ampdu.c

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/*
 * Copyright (c) 2010 Broadcom Corporation
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <net/mac80211.h>

#include "rate.h"
#include "scb.h"
#include "phy/phy_hal.h"
#include "antsel.h"
#include "main.h"
#include "ampdu.h"

/* max number of mpdus in an ampdu */
#define AMPDU_MAX_MPDU          32
/* max number of mpdus in an ampdu to a legacy */
#define AMPDU_NUM_MPDU_LEGACY       16
/* max Tx ba window size (in pdu) */
#define AMPDU_TX_BA_MAX_WSIZE       64
/* default Tx ba window size (in pdu) */
#define AMPDU_TX_BA_DEF_WSIZE       64
/* default Rx ba window size (in pdu) */
#define AMPDU_RX_BA_DEF_WSIZE       64
/* max Rx ba window size (in pdu) */
#define AMPDU_RX_BA_MAX_WSIZE       64
/* max dur of tx ampdu (in msec) */
#define AMPDU_MAX_DUR           5
/* default tx retry limit */
#define AMPDU_DEF_RETRY_LIMIT       5
/* default tx retry limit at reg rate */
#define AMPDU_DEF_RR_RETRY_LIMIT    2
/* default weight of ampdu in txfifo */
#define AMPDU_DEF_TXPKT_WEIGHT      2
/* default ffpld reserved bytes */
#define AMPDU_DEF_FFPLD_RSVD        2048
/* # of inis to be freed on detach */
#define AMPDU_INI_FREE          10
/* max # of mpdus released at a time */
#define AMPDU_SCB_MAX_RELEASE       20

#define NUM_FFPLD_FIFO 4    /* number of fifo concerned by pre-loading */
#define FFPLD_TX_MAX_UNFL   200 /* default value of the average number of ampdu
                 * without underflows
                 */
#define FFPLD_MPDU_SIZE 1800    /* estimate of maximum mpdu size */
#define FFPLD_MAX_MCS 23    /* we don't deal with mcs 32 */
#define FFPLD_PLD_INCR 1000 /* increments in bytes */
#define FFPLD_MAX_AMPDU_CNT 5000    /* maximum number of ampdu we
                     * accumulate between resets.
                     */

#define AMPDU_DELIMITER_LEN 4

/* max allowed number of mpdus in an ampdu (2 streams) */
#define AMPDU_NUM_MPDU      16

#define TX_SEQ_TO_INDEX(seq) ((seq) % AMPDU_TX_BA_MAX_WSIZE)

/* max possible overhead per mpdu in the ampdu; 3 is for roundup if needed */
#define AMPDU_MAX_MPDU_OVERHEAD (FCS_LEN + DOT11_ICV_AES_LEN +\
    AMPDU_DELIMITER_LEN + 3\
    + DOT11_A4_HDR_LEN + DOT11_QOS_LEN + DOT11_IV_MAX_LEN)

/* modulo add/sub, bound = 2^k */
#define MODADD_POW2(x, y, bound) (((x) + (y)) & ((bound) - 1))
#define MODSUB_POW2(x, y, bound) (((x) - (y)) & ((bound) - 1))

/* structure to hold tx fifo information and pre-loading state
 * counters specific to tx underflows of ampdus
 * some counters might be redundant with the ones in wlc or ampdu structures.
 * This allows to maintain a specific state independently of
 * how often and/or when the wlc counters are updated.
 *
 * ampdu_pld_size: number of bytes to be pre-loaded
 * mcs2ampdu_table: per-mcs max # of mpdus in an ampdu
 * prev_txfunfl: num of underflows last read from the HW macstats counter
 * accum_txfunfl: num of underflows since we modified pld params
 * accum_txampdu: num of tx ampdu since we modified pld params
 * prev_txampdu: previous reading of tx ampdu
 * dmaxferrate: estimated dma avg xfer rate in kbits/sec
 */
struct brcms_fifo_info {
    u16 ampdu_pld_size;
    u8 mcs2ampdu_table[FFPLD_MAX_MCS + 1];
    u16 prev_txfunfl;
    u32 accum_txfunfl;
    u32 accum_txampdu;
    u32 prev_txampdu;
    u32 dmaxferrate;
};

/* AMPDU module specific state
 *
 * wlc: pointer to main wlc structure
 * scb_handle: scb cubby handle to retrieve data from scb
 * ini_enable: per-tid initiator enable/disable of ampdu
 * ba_tx_wsize: Tx ba window size (in pdu)
 * ba_rx_wsize: Rx ba window size (in pdu)
 * retry_limit: mpdu transmit retry limit
 * rr_retry_limit: mpdu transmit retry limit at regular rate
 * retry_limit_tid: per-tid mpdu transmit retry limit
 * rr_retry_limit_tid: per-tid mpdu transmit retry limit at regular rate
 * mpdu_density: min mpdu spacing (0-7) ==> 2^(x-1)/8 usec
 * max_pdu: max pdus allowed in ampdu
 * dur: max duration of an ampdu (in msec)
 * txpkt_weight: weight of ampdu in txfifo; reduces rate lag
 * rx_factor: maximum rx ampdu factor (0-3) ==> 2^(13+x) bytes
 * ffpld_rsvd: number of bytes to reserve for preload
 * max_txlen: max size of ampdu per mcs, bw and sgi
 * mfbr: enable multiple fallback rate
 * tx_max_funl: underflows should be kept such that
 *      (tx_max_funfl*underflows) < tx frames
 * fifo_tb: table of fifo infos
 */
struct ampdu_info {
    struct brcms_c_info *wlc;
    int scb_handle;
    u8 ini_enable[AMPDU_MAX_SCB_TID];
    u8 ba_tx_wsize;
    u8 ba_rx_wsize;
    u8 retry_limit;
    u8 rr_retry_limit;
    u8 retry_limit_tid[AMPDU_MAX_SCB_TID];
    u8 rr_retry_limit_tid[AMPDU_MAX_SCB_TID];
    u8 mpdu_density;
    s8 max_pdu;
    u8 dur;
    u8 txpkt_weight;
    u8 rx_factor;
    u32 ffpld_rsvd;
    u32 max_txlen[MCS_TABLE_SIZE][2][2];
    bool mfbr;
    u32 tx_max_funl;
    struct brcms_fifo_info fifo_tb[NUM_FFPLD_FIFO];
};

/* used for flushing ampdu packets */
struct cb_del_ampdu_pars {
    struct ieee80211_sta *sta;
    u16 tid;
};

static void brcms_c_scb_ampdu_update_max_txlen(struct ampdu_info *ampdu, u8 dur)
{
    u32 rate, mcs;

    for (mcs = 0; mcs < MCS_TABLE_SIZE; mcs++) {
        /* rate is in Kbps; dur is in msec ==> len = (rate * dur) / 8 */
        /* 20MHz, No SGI */
        rate = mcs_2_rate(mcs, false, false);
        ampdu->max_txlen[mcs][0][0] = (rate * dur) >> 3;
        /* 40 MHz, No SGI */
        rate = mcs_2_rate(mcs, true, false);
        ampdu->max_txlen[mcs][1][0] = (rate * dur) >> 3;
        /* 20MHz, SGI */
        rate = mcs_2_rate(mcs, false, true);
        ampdu->max_txlen[mcs][0][1] = (rate * dur) >> 3;
        /* 40 MHz, SGI */
        rate = mcs_2_rate(mcs, true, true);
        ampdu->max_txlen[mcs][1][1] = (rate * dur) >> 3;
    }
}

static bool brcms_c_ampdu_cap(struct ampdu_info *ampdu)
{
    if (BRCMS_PHY_11N_CAP(ampdu->wlc->band))
        return true;
    else
        return false;
}

static int brcms_c_ampdu_set(struct ampdu_info *ampdu, bool on)
{
    struct brcms_c_info *wlc = ampdu->wlc;

    wlc->pub->_ampdu = false;

    if (on) {
        if (!(wlc->pub->_n_enab & SUPPORT_11N)) {
            wiphy_err(ampdu->wlc->wiphy, "wl%d: driver not "
                "nmode enabled\n", wlc->pub->unit);
            return -ENOTSUPP;
        }
        if (!brcms_c_ampdu_cap(ampdu)) {
            wiphy_err(ampdu->wlc->wiphy, "wl%d: device not "
                "ampdu capable\n", wlc->pub->unit);
            return -ENOTSUPP;
        }
        wlc->pub->_ampdu = on;
    }

    return 0;
}

static void brcms_c_ffpld_init(struct ampdu_info *ampdu)
{
    int i, j;
    struct brcms_fifo_info *fifo;

    for (j = 0; j < NUM_FFPLD_FIFO; j++) {
        fifo = (ampdu->fifo_tb + j);
        fifo->ampdu_pld_size = 0;
        for (i = 0; i <= FFPLD_MAX_MCS; i++)
            fifo->mcs2ampdu_table[i] = 255;
        fifo->dmaxferrate = 0;
        fifo->accum_txampdu = 0;
        fifo->prev_txfunfl = 0;
        fifo->accum_txfunfl = 0;

    }
}

struct ampdu_info *brcms_c_ampdu_attach(struct brcms_c_info *wlc)
{
    struct ampdu_info *ampdu;
    int i;

    ampdu = kzalloc(sizeof(struct ampdu_info), GFP_ATOMIC);
    if (!ampdu)
        return NULL;

    ampdu->wlc = wlc;

    for (i = 0; i < AMPDU_MAX_SCB_TID; i++)
        ampdu->ini_enable[i] = true;
    /* Disable ampdu for VO by default */
    ampdu->ini_enable[PRIO_8021D_VO] = false;
    ampdu->ini_enable[PRIO_8021D_NC] = false;

    /* Disable ampdu for BK by default since not enough fifo space */
    ampdu->ini_enable[PRIO_8021D_NONE] = false;
    ampdu->ini_enable[PRIO_8021D_BK] = false;

    ampdu->ba_tx_wsize = AMPDU_TX_BA_DEF_WSIZE;
    ampdu->ba_rx_wsize = AMPDU_RX_BA_DEF_WSIZE;
    ampdu->mpdu_density = AMPDU_DEF_MPDU_DENSITY;
    ampdu->max_pdu = AUTO;
    ampdu->dur = AMPDU_MAX_DUR;
    ampdu->txpkt_weight = AMPDU_DEF_TXPKT_WEIGHT;

    ampdu->ffpld_rsvd = AMPDU_DEF_FFPLD_RSVD;
    /*
     * bump max ampdu rcv size to 64k for all 11n
     * devices except 4321A0 and 4321A1
     */
    if (BRCMS_ISNPHY(wlc->band) && NREV_LT(wlc->band->phyrev, 2))
        ampdu->rx_factor = IEEE80211_HT_MAX_AMPDU_32K;
    else
        ampdu->rx_factor = IEEE80211_HT_MAX_AMPDU_64K;
    ampdu->retry_limit = AMPDU_DEF_RETRY_LIMIT;
    ampdu->rr_retry_limit = AMPDU_DEF_RR_RETRY_LIMIT;

    for (i = 0; i < AMPDU_MAX_SCB_TID; i++) {
        ampdu->retry_limit_tid[i] = ampdu->retry_limit;
        ampdu->rr_retry_limit_tid[i] = ampdu->rr_retry_limit;
    }

    brcms_c_scb_ampdu_update_max_txlen(ampdu, ampdu->dur);
    ampdu->mfbr = false;
    /* try to set ampdu to the default value */
    brcms_c_ampdu_set(ampdu, wlc->pub->_ampdu);

    ampdu->tx_max_funl = FFPLD_TX_MAX_UNFL;
    brcms_c_ffpld_init(ampdu);

    return ampdu;
}

void brcms_c_ampdu_detach(struct ampdu_info *ampdu)
{
    kfree(ampdu);
}

static void brcms_c_scb_ampdu_update_config(struct ampdu_info *ampdu,
                        struct scb *scb)
{
    struct scb_ampdu *scb_ampdu = &scb->scb_ampdu;
    int i;

    scb_ampdu->max_pdu = AMPDU_NUM_MPDU;

    /* go back to legacy size if some preloading is occurring */
    for (i = 0; i < NUM_FFPLD_FIFO; i++) {
        if (ampdu->fifo_tb[i].ampdu_pld_size > FFPLD_PLD_INCR)
            scb_ampdu->max_pdu = AMPDU_NUM_MPDU_LEGACY;
    }

    /* apply user override */
    if (ampdu->max_pdu != AUTO)
        scb_ampdu->max_pdu = (u8) ampdu->max_pdu;

    scb_ampdu->release = min_t(u8, scb_ampdu->max_pdu,
                   AMPDU_SCB_MAX_RELEASE);

    if (scb_ampdu->max_rx_ampdu_bytes)
        scb_ampdu->release = min_t(u8, scb_ampdu->release,
            scb_ampdu->max_rx_ampdu_bytes / 1600);

    scb_ampdu->release = min(scb_ampdu->release,
                 ampdu->fifo_tb[TX_AC_BE_FIFO].
                 mcs2ampdu_table[FFPLD_MAX_MCS]);
}

static void brcms_c_scb_ampdu_update_config_all(struct ampdu_info *ampdu)
{
    brcms_c_scb_ampdu_update_config(ampdu, &ampdu->wlc->pri_scb);
}

static void brcms_c_ffpld_calc_mcs2ampdu_table(struct ampdu_info *ampdu, int f)
{
    int i;
    u32 phy_rate, dma_rate, tmp;
    u8 max_mpdu;
    struct brcms_fifo_info *fifo = (ampdu->fifo_tb + f);

    /* recompute the dma rate */
    /* note : we divide/multiply by 100 to avoid integer overflows */
    max_mpdu = min_t(u8, fifo->mcs2ampdu_table[FFPLD_MAX_MCS],
             AMPDU_NUM_MPDU_LEGACY);
    phy_rate = mcs_2_rate(FFPLD_MAX_MCS, true, false);
    dma_rate =
        (((phy_rate / 100) *
          (max_mpdu * FFPLD_MPDU_SIZE - fifo->ampdu_pld_size))
         / (max_mpdu * FFPLD_MPDU_SIZE)) * 100;
    fifo->dmaxferrate = dma_rate;

    /* fill up the mcs2ampdu table; do not recalc the last mcs */
    dma_rate = dma_rate >> 7;
    for (i = 0; i < FFPLD_MAX_MCS; i++) {
        /* shifting to keep it within integer range */
        phy_rate = mcs_2_rate(i, true, false) >> 7;
        if (phy_rate > dma_rate) {
            tmp = ((fifo->ampdu_pld_size * phy_rate) /
                   ((phy_rate - dma_rate) * FFPLD_MPDU_SIZE)) + 1;
            tmp = min_t(u32, tmp, 255);
            fifo->mcs2ampdu_table[i] = (u8) tmp;
        }
    }
}

/* evaluate the dma transfer rate using the tx underflows as feedback.
 * If necessary, increase tx fifo preloading. If not enough,
 * decrease maximum ampdu size for each mcs till underflows stop
 * Return 1 if pre-loading not active, -1 if not an underflow event,
 * 0 if pre-loading module took care of the event.
 */
static int brcms_c_ffpld_check_txfunfl(struct brcms_c_info *wlc, int fid)
{
    struct ampdu_info *ampdu = wlc->ampdu;
    u32 phy_rate = mcs_2_rate(FFPLD_MAX_MCS, true, false);
    u32 txunfl_ratio;
    u8 max_mpdu;
    u32 current_ampdu_cnt = 0;
    u16 max_pld_size;
    u32 new_txunfl;
    struct brcms_fifo_info *fifo = (ampdu->fifo_tb + fid);
    uint xmtfifo_sz;
    u16 cur_txunfl;

    /* return if we got here for a different reason than underflows */
    cur_txunfl = brcms_b_read_shm(wlc->hw,
                      M_UCODE_MACSTAT +
                      offsetof(struct macstat, txfunfl[fid]));
    new_txunfl = (u16) (cur_txunfl - fifo->prev_txfunfl);
    if (new_txunfl == 0) {
        BCMMSG(wlc->wiphy, "TX status FRAG set but no tx underflows\n");
        return -1;
    }
    fifo->prev_txfunfl = cur_txunfl;

    if (!ampdu->tx_max_funl)
        return 1;

    /* check if fifo is big enough */
    if (brcms_b_xmtfifo_sz_get(wlc->hw, fid, &xmtfifo_sz))
        return -1;

    if ((TXFIFO_SIZE_UNIT * (u32) xmtfifo_sz) <= ampdu->ffpld_rsvd)
        return 1;

    max_pld_size = TXFIFO_SIZE_UNIT * xmtfifo_sz - ampdu->ffpld_rsvd;
    fifo->accum_txfunfl += new_txunfl;

    /* we need to wait for at least 10 underflows */
    if (fifo->accum_txfunfl < 10)
        return 0;

    BCMMSG(wlc->wiphy, "ampdu_count %d  tx_underflows %d\n",
        current_ampdu_cnt, fifo->accum_txfunfl);

    /*
       compute the current ratio of tx unfl per ampdu.
       When the current ampdu count becomes too
       big while the ratio remains small, we reset
       the current count in order to not
       introduce too big of a latency in detecting a
       large amount of tx underflows later.
     */

    txunfl_ratio = current_ampdu_cnt / fifo->accum_txfunfl;

    if (txunfl_ratio > ampdu->tx_max_funl) {
        if (current_ampdu_cnt >= FFPLD_MAX_AMPDU_CNT)
            fifo->accum_txfunfl = 0;

        return 0;
    }
    max_mpdu = min_t(u8, fifo->mcs2ampdu_table[FFPLD_MAX_MCS],
             AMPDU_NUM_MPDU_LEGACY);

    /* In case max value max_pdu is already lower than
       the fifo depth, there is nothing more we can do.
     */

    if (fifo->ampdu_pld_size >= max_mpdu * FFPLD_MPDU_SIZE) {
        fifo->accum_txfunfl = 0;
        return 0;
    }

    if (fifo->ampdu_pld_size < max_pld_size) {

        /* increment by TX_FIFO_PLD_INC bytes */
        fifo->ampdu_pld_size += FFPLD_PLD_INCR;
        if (fifo->ampdu_pld_size > max_pld_size)
            fifo->ampdu_pld_size = max_pld_size;

        /* update scb release size */
        brcms_c_scb_ampdu_update_config_all(ampdu);

        /*
         * compute a new dma xfer rate for max_mpdu @ max mcs.
         * This is the minimum dma rate that can achieve no
         * underflow condition for the current mpdu size.
         *
         * note : we divide/multiply by 100 to avoid integer overflows
         */
        fifo->dmaxferrate =
            (((phy_rate / 100) *
              (max_mpdu * FFPLD_MPDU_SIZE - fifo->ampdu_pld_size))
             / (max_mpdu * FFPLD_MPDU_SIZE)) * 100;

        BCMMSG(wlc->wiphy, "DMA estimated transfer rate %d; "
            "pre-load size %d\n",
            fifo->dmaxferrate, fifo->ampdu_pld_size);
    } else {

        /* decrease ampdu size */
        if (fifo->mcs2ampdu_table[FFPLD_MAX_MCS] > 1) {
            if (fifo->mcs2ampdu_table[FFPLD_MAX_MCS] == 255)
                fifo->mcs2ampdu_table[FFPLD_MAX_MCS] =
                    AMPDU_NUM_MPDU_LEGACY - 1;
            else
                fifo->mcs2ampdu_table[FFPLD_MAX_MCS] -= 1;

            /* recompute the table */
            brcms_c_ffpld_calc_mcs2ampdu_table(ampdu, fid);

            /* update scb release size */
            brcms_c_scb_ampdu_update_config_all(ampdu);
        }
    }
    fifo->accum_txfunfl = 0;
    return 0;
}

void
brcms_c_ampdu_tx_operational(struct brcms_c_info *wlc, u8 tid,
    u8 ba_wsize,        /* negotiated ba window size (in pdu) */
    uint max_rx_ampdu_bytes) /* from ht_cap in beacon */
{
    struct scb_ampdu *scb_ampdu;
    struct scb_ampdu_tid_ini *ini;
    struct ampdu_info *ampdu = wlc->ampdu;
    struct scb *scb = &wlc->pri_scb;
    scb_ampdu = &scb->scb_ampdu;

    if (!ampdu->ini_enable[tid]) {
        wiphy_err(ampdu->wlc->wiphy, "%s: Rejecting tid %d\n",
              __func__, tid);
        return;
    }

    ini = &scb_ampdu->ini[tid];
    ini->tid = tid;
    ini->scb = scb_ampdu->scb;
    ini->ba_wsize = ba_wsize;
    scb_ampdu->max_rx_ampdu_bytes = max_rx_ampdu_bytes;
}

int
brcms_c_sendampdu(struct ampdu_info *ampdu, struct brcms_txq_info *qi,
          struct sk_buff **pdu, int prec)
{
    struct brcms_c_info *wlc;
    struct sk_buff *p, *pkt[AMPDU_MAX_MPDU];
    u8 tid, ndelim;
    int err = 0;
    u8 preamble_type = BRCMS_GF_PREAMBLE;
    u8 fbr_preamble_type = BRCMS_GF_PREAMBLE;
    u8 rts_preamble_type = BRCMS_LONG_PREAMBLE;
    u8 rts_fbr_preamble_type = BRCMS_LONG_PREAMBLE;

    bool rr = true, fbr = false;
    uint i, count = 0, fifo, seg_cnt = 0;
    u16 plen, len, seq = 0, mcl, mch, index, frameid, dma_len = 0;
    u32 ampdu_len, max_ampdu_bytes = 0;
    struct d11txh *txh = NULL;
    u8 *plcp;
    struct ieee80211_hdr *h;
    struct scb *scb;
    struct scb_ampdu *scb_ampdu;
    struct scb_ampdu_tid_ini *ini;
    u8 mcs = 0;
    bool use_rts = false, use_cts = false;
    u32 rspec = 0, rspec_fallback = 0;
    u32 rts_rspec = 0, rts_rspec_fallback = 0;
    u16 mimo_ctlchbw = PHY_TXC1_BW_20MHZ;
    struct ieee80211_rts *rts;
    u8 rr_retry_limit;
    struct brcms_fifo_info *f;
    bool fbr_iscck;
    struct ieee80211_tx_info *tx_info;
    u16 qlen;
    struct wiphy *wiphy;

    wlc = ampdu->wlc;
    wiphy = wlc->wiphy;
    p = *pdu;

    tid = (u8) (p->priority);

    f = ampdu->fifo_tb + prio2fifo[tid];

    scb = &wlc->pri_scb;
    scb_ampdu = &scb->scb_ampdu;
    ini = &scb_ampdu->ini[tid];

    /* Let pressure continue to build ... */
    qlen = pktq_plen(&qi->q, prec);
    if (ini->tx_in_transit > 0 &&
        qlen < min(scb_ampdu->max_pdu, ini->ba_wsize))
        /* Collect multiple MPDU's to be sent in the next AMPDU */
        return -EBUSY;

    /* at this point we intend to transmit an AMPDU */
    rr_retry_limit = ampdu->rr_retry_limit_tid[tid];
    ampdu_len = 0;
    dma_len = 0;
    while (p) {
        struct ieee80211_tx_rate *txrate;

        tx_info = IEEE80211_SKB_CB(p);
        txrate = tx_info->status.rates;

        if (tx_info->flags & IEEE80211_TX_CTL_AMPDU) {
            err = brcms_c_prep_pdu(wlc, p, &fifo);
        } else {
            wiphy_err(wiphy, "%s: AMPDU flag is off!\n", __func__);
            *pdu = NULL;
            err = 0;
            break;
        }

        if (err) {
            if (err == -EBUSY) {
                wiphy_err(wiphy, "wl%d: sendampdu: "
                      "prep_xdu retry; seq 0x%x\n",
                      wlc->pub->unit, seq);
                *pdu = p;
                break;
            }

            /* error in the packet; reject it */
            wiphy_err(wiphy, "wl%d: sendampdu: prep_xdu "
                  "rejected; seq 0x%x\n", wlc->pub->unit, seq);
            *pdu = NULL;
            break;
        }

        /* pkt is good to be aggregated */
        txh = (struct d11txh *) p->data;
        plcp = (u8 *) (txh + 1);
        h = (struct ieee80211_hdr *)(plcp + D11_PHY_HDR_LEN);
        seq = le16_to_cpu(h->seq_ctrl) >> SEQNUM_SHIFT;
        index = TX_SEQ_TO_INDEX(seq);

        /* check mcl fields and test whether it can be agg'd */
        mcl = le16_to_cpu(txh->MacTxControlLow);
        mcl &= ~TXC_AMPDU_MASK;
        fbr_iscck = !(le16_to_cpu(txh->XtraFrameTypes) & 0x3);
        txh->PreloadSize = 0;   /* always default to 0 */

        /*  Handle retry limits */
        if (txrate[0].count <= rr_retry_limit) {
            txrate[0].count++;
            rr = true;
            fbr = false;
        } else {
            fbr = true;
            rr = false;
            txrate[1].count++;
        }

        /* extract the length info */
        len = fbr_iscck ? BRCMS_GET_CCK_PLCP_LEN(txh->FragPLCPFallback)
            : BRCMS_GET_MIMO_PLCP_LEN(txh->FragPLCPFallback);

        /* retrieve null delimiter count */
        ndelim = txh->RTSPLCPFallback[AMPDU_FBR_NULL_DELIM];
        seg_cnt += 1;

        BCMMSG(wlc->wiphy, "wl%d: mpdu %d plcp_len %d\n",
            wlc->pub->unit, count, len);

        /*
         * aggregateable mpdu. For ucode/hw agg,
         * test whether need to break or change the epoch
         */
        if (count == 0) {
            mcl |= (TXC_AMPDU_FIRST << TXC_AMPDU_SHIFT);
            /* refill the bits since might be a retx mpdu */
            mcl |= TXC_STARTMSDU;
            rts = (struct ieee80211_rts *)&txh->rts_frame;

            if (ieee80211_is_rts(rts->frame_control)) {
                mcl |= TXC_SENDRTS;
                use_rts = true;
            }
            if (ieee80211_is_cts(rts->frame_control)) {
                mcl |= TXC_SENDCTS;
                use_cts = true;
            }
        } else {
            mcl |= (TXC_AMPDU_MIDDLE << TXC_AMPDU_SHIFT);
            mcl &= ~(TXC_STARTMSDU | TXC_SENDRTS | TXC_SENDCTS);
        }

        len = roundup(len, 4);
        ampdu_len += (len + (ndelim + 1) * AMPDU_DELIMITER_LEN);

        dma_len += (u16) p->len;

        BCMMSG(wlc->wiphy, "wl%d: ampdu_len %d"
            " seg_cnt %d null delim %d\n",
            wlc->pub->unit, ampdu_len, seg_cnt, ndelim);

        txh->MacTxControlLow = cpu_to_le16(mcl);

        /* this packet is added */
        pkt[count++] = p;

        /* patch the first MPDU */
        if (count == 1) {
            u8 plcp0, plcp3, is40, sgi;

            if (rr) {
                plcp0 = plcp[0];
                plcp3 = plcp[3];
            } else {
                plcp0 = txh->FragPLCPFallback[0];
                plcp3 = txh->FragPLCPFallback[3];

            }
            is40 = (plcp0 & MIMO_PLCP_40MHZ) ? 1 : 0;
            sgi = plcp3_issgi(plcp3) ? 1 : 0;
            mcs = plcp0 & ~MIMO_PLCP_40MHZ;
            max_ampdu_bytes =
                min(scb_ampdu->max_rx_ampdu_bytes,
                ampdu->max_txlen[mcs][is40][sgi]);

            if (is40)
                mimo_ctlchbw =
                   CHSPEC_SB_UPPER(wlc_phy_chanspec_get(
                                 wlc->band->pi))
                   ? PHY_TXC1_BW_20MHZ_UP : PHY_TXC1_BW_20MHZ;

            /* rebuild the rspec and rspec_fallback */
            rspec = RSPEC_MIMORATE;
            rspec |= plcp[0] & ~MIMO_PLCP_40MHZ;
            if (plcp[0] & MIMO_PLCP_40MHZ)
                rspec |= (PHY_TXC1_BW_40MHZ << RSPEC_BW_SHIFT);

            if (fbr_iscck)  /* CCK */
                rspec_fallback = cck_rspec(cck_phy2mac_rate
                            (txh->FragPLCPFallback[0]));
            else {  /* MIMO */
                rspec_fallback = RSPEC_MIMORATE;
                rspec_fallback |=
                    txh->FragPLCPFallback[0] & ~MIMO_PLCP_40MHZ;
                if (txh->FragPLCPFallback[0] & MIMO_PLCP_40MHZ)
                    rspec_fallback |=
                        (PHY_TXC1_BW_40MHZ <<
                         RSPEC_BW_SHIFT);
            }

            if (use_rts || use_cts) {
                rts_rspec =
                    brcms_c_rspec_to_rts_rspec(wlc,
                    rspec, false, mimo_ctlchbw);
                rts_rspec_fallback =
                    brcms_c_rspec_to_rts_rspec(wlc,
                    rspec_fallback, false, mimo_ctlchbw);
            }
        }

        /* if (first mpdu for host agg) */
        /* test whether to add more */
        if ((mcs_2_rate(mcs, true, false) >= f->dmaxferrate) &&
            (count == f->mcs2ampdu_table[mcs])) {
            BCMMSG(wlc->wiphy, "wl%d: PR 37644: stopping"
                " ampdu at %d for mcs %d\n",
                wlc->pub->unit, count, mcs);
            break;
        }

        if (count == scb_ampdu->max_pdu)
            break;

        /*
         * check to see if the next pkt is
         * a candidate for aggregation
         */
        p = pktq_ppeek(&qi->q, prec);
        if (p) {
            tx_info = IEEE80211_SKB_CB(p);
            if ((tx_info->flags & IEEE80211_TX_CTL_AMPDU) &&
                ((u8) (p->priority) == tid)) {
                plen = p->len + AMPDU_MAX_MPDU_OVERHEAD;
                plen = max(scb_ampdu->min_len, plen);

                if ((plen + ampdu_len) > max_ampdu_bytes) {
                    p = NULL;
                    continue;
                }

                /*
                 * check if there are enough
                 * descriptors available
                 */
                if (*wlc->core->txavail[fifo] <= seg_cnt + 1) {
                    wiphy_err(wiphy, "%s: No fifo space  "
                          "!!\n", __func__);
                    p = NULL;
                    continue;
                }
                /* next packet fit for aggregation so dequeue */
                p = brcmu_pktq_pdeq(&qi->q, prec);
            } else {
                p = NULL;
            }
        }
    }           /* end while(p) */

    ini->tx_in_transit += count;

    if (count) {
        /* patch up the last txh */
        txh = (struct d11txh *) pkt[count - 1]->data;
        mcl = le16_to_cpu(txh->MacTxControlLow);
        mcl &= ~TXC_AMPDU_MASK;
        mcl |= (TXC_AMPDU_LAST << TXC_AMPDU_SHIFT);
        txh->MacTxControlLow = cpu_to_le16(mcl);

        /* remove the null delimiter after last mpdu */
        ndelim = txh->RTSPLCPFallback[AMPDU_FBR_NULL_DELIM];
        txh->RTSPLCPFallback[AMPDU_FBR_NULL_DELIM] = 0;
        ampdu_len -= ndelim * AMPDU_DELIMITER_LEN;

        /* remove the pad len from last mpdu */
        fbr_iscck = ((le16_to_cpu(txh->XtraFrameTypes) & 0x3) == 0);
        len = fbr_iscck ? BRCMS_GET_CCK_PLCP_LEN(txh->FragPLCPFallback)
            : BRCMS_GET_MIMO_PLCP_LEN(txh->FragPLCPFallback);
        ampdu_len -= roundup(len, 4) - len;

        /* patch up the first txh & plcp */
        txh = (struct d11txh *) pkt[0]->data;
        plcp = (u8 *) (txh + 1);

        BRCMS_SET_MIMO_PLCP_LEN(plcp, ampdu_len);
        /* mark plcp to indicate ampdu */
        BRCMS_SET_MIMO_PLCP_AMPDU(plcp);

        /* reset the mixed mode header durations */
        if (txh->MModeLen) {
            u16 mmodelen =
                brcms_c_calc_lsig_len(wlc, rspec, ampdu_len);
            txh->MModeLen = cpu_to_le16(mmodelen);
            preamble_type = BRCMS_MM_PREAMBLE;
        }
        if (txh->MModeFbrLen) {
            u16 mmfbrlen =
                brcms_c_calc_lsig_len(wlc, rspec_fallback,
                          ampdu_len);
            txh->MModeFbrLen = cpu_to_le16(mmfbrlen);
            fbr_preamble_type = BRCMS_MM_PREAMBLE;
        }

        /* set the preload length */
        if (mcs_2_rate(mcs, true, false) >= f->dmaxferrate) {
            dma_len = min(dma_len, f->ampdu_pld_size);
            txh->PreloadSize = cpu_to_le16(dma_len);
        } else
            txh->PreloadSize = 0;

        mch = le16_to_cpu(txh->MacTxControlHigh);

        /* update RTS dur fields */
        if (use_rts || use_cts) {
            u16 durid;
            rts = (struct ieee80211_rts *)&txh->rts_frame;
            if ((mch & TXC_PREAMBLE_RTS_MAIN_SHORT) ==
                TXC_PREAMBLE_RTS_MAIN_SHORT)
                rts_preamble_type = BRCMS_SHORT_PREAMBLE;

            if ((mch & TXC_PREAMBLE_RTS_FB_SHORT) ==
                TXC_PREAMBLE_RTS_FB_SHORT)
                rts_fbr_preamble_type = BRCMS_SHORT_PREAMBLE;

            durid =
                brcms_c_compute_rtscts_dur(wlc, use_cts, rts_rspec,
                           rspec, rts_preamble_type,
                           preamble_type, ampdu_len,
                           true);
            rts->duration = cpu_to_le16(durid);
            durid = brcms_c_compute_rtscts_dur(wlc, use_cts,
                               rts_rspec_fallback,
                               rspec_fallback,
                               rts_fbr_preamble_type,
                               fbr_preamble_type,
                               ampdu_len, true);
            txh->RTSDurFallback = cpu_to_le16(durid);
            /* set TxFesTimeNormal */
            txh->TxFesTimeNormal = rts->duration;
            /* set fallback rate version of TxFesTimeNormal */
            txh->TxFesTimeFallback = txh->RTSDurFallback;
        }

        /* set flag and plcp for fallback rate */
        if (fbr) {
            mch |= TXC_AMPDU_FBR;
            txh->MacTxControlHigh = cpu_to_le16(mch);
            BRCMS_SET_MIMO_PLCP_AMPDU(plcp);
            BRCMS_SET_MIMO_PLCP_AMPDU(txh->FragPLCPFallback);
        }

        BCMMSG(wlc->wiphy, "wl%d: count %d ampdu_len %d\n",
            wlc->pub->unit, count, ampdu_len);

        /* inform rate_sel if it this is a rate probe pkt */
        frameid = le16_to_cpu(txh->TxFrameID);
        if (frameid & TXFID_RATE_PROBE_MASK)
            wiphy_err(wiphy, "%s: XXX what to do with "
                  "TXFID_RATE_PROBE_MASK!?\n", __func__);

        for (i = 0; i < count; i++)
            brcms_c_txfifo(wlc, fifo, pkt[i], i == (count - 1),
                   ampdu->txpkt_weight);

    }
    /* endif (count) */
    return err;
}

static void
brcms_c_ampdu_rate_status(struct brcms_c_info *wlc,
              struct ieee80211_tx_info *tx_info,
              struct tx_status *txs, u8 mcs)
{
    struct ieee80211_tx_rate *txrate = tx_info->status.rates;
    int i;

    /* clear the rest of the rates */
    for (i = 2; i < IEEE80211_TX_MAX_RATES; i++) {
        txrate[i].idx = -1;
        txrate[i].count = 0;
    }
}

static void
brcms_c_ampdu_dotxstatus_complete(struct ampdu_info *ampdu, struct scb *scb,
                  struct sk_buff *p, struct tx_status *txs,
                  u32 s1, u32 s2)
{
    struct scb_ampdu *scb_ampdu;
    struct brcms_c_info *wlc = ampdu->wlc;
    struct scb_ampdu_tid_ini *ini;
    u8 bitmap[8], queue, tid;
    struct d11txh *txh;
    u8 *plcp;
    struct ieee80211_hdr *h;
    u16 seq, start_seq = 0, bindex, index, mcl;
    u8 mcs = 0;
    bool ba_recd = false, ack_recd = false;
    u8 suc_mpdu = 0, tot_mpdu = 0;
    uint supr_status;
    bool update_rate = true, retry = true, tx_error = false;
    u16 mimoantsel = 0;
    u8 antselid = 0;
    u8 retry_limit, rr_retry_limit;
    struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(p);
    struct wiphy *wiphy = wlc->wiphy;

#ifdef DEBUG
    u8 hole[AMPDU_MAX_MPDU];
    memset(hole, 0, sizeof(hole));
#endif

    scb_ampdu = &scb->scb_ampdu;
    tid = (u8) (p->priority);

    ini = &scb_ampdu->ini[tid];
    retry_limit = ampdu->retry_limit_tid[tid];
    rr_retry_limit = ampdu->rr_retry_limit_tid[tid];
    memset(bitmap, 0, sizeof(bitmap));
    queue = txs->frameid & TXFID_QUEUE_MASK;
    supr_status = txs->status & TX_STATUS_SUPR_MASK;

    if (txs->status & TX_STATUS_ACK_RCV) {
        if (TX_STATUS_SUPR_UF == supr_status)
            update_rate = false;

        WARN_ON(!(txs->status & TX_STATUS_INTERMEDIATE));
        start_seq = txs->sequence >> SEQNUM_SHIFT;
        bitmap[0] = (txs->status & TX_STATUS_BA_BMAP03_MASK) >>
            TX_STATUS_BA_BMAP03_SHIFT;

        WARN_ON(s1 & TX_STATUS_INTERMEDIATE);
        WARN_ON(!(s1 & TX_STATUS_AMPDU));

        bitmap[0] |=
            (s1 & TX_STATUS_BA_BMAP47_MASK) <<
            TX_STATUS_BA_BMAP47_SHIFT;
        bitmap[1] = (s1 >> 8) & 0xff;
        bitmap[2] = (s1 >> 16) & 0xff;
        bitmap[3] = (s1 >> 24) & 0xff;

        bitmap[4] = s2 & 0xff;
        bitmap[5] = (s2 >> 8) & 0xff;
        bitmap[6] = (s2 >> 16) & 0xff;
        bitmap[7] = (s2 >> 24) & 0xff;

        ba_recd = true;
    } else {
        if (supr_status) {
            update_rate = false;
            if (supr_status == TX_STATUS_SUPR_BADCH) {
                wiphy_err(wiphy,
                      "%s: Pkt tx suppressed, illegal channel possibly %d\n",
                      __func__, CHSPEC_CHANNEL(
                      wlc->default_bss->chanspec));
            } else {
                if (supr_status != TX_STATUS_SUPR_FRAG)
                    wiphy_err(wiphy, "%s: supr_status 0x%x\n",
                          __func__, supr_status);
            }
            /* no need to retry for badch; will fail again */
            if (supr_status == TX_STATUS_SUPR_BADCH ||
                supr_status == TX_STATUS_SUPR_EXPTIME) {
                retry = false;
            } else if (supr_status == TX_STATUS_SUPR_EXPTIME) {
                /* TX underflow:
                 *   try tuning pre-loading or ampdu size
                 */
            } else if (supr_status == TX_STATUS_SUPR_FRAG) {
                /*
                 * if there were underflows, but pre-loading
                 * is not active, notify rate adaptation.
                 */
                if (brcms_c_ffpld_check_txfunfl(wlc,
                    prio2fifo[tid]) > 0)
                    tx_error = true;
            }
        } else if (txs->phyerr) {
            update_rate = false;
            wiphy_err(wiphy, "%s: ampdu tx phy error (0x%x)\n",
                  __func__, txs->phyerr);

            if (brcm_msg_level & LOG_ERROR_VAL) {
                brcmu_prpkt("txpkt (AMPDU)", p);
                brcms_c_print_txdesc((struct d11txh *) p->data);
            }
            brcms_c_print_txstatus(txs);
        }
    }

    /* loop through all pkts and retry if not acked */
    while (p) {
        tx_info = IEEE80211_SKB_CB(p);
        txh = (struct d11txh *) p->data;
        mcl = le16_to_cpu(txh->MacTxControlLow);
        plcp = (u8 *) (txh + 1);
        h = (struct ieee80211_hdr *)(plcp + D11_PHY_HDR_LEN);
        seq = le16_to_cpu(h->seq_ctrl) >> SEQNUM_SHIFT;

        if (tot_mpdu == 0) {
            mcs = plcp[0] & MIMO_PLCP_MCS_MASK;
            mimoantsel = le16_to_cpu(txh->ABI_MimoAntSel);
        }

        index = TX_SEQ_TO_INDEX(seq);
        ack_recd = false;
        if (ba_recd) {
            bindex = MODSUB_POW2(seq, start_seq, SEQNUM_MAX);
            BCMMSG(wiphy,
                   "tid %d seq %d, start_seq %d, bindex %d set %d, index %d\n",
                   tid, seq, start_seq, bindex,
                   isset(bitmap, bindex), index);
            /* if acked then clear bit and free packet */
            if ((bindex < AMPDU_TX_BA_MAX_WSIZE)
                && isset(bitmap, bindex)) {
                ini->tx_in_transit--;
                ini->txretry[index] = 0;

                /*
                 * ampdu_ack_len:
                 *   number of acked aggregated frames
                 */
                /* ampdu_len: number of aggregated frames */
                brcms_c_ampdu_rate_status(wlc, tx_info, txs,
                              mcs);
                tx_info->flags |= IEEE80211_TX_STAT_ACK;
                tx_info->flags |= IEEE80211_TX_STAT_AMPDU;
                tx_info->status.ampdu_ack_len =
                    tx_info->status.ampdu_len = 1;

                skb_pull(p, D11_PHY_HDR_LEN);
                skb_pull(p, D11_TXH_LEN);

                ieee80211_tx_status_irqsafe(wlc->pub->ieee_hw,
                                p);
                ack_recd = true;
                suc_mpdu++;
            }
        }
        /* either retransmit or send bar if ack not recd */
        if (!ack_recd) {
            if (retry && (ini->txretry[index] < (int)retry_limit)) {
                ini->txretry[index]++;
                ini->tx_in_transit--;
                /*
                 * Use high prededence for retransmit to
                 * give some punch
                 */
                brcms_c_txq_enq(wlc, scb, p,
                        BRCMS_PRIO_TO_HI_PREC(tid));
            } else {
                /* Retry timeout */
                ini->tx_in_transit--;
                ieee80211_tx_info_clear_status(tx_info);
                tx_info->status.ampdu_ack_len = 0;
                tx_info->status.ampdu_len = 1;
                tx_info->flags |=
                    IEEE80211_TX_STAT_AMPDU_NO_BACK;
                skb_pull(p, D11_PHY_HDR_LEN);
                skb_pull(p, D11_TXH_LEN);
                BCMMSG(wiphy,
                       "BA Timeout, seq %d, in_transit %d\n",
                       seq, ini->tx_in_transit);
                ieee80211_tx_status_irqsafe(wlc->pub->ieee_hw,
                                p);
            }
        }
        tot_mpdu++;

        /* break out if last packet of ampdu */
        if (((mcl & TXC_AMPDU_MASK) >> TXC_AMPDU_SHIFT) ==
            TXC_AMPDU_LAST)
            break;

        p = dma_getnexttxp(wlc->hw->di[queue], DMA_RANGE_TRANSMITTED);
    }
    brcms_c_send_q(wlc);

    /* update rate state */
    antselid = brcms_c_antsel_antsel2id(wlc->asi, mimoantsel);

    brcms_c_txfifo_complete(wlc, queue, ampdu->txpkt_weight);
}

void
brcms_c_ampdu_dotxstatus(struct ampdu_info *ampdu, struct scb *scb,
             struct sk_buff *p, struct tx_status *txs)
{
    struct scb_ampdu *scb_ampdu;
    struct brcms_c_info *wlc = ampdu->wlc;
    struct scb_ampdu_tid_ini *ini;
    u32 s1 = 0, s2 = 0;
    struct ieee80211_tx_info *tx_info;

    tx_info = IEEE80211_SKB_CB(p);

    /* BMAC_NOTE: For the split driver, second level txstatus comes later
     * So if the ACK was received then wait for the second level else just
     * call the first one
     */
    if (txs->status & TX_STATUS_ACK_RCV) {
        u8 status_delay = 0;

        /* wait till the next 8 bytes of txstatus is available */
        s1 = bcma_read32(wlc->hw->d11core, D11REGOFFS(frmtxstatus));
        while ((s1 & TXS_V) == 0) {
            udelay(1);
            status_delay++;
            if (status_delay > 10)
                return; /* error condition */
            s1 = bcma_read32(wlc->hw->d11core,
                     D11REGOFFS(frmtxstatus));
        }

        s2 = bcma_read32(wlc->hw->d11core, D11REGOFFS(frmtxstatus2));
    }

    if (scb) {
        scb_ampdu = &scb->scb_ampdu;
        ini = &scb_ampdu->ini[p->priority];
        brcms_c_ampdu_dotxstatus_complete(ampdu, scb, p, txs, s1, s2);
    } else {
        /* loop through all pkts and free */
        u8 queue = txs->frameid & TXFID_QUEUE_MASK;
        struct d11txh *txh;
        u16 mcl;
        while (p) {
            tx_info = IEEE80211_SKB_CB(p);
            txh = (struct d11txh *) p->data;
            mcl = le16_to_cpu(txh->MacTxControlLow);
            brcmu_pkt_buf_free_skb(p);
            /* break out if last packet of ampdu */
            if (((mcl & TXC_AMPDU_MASK) >> TXC_AMPDU_SHIFT) ==
                TXC_AMPDU_LAST)
                break;
            p = dma_getnexttxp(wlc->hw->di[queue],
                       DMA_RANGE_TRANSMITTED);
        }
        brcms_c_txfifo_complete(wlc, queue, ampdu->txpkt_weight);
    }
}

void brcms_c_ampdu_macaddr_upd(struct brcms_c_info *wlc)
{
    char template[T_RAM_ACCESS_SZ * 2];

    /* driver needs to write the ta in the template; ta is at offset 16 */
    memset(template, 0, sizeof(template));
    memcpy(template, wlc->pub->cur_etheraddr, ETH_ALEN);
    brcms_b_write_template_ram(wlc->hw, (T_BA_TPL_BASE + 16),
                  (T_RAM_ACCESS_SZ * 2),
                  template);
}

bool brcms_c_aggregatable(struct brcms_c_info *wlc, u8 tid)
{
    return wlc->ampdu->ini_enable[tid];
}

void brcms_c_ampdu_shm_upd(struct ampdu_info *ampdu)
{
    struct brcms_c_info *wlc = ampdu->wlc;

    /*
     * Extend ucode internal watchdog timer to
     * match larger received frames
     */
    if ((ampdu->rx_factor & IEEE80211_HT_AMPDU_PARM_FACTOR) ==
        IEEE80211_HT_MAX_AMPDU_64K) {
        brcms_b_write_shm(wlc->hw, M_MIMO_MAXSYM, MIMO_MAXSYM_MAX);
        brcms_b_write_shm(wlc->hw, M_WATCHDOG_8TU, WATCHDOG_8TU_MAX);
    } else {
        brcms_b_write_shm(wlc->hw, M_MIMO_MAXSYM, MIMO_MAXSYM_DEF);
        brcms_b_write_shm(wlc->hw, M_WATCHDOG_8TU, WATCHDOG_8TU_DEF);
    }
}

/*
 * callback function that helps flushing ampdu packets from a priority queue
 */
static bool cb_del_ampdu_pkt(struct sk_buff *mpdu, void *arg_a)
{
    struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(mpdu);
    struct cb_del_ampdu_pars *ampdu_pars =
                 (struct cb_del_ampdu_pars *)arg_a;
    bool rc;

    rc = tx_info->flags & IEEE80211_TX_CTL_AMPDU ? true : false;
    rc = rc && (tx_info->rate_driver_data[0] == NULL || ampdu_pars->sta == NULL ||
            tx_info->rate_driver_data[0] == ampdu_pars->sta);
    rc = rc && ((u8)(mpdu->priority) == ampdu_pars->tid);
    return rc;
}

/*
 * callback function that helps invalidating ampdu packets in a DMA queue
 */
static void dma_cb_fn_ampdu(void *txi, void *arg_a)
{
    struct ieee80211_sta *sta = arg_a;
    struct ieee80211_tx_info *tx_info = (struct ieee80211_tx_info *)txi;

    if ((tx_info->flags & IEEE80211_TX_CTL_AMPDU) &&
        (tx_info->rate_driver_data[0] == sta || sta == NULL))
        tx_info->rate_driver_data[0] = NULL;
}

/*
 * When a remote party is no longer available for ampdu communication, any
 * pending tx ampdu packets in the driver have to be flushed.
 */
void brcms_c_ampdu_flush(struct brcms_c_info *wlc,
             struct ieee80211_sta *sta, u16 tid)
{
    struct brcms_txq_info *qi = wlc->pkt_queue;
    struct pktq *pq = &qi->q;
    int prec;
    struct cb_del_ampdu_pars ampdu_pars;

    ampdu_pars.sta = sta;
    ampdu_pars.tid = tid;
    for (prec = 0; prec < pq->num_prec; prec++)
        brcmu_pktq_pflush(pq, prec, true, cb_del_ampdu_pkt,
                (void *)&ampdu_pars);
    brcms_c_inval_dma_pkts(wlc->hw, sta, dma_cb_fn_ampdu);
}