Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6

[linux-2.6] / drivers / net / wireless / ath9k / xmit.c

/*
 * Copyright (c) 2008 Atheros Communications Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * 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 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;

        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->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.hw_key->icv_len;

                if (tx_info->control.hw_key->alg == ALG_WEP)
                        txctl->keytype = ATH9K_KEY_TYPE_WEP;
                else if (tx_info->control.hw_key->alg == ALG_TKIP)
                        txctl->keytype = ATH9K_KEY_TYPE_TKIP;
                else if (tx_info->control.hw_key->alg == ALG_CCMP)
                        txctl->keytype = ATH9K_KEY_TYPE_AES;
        }

        /* Fill packet type */

        txctl->atype = get_hal_packet_type(hdr);

        /* Fill qnum */

        if (unlikely(txctl->flags & ATH9K_TXDESC_CAB)) {
                txctl->qnum = 0;
                txq = sc->sc_cabq;
        } else {
                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) &&
            !(txctl->flags & ATH9K_TXDESC_CAB)) {
                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)
                txctl->flags |= ATH9K_TXDESC_NOACK;
        if (tx_info->flags & IEEE80211_TX_CTL_USE_RTS_CTS)
                txctl->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_flags & SC_OP_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 = 0;
                rcs[0].tries = ATH_MGT_TXMAXTRY;
        }
        rix = rcs[0].rix;

        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;
        }

        /*
         * 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;
        }

        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;

        /*
         * 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_isxretried(bf))
                        tx_status.flags |= ATH_TX_XRETRY;
        }
        /* Unmap this frame */
        pci_unmap_single(sc->pdev,
                         bf->bf_dmacontext,
                         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_isaggr(bf);
        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_state.bf_type |= BUF_RETRY;
        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_isaggr(bf) ? 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 = ah->ah_caps.rts_aggr_limit;
        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.hw_caps & ATH9K_HW_CAP_HT) && bf_isdata(bf)) {
                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_isaggrburst(bf)) {
                                flags = ATH9K_TXDESC_RTSENA;
                                dynamic_mimops = 1;
                        } else {
                                flags = 0;
                        }
                }
        }

        /*
         * Set protection if aggregate protection on
         */
        if (sc->sc_config.ath_aggr_prot &&
            (!bf_isaggr(bf) || (bf_isaggr(bf) && 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_isaggr(bf) && (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_isshpreamble(bf) ? rt->info[cix].shortPreamble : 0);

        /*
         * Setup HAL rate series
         */
        memset(series, 0, 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_isshpreamble(bf) ? 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_isshpreamble(bf));

                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_isht(bf))
                                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.hw_caps & ATH9K_HW_CAP_HT)) {
                /*
                 * 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_isshpreamble(bf) ?
                                rt->info[cix].spAckDuration :
                                rt->info[cix].lpAckDuration;
                }

                ctsduration += series[0].PktDuration;

                if ((bf->bf_flags & ATH9K_TXDESC_NOACK) == 0) { /* SIFS + ACK */
                        ctsduration += bf_isshpreamble(bf) ?
                                rt->info[rix].spAckDuration :
                                rt->info[rix].lpAckDuration;
                }

                /*
                 * Disable multi-rate retry when using RTS/CTS by clearing
                 * series 1, 2 and 3.
                 */
                memset(&series[1], 0, 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_ispspoll(bf),
                                     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_state.bf_type &= ~BUF_AMPDU; /* 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_isretried(bf));
                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_isaggr(bf);
        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 {
                                memset(ba, 0, 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_ah->ah_opmode == ATH9K_M_STA)
                                        needreset = 1;
                        }
                } else {
                        memset(ba, 0, 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_state.bf_type |= BUF_XRETRY;
                                        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 */
                                        tbf->bf_dmacontext =
                                                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_reset(sc, false);

        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_isaggr(bf))
                        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_isampdu(bf)) {
                        /*
                         * 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_state.bf_type |= BUF_XRETRY;
                        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_isdata(bf)) {
                                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_isampdu(bf))
                        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_flags & SC_OP_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;

        /* XXX return value */
        if (!(sc->sc_flags & SC_OP_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_ah->ah_curchan,
                                    sc->sc_ht_info.tx_chan_width,
                                    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_isretried(bf))
                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_state.bf_type |= BUF_AMPDU;
        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_state.bf_type &= ~BUF_AGGR;
                        /*
                         * 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_state.bf_type |= BUF_AGGR;
                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_isretried(bf))
                        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;
        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;

        if (unlikely(txctl->flags & ATH9K_TXDESC_CAB))
                txq = sc->sc_cabq;
        else
                txq = &sc->sc_txq[txctl->qnum];

        /* 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;

        ieee80211_is_data(fc) ?
                (bf->bf_state.bf_type |= BUF_DATA) :
                (bf->bf_state.bf_type &= ~BUF_DATA);
        ieee80211_is_back_req(fc) ?
                (bf->bf_state.bf_type |= BUF_BAR) :
                (bf->bf_state.bf_type &= ~BUF_BAR);
        ieee80211_is_pspoll(fc) ?
                (bf->bf_state.bf_type |= BUF_PSPOLL) :
                (bf->bf_state.bf_type &= ~BUF_PSPOLL);
        (sc->sc_flags & SC_OP_PREAMBLE_SHORT) ?
                (bf->bf_state.bf_type |= BUF_SHORT_PREAMBLE) :
                (bf->bf_state.bf_type &= ~BUF_SHORT_PREAMBLE);

        bf->bf_flags = txctl->flags;
        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
         */
        bf->bf_dmacontext = 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;
        (txctl->ht) ?
                (bf->bf_state.bf_type |= BUF_HT) :
                (bf->bf_state.bf_type &= ~BUF_HT);

        spin_lock_bh(&txq->axq_lock);

        if (txctl->ht && (sc->sc_flags & SC_OP_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;
                }

                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,
                        struct ath_tx_control *txctl)
{
        struct ath_xmit_status tx_status;
        struct ath_atx_tid *tid;
        struct scatterlist sg;

        txctl->dmacontext = 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) = txctl->dmacontext;
        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, txctl->dmacontext,
                                 skb->len, PCI_DMA_TODEVICE);

                tx_status.retries = 0;
                tx_status.flags = ATH_TX_ERROR;

                if (txctl->ht && (sc->sc_flags & SC_OP_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, 1);
                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_tx_queue_info qi;
        int qnum;

        memset(&qi, 0, 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_physCompBuf = 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_tx_queue_info *qinfo)
{
        struct ath_hal *ah = sc->sc_ah;
        int error = 0;
        struct ath9k_tx_queue_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 = *qinfo;
                return 0;
        }

        ASSERT(sc->sc_txq[qnum].axq_qnum == qnum);

        ath9k_hw_get_txq_props(ah, qnum, &qi);
        qi.tqi_aifs = qinfo->tqi_aifs;
        qi.tqi_cwmin = qinfo->tqi_cwmin;
        qi.tqi_cwmax = qinfo->tqi_cwmax;
        qi.tqi_burstTime = qinfo->tqi_burstTime;
        qi.tqi_readyTime = qinfo->tqi_readyTime;

        if (!ath9k_hw_set_txq_props(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_tx_queue_info qi;
        int qnum = sc->sc_cabq->axq_qnum;
        struct ath_beacon_config conf;

        ath9k_hw_get_txq_props(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;

        memset(&txctl, 0, sizeof(struct ath_tx_control));
        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, &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)
{
        int i;
        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)))
                        ath_tx_processq(sc, &sc->sc_txq[i]);
        }
}

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_isampdu(bf))
                        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_flags & SC_OP_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_flags & SC_OP_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;

        if (!(sc->sc_flags & SC_OP_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_flags & SC_OP_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_isretried(bf)) {
                        /*
                         * 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_flags & SC_OP_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_flags & SC_OP_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);
                }
        }
}

void ath_tx_cabq(struct ath_softc *sc, struct sk_buff *skb)
{
        int hdrlen, padsize;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        struct ath_tx_control txctl;

        /*
         * As a temporary workaround, assign seq# here; this will likely need
         * to be cleaned up to work better with Beacon transmission and virtual
         * BSSes.
         */
        if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
                struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
                if (info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT)
                        sc->seq_no += 0x10;
                hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
                hdr->seq_ctrl |= cpu_to_le16(sc->seq_no);
        }

        /* Add the padding after the header if this is not already done */
        hdrlen = ieee80211_get_hdrlen_from_skb(skb);
        if (hdrlen & 3) {
                padsize = hdrlen % 4;
                if (skb_headroom(skb) < padsize) {
                        DPRINTF(sc, ATH_DBG_XMIT, "%s: TX CABQ padding "
                                "failed\n", __func__);
                        dev_kfree_skb_any(skb);
                        return;
                }
                skb_push(skb, padsize);
                memmove(skb->data, skb->data + padsize, hdrlen);
        }

        DPRINTF(sc, ATH_DBG_XMIT, "%s: transmitting CABQ packet, skb: %p\n",
                __func__,
                skb);

        memset(&txctl, 0, sizeof(struct ath_tx_control));
        txctl.flags = ATH9K_TXDESC_CAB;
        if (ath_tx_prepare(sc, skb, &txctl) == 0) {
                /*
                 * Start DMA mapping.
                 * ath_tx_start_dma() will be called either synchronously
                 * or asynchrounsly once DMA is complete.
                 */
                xmit_map_sg(sc, skb, &txctl);
        } else {
                ath_node_put(sc, txctl.an, ATH9K_BH_STATUS_CHANGE);
                DPRINTF(sc, ATH_DBG_XMIT, "%s: TX CABQ failed\n", __func__);
                dev_kfree_skb_any(skb);
        }
}