/*
+	 * get the cix for the lowest valid rix.
+	 */
+	rt = sc->sc_currates;
+	for (i = 4; i--;) {
+		if (bf->bf_rcs[i].tries) {
+			rix = bf->bf_rcs[i].rix;
+			break;
+		}
+	}
+	flags = (bf->bf_flags & (ATH9K_TXDESC_RTSENA | ATH9K_TXDESC_CTSENA));
+	cix = rt->info[rix].controlRate;
+
+	/*
+	 * If 802.11g protection is enabled, determine whether
+	 * to use RTS/CTS or just CTS.  Note that this is only
+	 * done for OFDM/HT unicast frames.
+	 */
+	if (sc->sc_protmode != PROT_M_NONE &&
+	    (rt->info[rix].phy == PHY_OFDM ||
+	     rt->info[rix].phy == PHY_HT) &&
+	    (bf->bf_flags & ATH9K_TXDESC_NOACK) == 0) {
+		if (sc->sc_protmode == PROT_M_RTSCTS)
+			flags = ATH9K_TXDESC_RTSENA;
+		else if (sc->sc_protmode == PROT_M_CTSONLY)
+			flags = ATH9K_TXDESC_CTSENA;
+
+		cix = rt->info[sc->sc_protrix].controlRate;
+		rtsctsena = 1;
+	}
+
+	/* For 11n, the default behavior is to enable RTS for
+	 * hw retried frames. We enable the global flag here and
+	 * let rate series flags determine which rates will actually
+	 * use RTS.
+	 */
+	if (ah->ah_caps.halHTSupport && bf->bf_isdata) {
+		BUG_ON(!an);
+		/*
+		 * 802.11g protection not needed, use our default behavior
+		 */
+		if (!rtsctsena)
+			flags = ATH9K_TXDESC_RTSENA;
+		/*
+		 * For dynamic MIMO PS, RTS needs to precede the first aggregate
+		 * and the second aggregate should have any protection at all.
+		 */
+		if (an->an_smmode == ATH_SM_PWRSAV_DYNAMIC) {
+			if (!bf->bf_aggrburst) {
+				flags = ATH9K_TXDESC_RTSENA;
+				dynamic_mimops = 1;
+			} else {
+				flags = 0;
+			}
+		}
+	}
+
+	/*
+	 * Set protection if aggregate protection on
+	 */
+	if (sc->sc_config.ath_aggr_prot &&
+	    (!bf->bf_isaggr || (bf->bf_isaggr && bf->bf_al < 8192))) {
+		flags = ATH9K_TXDESC_RTSENA;
+		cix = rt->info[sc->sc_protrix].controlRate;
+		rtsctsena = 1;
+	}
+
+	/*
+	 *  For AR5416 - RTS cannot be followed by a frame larger than 8K.
+	 */
+	if (bf->bf_isaggr && (bf->bf_al > aggr_limit_with_rts)) {
+		/*
+		 * Ensure that in the case of SM Dynamic power save
+		 * while we are bursting the second aggregate the
+		 * RTS is cleared.
+		 */
+		flags &= ~(ATH9K_TXDESC_RTSENA);
+	}
+
+	/*
+	 * CTS transmit rate is derived from the transmit rate
+	 * by looking in the h/w rate table.  We must also factor
+	 * in whether or not a short preamble is to be used.
+	 */
+	/* NB: cix is set above where RTS/CTS is enabled */
+	BUG_ON(cix == 0xff);
+	ctsrate = rt->info[cix].rateCode |
+		(bf->bf_shpreamble ? rt->info[cix].shortPreamble : 0);
+
+	/*
+	 * Setup HAL rate series
+	 */
+	memzero(series, sizeof(struct ath9k_11n_rate_series) * 4);
+
+	for (i = 0; i < 4; i++) {
+		if (!bf->bf_rcs[i].tries)
+			continue;
+
+		rix = bf->bf_rcs[i].rix;
+
+		series[i].Rate = rt->info[rix].rateCode |
+			(bf->bf_shpreamble ? rt->info[rix].shortPreamble : 0);
+
+		series[i].Tries = bf->bf_rcs[i].tries;
+
+		series[i].RateFlags = (
+			(bf->bf_rcs[i].flags & ATH_RC_RTSCTS_FLAG) ?
+				ATH9K_RATESERIES_RTS_CTS : 0) |
+			((bf->bf_rcs[i].flags & ATH_RC_CW40_FLAG) ?
+				ATH9K_RATESERIES_2040 : 0) |
+			((bf->bf_rcs[i].flags & ATH_RC_SGI_FLAG) ?
+				ATH9K_RATESERIES_HALFGI : 0);
+
+		series[i].PktDuration = ath_pkt_duration(
+			sc, rix, bf,
+			(bf->bf_rcs[i].flags & ATH_RC_CW40_FLAG) != 0,
+			(bf->bf_rcs[i].flags & ATH_RC_SGI_FLAG),
+			bf->bf_shpreamble);
+
+		if ((an->an_smmode == ATH_SM_PWRSAV_STATIC) &&
+		    (bf->bf_rcs[i].flags & ATH_RC_DS_FLAG) == 0) {
+			/*
+			 * When sending to an HT node that has enabled static
+			 * SM/MIMO power save, send at single stream rates but
+			 * use maximum allowed transmit chains per user,
+			 * hardware, regulatory, or country limits for
+			 * better range.
+			 */
+			series[i].ChSel = sc->sc_tx_chainmask;
+		} else {
+			if (bf->bf_ht)
+				series[i].ChSel =
+					ath_chainmask_sel_logic(sc, an);
+			else
+				series[i].ChSel = sc->sc_tx_chainmask;
+		}
+
+		if (rtsctsena)
+			series[i].RateFlags |= ATH9K_RATESERIES_RTS_CTS;
+
+		/*
+		 * Set RTS for all rates if node is in dynamic powersave
+		 * mode and we are using dual stream rates.
+		 */
+		if (dynamic_mimops && (bf->bf_rcs[i].flags & ATH_RC_DS_FLAG))
+			series[i].RateFlags |= ATH9K_RATESERIES_RTS_CTS;
+	}
+
+	/*
+	 * For non-HT devices, calculate RTS/CTS duration in software
+	 * and disable multi-rate retry.
+	 */
+	if (flags && !ah->ah_caps.halHTSupport) {
+		/*
+		 * Compute the transmit duration based on the frame
+		 * size and the size of an ACK frame.  We call into the
+		 * HAL to do the computation since it depends on the
+		 * characteristics of the actual PHY being used.
+		 *
+		 * NB: CTS is assumed the same size as an ACK so we can
+		 *     use the precalculated ACK durations.
+		 */
+		if (flags & ATH9K_TXDESC_RTSENA) {    /* SIFS + CTS */
+			ctsduration += bf->bf_shpreamble ?
+				rt->info[cix].spAckDuration :
+				rt->info[cix].lpAckDuration;
+		}
+
+		ctsduration += series[0].PktDuration;
+
+		if ((bf->bf_flags & ATH9K_TXDESC_NOACK) == 0) { /* SIFS + ACK */
+			ctsduration += bf->bf_shpreamble ?
+				rt->info[rix].spAckDuration :
+				rt->info[rix].lpAckDuration;
+		}
+
+		/*
+		 * Disable multi-rate retry when using RTS/CTS by clearing
+		 * series 1, 2 and 3.
+		 */
+		memzero(&series[1], sizeof(struct ath9k_11n_rate_series) * 3);
+	}
+
+	/*
+	 * set dur_update_en for l-sig computation except for PS-Poll frames
+	 */
+	ath9k_hw_set11n_ratescenario(ah, ds, lastds,
+				    !bf->bf_ispspoll,
+				    ctsrate,
+				    ctsduration,
+				    series, 4, flags);
+	if (sc->sc_config.ath_aggr_prot && flags)
+		ath9k_hw_set11n_burstduration(ah, ds, 8192);
+}
+
+/*
+ * Function to send a normal HT (non-AMPDU) frame
+ * NB: must be called with txq lock held
+ */
+
+static int ath_tx_send_normal(struct ath_softc *sc,
+			      struct ath_txq *txq,
+			      struct ath_atx_tid *tid,
+			      struct list_head *bf_head)
+{
+	struct ath_buf *bf;
+	struct sk_buff *skb;
+	struct ieee80211_tx_info *tx_info;
+	struct ath_tx_info_priv *tx_info_priv;
+
+	BUG_ON(list_empty(bf_head));
+
+	bf = list_first_entry(bf_head, struct ath_buf, list);
+	bf->bf_isampdu = 0; /* regular HT frame */
+
+	skb = (struct sk_buff *)bf->bf_mpdu;
+	tx_info = IEEE80211_SKB_CB(skb);
+	tx_info_priv = (struct ath_tx_info_priv *)tx_info->driver_data[0];
+	memcpy(bf->bf_rcs, tx_info_priv->rcs, 4 * sizeof(tx_info_priv->rcs[0]));
+
+	/* update starting sequence number for subsequent ADDBA request */
+	INCR(tid->seq_start, IEEE80211_SEQ_MAX);
+
+	/* Queue to h/w without aggregation */
+	bf->bf_nframes = 1;
+	bf->bf_lastbf = bf->bf_lastfrm; /* one single frame */
+	ath_buf_set_rate(sc, bf);
+	ath_tx_txqaddbuf(sc, txq, bf_head);
+
+	return 0;
+}
+
+/* flush tid's software queue and send frames as non-ampdu's */
+
+static void ath_tx_flush_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
+{
+	struct ath_txq *txq = &sc->sc_txq[tid->ac->qnum];
+	struct ath_buf *bf;
+	struct list_head bf_head;
+	INIT_LIST_HEAD(&bf_head);
+
+	ASSERT(tid->paused > 0);
+	spin_lock_bh(&txq->axq_lock);
+
+	tid->paused--;
+
+	if (tid->paused > 0) {
+		spin_unlock_bh(&txq->axq_lock);
+		return;
+	}
+
+	while (!list_empty(&tid->buf_q)) {
+		bf = list_first_entry(&tid->buf_q, struct ath_buf, list);
+		ASSERT(!bf->bf_isretried);
+		list_cut_position(&bf_head, &tid->buf_q, &bf->bf_lastfrm->list);
+		ath_tx_send_normal(sc, txq, tid, &bf_head);
+	}
+
+	spin_unlock_bh(&txq->axq_lock);
+}
+
+/* Completion routine of an aggregate */
+
+static void ath_tx_complete_aggr_rifs(struct ath_softc *sc,
+				      struct ath_txq *txq,
+				      struct ath_buf *bf,
+				      struct list_head *bf_q,
+				      int txok)
+{
+	struct ath_node *an = bf->bf_node;
+	struct ath_atx_tid *tid = ATH_AN_2_TID(an, bf->bf_tidno);
+	struct ath_buf *bf_last = bf->bf_lastbf;
+	struct ath_desc *ds = bf_last->bf_desc;
+	struct ath_buf *bf_next, *bf_lastq = NULL;
+	struct list_head bf_head, bf_pending;
+	u16 seq_st = 0;
+	u32 ba[WME_BA_BMP_SIZE >> 5];
+	int isaggr, txfail, txpending, sendbar = 0, needreset = 0;
+	int isnodegone = (an->an_flags & ATH_NODE_CLEAN);
+
+	isaggr = bf->bf_isaggr;
+	if (isaggr) {
+		if (txok) {
+			if (ATH_DS_TX_BA(ds)) {
+				/*
+				 * extract starting sequence and
+				 * block-ack bitmap
+				 */
+				seq_st = ATH_DS_BA_SEQ(ds);
+				memcpy(ba,
+					ATH_DS_BA_BITMAP(ds),
+					WME_BA_BMP_SIZE >> 3);
+			} else {
+				memzero(ba, WME_BA_BMP_SIZE >> 3);
+
+				/*
+				 * AR5416 can become deaf/mute when BA
+				 * issue happens. Chip needs to be reset.
+				 * But AP code may have sychronization issues
+				 * when perform internal reset in this routine.
+				 * Only enable reset in STA mode for now.
+				 */
+				if (sc->sc_opmode == ATH9K_M_STA)
+					needreset = 1;
+			}
+		} else {
+			memzero(ba, WME_BA_BMP_SIZE >> 3);
+		}
+	}
+
+	INIT_LIST_HEAD(&bf_pending);
+	INIT_LIST_HEAD(&bf_head);
+
+	while (bf) {
+		txfail = txpending = 0;
+		bf_next = bf->bf_next;
+
+		if (ATH_BA_ISSET(ba, ATH_BA_INDEX(seq_st, bf->bf_seqno))) {
+			/* transmit completion, subframe is
+			 * acked by block ack */
+		} else if (!isaggr && txok) {
+			/* transmit completion */
+		} else {
+
+			if (!tid->cleanup_inprogress && !isnodegone &&
+			    ds->ds_txstat.ts_flags != ATH9K_TX_SW_ABORTED) {
+				if (bf->bf_retries < ATH_MAX_SW_RETRIES) {
+					ath_tx_set_retry(sc, bf);
+					txpending = 1;
+				} else {
+					bf->bf_isxretried = 1;
+					txfail = 1;
+					sendbar = 1;
+				}
+			} else {
+				/*
+				 * cleanup in progress, just fail
+				 * the un-acked sub-frames
+				 */
+				txfail = 1;
+			}
+		}
+		/*
+		 * Remove ath_buf's of this sub-frame from aggregate queue.
+		 */
+		if (bf_next == NULL) {  /* last subframe in the aggregate */
+			ASSERT(bf->bf_lastfrm == bf_last);
+
+			/*
+			 * The last descriptor of the last sub frame could be
+			 * a holding descriptor for h/w. If that's the case,
+			 * bf->bf_lastfrm won't be in the bf_q.
+			 * Make sure we handle bf_q properly here.
+			 */
+
+			if (!list_empty(bf_q)) {
+				bf_lastq = list_entry(bf_q->prev,
+					struct ath_buf, list);
+				list_cut_position(&bf_head,
+					bf_q, &bf_lastq->list);
+			} else {
+				/*
+				 * XXX: if the last subframe only has one
+				 * descriptor which is also being used as
+				 * a holding descriptor. Then the ath_buf
+				 * is not in the bf_q at all.
+				 */
+				INIT_LIST_HEAD(&bf_head);
+			}
+		} else {
+			ASSERT(!list_empty(bf_q));
+			list_cut_position(&bf_head,
+				bf_q, &bf->bf_lastfrm->list);
+		}
+
+		if (!txpending) {
+			/*
+			 * complete the acked-ones/xretried ones; update
+			 * block-ack window
+			 */
+			spin_lock_bh(&txq->axq_lock);
+			ath_tx_update_baw(sc, tid, bf->bf_seqno);
+			spin_unlock_bh(&txq->axq_lock);
+
+			/* complete this sub-frame */
+			ath_tx_complete_buf(sc, bf, &bf_head, !txfail, sendbar);
+		} else {
+			/*
+			 * retry the un-acked ones
+			 */
+			/*
+			 * XXX: if the last descriptor is holding descriptor,
+			 * in order to requeue the frame to software queue, we
+			 * need to allocate a new descriptor and
+			 * copy the content of holding descriptor to it.
+			 */
+			if (bf->bf_next == NULL &&
+			    bf_last->bf_status & ATH_BUFSTATUS_STALE) {
+				struct ath_buf *tbf;
+
+				/* allocate new descriptor */
+				spin_lock_bh(&sc->sc_txbuflock);
+				ASSERT(!list_empty((&sc->sc_txbuf)));
+				tbf = list_first_entry(&sc->sc_txbuf,
+						struct ath_buf, list);
+				list_del(&tbf->list);
+				spin_unlock_bh(&sc->sc_txbuflock);
+
+				ATH_TXBUF_RESET(tbf);
+
+				/* copy descriptor content */
+				tbf->bf_mpdu = bf_last->bf_mpdu;
+				tbf->bf_node = bf_last->bf_node;
+				tbf->bf_buf_addr = bf_last->bf_buf_addr;
+				*(tbf->bf_desc) = *(bf_last->bf_desc);
+
+				/* link it to the frame */
+				if (bf_lastq) {
+					bf_lastq->bf_desc->ds_link =
+						tbf->bf_daddr;
+					bf->bf_lastfrm = tbf;
+					ath9k_hw_cleartxdesc(sc->sc_ah,
+						bf->bf_lastfrm->bf_desc);
+				} else {
+					tbf->bf_state = bf_last->bf_state;
+					tbf->bf_lastfrm = tbf;
+					ath9k_hw_cleartxdesc(sc->sc_ah,
+						tbf->bf_lastfrm->bf_desc);
+
+					/* copy the DMA context */
+					copy_dma_mem_context(
+						get_dma_mem_context(tbf,
+							bf_dmacontext),
+						get_dma_mem_context(bf_last,
+							bf_dmacontext));
+				}
+				list_add_tail(&tbf->list, &bf_head);
+			} else {
+				/*
+				 * Clear descriptor status words for
+				 * software retry
+				 */
+				ath9k_hw_cleartxdesc(sc->sc_ah,
+					bf->bf_lastfrm->bf_desc);
+			}
+
+			/*
+			 * Put this buffer to the temporary pending
+			 * queue to retain ordering
+			 */
+			list_splice_tail_init(&bf_head, &bf_pending);
+		}
+
+		bf = bf_next;
+	}
+
+	/*
+	 * node is already gone. no more assocication
+	 * with the node. the node might have been freed
+	 * any  node acces can result in panic.note tid
+	 * is part of the node.
+	 */
+	if (isnodegone)
+		return;
+
+	if (tid->cleanup_inprogress) {
+		/* check to see if we're done with cleaning the h/w queue */
+		spin_lock_bh(&txq->axq_lock);
+
+		if (tid->baw_head == tid->baw_tail) {
+			tid->addba_exchangecomplete = 0;
+			tid->addba_exchangeattempts = 0;
+			spin_unlock_bh(&txq->axq_lock);
+
+			tid->cleanup_inprogress = false;
+
+			/* send buffered frames as singles */
+			ath_tx_flush_tid(sc, tid);
+		} else
+			spin_unlock_bh(&txq->axq_lock);
+
+		return;
+	}
+
+	/*
+	 * prepend un-acked frames to the beginning of the pending frame queue
+	 */
+	if (!list_empty(&bf_pending)) {
+		spin_lock_bh(&txq->axq_lock);
+		/* Note: we _prepend_, we _do_not_ at to
+		 * the end of the queue ! */
+		list_splice(&bf_pending, &tid->buf_q);
+		ath_tx_queue_tid(txq, tid);
+		spin_unlock_bh(&txq->axq_lock);
+	}
+
+	if (needreset)
+		ath_internal_reset(sc);
+
+	return;
+}
+
+/* Process completed xmit descriptors from the specified queue */
+
+static int ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq)
+{
+	struct ath_hal *ah = sc->sc_ah;
+	struct ath_buf *bf, *lastbf, *bf_held = NULL;
+	struct list_head bf_head;
+	struct ath_desc *ds, *tmp_ds;
+	struct sk_buff *skb;
+	struct ieee80211_tx_info *tx_info;
+	struct ath_tx_info_priv *tx_info_priv;
+	int nacked, txok, nbad = 0, isrifs = 0;
+	int status;
+
+	DPRINTF(sc, ATH_DBG_QUEUE,
+		"%s: tx queue %d (%x), link %p\n", __func__,
+		txq->axq_qnum, ath9k_hw_gettxbuf(sc->sc_ah, txq->axq_qnum),
+		txq->axq_link);
+
+	nacked = 0;
+	for (;;) {
+		spin_lock_bh(&txq->axq_lock);
+		txq->axq_intrcnt = 0; /* reset periodic desc intr count */
+		if (list_empty(&txq->axq_q)) {
+			txq->axq_link = NULL;
+			txq->axq_linkbuf = NULL;
+			spin_unlock_bh(&txq->axq_lock);
+			break;
+		}
+		bf = list_first_entry(&txq->axq_q, struct ath_buf, list);
+
+		/*
+		 * There is a race condition that a BH gets scheduled
+		 * after sw writes TxE and before hw re-load the last
+		 * descriptor to get the newly chained one.
+		 * Software must keep the last DONE descriptor as a
+		 * holding descriptor - software does so by marking
+		 * it with the STALE flag.
+		 */
+		bf_held = NULL;
+		if (bf->bf_status & ATH_BUFSTATUS_STALE) {
+			bf_held = bf;
+			if (list_is_last(&bf_held->list, &txq->axq_q)) {
+				/* FIXME:
+				 * The holding descriptor is the last
+				 * descriptor in queue. It's safe to remove
+				 * the last holding descriptor in BH context.
+				 */
+				spin_unlock_bh(&txq->axq_lock);
+				break;
+			} else {
+				/* Lets work with the next buffer now */
+				bf = list_entry(bf_held->list.next,
+					struct ath_buf, list);
+			}
+		}
+
+		lastbf = bf->bf_lastbf;
+		ds = lastbf->bf_desc;    /* NB: last decriptor */
+
+		status = ath9k_hw_txprocdesc(ah, ds);
+		if (status == -EINPROGRESS) {
+			spin_unlock_bh(&txq->axq_lock);
+			break;
+		}
+		if (bf->bf_desc == txq->axq_lastdsWithCTS)
+			txq->axq_lastdsWithCTS = NULL;
+		if (ds == txq->axq_gatingds)
+			txq->axq_gatingds = NULL;
+
+		/*
+		 * Remove ath_buf's of the same transmit unit from txq,
+		 * however leave the last descriptor back as the holding
+		 * descriptor for hw.
+		 */
+		lastbf->bf_status |= ATH_BUFSTATUS_STALE;
+		INIT_LIST_HEAD(&bf_head);
+
+		if (!list_is_singular(&lastbf->list))
+			list_cut_position(&bf_head,
+				&txq->axq_q, lastbf->list.prev);
+
+		txq->axq_depth--;
+
+		if (bf->bf_isaggr)
+			txq->axq_aggr_depth--;
+
+		txok = (ds->ds_txstat.ts_status == 0);
+
+		spin_unlock_bh(&txq->axq_lock);
+
+		if (bf_held) {
+			list_del(&bf_held->list);
+			spin_lock_bh(&sc->sc_txbuflock);
+			list_add_tail(&bf_held->list, &sc->sc_txbuf);
+			spin_unlock_bh(&sc->sc_txbuflock);
+		}
+
+		if (!bf->bf_isampdu) {
+			/*
+			 * This frame is sent out as a single frame.
+			 * Use hardware retry status for this frame.
+			 */
+			bf->bf_retries = ds->ds_txstat.ts_longretry;
+			if (ds->ds_txstat.ts_status & ATH9K_TXERR_XRETRY)
+				bf->bf_isxretried = 1;
+			nbad = 0;
+		} else {
+			nbad = ath_tx_num_badfrms(sc, bf, txok);
+		}
+		skb = bf->bf_mpdu;
+		tx_info = IEEE80211_SKB_CB(skb);
+		tx_info_priv = (struct ath_tx_info_priv *)
+			tx_info->driver_data[0];
+		if (ds->ds_txstat.ts_status & ATH9K_TXERR_FILT)
+			tx_info->flags |= IEEE80211_TX_STAT_TX_FILTERED;
+		if ((ds->ds_txstat.ts_status & ATH9K_TXERR_FILT) == 0 &&
+				(bf->bf_flags & ATH9K_TXDESC_NOACK) == 0) {
+			if (ds->ds_txstat.ts_status == 0)
+				nacked++;
+
+			if (bf->bf_isdata) {
+				if (isrifs)
+					tmp_ds = bf->bf_rifslast->bf_desc;
+				else
+					tmp_ds = ds;
+				memcpy(&tx_info_priv->tx,
+					&tmp_ds->ds_txstat,
+					sizeof(tx_info_priv->tx));
+				tx_info_priv->n_frames = bf->bf_nframes;
+				tx_info_priv->n_bad_frames = nbad;
+			}
+		}
+
+		/*
+		 * Complete this transmit unit
+		 */
+		if (bf->bf_isampdu)
+			ath_tx_complete_aggr_rifs(sc, txq, bf, &bf_head, txok);
+		else
+			ath_tx_complete_buf(sc, bf, &bf_head, txok, 0);
+
+		/* Wake up mac80211 queue */
+
+		spin_lock_bh(&txq->axq_lock);
+		if (txq->stopped && ath_txq_depth(sc, txq->axq_qnum) <=
+				(ATH_TXBUF - 20)) {
+			int qnum;
+			qnum = ath_get_mac80211_qnum(txq->axq_qnum, sc);
+			if (qnum != -1) {
+				ieee80211_wake_queue(sc->hw, qnum);
+				txq->stopped = 0;
+			}
+
+		}
+
+		/*
+		 * schedule any pending packets if aggregation is enabled
+		 */
+		if (sc->sc_txaggr)
+			ath_txq_schedule(sc, txq);
+		spin_unlock_bh(&txq->axq_lock);
+	}
+	return nacked;
+}
+
+static void ath_tx_stopdma(struct ath_softc *sc, struct ath_txq *txq)
+{
+	struct ath_hal *ah = sc->sc_ah;
+
+	(void) ath9k_hw_stoptxdma(ah, txq->axq_qnum);
+	DPRINTF(sc, ATH_DBG_XMIT, "%s: tx queue [%u] %x, link %p\n",
+		__func__, txq->axq_qnum,
+		ath9k_hw_gettxbuf(ah, txq->axq_qnum), txq->axq_link);
+}
+
+/* Drain only the data queues */
+
+static void ath_drain_txdataq(struct ath_softc *sc, bool retry_tx)
+{
+	struct ath_hal *ah = sc->sc_ah;
+	int i;
+	int npend = 0;
+	enum ath9k_ht_macmode ht_macmode = ath_cwm_macmode(sc);
+
+	/* XXX return value */
+	if (!sc->sc_invalid) {
+		for (i = 0; i < ATH9K_NUM_TX_QUEUES; i++) {
+			if (ATH_TXQ_SETUP(sc, i)) {
+				ath_tx_stopdma(sc, &sc->sc_txq[i]);
+
+				/* The TxDMA may not really be stopped.
+				 * Double check the hal tx pending count */
+				npend += ath9k_hw_numtxpending(ah,
+					sc->sc_txq[i].axq_qnum);
+			}
+		}
+	}
+
+	if (npend) {
+		int status;
+
+		/* TxDMA not stopped, reset the hal */
+		DPRINTF(sc, ATH_DBG_XMIT,
+			"%s: Unable to stop TxDMA. Reset HAL!\n", __func__);
+
+		spin_lock_bh(&sc->sc_resetlock);
+		if (!ath9k_hw_reset(ah, sc->sc_opmode,
+			&sc->sc_curchan, ht_macmode,
+			sc->sc_tx_chainmask, sc->sc_rx_chainmask,
+			sc->sc_ht_extprotspacing, true, &status)) {
+
+			DPRINTF(sc, ATH_DBG_FATAL,
+				"%s: unable to reset hardware; hal status %u\n",
+				__func__,
+				status);
+		}
+		spin_unlock_bh(&sc->sc_resetlock);
+	}
+
+	for (i = 0; i < ATH9K_NUM_TX_QUEUES; i++) {
+		if (ATH_TXQ_SETUP(sc, i))
+			ath_tx_draintxq(sc, &sc->sc_txq[i], retry_tx);
+	}
+}
+
+/* Add a sub-frame to block ack window */
+
+static void ath_tx_addto_baw(struct ath_softc *sc,
+			     struct ath_atx_tid *tid,
+			     struct ath_buf *bf)
+{
+	int index, cindex;
+
+	if (bf->bf_isretried)
+		return;
+
+	index  = ATH_BA_INDEX(tid->seq_start, bf->bf_seqno);
+	cindex = (tid->baw_head + index) & (ATH_TID_MAX_BUFS - 1);
+
+	ASSERT(tid->tx_buf[cindex] == NULL);
+	tid->tx_buf[cindex] = bf;
+
+	if (index >= ((tid->baw_tail - tid->baw_head) &
+		(ATH_TID_MAX_BUFS - 1))) {
+		tid->baw_tail = cindex;
+		INCR(tid->baw_tail, ATH_TID_MAX_BUFS);
+	}
+}
+
+/*
+ * Function to send an A-MPDU
+ * NB: must be called with txq lock held
+ */
+
+static int ath_tx_send_ampdu(struct ath_softc *sc,
+			     struct ath_txq *txq,
+			     struct ath_atx_tid *tid,
+			     struct list_head *bf_head,
+			     struct ath_tx_control *txctl)
+{
+	struct ath_buf *bf;
+	struct sk_buff *skb;
+	struct ieee80211_tx_info *tx_info;
+	struct ath_tx_info_priv *tx_info_priv;
+
+	BUG_ON(list_empty(bf_head));
+
+	bf = list_first_entry(bf_head, struct ath_buf, list);
+	bf->bf_isampdu = 1;
+	bf->bf_seqno = txctl->seqno; /* save seqno and tidno in buffer */
+	bf->bf_tidno = txctl->tidno;
+
+	/*
+	 * Do not queue to h/w when any of the following conditions is true:
+	 * - there are pending frames in software queue
+	 * - the TID is currently paused for ADDBA/BAR request
+	 * - seqno is not within block-ack window
+	 * - h/w queue depth exceeds low water mark
+	 */
+	if (!list_empty(&tid->buf_q) || tid->paused ||
+	    !BAW_WITHIN(tid->seq_start, tid->baw_size, bf->bf_seqno) ||
+	    txq->axq_depth >= ATH_AGGR_MIN_QDEPTH) {
+		/*
+		 * Add this frame to software queue for scheduling later
+		 * for aggregation.
+		 */
+		list_splice_tail_init(bf_head, &tid->buf_q);
+		ath_tx_queue_tid(txq, tid);
+		return 0;
+	}
+
+	skb = (struct sk_buff *)bf->bf_mpdu;
+	tx_info = IEEE80211_SKB_CB(skb);
+	tx_info_priv = (struct ath_tx_info_priv *)tx_info->driver_data[0];
+	memcpy(bf->bf_rcs, tx_info_priv->rcs, 4 * sizeof(tx_info_priv->rcs[0]));
+
+	/* Add sub-frame to BAW */
+	ath_tx_addto_baw(sc, tid, bf);
+
+	/* Queue to h/w without aggregation */
+	bf->bf_nframes = 1;
+	bf->bf_lastbf = bf->bf_lastfrm; /* one single frame */
+	ath_buf_set_rate(sc, bf);
+	ath_tx_txqaddbuf(sc, txq, bf_head);
+	return 0;
+}
+
+/*
+ * looks up the rate
+ * returns aggr limit based on lowest of the rates
+ */
+
+static u32 ath_lookup_rate(struct ath_softc *sc,
+				 struct ath_buf *bf)
+{
+	const struct ath9k_rate_table *rt = sc->sc_currates;
+	struct sk_buff *skb;
+	struct ieee80211_tx_info *tx_info;
+	struct ath_tx_info_priv *tx_info_priv;
+	u32 max_4ms_framelen, frame_length;
+	u16 aggr_limit, legacy = 0, maxampdu;
+	int i;
+
+
+	skb = (struct sk_buff *)bf->bf_mpdu;
+	tx_info = IEEE80211_SKB_CB(skb);
+	tx_info_priv = (struct ath_tx_info_priv *)
+		tx_info->driver_data[0];
+	memcpy(bf->bf_rcs,
+		tx_info_priv->rcs, 4 * sizeof(tx_info_priv->rcs[0]));
+
+	/*
+	 * Find the lowest frame length among the rate series that will have a
+	 * 4ms transmit duration.
+	 * TODO - TXOP limit needs to be considered.
+	 */
+	max_4ms_framelen = ATH_AMPDU_LIMIT_MAX;
+
+	for (i = 0; i < 4; i++) {
+		if (bf->bf_rcs[i].tries) {
+			frame_length = bf->bf_rcs[i].max_4ms_framelen;
+
+			if (rt->info[bf->bf_rcs[i].rix].phy != PHY_HT) {
+				legacy = 1;
+				break;
+			}
+
+			max_4ms_framelen = min(max_4ms_framelen, frame_length);
+		}
+	}
+
+	/*
+	 * limit aggregate size by the minimum rate if rate selected is
+	 * not a probe rate, if rate selected is a probe rate then
+	 * avoid aggregation of this packet.
+	 */
+	if (tx_info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE || legacy)
+		return 0;
+
+	aggr_limit = min(max_4ms_framelen,
+		(u32)ATH_AMPDU_LIMIT_DEFAULT);
+
+	/*
+	 * h/w can accept aggregates upto 16 bit lengths (65535).
+	 * The IE, however can hold upto 65536, which shows up here
+	 * as zero. Ignore 65536 since we  are constrained by hw.
+	 */
+	maxampdu = sc->sc_ht_info.maxampdu;
+	if (maxampdu)
+		aggr_limit = min(aggr_limit, maxampdu);
+
+	return aggr_limit;
+}
+
+/*
+ * returns the number of delimiters to be added to
+ * meet the minimum required mpdudensity.
+ * caller should make sure that the rate is  HT rate .
+ */
+
+static int ath_compute_num_delims(struct ath_softc *sc,
+				  struct ath_buf *bf,
+				  u16 frmlen)
+{
+	const struct ath9k_rate_table *rt = sc->sc_currates;
+	u32 nsymbits, nsymbols, mpdudensity;
+	u16 minlen;
+	u8 rc, flags, rix;
+	int width, half_gi, ndelim, mindelim;
+
+	/* Select standard number of delimiters based on frame length alone */
+	ndelim = ATH_AGGR_GET_NDELIM(frmlen);
+
+	/*
+	 * If encryption enabled, hardware requires some more padding between
+	 * subframes.
+	 * TODO - this could be improved to be dependent on the rate.
+	 *      The hardware can keep up at lower rates, but not higher rates
+	 */
+	if (bf->bf_keytype != ATH9K_KEY_TYPE_CLEAR)
+		ndelim += ATH_AGGR_ENCRYPTDELIM;
+
+	/*
+	 * Convert desired mpdu density from microeconds to bytes based
+	 * on highest rate in rate series (i.e. first rate) to determine
+	 * required minimum length for subframe. Take into account
+	 * whether high rate is 20 or 40Mhz and half or full GI.
+	 */
+	mpdudensity = sc->sc_ht_info.mpdudensity;
+
+	/*
+	 * If there is no mpdu density restriction, no further calculation
+	 * is needed.
+	 */
+	if (mpdudensity == 0)
+		return ndelim;
+
+	rix = bf->bf_rcs[0].rix;
+	flags = bf->bf_rcs[0].flags;
+	rc = rt->info[rix].rateCode;
+	width = (flags & ATH_RC_CW40_FLAG) ? 1 : 0;
+	half_gi = (flags & ATH_RC_SGI_FLAG) ? 1 : 0;
+
+	if (half_gi)
+		nsymbols = NUM_SYMBOLS_PER_USEC_HALFGI(mpdudensity);
+	else
+		nsymbols = NUM_SYMBOLS_PER_USEC(mpdudensity);
+
+	if (nsymbols == 0)
+		nsymbols = 1;
+
+	nsymbits = bits_per_symbol[HT_RC_2_MCS(rc)][width];
+	minlen = (nsymbols * nsymbits) / BITS_PER_BYTE;
+
+	/* Is frame shorter than required minimum length? */
+	if (frmlen < minlen) {
+		/* Get the minimum number of delimiters required. */
+		mindelim = (minlen - frmlen) / ATH_AGGR_DELIM_SZ;
+		ndelim = max(mindelim, ndelim);
+	}
+
+	return ndelim;
+}
+
+/*
+ * For aggregation from software buffer queue.
+ * NB: must be called with txq lock held
+ */
+
+static enum ATH_AGGR_STATUS ath_tx_form_aggr(struct ath_softc *sc,
+					struct ath_atx_tid *tid,
+					struct list_head *bf_q,
+					struct ath_buf **bf_last,
+					struct aggr_rifs_param *param,
+					int *prev_frames)
+{
+#define PADBYTES(_len) ((4 - ((_len) % 4)) % 4)
+	struct ath_buf *bf, *tbf, *bf_first, *bf_prev = NULL;
+	struct list_head bf_head;
+	int rl = 0, nframes = 0, ndelim;
+	u16 aggr_limit = 0, al = 0, bpad = 0,
+		al_delta, h_baw = tid->baw_size / 2;
+	enum ATH_AGGR_STATUS status = ATH_AGGR_DONE;
+	int prev_al = 0, is_ds_rate = 0;
+	INIT_LIST_HEAD(&bf_head);
+
+	BUG_ON(list_empty(&tid->buf_q));
+
+	bf_first = list_first_entry(&tid->buf_q, struct ath_buf, list);
+
+	do {
+		bf = list_first_entry(&tid->buf_q, struct ath_buf, list);
+
+		/*
+		 * do not step over block-ack window
+		 */
+		if (!BAW_WITHIN(tid->seq_start, tid->baw_size, bf->bf_seqno)) {
+			status = ATH_AGGR_BAW_CLOSED;
+			break;
+		}
+
+		if (!rl) {
+			aggr_limit = ath_lookup_rate(sc, bf);
+			rl = 1;
+			/*
+			 * Is rate dual stream
+			 */
+			is_ds_rate =
+				(bf->bf_rcs[0].flags & ATH_RC_DS_FLAG) ? 1 : 0;
+		}
+
+		/*
+		 * do not exceed aggregation limit
+		 */
+		al_delta = ATH_AGGR_DELIM_SZ + bf->bf_frmlen;
+
+		if (nframes && (aggr_limit <
+			(al + bpad + al_delta + prev_al))) {
+			status = ATH_AGGR_LIMITED;
+			break;
+		}
+
+		/*
+		 * do not exceed subframe limit
+		 */
+		if ((nframes + *prev_frames) >=
+		    min((int)h_baw, ATH_AMPDU_SUBFRAME_DEFAULT)) {
+			status = ATH_AGGR_LIMITED;
+			break;
+		}
+
+		/*
+		 * add padding for previous frame to aggregation length
+		 */
+		al += bpad + al_delta;
+
+		/*
+		 * Get the delimiters needed to meet the MPDU
+		 * density for this node.
+		 */
+		ndelim = ath_compute_num_delims(sc, bf_first, bf->bf_frmlen);
+
+		bpad = PADBYTES(al_delta) + (ndelim << 2);
+
+		bf->bf_next = NULL;
+		bf->bf_lastfrm->bf_desc->ds_link = 0;
+
+		/*
+		 * this packet is part of an aggregate
+		 * - remove all descriptors belonging to this frame from
+		 *   software queue
+		 * - add it to block ack window
+		 * - set up descriptors for aggregation
+		 */
+		list_cut_position(&bf_head, &tid->buf_q, &bf->bf_lastfrm->list);
+		ath_tx_addto_baw(sc, tid, bf);
+
+		list_for_each_entry(tbf, &bf_head, list) {
+			ath9k_hw_set11n_aggr_middle(sc->sc_ah,
+				tbf->bf_desc, ndelim);
+		}
+
+		/*
+		 * link buffers of this frame to the aggregate
+		 */
+		list_splice_tail_init(&bf_head, bf_q);
+		nframes++;
+
+		if (bf_prev) {
+			bf_prev->bf_next = bf;
+			bf_prev->bf_lastfrm->bf_desc->ds_link = bf->bf_daddr;
+		}
+		bf_prev = bf;
+
+#ifdef AGGR_NOSHORT
+		/*
+		 * terminate aggregation on a small packet boundary
+		 */
+		if (bf->bf_frmlen < ATH_AGGR_MINPLEN) {
+			status = ATH_AGGR_SHORTPKT;
+			break;
+		}
+#endif
+	} while (!list_empty(&tid->buf_q));
+
+	bf_first->bf_al = al;
+	bf_first->bf_nframes = nframes;
+	*bf_last = bf_prev;
+	return status;
+#undef PADBYTES
+}
+
+/*
+ * process pending frames possibly doing a-mpdu aggregation
+ * NB: must be called with txq lock held
+ */
+
+static void ath_tx_sched_aggr(struct ath_softc *sc,
+	struct ath_txq *txq, struct ath_atx_tid *tid)
+{
+	struct ath_buf *bf, *tbf, *bf_last, *bf_lastaggr = NULL;
+	enum ATH_AGGR_STATUS status;
+	struct list_head bf_q;
+	struct aggr_rifs_param param = {0, 0, 0, 0, NULL};
+	int prev_frames = 0;
+
+	do {
+		if (list_empty(&tid->buf_q))
+			return;
+
+		INIT_LIST_HEAD(&bf_q);
+
+		status = ath_tx_form_aggr(sc, tid, &bf_q, &bf_lastaggr, &param,
+					  &prev_frames);
+
+		/*
+		 * no frames picked up to be aggregated; block-ack
+		 * window is not open
+		 */
+		if (list_empty(&bf_q))
+			break;
+
+		bf = list_first_entry(&bf_q, struct ath_buf, list);
+		bf_last = list_entry(bf_q.prev, struct ath_buf, list);
+		bf->bf_lastbf = bf_last;
+
+		/*
+		 * if only one frame, send as non-aggregate
+		 */
+		if (bf->bf_nframes == 1) {
+			ASSERT(bf->bf_lastfrm == bf_last);
+
+			bf->bf_isaggr = 0;
+			/*
+			 * clear aggr bits for every descriptor
+			 * XXX TODO: is there a way to optimize it?
+			 */
+			list_for_each_entry(tbf, &bf_q, list) {
+				ath9k_hw_clr11n_aggr(sc->sc_ah, tbf->bf_desc);
+			}
+
+			ath_buf_set_rate(sc, bf);
+			ath_tx_txqaddbuf(sc, txq, &bf_q);
+			continue;
+		}
+
+		/*
+		 * setup first desc with rate and aggr info
+		 */
+		bf->bf_isaggr  = 1;
+		ath_buf_set_rate(sc, bf);
+		ath9k_hw_set11n_aggr_first(sc->sc_ah, bf->bf_desc, bf->bf_al);
+
+		/*
+		 * anchor last frame of aggregate correctly
+		 */
+		ASSERT(bf_lastaggr);
+		ASSERT(bf_lastaggr->bf_lastfrm == bf_last);
+		tbf = bf_lastaggr;
+		ath9k_hw_set11n_aggr_last(sc->sc_ah, tbf->bf_desc);
+
+		/* XXX: We don't enter into this loop, consider removing this */
+		while (!list_empty(&bf_q) && !list_is_last(&tbf->list, &bf_q)) {
+			tbf = list_entry(tbf->list.next, struct ath_buf, list);
+			ath9k_hw_set11n_aggr_last(sc->sc_ah, tbf->bf_desc);
+		}
+
+		txq->axq_aggr_depth++;
+
+		/*
+		 * Normal aggregate, queue to hardware
+		 */
+		ath_tx_txqaddbuf(sc, txq, &bf_q);
+
+	} while (txq->axq_depth < ATH_AGGR_MIN_QDEPTH &&
+		 status != ATH_AGGR_BAW_CLOSED);
+}
+
+/* Called with txq lock held */
+
+static void ath_tid_drain(struct ath_softc *sc,
+			  struct ath_txq *txq,
+			  struct ath_atx_tid *tid,
+			  bool bh_flag)
+{
+	struct ath_buf *bf;
+	struct list_head bf_head;
+	INIT_LIST_HEAD(&bf_head);
+
+	for (;;) {
+		if (list_empty(&tid->buf_q))
+			break;
+		bf = list_first_entry(&tid->buf_q, struct ath_buf, list);
+
+		list_cut_position(&bf_head, &tid->buf_q, &bf->bf_lastfrm->list);
+
+		/* update baw for software retried frame */
+		if (bf->bf_isretried)
+			ath_tx_update_baw(sc, tid, bf->bf_seqno);
+
+		/*
+		 * do not indicate packets while holding txq spinlock.
+		 * unlock is intentional here
+		 */
+		if (likely(bh_flag))
+			spin_unlock_bh(&txq->axq_lock);
+		else
+			spin_unlock(&txq->axq_lock);
+
+		/* complete this sub-frame */
+		ath_tx_complete_buf(sc, bf, &bf_head, 0, 0);
+
+		if (likely(bh_flag))
+			spin_lock_bh(&txq->axq_lock);
+		else
+			spin_lock(&txq->axq_lock);
+	}
+
+	/*
+	 * TODO: For frame(s) that are in the retry state, we will reuse the
+	 * sequence number(s) without setting the retry bit. The
+	 * alternative is to give up on these and BAR the receiver's window
+	 * forward.
+	 */
+	tid->seq_next = tid->seq_start;
+	tid->baw_tail = tid->baw_head;
+}
+
+/*
+ * Drain all pending buffers
+ * NB: must be called with txq lock held
+ */
+
+static void ath_txq_drain_pending_buffers(struct ath_softc *sc,
+					  struct ath_txq *txq,
+					  bool bh_flag)
+{
+	struct ath_atx_ac *ac, *ac_tmp;
+	struct ath_atx_tid *tid, *tid_tmp;
+
+	list_for_each_entry_safe(ac, ac_tmp, &txq->axq_acq, list) {
+		list_del(&ac->list);
+		ac->sched = false;
+		list_for_each_entry_safe(tid, tid_tmp, &ac->tid_q, list) {
+			list_del(&tid->list);
+			tid->sched = false;
+			ath_tid_drain(sc, txq, tid, bh_flag);
+		}
+	}
+}
+
+static int ath_tx_start_dma(struct ath_softc *sc,
+			    struct sk_buff *skb,
+			    struct scatterlist *sg,
+			    u32 n_sg,
+			    struct ath_tx_control *txctl)
+{
+	struct ath_node *an = txctl->an;
+	struct ath_buf *bf = NULL;
+	struct list_head bf_head;
+	struct ath_desc *ds;
+	struct ath_hal *ah = sc->sc_ah;
+	struct ath_txq *txq = &sc->sc_txq[txctl->qnum];
+	struct ath_tx_info_priv *tx_info_priv;
+	struct ath_rc_series *rcs;
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
+	struct ieee80211_tx_info *tx_info =  IEEE80211_SKB_CB(skb);
+	__le16 fc = hdr->frame_control;
+
+	/* For each sglist entry, allocate an ath_buf for DMA */
+	INIT_LIST_HEAD(&bf_head);
+	spin_lock_bh(&sc->sc_txbuflock);
+	if (unlikely(list_empty(&sc->sc_txbuf))) {
+		spin_unlock_bh(&sc->sc_txbuflock);
+		return -ENOMEM;
+	}
+
+	bf = list_first_entry(&sc->sc_txbuf, struct ath_buf, list);
+	list_del(&bf->list);
+	spin_unlock_bh(&sc->sc_txbuflock);
+
+	list_add_tail(&bf->list, &bf_head);
+
+	/* set up this buffer */
+	ATH_TXBUF_RESET(bf);
+	bf->bf_frmlen = txctl->frmlen;
+	bf->bf_isdata = ieee80211_is_data(fc);
+	bf->bf_isbar = ieee80211_is_back_req(fc);
+	bf->bf_ispspoll = ieee80211_is_pspoll(fc);
+	bf->bf_flags = txctl->flags;
+	bf->bf_shpreamble = sc->sc_flags & ATH_PREAMBLE_SHORT;
+	bf->bf_keytype = txctl->keytype;
+	tx_info_priv = (struct ath_tx_info_priv *)tx_info->driver_data[0];
+	rcs = tx_info_priv->rcs;
+	bf->bf_rcs[0] = rcs[0];
+	bf->bf_rcs[1] = rcs[1];
+	bf->bf_rcs[2] = rcs[2];
+	bf->bf_rcs[3] = rcs[3];
+	bf->bf_node = an;
+	bf->bf_mpdu = skb;
+	bf->bf_buf_addr = sg_dma_address(sg);
+
+	/* setup descriptor */
+	ds = bf->bf_desc;
+	ds->ds_link = 0;
+	ds->ds_data = bf->bf_buf_addr;
+
+	/*
+	 * Save the DMA context in the first ath_buf
+	 */
+	copy_dma_mem_context(get_dma_mem_context(bf, bf_dmacontext),
+			     get_dma_mem_context(txctl, dmacontext));
+
+	/*
+	 * Formulate first tx descriptor with tx controls.
+	 */
+	ath9k_hw_set11n_txdesc(ah,
+			       ds,
+			       bf->bf_frmlen, /* frame length */
+			       txctl->atype, /* Atheros packet type */
+			       min(txctl->txpower, (u16)60), /* txpower */
+			       txctl->keyix,            /* key cache index */
+			       txctl->keytype,          /* key type */
+			       txctl->flags);           /* flags */
+	ath9k_hw_filltxdesc(ah,
+			    ds,
+			    sg_dma_len(sg),     /* segment length */
+			    true,            /* first segment */
+			    (n_sg == 1) ? true : false, /* last segment */
+			    ds);                /* first descriptor */
+
+	bf->bf_lastfrm = bf;
+	bf->bf_ht = txctl->ht;
+
+	spin_lock_bh(&txq->axq_lock);
+
+	if (txctl->ht && sc->sc_txaggr) {
+		struct ath_atx_tid *tid = ATH_AN_2_TID(an, txctl->tidno);
+		if (ath_aggr_query(sc, an, txctl->tidno)) {
+			/*
+			 * Try aggregation if it's a unicast data frame
+			 * and the destination is HT capable.
+			 */
+			ath_tx_send_ampdu(sc, txq, tid, &bf_head, txctl);
+		} else {
+			/*
+			 * Send this frame as regular when ADDBA exchange
+			 * is neither complete nor pending.
+			 */
+			ath_tx_send_normal(sc, txq, tid, &bf_head);
+		}
+	} else {
+		bf->bf_lastbf = bf;
+		bf->bf_nframes = 1;
+		ath_buf_set_rate(sc, bf);
+
+		if (ieee80211_is_back_req(fc)) {
+			/* This is required for resuming tid
+			 * during BAR completion */
+			bf->bf_tidno = txctl->tidno;
+		}
+
+		if (is_multicast_ether_addr(hdr->addr1)) {
+			struct ath_vap *avp = sc->sc_vaps[txctl->if_id];
+
+			/*
+			 * When servicing one or more stations in power-save
+			 * mode (or) if there is some mcast data waiting on
+			 * mcast queue (to prevent out of order delivery of
+			 * mcast,bcast packets) multicast frames must be
+			 * buffered until after the beacon. We use the private
+			 * mcast queue for that.
+			 */
+			/* XXX? more bit in 802.11 frame header */
+			spin_lock_bh(&avp->av_mcastq.axq_lock);
+			if (txctl->ps || avp->av_mcastq.axq_depth)
+				ath_tx_mcastqaddbuf(sc,
+					&avp->av_mcastq, &bf_head);
+			else
+				ath_tx_txqaddbuf(sc, txq, &bf_head);
+			spin_unlock_bh(&avp->av_mcastq.axq_lock);
+		} else
+			ath_tx_txqaddbuf(sc, txq, &bf_head);
+	}
+	spin_unlock_bh(&txq->axq_lock);
+	return 0;
+}
+
+static void xmit_map_sg(struct ath_softc *sc,
+			struct sk_buff *skb,
+			dma_addr_t *pa,
+			struct ath_tx_control *txctl)
+{
+	struct ath_xmit_status tx_status;
+	struct ath_atx_tid *tid;
+	struct scatterlist sg;
+
+	*pa = pci_map_single(sc->pdev, skb->data, skb->len, PCI_DMA_TODEVICE);
+
+	/* setup S/G list */
+	memset(&sg, 0, sizeof(struct scatterlist));
+	sg_dma_address(&sg) = *pa;
+	sg_dma_len(&sg) = skb->len;
+
+	if (ath_tx_start_dma(sc, skb, &sg, 1, txctl) != 0) {
+		/*
+		 *  We have to do drop frame here.
+		 */
+		pci_unmap_single(sc->pdev, *pa, skb->len, PCI_DMA_TODEVICE);
+
+		tx_status.retries = 0;
+		tx_status.flags = ATH_TX_ERROR;
+
+		if (txctl->ht && sc->sc_txaggr) {
+			/* Reclaim the seqno. */
+			tid = ATH_AN_2_TID((struct ath_node *)
+				txctl->an, txctl->tidno);
+			DECR(tid->seq_next, IEEE80211_SEQ_MAX);
+		}
+		ath_tx_complete(sc, skb, &tx_status, txctl->an);
+	}
+}
+
+/* Initialize TX queue and h/w */
+
+int ath_tx_init(struct ath_softc *sc, int nbufs)
+{
+	int error = 0;
+
+	do {
+		spin_lock_init(&sc->sc_txbuflock);
+
+		/* Setup tx descriptors */
+		error = ath_descdma_setup(sc, &sc->sc_txdma, &sc->sc_txbuf,
+			"tx", nbufs * ATH_FRAG_PER_MSDU, ATH_TXDESC);
+		if (error != 0) {
+			DPRINTF(sc, ATH_DBG_FATAL,
+				"%s: failed to allocate tx descriptors: %d\n",
+				__func__, error);
+			break;
+		}
+
+		/* XXX allocate beacon state together with vap */
+		error = ath_descdma_setup(sc, &sc->sc_bdma, &sc->sc_bbuf,
+					  "beacon", ATH_BCBUF, 1);
+		if (error != 0) {
+			DPRINTF(sc, ATH_DBG_FATAL,
+				"%s: failed to allocate "
+				"beacon descripotrs: %d\n",
+				__func__, error);
+			break;
+		}
+
+	} while (0);
+
+	if (error != 0)
+		ath_tx_cleanup(sc);
+
+	return error;
+}
+
+/* Reclaim all tx queue resources */
+
+int ath_tx_cleanup(struct ath_softc *sc)
+{
+	/* cleanup beacon descriptors */
+	if (sc->sc_bdma.dd_desc_len != 0)
+		ath_descdma_cleanup(sc, &sc->sc_bdma, &sc->sc_bbuf);
+
+	/* cleanup tx descriptors */
+	if (sc->sc_txdma.dd_desc_len != 0)
+		ath_descdma_cleanup(sc, &sc->sc_txdma, &sc->sc_txbuf);
+
+	return 0;
+}
+
+/* Setup a h/w transmit queue */
+
+struct ath_txq *ath_txq_setup(struct ath_softc *sc, int qtype, int subtype)
+{
+	struct ath_hal *ah = sc->sc_ah;
+	struct ath9k_txq_info qi;
+	int qnum;
+
+	memzero(&qi, sizeof(qi));
+	qi.tqi_subtype = subtype;
+	qi.tqi_aifs = ATH9K_TXQ_USEDEFAULT;
+	qi.tqi_cwmin = ATH9K_TXQ_USEDEFAULT;
+	qi.tqi_cwmax = ATH9K_TXQ_USEDEFAULT;
+	qi.tqi_compBuf = 0;
+
+	/*
+	 * Enable interrupts only for EOL and DESC conditions.
+	 * We mark tx descriptors to receive a DESC interrupt
+	 * when a tx queue gets deep; otherwise waiting for the
+	 * EOL to reap descriptors.  Note that this is done to
+	 * reduce interrupt load and this only defers reaping
+	 * descriptors, never transmitting frames.  Aside from
+	 * reducing interrupts this also permits more concurrency.
+	 * The only potential downside is if the tx queue backs
+	 * up in which case the top half of the kernel may backup
+	 * due to a lack of tx descriptors.
+	 *
+	 * The UAPSD queue is an exception, since we take a desc-
+	 * based intr on the EOSP frames.
+	 */
+	if (qtype == ATH9K_TX_QUEUE_UAPSD)
+		qi.tqi_qflags = TXQ_FLAG_TXDESCINT_ENABLE;
+	else
+		qi.tqi_qflags = TXQ_FLAG_TXEOLINT_ENABLE |
+			TXQ_FLAG_TXDESCINT_ENABLE;
+	qnum = ath9k_hw_setuptxqueue(ah, qtype, &qi);
+	if (qnum == -1) {
+		/*
+		 * NB: don't print a message, this happens
+		 * normally on parts with too few tx queues
+		 */
+		return NULL;
+	}
+	if (qnum >= ARRAY_SIZE(sc->sc_txq)) {
+		DPRINTF(sc, ATH_DBG_FATAL,
+			"%s: hal qnum %u out of range, max %u!\n",
+			__func__, qnum, (unsigned int)ARRAY_SIZE(sc->sc_txq));
+		ath9k_hw_releasetxqueue(ah, qnum);
+		return NULL;
+	}
+	if (!ATH_TXQ_SETUP(sc, qnum)) {
+		struct ath_txq *txq = &sc->sc_txq[qnum];
+
+		txq->axq_qnum = qnum;
+		txq->axq_link = NULL;
+		INIT_LIST_HEAD(&txq->axq_q);
+		INIT_LIST_HEAD(&txq->axq_acq);
+		spin_lock_init(&txq->axq_lock);
+		txq->axq_depth = 0;
+		txq->axq_aggr_depth = 0;
+		txq->axq_totalqueued = 0;
+		txq->axq_intrcnt = 0;
+		txq->axq_linkbuf = NULL;
+		sc->sc_txqsetup |= 1<<qnum;
+	}
+	return &sc->sc_txq[qnum];
+}
+
+/* Reclaim resources for a setup queue */
+
+void ath_tx_cleanupq(struct ath_softc *sc, struct ath_txq *txq)
+{
+	ath9k_hw_releasetxqueue(sc->sc_ah, txq->axq_qnum);
+	sc->sc_txqsetup &= ~(1<<txq->axq_qnum);
+}
+
+/*
+ * Setup a hardware data transmit queue for the specified
+ * access control.  The hal may not support all requested
+ * queues in which case it will return a reference to a
+ * previously setup queue.  We record the mapping from ac's
+ * to h/w queues for use by ath_tx_start and also track
+ * the set of h/w queues being used to optimize work in the
+ * transmit interrupt handler and related routines.
+ */
+
+int ath_tx_setup(struct ath_softc *sc, int haltype)
+{
+	struct ath_txq *txq;
+
+	if (haltype >= ARRAY_SIZE(sc->sc_haltype2q)) {
+		DPRINTF(sc, ATH_DBG_FATAL,
+			"%s: HAL AC %u out of range, max %zu!\n",
+			__func__, haltype, ARRAY_SIZE(sc->sc_haltype2q));
+		return 0;
+	}
+	txq = ath_txq_setup(sc, ATH9K_TX_QUEUE_DATA, haltype);
+	if (txq != NULL) {
+		sc->sc_haltype2q[haltype] = txq->axq_qnum;
+		return 1;
+	} else
+		return 0;
+}
+
+int ath_tx_get_qnum(struct ath_softc *sc, int qtype, int haltype)
+{
+	int qnum;
+
+	switch (qtype) {
+	case ATH9K_TX_QUEUE_DATA:
+		if (haltype >= ARRAY_SIZE(sc->sc_haltype2q)) {
+			DPRINTF(sc, ATH_DBG_FATAL,
+				"%s: HAL AC %u out of range, max %zu!\n",
+				__func__,
+				haltype, ARRAY_SIZE(sc->sc_haltype2q));
+			return -1;
+		}
+		qnum = sc->sc_haltype2q[haltype];
+		break;
+	case ATH9K_TX_QUEUE_BEACON:
+		qnum = sc->sc_bhalq;
+		break;
+	case ATH9K_TX_QUEUE_CAB:
+		qnum = sc->sc_cabq->axq_qnum;
+		break;
+	default:
+		qnum = -1;
+	}
+	return qnum;
+}
+
+/* Update parameters for a transmit queue */
+
+int ath_txq_update(struct ath_softc *sc, int qnum, struct ath9k_txq_info *qi0)
+{
+	struct ath_hal *ah = sc->sc_ah;
+	int error = 0;
+	struct ath9k_txq_info qi;
+
+	if (qnum == sc->sc_bhalq) {
+		/*
+		 * XXX: for beacon queue, we just save the parameter.
+		 * It will be picked up by ath_beaconq_config when
+		 * it's necessary.
+		 */
+		sc->sc_beacon_qi = *qi0;
+		return 0;
+	}
+
+	ASSERT(sc->sc_txq[qnum].axq_qnum == qnum);
+
+	ath9k_hw_gettxqueueprops(ah, qnum, &qi);
+	qi.tqi_aifs = qi0->tqi_aifs;
+	qi.tqi_cwmin = qi0->tqi_cwmin;
+	qi.tqi_cwmax = qi0->tqi_cwmax;
+	qi.tqi_burstTime = qi0->tqi_burstTime;
+	qi.tqi_readyTime = qi0->tqi_readyTime;
+
+	if (!ath9k_hw_settxqueueprops(ah, qnum, &qi)) {
+		DPRINTF(sc, ATH_DBG_FATAL,
+			"%s: unable to update hardware queue %u!\n",
+			__func__, qnum);
+		error = -EIO;
+	} else {
+		ath9k_hw_resettxqueue(ah, qnum); /* push to h/w */
+	}
+
+	return error;
+}
+
+int ath_cabq_update(struct ath_softc *sc)
+{
+	struct ath9k_txq_info qi;
+	int qnum = sc->sc_cabq->axq_qnum;
+	struct ath_beacon_config conf;
+
+	ath9k_hw_gettxqueueprops(sc->sc_ah, qnum, &qi);
+	/*
+	 * Ensure the readytime % is within the bounds.
+	 */
+	if (sc->sc_config.cabqReadytime < ATH9K_READY_TIME_LO_BOUND)
+		sc->sc_config.cabqReadytime = ATH9K_READY_TIME_LO_BOUND;
+	else if (sc->sc_config.cabqReadytime > ATH9K_READY_TIME_HI_BOUND)
+		sc->sc_config.cabqReadytime = ATH9K_READY_TIME_HI_BOUND;
+
+	ath_get_beaconconfig(sc, ATH_IF_ID_ANY, &conf);
+	qi.tqi_readyTime =
+		(conf.beacon_interval * sc->sc_config.cabqReadytime) / 100;
+	ath_txq_update(sc, qnum, &qi);
+
+	return 0;
+}
+
+int ath_tx_start(struct ath_softc *sc, struct sk_buff *skb)
+{
+	struct ath_tx_control txctl;
+	int error = 0;
+
+	error = ath_tx_prepare(sc, skb, &txctl);
+	if (error == 0)
+		/*
+		 * Start DMA mapping.
+		 * ath_tx_start_dma() will be called either synchronously
+		 * or asynchrounsly once DMA is complete.
+		 */
+		xmit_map_sg(sc, skb,
+			    get_dma_mem_context(&txctl, dmacontext),
+			    &txctl);
+	else
+		ath_node_put(sc, txctl.an, ATH9K_BH_STATUS_CHANGE);
+
+	/* failed packets will be dropped by the caller */
+	return error;
+}
+
+/* Deferred processing of transmit interrupt */
+
+void ath_tx_tasklet(struct ath_softc *sc)
+{
+	u64 tsf = ath9k_hw_gettsf64(sc->sc_ah);
+	int i, nacked = 0;
+	u32 qcumask = ((1 << ATH9K_NUM_TX_QUEUES) - 1);
+
+	ath9k_hw_gettxintrtxqs(sc->sc_ah, &qcumask);
+
+	/*
+	 * Process each active queue.
+	 */
+	for (i = 0; i < ATH9K_NUM_TX_QUEUES; i++) {
+		if (ATH_TXQ_SETUP(sc, i) && (qcumask & (1 << i)))
+			nacked += ath_tx_processq(sc, &sc->sc_txq[i]);
+	}
+	if (nacked)
+		sc->sc_lastrx = tsf;
+}
+
+void ath_tx_draintxq(struct ath_softc *sc,
+	struct ath_txq *txq, bool retry_tx)
+{
+	struct ath_buf *bf, *lastbf;
+	struct list_head bf_head;
+
+	INIT_LIST_HEAD(&bf_head);
+
+	/*
+	 * NB: this assumes output has been stopped and
+	 *     we do not need to block ath_tx_tasklet
+	 */
+	for (;;) {
+		spin_lock_bh(&txq->axq_lock);
+
+		if (list_empty(&txq->axq_q)) {
+			txq->axq_link = NULL;
+			txq->axq_linkbuf = NULL;
+			spin_unlock_bh(&txq->axq_lock);
+			break;
+		}
+
+		bf = list_first_entry(&txq->axq_q, struct ath_buf, list);
+
+		if (bf->bf_status & ATH_BUFSTATUS_STALE) {
+			list_del(&bf->list);
+			spin_unlock_bh(&txq->axq_lock);
+
+			spin_lock_bh(&sc->sc_txbuflock);
+			list_add_tail(&bf->list, &sc->sc_txbuf);
+			spin_unlock_bh(&sc->sc_txbuflock);
+			continue;
+		}
+
+		lastbf = bf->bf_lastbf;
+		if (!retry_tx)
+			lastbf->bf_desc->ds_txstat.ts_flags =
+				ATH9K_TX_SW_ABORTED;
+
+		/* remove ath_buf's of the same mpdu from txq */
+		list_cut_position(&bf_head, &txq->axq_q, &lastbf->list);
+		txq->axq_depth--;
+
+		spin_unlock_bh(&txq->axq_lock);
+
+		if (bf->bf_isampdu)
+			ath_tx_complete_aggr_rifs(sc, txq, bf, &bf_head, 0);
+		else
+			ath_tx_complete_buf(sc, bf, &bf_head, 0, 0);
+	}
+
+	/* flush any pending frames if aggregation is enabled */
+	if (sc->sc_txaggr) {
+		if (!retry_tx) {
+			spin_lock_bh(&txq->axq_lock);
+			ath_txq_drain_pending_buffers(sc, txq,
+				ATH9K_BH_STATUS_CHANGE);
+			spin_unlock_bh(&txq->axq_lock);
+		}
+	}
+}
+
+/* Drain the transmit queues and reclaim resources */
+
+void ath_draintxq(struct ath_softc *sc, bool retry_tx)
+{
+	/* stop beacon queue. The beacon will be freed when
+	 * we go to INIT state */
+	if (!sc->sc_invalid) {
+		(void) ath9k_hw_stoptxdma(sc->sc_ah, sc->sc_bhalq);
+		DPRINTF(sc, ATH_DBG_XMIT, "%s: beacon queue %x\n", __func__,
+			ath9k_hw_gettxbuf(sc->sc_ah, sc->sc_bhalq));
+	}
+
+	ath_drain_txdataq(sc, retry_tx);
+}
+
+u32 ath_txq_depth(struct ath_softc *sc, int qnum)
+{
+	return sc->sc_txq[qnum].axq_depth;
+}
+
+u32 ath_txq_aggr_depth(struct ath_softc *sc, int qnum)
+{
+	return sc->sc_txq[qnum].axq_aggr_depth;
+}
+
+/* Check if an ADDBA is required. A valid node must be passed. */
+enum ATH_AGGR_CHECK ath_tx_aggr_check(struct ath_softc *sc,
+				      struct ath_node *an,
+				      u8 tidno)
+{
+	struct ath_atx_tid *txtid;
+	DECLARE_MAC_BUF(mac);
+
+	if (!sc->sc_txaggr)
+		return AGGR_NOT_REQUIRED;
+
+	/* ADDBA exchange must be completed before sending aggregates */
+	txtid = ATH_AN_2_TID(an, tidno);
+
+	if (txtid->addba_exchangecomplete)
+		return AGGR_EXCHANGE_DONE;
+
+	if (txtid->cleanup_inprogress)
+		return AGGR_CLEANUP_PROGRESS;
+
+	if (txtid->addba_exchangeinprogress)
+		return AGGR_EXCHANGE_PROGRESS;
+
+	if (!txtid->addba_exchangecomplete) {
+		if (!txtid->addba_exchangeinprogress &&
+		    (txtid->addba_exchangeattempts < ADDBA_EXCHANGE_ATTEMPTS)) {
+			txtid->addba_exchangeattempts++;
+			return AGGR_REQUIRED;
+		}
+	}
+
+	return AGGR_NOT_REQUIRED;
+}
+
+/* Start TX aggregation */
+
+int ath_tx_aggr_start(struct ath_softc *sc,
+		      const u8 *addr,
+		      u16 tid,
+		      u16 *ssn)
+{
+	struct ath_atx_tid *txtid;
+	struct ath_node *an;
+
+	spin_lock_bh(&sc->node_lock);
+	an = ath_node_find(sc, (u8 *) addr);
+	spin_unlock_bh(&sc->node_lock);
+
+	if (!an) {
+		DPRINTF(sc, ATH_DBG_AGGR,
+			"%s: Node not found to initialize "
+			"TX aggregation\n", __func__);
+		return -1;
+	}
+
+	if (sc->sc_txaggr) {
+		txtid = ATH_AN_2_TID(an, tid);
+		txtid->addba_exchangeinprogress = 1;
+		ath_tx_pause_tid(sc, txtid);
+	}
+
+	return 0;
+}
+
+/* Stop tx aggregation */
+
+int ath_tx_aggr_stop(struct ath_softc *sc,
+		     const u8 *addr,
+		     u16 tid)
+{
+	struct ath_node *an;
+
+	spin_lock_bh(&sc->node_lock);
+	an = ath_node_find(sc, (u8 *) addr);
+	spin_unlock_bh(&sc->node_lock);
+
+	if (!an) {
+		DPRINTF(sc, ATH_DBG_AGGR,
+			"%s: TX aggr stop for non-existent node\n", __func__);
+		return -1;
+	}
+
+	ath_tx_aggr_teardown(sc, an, tid);
+	return 0;
+}
+
+/*
+ * Performs transmit side cleanup when TID changes from aggregated to
+ * unaggregated.
+ * - Pause the TID and mark cleanup in progress
+ * - Discard all retry frames from the s/w queue.
+ */
+
+void ath_tx_aggr_teardown(struct ath_softc *sc,
+	struct ath_node *an, u8 tid)
+{
+	struct ath_atx_tid *txtid = ATH_AN_2_TID(an, tid);
+	struct ath_txq *txq = &sc->sc_txq[txtid->ac->qnum];
+	struct ath_buf *bf;
+	struct list_head bf_head;
+	INIT_LIST_HEAD(&bf_head);
+
+	DPRINTF(sc, ATH_DBG_AGGR, "%s: teardown TX aggregation\n", __func__);
+
+	if (txtid->cleanup_inprogress) /* cleanup is in progress */
+		return;
+
+	if (!txtid->addba_exchangecomplete) {
+		txtid->addba_exchangeattempts = 0;
+		return;
+	}
+
+	/* TID must be paused first */
+	ath_tx_pause_tid(sc, txtid);
+
+	/* drop all software retried frames and mark this TID */
+	spin_lock_bh(&txq->axq_lock);
+	while (!list_empty(&txtid->buf_q)) {
+		bf = list_first_entry(&txtid->buf_q, struct ath_buf, list);
+		if (!bf->bf_isretried) {
+			/*
+			 * NB: it's based on the assumption that
+			 * software retried frame will always stay
+			 * at the head of software queue.
+			 */
+			break;
+		}
+		list_cut_position(&bf_head,
+			&txtid->buf_q, &bf->bf_lastfrm->list);
+		ath_tx_update_baw(sc, txtid, bf->bf_seqno);
+
+		/* complete this sub-frame */
+		ath_tx_complete_buf(sc, bf, &bf_head, 0, 0);
+	}
+
+	if (txtid->baw_head != txtid->baw_tail) {
+		spin_unlock_bh(&txq->axq_lock);
+		txtid->cleanup_inprogress = true;
+	} else {
+		txtid->addba_exchangecomplete = 0;
+		txtid->addba_exchangeattempts = 0;
+		spin_unlock_bh(&txq->axq_lock);
+		ath_tx_flush_tid(sc, txtid);
+	}
+}
+
+/*
+ * Tx scheduling logic
+ * NB: must be called with txq lock held
+ */
+
+void ath_txq_schedule(struct ath_softc *sc, struct ath_txq *txq)
+{
+	struct ath_atx_ac *ac;
+	struct ath_atx_tid *tid;
+
+	/* nothing to schedule */
+	if (list_empty(&txq->axq_acq))
+		return;
+	/*
+	 * get the first node/ac pair on the queue
+	 */
+	ac = list_first_entry(&txq->axq_acq, struct ath_atx_ac, list);
+	list_del(&ac->list);
+	ac->sched = false;
+
+	/*
+	 * process a single tid per destination
+	 */
+	do {
+		/* nothing to schedule */
+		if (list_empty(&ac->tid_q))
+			return;
+
+		tid = list_first_entry(&ac->tid_q, struct ath_atx_tid, list);
+		list_del(&tid->list);
+		tid->sched = false;
+
+		if (tid->paused)    /* check next tid to keep h/w busy */
+			continue;
+
+		if (!(tid->an->an_smmode == ATH_SM_PWRSAV_DYNAMIC) ||
+		    ((txq->axq_depth % 2) == 0)) {
+			ath_tx_sched_aggr(sc, txq, tid);
+		}
+
+		/*
+		 * add tid to round-robin queue if more frames
+		 * are pending for the tid
+		 */
+		if (!list_empty(&tid->buf_q))
+			ath_tx_queue_tid(txq, tid);
+
+		/* only schedule one TID at a time */
+		break;
+	} while (!list_empty(&ac->tid_q));
+
+	/*
+	 * schedule AC if more TIDs need processing
+	 */
+	if (!list_empty(&ac->tid_q)) {
+		/*
+		 * add dest ac to txq if not already added
+		 */
+		if (!ac->sched) {
+			ac->sched = true;
+			list_add_tail(&ac->list, &txq->axq_acq);
+		}
+	}
+}
+
+/* Initialize per-node transmit state */
+
+void ath_tx_node_init(struct ath_softc *sc, struct ath_node *an)
+{
+	if (sc->sc_txaggr) {
+		struct ath_atx_tid *tid;
+		struct ath_atx_ac *ac;
+		int tidno, acno;
+
+		sc->sc_ht_info.maxampdu = ATH_AMPDU_LIMIT_DEFAULT;
+
+		/*
+		 * Init per tid tx state
+		 */
+		for (tidno = 0, tid = &an->an_aggr.tx.tid[tidno];
+				tidno < WME_NUM_TID;
+				tidno++, tid++) {
+			tid->an        = an;
+			tid->tidno     = tidno;
+			tid->seq_start = tid->seq_next = 0;
+			tid->baw_size  = WME_MAX_BA;
+			tid->baw_head  = tid->baw_tail = 0;
+			tid->sched     = false;
+			tid->paused = false;
+			tid->cleanup_inprogress = false;
+			INIT_LIST_HEAD(&tid->buf_q);
+
+			acno = TID_TO_WME_AC(tidno);
+			tid->ac = &an->an_aggr.tx.ac[acno];
+
+			/* ADDBA state */
+			tid->addba_exchangecomplete     = 0;
+			tid->addba_exchangeinprogress   = 0;
+			tid->addba_exchangeattempts     = 0;
+		}
+
+		/*
+		 * Init per ac tx state
+		 */
+		for (acno = 0, ac = &an->an_aggr.tx.ac[acno];
+				acno < WME_NUM_AC; acno++, ac++) {
+			ac->sched    = false;
+			INIT_LIST_HEAD(&ac->tid_q);
+
+			switch (acno) {
+			case WME_AC_BE:
+				ac->qnum = ath_tx_get_qnum(sc,
+					ATH9K_TX_QUEUE_DATA, ATH9K_WME_AC_BE);
+				break;
+			case WME_AC_BK:
+				ac->qnum = ath_tx_get_qnum(sc,
+					ATH9K_TX_QUEUE_DATA, ATH9K_WME_AC_BK);
+				break;
+			case WME_AC_VI:
+				ac->qnum = ath_tx_get_qnum(sc,
+					ATH9K_TX_QUEUE_DATA, ATH9K_WME_AC_VI);
+				break;
+			case WME_AC_VO:
+				ac->qnum = ath_tx_get_qnum(sc,
+					ATH9K_TX_QUEUE_DATA, ATH9K_WME_AC_VO);
+				break;
+			}
+		}
+	}
+}
+
+/* Cleanupthe pending buffers for the node. */
+
+void ath_tx_node_cleanup(struct ath_softc *sc,
+	struct ath_node *an, bool bh_flag)
+{
+	int i;
+	struct ath_atx_ac *ac, *ac_tmp;
+	struct ath_atx_tid *tid, *tid_tmp;
+	struct ath_txq *txq;
+	for (i = 0; i < ATH9K_NUM_TX_QUEUES; i++) {
+		if (ATH_TXQ_SETUP(sc, i)) {
+			txq = &sc->sc_txq[i];
+
+			if (likely(bh_flag))
+				spin_lock_bh(&txq->axq_lock);
+			else
+				spin_lock(&txq->axq_lock);
+
+			list_for_each_entry_safe(ac,
+					ac_tmp, &txq->axq_acq, list) {
+				tid = list_first_entry(&ac->tid_q,
+						struct ath_atx_tid, list);
+				if (tid && tid->an != an)
+					continue;
+				list_del(&ac->list);
+				ac->sched = false;
+
+				list_for_each_entry_safe(tid,
+						tid_tmp, &ac->tid_q, list) {
+					list_del(&tid->list);
+					tid->sched = false;
+					ath_tid_drain(sc, txq, tid, bh_flag);
+					tid->addba_exchangecomplete = 0;
+					tid->addba_exchangeattempts = 0;
+					tid->cleanup_inprogress = false;
+				}
+			}
+
+			if (likely(bh_flag))
+				spin_unlock_bh(&txq->axq_lock);
+			else
+				spin_unlock(&txq->axq_lock);
+		}
+	}
+}
+
+/* Cleanup per node transmit state */
+
+void ath_tx_node_free(struct ath_softc *sc, struct ath_node *an)
+{
+	if (sc->sc_txaggr) {
+		struct ath_atx_tid *tid;
+		int tidno, i;
+
+		/* Init per tid rx state */
+		for (tidno = 0, tid = &an->an_aggr.tx.tid[tidno];
+			tidno < WME_NUM_TID;
+		     tidno++, tid++) {
+
+			for (i = 0; i < ATH_TID_MAX_BUFS; i++)
+				ASSERT(tid->tx_buf[i] == NULL);
+		}
+	}
+}