tx.c

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/*
 * Atheros CARL9170 driver
 *
 * 802.11 xmit & status routines
 *
 * Copyright 2008, Johannes Berg <[email protected]>
 * Copyright 2009, 2010, Christian Lamparter <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, see
 * http://www.gnu.org/licenses/.
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *    Copyright (c) 2007-2008 Atheros Communications, Inc.
 *
 *    Permission to use, copy, modify, and/or distribute this software for any
 *    purpose with or without fee is hereby granted, provided that the above
 *    copyright notice and this permission notice appear in all copies.
 *
 *    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 *    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 *    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 *    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 *    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 *    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 *    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/etherdevice.h>
#include <net/mac80211.h>
#include "carl9170.h"
#include "hw.h"
#include "cmd.h"

static inline unsigned int __carl9170_get_queue(struct ar9170 *ar,
                        unsigned int queue)
{
    if (unlikely(modparam_noht)) {
        return queue;
    } else {
        /*
         * This is just another workaround, until
         * someone figures out how to get QoS and
         * AMPDU to play nicely together.
         */

        return 2;       /* AC_BE */
    }
}

static inline unsigned int carl9170_get_queue(struct ar9170 *ar,
                          struct sk_buff *skb)
{
    return __carl9170_get_queue(ar, skb_get_queue_mapping(skb));
}

static bool is_mem_full(struct ar9170 *ar)
{
    return (DIV_ROUND_UP(IEEE80211_MAX_FRAME_LEN, ar->fw.mem_block_size) >
        atomic_read(&ar->mem_free_blocks));
}

static void carl9170_tx_accounting(struct ar9170 *ar, struct sk_buff *skb)
{
    int queue, i;
    bool mem_full;

    atomic_inc(&ar->tx_total_queued);

    queue = skb_get_queue_mapping(skb);
    spin_lock_bh(&ar->tx_stats_lock);

    /*
     * The driver has to accept the frame, regardless if the queue is
     * full to the brim, or not. We have to do the queuing internally,
     * since mac80211 assumes that a driver which can operate with
     * aggregated frames does not reject frames for this reason.
     */
    ar->tx_stats[queue].len++;
    ar->tx_stats[queue].count++;

    mem_full = is_mem_full(ar);
    for (i = 0; i < ar->hw->queues; i++) {
        if (mem_full || ar->tx_stats[i].len >= ar->tx_stats[i].limit) {
            ieee80211_stop_queue(ar->hw, i);
            ar->queue_stop_timeout[i] = jiffies;
        }
    }

    spin_unlock_bh(&ar->tx_stats_lock);
}

/* needs rcu_read_lock */
static struct ieee80211_sta *__carl9170_get_tx_sta(struct ar9170 *ar,
                           struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super = (void *) skb->data;
    struct ieee80211_hdr *hdr = (void *) super->frame_data;
    struct ieee80211_vif *vif;
    unsigned int vif_id;

    vif_id = (super->s.misc & CARL9170_TX_SUPER_MISC_VIF_ID) >>
         CARL9170_TX_SUPER_MISC_VIF_ID_S;

    if (WARN_ON_ONCE(vif_id >= AR9170_MAX_VIRTUAL_MAC))
        return NULL;

    vif = rcu_dereference(ar->vif_priv[vif_id].vif);
    if (unlikely(!vif))
        return NULL;

    /*
     * Normally we should use wrappers like ieee80211_get_DA to get
     * the correct peer ieee80211_sta.
     *
     * But there is a problem with indirect traffic (broadcasts, or
     * data which is designated for other stations) in station mode.
     * The frame will be directed to the AP for distribution and not
     * to the actual destination.
     */

    return ieee80211_find_sta(vif, hdr->addr1);
}

static void carl9170_tx_ps_unblock(struct ar9170 *ar, struct sk_buff *skb)
{
    struct ieee80211_sta *sta;
    struct carl9170_sta_info *sta_info;

    rcu_read_lock();
    sta = __carl9170_get_tx_sta(ar, skb);
    if (unlikely(!sta))
        goto out_rcu;

    sta_info = (struct carl9170_sta_info *) sta->drv_priv;
    if (atomic_dec_return(&sta_info->pending_frames) == 0)
        ieee80211_sta_block_awake(ar->hw, sta, false);

out_rcu:
    rcu_read_unlock();
}

static void carl9170_tx_accounting_free(struct ar9170 *ar, struct sk_buff *skb)
{
    int queue;

    queue = skb_get_queue_mapping(skb);

    spin_lock_bh(&ar->tx_stats_lock);

    ar->tx_stats[queue].len--;

    if (!is_mem_full(ar)) {
        unsigned int i;
        for (i = 0; i < ar->hw->queues; i++) {
            if (ar->tx_stats[i].len >= CARL9170_NUM_TX_LIMIT_SOFT)
                continue;

            if (ieee80211_queue_stopped(ar->hw, i)) {
                unsigned long tmp;

                tmp = jiffies - ar->queue_stop_timeout[i];
                if (tmp > ar->max_queue_stop_timeout[i])
                    ar->max_queue_stop_timeout[i] = tmp;
            }

            ieee80211_wake_queue(ar->hw, i);
        }
    }

    spin_unlock_bh(&ar->tx_stats_lock);

    if (atomic_dec_and_test(&ar->tx_total_queued))
        complete(&ar->tx_flush);
}

static int carl9170_alloc_dev_space(struct ar9170 *ar, struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super = (void *) skb->data;
    unsigned int chunks;
    int cookie = -1;

    atomic_inc(&ar->mem_allocs);

    chunks = DIV_ROUND_UP(skb->len, ar->fw.mem_block_size);
    if (unlikely(atomic_sub_return(chunks, &ar->mem_free_blocks) < 0)) {
        atomic_add(chunks, &ar->mem_free_blocks);
        return -ENOSPC;
    }

    spin_lock_bh(&ar->mem_lock);
    cookie = bitmap_find_free_region(ar->mem_bitmap, ar->fw.mem_blocks, 0);
    spin_unlock_bh(&ar->mem_lock);

    if (unlikely(cookie < 0)) {
        atomic_add(chunks, &ar->mem_free_blocks);
        return -ENOSPC;
    }

    super = (void *) skb->data;

    /*
     * Cookie #0 serves two special purposes:
     *  1. The firmware might use it generate BlockACK frames
     *     in responds of an incoming BlockAckReqs.
     *
     *  2. Prevent double-free bugs.
     */
    super->s.cookie = (u8) cookie + 1;
    return 0;
}

static void carl9170_release_dev_space(struct ar9170 *ar, struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super = (void *) skb->data;
    int cookie;

    /* make a local copy of the cookie */
    cookie = super->s.cookie;
    /* invalidate cookie */
    super->s.cookie = 0;

    /*
     * Do a out-of-bounds check on the cookie:
     *
     *  * cookie "0" is reserved and won't be assigned to any
     *    out-going frame. Internally however, it is used to
     *    mark no longer/un-accounted frames and serves as a
     *    cheap way of preventing frames from being freed
     *    twice by _accident_. NB: There is a tiny race...
     *
     *  * obviously, cookie number is limited by the amount
     *    of available memory blocks, so the number can
     *    never execeed the mem_blocks count.
     */
    if (unlikely(WARN_ON_ONCE(cookie == 0) ||
        WARN_ON_ONCE(cookie > ar->fw.mem_blocks)))
        return;

    atomic_add(DIV_ROUND_UP(skb->len, ar->fw.mem_block_size),
           &ar->mem_free_blocks);

    spin_lock_bh(&ar->mem_lock);
    bitmap_release_region(ar->mem_bitmap, cookie - 1, 0);
    spin_unlock_bh(&ar->mem_lock);
}

/* Called from any context */
static void carl9170_tx_release(struct kref *ref)
{
    struct ar9170 *ar;
    struct carl9170_tx_info *arinfo;
    struct ieee80211_tx_info *txinfo;
    struct sk_buff *skb;

    arinfo = container_of(ref, struct carl9170_tx_info, ref);
    txinfo = container_of((void *) arinfo, struct ieee80211_tx_info,
                  rate_driver_data);
    skb = container_of((void *) txinfo, struct sk_buff, cb);

    ar = arinfo->ar;
    if (WARN_ON_ONCE(!ar))
        return;

    BUILD_BUG_ON(
        offsetof(struct ieee80211_tx_info, status.ack_signal) != 20);

    memset(&txinfo->status.ack_signal, 0,
           sizeof(struct ieee80211_tx_info) -
           offsetof(struct ieee80211_tx_info, status.ack_signal));

    if (atomic_read(&ar->tx_total_queued))
        ar->tx_schedule = true;

    if (txinfo->flags & IEEE80211_TX_CTL_AMPDU) {
        if (!atomic_read(&ar->tx_ampdu_upload))
            ar->tx_ampdu_schedule = true;

        if (txinfo->flags & IEEE80211_TX_STAT_AMPDU) {
            struct _carl9170_tx_superframe *super;

            super = (void *)skb->data;
            txinfo->status.ampdu_len = super->s.rix;
            txinfo->status.ampdu_ack_len = super->s.cnt;
        } else if ((txinfo->flags & IEEE80211_TX_STAT_ACK) &&
               !(txinfo->flags & IEEE80211_TX_CTL_REQ_TX_STATUS)) {
            /*
             * drop redundant tx_status reports:
             *
             * 1. ampdu_ack_len of the final tx_status does
             *    include the feedback of this particular frame.
             *
             * 2. tx_status_irqsafe only queues up to 128
             *    tx feedback reports and discards the rest.
             *
             * 3. minstrel_ht is picky, it only accepts
             *    reports of frames with the TX_STATUS_AMPDU flag.
             *
             * 4. mac80211 is not particularly interested in
             *    feedback either [CTL_REQ_TX_STATUS not set]
             */

            ieee80211_free_txskb(ar->hw, skb);
            return;
        } else {
            /*
             * Either the frame transmission has failed or
             * mac80211 requested tx status.
             */
        }
    }

    skb_pull(skb, sizeof(struct _carl9170_tx_superframe));
    ieee80211_tx_status_irqsafe(ar->hw, skb);
}

void carl9170_tx_get_skb(struct sk_buff *skb)
{
    struct carl9170_tx_info *arinfo = (void *)
        (IEEE80211_SKB_CB(skb))->rate_driver_data;
    kref_get(&arinfo->ref);
}

int carl9170_tx_put_skb(struct sk_buff *skb)
{
    struct carl9170_tx_info *arinfo = (void *)
        (IEEE80211_SKB_CB(skb))->rate_driver_data;

    return kref_put(&arinfo->ref, carl9170_tx_release);
}

/* Caller must hold the tid_info->lock & rcu_read_lock */
static void carl9170_tx_shift_bm(struct ar9170 *ar,
    struct carl9170_sta_tid *tid_info, u16 seq)
{
    u16 off;

    off = SEQ_DIFF(seq, tid_info->bsn);

    if (WARN_ON_ONCE(off >= CARL9170_BAW_BITS))
        return;

    /*
     * Sanity check. For each MPDU we set the bit in bitmap and
     * clear it once we received the tx_status.
     * But if the bit is already cleared then we've been bitten
     * by a bug.
     */
    WARN_ON_ONCE(!test_and_clear_bit(off, tid_info->bitmap));

    off = SEQ_DIFF(tid_info->snx, tid_info->bsn);
    if (WARN_ON_ONCE(off >= CARL9170_BAW_BITS))
        return;

    if (!bitmap_empty(tid_info->bitmap, off))
        off = find_first_bit(tid_info->bitmap, off);

    tid_info->bsn += off;
    tid_info->bsn &= 0x0fff;

    bitmap_shift_right(tid_info->bitmap, tid_info->bitmap,
               off, CARL9170_BAW_BITS);
}

static void carl9170_tx_status_process_ampdu(struct ar9170 *ar,
    struct sk_buff *skb, struct ieee80211_tx_info *txinfo)
{
    struct _carl9170_tx_superframe *super = (void *) skb->data;
    struct ieee80211_hdr *hdr = (void *) super->frame_data;
    struct ieee80211_sta *sta;
    struct carl9170_sta_info *sta_info;
    struct carl9170_sta_tid *tid_info;
    u8 tid;

    if (!(txinfo->flags & IEEE80211_TX_CTL_AMPDU) ||
        txinfo->flags & IEEE80211_TX_CTL_INJECTED ||
       (!(super->f.mac_control & cpu_to_le16(AR9170_TX_MAC_AGGR))))
        return;

    rcu_read_lock();
    sta = __carl9170_get_tx_sta(ar, skb);
    if (unlikely(!sta))
        goto out_rcu;

    tid = get_tid_h(hdr);

    sta_info = (void *) sta->drv_priv;
    tid_info = rcu_dereference(sta_info->agg[tid]);
    if (!tid_info)
        goto out_rcu;

    spin_lock_bh(&tid_info->lock);
    if (likely(tid_info->state >= CARL9170_TID_STATE_IDLE))
        carl9170_tx_shift_bm(ar, tid_info, get_seq_h(hdr));

    if (sta_info->stats[tid].clear) {
        sta_info->stats[tid].clear = false;
        sta_info->stats[tid].req = false;
        sta_info->stats[tid].ampdu_len = 0;
        sta_info->stats[tid].ampdu_ack_len = 0;
    }

    sta_info->stats[tid].ampdu_len++;
    if (txinfo->status.rates[0].count == 1)
        sta_info->stats[tid].ampdu_ack_len++;

    if (!(txinfo->flags & IEEE80211_TX_STAT_ACK))
        sta_info->stats[tid].req = true;

    if (super->f.mac_control & cpu_to_le16(AR9170_TX_MAC_IMM_BA)) {
        super->s.rix = sta_info->stats[tid].ampdu_len;
        super->s.cnt = sta_info->stats[tid].ampdu_ack_len;
        txinfo->flags |= IEEE80211_TX_STAT_AMPDU;
        if (sta_info->stats[tid].req)
            txinfo->flags |= IEEE80211_TX_STAT_AMPDU_NO_BACK;

        sta_info->stats[tid].clear = true;
    }
    spin_unlock_bh(&tid_info->lock);

out_rcu:
    rcu_read_unlock();
}

static void carl9170_tx_bar_status(struct ar9170 *ar, struct sk_buff *skb,
    struct ieee80211_tx_info *tx_info)
{
    struct _carl9170_tx_superframe *super = (void *) skb->data;
    struct ieee80211_bar *bar = (void *) super->frame_data;

    /*
     * Unlike all other frames, the status report for BARs does
     * not directly come from the hardware as it is incapable of
     * matching a BA to a previously send BAR.
     * Instead the RX-path will scan for incoming BAs and set the
     * IEEE80211_TX_STAT_ACK if it sees one that was likely
     * caused by a BAR from us.
     */

    if (unlikely(ieee80211_is_back_req(bar->frame_control)) &&
       !(tx_info->flags & IEEE80211_TX_STAT_ACK)) {
        struct carl9170_bar_list_entry *entry;
        int queue = skb_get_queue_mapping(skb);

        rcu_read_lock();
        list_for_each_entry_rcu(entry, &ar->bar_list[queue], list) {
            if (entry->skb == skb) {
                spin_lock_bh(&ar->bar_list_lock[queue]);
                list_del_rcu(&entry->list);
                spin_unlock_bh(&ar->bar_list_lock[queue]);
                kfree_rcu(entry, head);
                goto out;
            }
        }

        WARN(1, "bar not found in %d - ra:%pM ta:%pM c:%x ssn:%x\n",
               queue, bar->ra, bar->ta, bar->control,
            bar->start_seq_num);
out:
        rcu_read_unlock();
    }
}

void carl9170_tx_status(struct ar9170 *ar, struct sk_buff *skb,
            const bool success)
{
    struct ieee80211_tx_info *txinfo;

    carl9170_tx_accounting_free(ar, skb);

    txinfo = IEEE80211_SKB_CB(skb);

    carl9170_tx_bar_status(ar, skb, txinfo);

    if (success)
        txinfo->flags |= IEEE80211_TX_STAT_ACK;
    else
        ar->tx_ack_failures++;

    if (txinfo->flags & IEEE80211_TX_CTL_AMPDU)
        carl9170_tx_status_process_ampdu(ar, skb, txinfo);

    carl9170_tx_ps_unblock(ar, skb);
    carl9170_tx_put_skb(skb);
}

/* This function may be called form any context */
void carl9170_tx_callback(struct ar9170 *ar, struct sk_buff *skb)
{
    struct ieee80211_tx_info *txinfo = IEEE80211_SKB_CB(skb);

    atomic_dec(&ar->tx_total_pending);

    if (txinfo->flags & IEEE80211_TX_CTL_AMPDU)
        atomic_dec(&ar->tx_ampdu_upload);

    if (carl9170_tx_put_skb(skb))
        tasklet_hi_schedule(&ar->usb_tasklet);
}

static struct sk_buff *carl9170_get_queued_skb(struct ar9170 *ar, u8 cookie,
                           struct sk_buff_head *queue)
{
    struct sk_buff *skb;

    spin_lock_bh(&queue->lock);
    skb_queue_walk(queue, skb) {
        struct _carl9170_tx_superframe *txc = (void *) skb->data;

        if (txc->s.cookie != cookie)
            continue;

        __skb_unlink(skb, queue);
        spin_unlock_bh(&queue->lock);

        carl9170_release_dev_space(ar, skb);
        return skb;
    }
    spin_unlock_bh(&queue->lock);

    return NULL;
}

static void carl9170_tx_fill_rateinfo(struct ar9170 *ar, unsigned int rix,
    unsigned int tries, struct ieee80211_tx_info *txinfo)
{
    unsigned int i;

    for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
        if (txinfo->status.rates[i].idx < 0)
            break;

        if (i == rix) {
            txinfo->status.rates[i].count = tries;
            i++;
            break;
        }
    }

    for (; i < IEEE80211_TX_MAX_RATES; i++) {
        txinfo->status.rates[i].idx = -1;
        txinfo->status.rates[i].count = 0;
    }
}

static void carl9170_check_queue_stop_timeout(struct ar9170 *ar)
{
    int i;
    struct sk_buff *skb;
    struct ieee80211_tx_info *txinfo;
    struct carl9170_tx_info *arinfo;
    bool restart = false;

    for (i = 0; i < ar->hw->queues; i++) {
        spin_lock_bh(&ar->tx_status[i].lock);

        skb = skb_peek(&ar->tx_status[i]);

        if (!skb)
            goto next;

        txinfo = IEEE80211_SKB_CB(skb);
        arinfo = (void *) txinfo->rate_driver_data;

        if (time_is_before_jiffies(arinfo->timeout +
            msecs_to_jiffies(CARL9170_QUEUE_STUCK_TIMEOUT)) == true)
            restart = true;

next:
        spin_unlock_bh(&ar->tx_status[i].lock);
    }

    if (restart) {
        /*
         * At least one queue has been stuck for long enough.
         * Give the device a kick and hope it gets back to
         * work.
         *
         * possible reasons may include:
         *  - frames got lost/corrupted (bad connection to the device)
         *  - stalled rx processing/usb controller hiccups
         *  - firmware errors/bugs
         *  - every bug you can think of.
         *  - all bugs you can't...
         *  - ...
         */
        carl9170_restart(ar, CARL9170_RR_STUCK_TX);
    }
}

static void carl9170_tx_ampdu_timeout(struct ar9170 *ar)
{
    struct carl9170_sta_tid *iter;
    struct sk_buff *skb;
    struct ieee80211_tx_info *txinfo;
    struct carl9170_tx_info *arinfo;
    struct ieee80211_sta *sta;

    rcu_read_lock();
    list_for_each_entry_rcu(iter, &ar->tx_ampdu_list, list) {
        if (iter->state < CARL9170_TID_STATE_IDLE)
            continue;

        spin_lock_bh(&iter->lock);
        skb = skb_peek(&iter->queue);
        if (!skb)
            goto unlock;

        txinfo = IEEE80211_SKB_CB(skb);
        arinfo = (void *)txinfo->rate_driver_data;
        if (time_is_after_jiffies(arinfo->timeout +
            msecs_to_jiffies(CARL9170_QUEUE_TIMEOUT)))
            goto unlock;

        sta = __carl9170_get_tx_sta(ar, skb);
        if (WARN_ON(!sta))
            goto unlock;

        ieee80211_stop_tx_ba_session(sta, iter->tid);
unlock:
        spin_unlock_bh(&iter->lock);

    }
    rcu_read_unlock();
}

void carl9170_tx_janitor(struct work_struct *work)
{
    struct ar9170 *ar = container_of(work, struct ar9170,
                     tx_janitor.work);
    if (!IS_STARTED(ar))
        return;

    ar->tx_janitor_last_run = jiffies;

    carl9170_check_queue_stop_timeout(ar);
    carl9170_tx_ampdu_timeout(ar);

    if (!atomic_read(&ar->tx_total_queued))
        return;

    ieee80211_queue_delayed_work(ar->hw, &ar->tx_janitor,
        msecs_to_jiffies(CARL9170_TX_TIMEOUT));
}

static void __carl9170_tx_process_status(struct ar9170 *ar,
    const uint8_t cookie, const uint8_t info)
{
    struct sk_buff *skb;
    struct ieee80211_tx_info *txinfo;
    unsigned int r, t, q;
    bool success = true;

    q = ar9170_qmap[info & CARL9170_TX_STATUS_QUEUE];

    skb = carl9170_get_queued_skb(ar, cookie, &ar->tx_status[q]);
    if (!skb) {
        /*
         * We have lost the race to another thread.
         */

        return ;
    }

    txinfo = IEEE80211_SKB_CB(skb);

    if (!(info & CARL9170_TX_STATUS_SUCCESS))
        success = false;

    r = (info & CARL9170_TX_STATUS_RIX) >> CARL9170_TX_STATUS_RIX_S;
    t = (info & CARL9170_TX_STATUS_TRIES) >> CARL9170_TX_STATUS_TRIES_S;

    carl9170_tx_fill_rateinfo(ar, r, t, txinfo);
    carl9170_tx_status(ar, skb, success);
}

void carl9170_tx_process_status(struct ar9170 *ar,
                const struct carl9170_rsp *cmd)
{
    unsigned int i;

    for (i = 0;  i < cmd->hdr.ext; i++) {
        if (WARN_ON(i > ((cmd->hdr.len / 2) + 1))) {
            print_hex_dump_bytes("UU:", DUMP_PREFIX_NONE,
                         (void *) cmd, cmd->hdr.len + 4);
            break;
        }

        __carl9170_tx_process_status(ar, cmd->_tx_status[i].cookie,
                         cmd->_tx_status[i].info);
    }
}

static void carl9170_tx_rate_tpc_chains(struct ar9170 *ar,
    struct ieee80211_tx_info *info, struct ieee80211_tx_rate *txrate,
    unsigned int *phyrate, unsigned int *tpc, unsigned int *chains)
{
    struct ieee80211_rate *rate = NULL;
    u8 *txpower;
    unsigned int idx;

    idx = txrate->idx;
    *tpc = 0;
    *phyrate = 0;

    if (txrate->flags & IEEE80211_TX_RC_MCS) {
        if (txrate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH) {
            /* +1 dBm for HT40 */
            *tpc += 2;

            if (info->band == IEEE80211_BAND_2GHZ)
                txpower = ar->power_2G_ht40;
            else
                txpower = ar->power_5G_ht40;
        } else {
            if (info->band == IEEE80211_BAND_2GHZ)
                txpower = ar->power_2G_ht20;
            else
                txpower = ar->power_5G_ht20;
        }

        *phyrate = txrate->idx;
        *tpc += txpower[idx & 7];
    } else {
        if (info->band == IEEE80211_BAND_2GHZ) {
            if (idx < 4)
                txpower = ar->power_2G_cck;
            else
                txpower = ar->power_2G_ofdm;
        } else {
            txpower = ar->power_5G_leg;
            idx += 4;
        }

        rate = &__carl9170_ratetable[idx];
        *tpc += txpower[(rate->hw_value & 0x30) >> 4];
        *phyrate = rate->hw_value & 0xf;
    }

    if (ar->eeprom.tx_mask == 1) {
        *chains = AR9170_TX_PHY_TXCHAIN_1;
    } else {
        if (!(txrate->flags & IEEE80211_TX_RC_MCS) &&
            rate && rate->bitrate >= 360)
            *chains = AR9170_TX_PHY_TXCHAIN_1;
        else
            *chains = AR9170_TX_PHY_TXCHAIN_2;
    }

    *tpc = min_t(unsigned int, *tpc, ar->hw->conf.power_level * 2);
}

static __le32 carl9170_tx_physet(struct ar9170 *ar,
    struct ieee80211_tx_info *info, struct ieee80211_tx_rate *txrate)
{
    unsigned int power = 0, chains = 0, phyrate = 0;
    __le32 tmp;

    tmp = cpu_to_le32(0);

    if (txrate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH)
        tmp |= cpu_to_le32(AR9170_TX_PHY_BW_40MHZ <<
            AR9170_TX_PHY_BW_S);
    /* this works because 40 MHz is 2 and dup is 3 */
    if (txrate->flags & IEEE80211_TX_RC_DUP_DATA)
        tmp |= cpu_to_le32(AR9170_TX_PHY_BW_40MHZ_DUP <<
            AR9170_TX_PHY_BW_S);

    if (txrate->flags & IEEE80211_TX_RC_SHORT_GI)
        tmp |= cpu_to_le32(AR9170_TX_PHY_SHORT_GI);

    if (txrate->flags & IEEE80211_TX_RC_MCS) {
        SET_VAL(AR9170_TX_PHY_MCS, phyrate, txrate->idx);

        /* heavy clip control */
        tmp |= cpu_to_le32((txrate->idx & 0x7) <<
            AR9170_TX_PHY_TX_HEAVY_CLIP_S);

        tmp |= cpu_to_le32(AR9170_TX_PHY_MOD_HT);

        /*
         * green field preamble does not work.
         *
         * if (txrate->flags & IEEE80211_TX_RC_GREEN_FIELD)
         * tmp |= cpu_to_le32(AR9170_TX_PHY_GREENFIELD);
         */
    } else {
        if (info->band == IEEE80211_BAND_2GHZ) {
            if (txrate->idx <= AR9170_TX_PHY_RATE_CCK_11M)
                tmp |= cpu_to_le32(AR9170_TX_PHY_MOD_CCK);
            else
                tmp |= cpu_to_le32(AR9170_TX_PHY_MOD_OFDM);
        } else {
            tmp |= cpu_to_le32(AR9170_TX_PHY_MOD_OFDM);
        }

        /*
         * short preamble seems to be broken too.
         *
         * if (txrate->flags & IEEE80211_TX_RC_USE_SHORT_PREAMBLE)
         *  tmp |= cpu_to_le32(AR9170_TX_PHY_SHORT_PREAMBLE);
         */
    }
    carl9170_tx_rate_tpc_chains(ar, info, txrate,
                    &phyrate, &power, &chains);

    tmp |= cpu_to_le32(SET_CONSTVAL(AR9170_TX_PHY_MCS, phyrate));
    tmp |= cpu_to_le32(SET_CONSTVAL(AR9170_TX_PHY_TX_PWR, power));
    tmp |= cpu_to_le32(SET_CONSTVAL(AR9170_TX_PHY_TXCHAIN, chains));
    return tmp;
}

static bool carl9170_tx_rts_check(struct ar9170 *ar,
                  struct ieee80211_tx_rate *rate,
                  bool ampdu, bool multi)
{
    switch (ar->erp_mode) {
    case CARL9170_ERP_AUTO:
        if (ampdu)
            break;

    case CARL9170_ERP_MAC80211:
        if (!(rate->flags & IEEE80211_TX_RC_USE_RTS_CTS))
            break;

    case CARL9170_ERP_RTS:
        if (likely(!multi))
            return true;

    default:
        break;
    }

    return false;
}

static bool carl9170_tx_cts_check(struct ar9170 *ar,
                  struct ieee80211_tx_rate *rate)
{
    switch (ar->erp_mode) {
    case CARL9170_ERP_AUTO:
    case CARL9170_ERP_MAC80211:
        if (!(rate->flags & IEEE80211_TX_RC_USE_CTS_PROTECT))
            break;

    case CARL9170_ERP_CTS:
        return true;

    default:
        break;
    }

    return false;
}

static int carl9170_tx_prepare(struct ar9170 *ar,
                   struct ieee80211_sta *sta,
                   struct sk_buff *skb)
{
    struct ieee80211_hdr *hdr;
    struct _carl9170_tx_superframe *txc;
    struct carl9170_vif_info *cvif;
    struct ieee80211_tx_info *info;
    struct ieee80211_tx_rate *txrate;
    struct carl9170_tx_info *arinfo;
    unsigned int hw_queue;
    int i;
    __le16 mac_tmp;
    u16 len;
    bool ampdu, no_ack;

    BUILD_BUG_ON(sizeof(*arinfo) > sizeof(info->rate_driver_data));
    BUILD_BUG_ON(sizeof(struct _carl9170_tx_superdesc) !=
             CARL9170_TX_SUPERDESC_LEN);

    BUILD_BUG_ON(sizeof(struct _ar9170_tx_hwdesc) !=
             AR9170_TX_HWDESC_LEN);

    BUILD_BUG_ON(IEEE80211_TX_MAX_RATES < CARL9170_TX_MAX_RATES);

    BUILD_BUG_ON(AR9170_MAX_VIRTUAL_MAC >
        ((CARL9170_TX_SUPER_MISC_VIF_ID >>
         CARL9170_TX_SUPER_MISC_VIF_ID_S) + 1));

    hw_queue = ar9170_qmap[carl9170_get_queue(ar, skb)];

    hdr = (void *)skb->data;
    info = IEEE80211_SKB_CB(skb);
    len = skb->len;

    /*
     * Note: If the frame was sent through a monitor interface,
     * the ieee80211_vif pointer can be NULL.
     */
    if (likely(info->control.vif))
        cvif = (void *) info->control.vif->drv_priv;
    else
        cvif = NULL;

    txc = (void *)skb_push(skb, sizeof(*txc));
    memset(txc, 0, sizeof(*txc));

    SET_VAL(CARL9170_TX_SUPER_MISC_QUEUE, txc->s.misc, hw_queue);

    if (likely(cvif))
        SET_VAL(CARL9170_TX_SUPER_MISC_VIF_ID, txc->s.misc, cvif->id);

    if (unlikely(info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM))
        txc->s.misc |= CARL9170_TX_SUPER_MISC_CAB;

    if (unlikely(info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ))
        txc->s.misc |= CARL9170_TX_SUPER_MISC_ASSIGN_SEQ;

    if (unlikely(ieee80211_is_probe_resp(hdr->frame_control)))
        txc->s.misc |= CARL9170_TX_SUPER_MISC_FILL_IN_TSF;

    mac_tmp = cpu_to_le16(AR9170_TX_MAC_HW_DURATION |
                  AR9170_TX_MAC_BACKOFF);
    mac_tmp |= cpu_to_le16((hw_queue << AR9170_TX_MAC_QOS_S) &
                   AR9170_TX_MAC_QOS);

    no_ack = !!(info->flags & IEEE80211_TX_CTL_NO_ACK);
    if (unlikely(no_ack))
        mac_tmp |= cpu_to_le16(AR9170_TX_MAC_NO_ACK);

    if (info->control.hw_key) {
        len += info->control.hw_key->icv_len;

        switch (info->control.hw_key->cipher) {
        case WLAN_CIPHER_SUITE_WEP40:
        case WLAN_CIPHER_SUITE_WEP104:
        case WLAN_CIPHER_SUITE_TKIP:
            mac_tmp |= cpu_to_le16(AR9170_TX_MAC_ENCR_RC4);
            break;
        case WLAN_CIPHER_SUITE_CCMP:
            mac_tmp |= cpu_to_le16(AR9170_TX_MAC_ENCR_AES);
            break;
        default:
            WARN_ON(1);
            goto err_out;
        }
    }

    ampdu = !!(info->flags & IEEE80211_TX_CTL_AMPDU);
    if (ampdu) {
        unsigned int density, factor;

        if (unlikely(!sta || !cvif))
            goto err_out;

        factor = min_t(unsigned int, 1u, sta->ht_cap.ampdu_factor);
        density = sta->ht_cap.ampdu_density;

        if (density) {
            /*
             * Watch out!
             *
             * Otus uses slightly different density values than
             * those from the 802.11n spec.
             */

            density = max_t(unsigned int, density + 1, 7u);
        }

        SET_VAL(CARL9170_TX_SUPER_AMPDU_DENSITY,
            txc->s.ampdu_settings, density);

        SET_VAL(CARL9170_TX_SUPER_AMPDU_FACTOR,
            txc->s.ampdu_settings, factor);

        for (i = 0; i < CARL9170_TX_MAX_RATES; i++) {
            txrate = &info->control.rates[i];
            if (txrate->idx >= 0) {
                txc->s.ri[i] =
                    CARL9170_TX_SUPER_RI_AMPDU;

                if (WARN_ON(!(txrate->flags &
                          IEEE80211_TX_RC_MCS))) {
                    /*
                     * Not sure if it's even possible
                     * to aggregate non-ht rates with
                     * this HW.
                     */
                    goto err_out;
                }
                continue;
            }

            txrate->idx = 0;
            txrate->count = ar->hw->max_rate_tries;
        }

        mac_tmp |= cpu_to_le16(AR9170_TX_MAC_AGGR);
    }

    /*
     * NOTE: For the first rate, the ERP & AMPDU flags are directly
     * taken from mac_control. For all fallback rate, the firmware
     * updates the mac_control flags from the rate info field.
     */
    for (i = 1; i < CARL9170_TX_MAX_RATES; i++) {
        txrate = &info->control.rates[i];
        if (txrate->idx < 0)
            break;

        SET_VAL(CARL9170_TX_SUPER_RI_TRIES, txc->s.ri[i],
            txrate->count);

        if (carl9170_tx_rts_check(ar, txrate, ampdu, no_ack))
            txc->s.ri[i] |= (AR9170_TX_MAC_PROT_RTS <<
                CARL9170_TX_SUPER_RI_ERP_PROT_S);
        else if (carl9170_tx_cts_check(ar, txrate))
            txc->s.ri[i] |= (AR9170_TX_MAC_PROT_CTS <<
                CARL9170_TX_SUPER_RI_ERP_PROT_S);

        txc->s.rr[i - 1] = carl9170_tx_physet(ar, info, txrate);
    }

    txrate = &info->control.rates[0];
    SET_VAL(CARL9170_TX_SUPER_RI_TRIES, txc->s.ri[0], txrate->count);

    if (carl9170_tx_rts_check(ar, txrate, ampdu, no_ack))
        mac_tmp |= cpu_to_le16(AR9170_TX_MAC_PROT_RTS);
    else if (carl9170_tx_cts_check(ar, txrate))
        mac_tmp |= cpu_to_le16(AR9170_TX_MAC_PROT_CTS);

    txc->s.len = cpu_to_le16(skb->len);
    txc->f.length = cpu_to_le16(len + FCS_LEN);
    txc->f.mac_control = mac_tmp;
    txc->f.phy_control = carl9170_tx_physet(ar, info, txrate);

    arinfo = (void *)info->rate_driver_data;
    arinfo->timeout = jiffies;
    arinfo->ar = ar;
    kref_init(&arinfo->ref);
    return 0;

err_out:
    skb_pull(skb, sizeof(*txc));
    return -EINVAL;
}

static void carl9170_set_immba(struct ar9170 *ar, struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super;

    super = (void *) skb->data;
    super->f.mac_control |= cpu_to_le16(AR9170_TX_MAC_IMM_BA);
}

static void carl9170_set_ampdu_params(struct ar9170 *ar, struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super;
    int tmp;

    super = (void *) skb->data;

    tmp = (super->s.ampdu_settings & CARL9170_TX_SUPER_AMPDU_DENSITY) <<
        CARL9170_TX_SUPER_AMPDU_DENSITY_S;

    /*
     * If you haven't noticed carl9170_tx_prepare has already filled
     * in all ampdu spacing & factor parameters.
     * Now it's the time to check whenever the settings have to be
     * updated by the firmware, or if everything is still the same.
     *
     * There's no sane way to handle different density values with
     * this hardware, so we may as well just do the compare in the
     * driver.
     */

    if (tmp != ar->current_density) {
        ar->current_density = tmp;
        super->s.ampdu_settings |=
            CARL9170_TX_SUPER_AMPDU_COMMIT_DENSITY;
    }

    tmp = (super->s.ampdu_settings & CARL9170_TX_SUPER_AMPDU_FACTOR) <<
        CARL9170_TX_SUPER_AMPDU_FACTOR_S;

    if (tmp != ar->current_factor) {
        ar->current_factor = tmp;
        super->s.ampdu_settings |=
            CARL9170_TX_SUPER_AMPDU_COMMIT_FACTOR;
    }
}

static bool carl9170_tx_rate_check(struct ar9170 *ar, struct sk_buff *_dest,
                   struct sk_buff *_src)
{
    struct _carl9170_tx_superframe *dest, *src;

    dest = (void *) _dest->data;
    src = (void *) _src->data;

    /*
     * The mac80211 rate control algorithm expects that all MPDUs in
     * an AMPDU share the same tx vectors.
     * This is not really obvious right now, because the hardware
     * does the AMPDU setup according to its own rulebook.
     * Our nicely assembled, strictly monotonic increasing mpdu
     * chains will be broken up, mashed back together...
     */

    return (dest->f.phy_control == src->f.phy_control);
}

static void carl9170_tx_ampdu(struct ar9170 *ar)
{
    struct sk_buff_head agg;
    struct carl9170_sta_tid *tid_info;
    struct sk_buff *skb, *first;
    unsigned int i = 0, done_ampdus = 0;
    u16 seq, queue, tmpssn;

    atomic_inc(&ar->tx_ampdu_scheduler);
    ar->tx_ampdu_schedule = false;

    if (atomic_read(&ar->tx_ampdu_upload))
        return;

    if (!ar->tx_ampdu_list_len)
        return;

    __skb_queue_head_init(&agg);

    rcu_read_lock();
    tid_info = rcu_dereference(ar->tx_ampdu_iter);
    if (WARN_ON_ONCE(!tid_info)) {
        rcu_read_unlock();
        return;
    }

retry:
    list_for_each_entry_continue_rcu(tid_info, &ar->tx_ampdu_list, list) {
        i++;

        if (tid_info->state < CARL9170_TID_STATE_PROGRESS)
            continue;

        queue = TID_TO_WME_AC(tid_info->tid);

        spin_lock_bh(&tid_info->lock);
        if (tid_info->state != CARL9170_TID_STATE_XMIT)
            goto processed;

        tid_info->counter++;
        first = skb_peek(&tid_info->queue);
        tmpssn = carl9170_get_seq(first);
        seq = tid_info->snx;

        if (unlikely(tmpssn != seq)) {
            tid_info->state = CARL9170_TID_STATE_IDLE;

            goto processed;
        }

        while ((skb = skb_peek(&tid_info->queue))) {
            /* strict 0, 1, ..., n - 1, n frame sequence order */
            if (unlikely(carl9170_get_seq(skb) != seq))
                break;

            /* don't upload more than AMPDU FACTOR allows. */
            if (unlikely(SEQ_DIFF(tid_info->snx, tid_info->bsn) >=
                (tid_info->max - 1)))
                break;

            if (!carl9170_tx_rate_check(ar, skb, first))
                break;

            atomic_inc(&ar->tx_ampdu_upload);
            tid_info->snx = seq = SEQ_NEXT(seq);
            __skb_unlink(skb, &tid_info->queue);

            __skb_queue_tail(&agg, skb);

            if (skb_queue_len(&agg) >= CARL9170_NUM_TX_AGG_MAX)
                break;
        }

        if (skb_queue_empty(&tid_info->queue) ||
            carl9170_get_seq(skb_peek(&tid_info->queue)) !=
            tid_info->snx) {
            /*
             * stop TID, if A-MPDU frames are still missing,
             * or whenever the queue is empty.
             */

            tid_info->state = CARL9170_TID_STATE_IDLE;
        }
        done_ampdus++;

processed:
        spin_unlock_bh(&tid_info->lock);

        if (skb_queue_empty(&agg))
            continue;

        /* apply ampdu spacing & factor settings */
        carl9170_set_ampdu_params(ar, skb_peek(&agg));

        /* set aggregation push bit */
        carl9170_set_immba(ar, skb_peek_tail(&agg));

        spin_lock_bh(&ar->tx_pending[queue].lock);
        skb_queue_splice_tail_init(&agg, &ar->tx_pending[queue]);
        spin_unlock_bh(&ar->tx_pending[queue].lock);
        ar->tx_schedule = true;
    }
    if ((done_ampdus++ == 0) && (i++ == 0))
        goto retry;

    rcu_assign_pointer(ar->tx_ampdu_iter, tid_info);
    rcu_read_unlock();
}

static struct sk_buff *carl9170_tx_pick_skb(struct ar9170 *ar,
                        struct sk_buff_head *queue)
{
    struct sk_buff *skb;
    struct ieee80211_tx_info *info;
    struct carl9170_tx_info *arinfo;

    BUILD_BUG_ON(sizeof(*arinfo) > sizeof(info->rate_driver_data));

    spin_lock_bh(&queue->lock);
    skb = skb_peek(queue);
    if (unlikely(!skb))
        goto err_unlock;

    if (carl9170_alloc_dev_space(ar, skb))
        goto err_unlock;

    __skb_unlink(skb, queue);
    spin_unlock_bh(&queue->lock);

    info = IEEE80211_SKB_CB(skb);
    arinfo = (void *) info->rate_driver_data;

    arinfo->timeout = jiffies;
    return skb;

err_unlock:
    spin_unlock_bh(&queue->lock);
    return NULL;
}

void carl9170_tx_drop(struct ar9170 *ar, struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super;
    uint8_t q = 0;

    ar->tx_dropped++;

    super = (void *)skb->data;
    SET_VAL(CARL9170_TX_SUPER_MISC_QUEUE, q,
        ar9170_qmap[carl9170_get_queue(ar, skb)]);
    __carl9170_tx_process_status(ar, super->s.cookie, q);
}

static bool carl9170_tx_ps_drop(struct ar9170 *ar, struct sk_buff *skb)
{
    struct ieee80211_sta *sta;
    struct carl9170_sta_info *sta_info;
    struct ieee80211_tx_info *tx_info;

    rcu_read_lock();
    sta = __carl9170_get_tx_sta(ar, skb);
    if (!sta)
        goto out_rcu;

    sta_info = (void *) sta->drv_priv;
    tx_info = IEEE80211_SKB_CB(skb);

    if (unlikely(sta_info->sleeping) &&
        !(tx_info->flags & (IEEE80211_TX_CTL_NO_PS_BUFFER |
                IEEE80211_TX_CTL_CLEAR_PS_FILT))) {
        rcu_read_unlock();

        if (tx_info->flags & IEEE80211_TX_CTL_AMPDU)
            atomic_dec(&ar->tx_ampdu_upload);

        tx_info->flags |= IEEE80211_TX_STAT_TX_FILTERED;
        carl9170_release_dev_space(ar, skb);
        carl9170_tx_status(ar, skb, false);
        return true;
    }

out_rcu:
    rcu_read_unlock();
    return false;
}

static void carl9170_bar_check(struct ar9170 *ar, struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super = (void *) skb->data;
    struct ieee80211_bar *bar = (void *) super->frame_data;

    if (unlikely(ieee80211_is_back_req(bar->frame_control)) &&
        skb->len >= sizeof(struct ieee80211_bar)) {
        struct carl9170_bar_list_entry *entry;
        unsigned int queue = skb_get_queue_mapping(skb);

        entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
        if (!WARN_ON_ONCE(!entry)) {
            entry->skb = skb;
            spin_lock_bh(&ar->bar_list_lock[queue]);
            list_add_tail_rcu(&entry->list, &ar->bar_list[queue]);
            spin_unlock_bh(&ar->bar_list_lock[queue]);
        }
    }
}

static void carl9170_tx(struct ar9170 *ar)
{
    struct sk_buff *skb;
    unsigned int i, q;
    bool schedule_garbagecollector = false;

    ar->tx_schedule = false;

    if (unlikely(!IS_STARTED(ar)))
        return;

    carl9170_usb_handle_tx_err(ar);

    for (i = 0; i < ar->hw->queues; i++) {
        while (!skb_queue_empty(&ar->tx_pending[i])) {
            skb = carl9170_tx_pick_skb(ar, &ar->tx_pending[i]);
            if (unlikely(!skb))
                break;

            if (unlikely(carl9170_tx_ps_drop(ar, skb)))
                continue;

            carl9170_bar_check(ar, skb);

            atomic_inc(&ar->tx_total_pending);

            q = __carl9170_get_queue(ar, i);
            /*
             * NB: tx_status[i] vs. tx_status[q],
             * TODO: Move into pick_skb or alloc_dev_space.
             */
            skb_queue_tail(&ar->tx_status[q], skb);

            /*
             * increase ref count to "2".
             * Ref counting is the easiest way to solve the
             * race between the urb's completion routine:
             *  carl9170_tx_callback
             * and wlan tx status functions:
             *  carl9170_tx_status/janitor.
             */
            carl9170_tx_get_skb(skb);

            carl9170_usb_tx(ar, skb);
            schedule_garbagecollector = true;
        }
    }

    if (!schedule_garbagecollector)
        return;

    ieee80211_queue_delayed_work(ar->hw, &ar->tx_janitor,
        msecs_to_jiffies(CARL9170_TX_TIMEOUT));
}

static bool carl9170_tx_ampdu_queue(struct ar9170 *ar,
    struct ieee80211_sta *sta, struct sk_buff *skb)
{
    struct _carl9170_tx_superframe *super = (void *) skb->data;
    struct carl9170_sta_info *sta_info;
    struct carl9170_sta_tid *agg;
    struct sk_buff *iter;
    u16 tid, seq, qseq, off;
    bool run = false;

    tid = carl9170_get_tid(skb);
    seq = carl9170_get_seq(skb);
    sta_info = (void *) sta->drv_priv;

    rcu_read_lock();
    agg = rcu_dereference(sta_info->agg[tid]);

    if (!agg)
        goto err_unlock_rcu;

    spin_lock_bh(&agg->lock);
    if (unlikely(agg->state < CARL9170_TID_STATE_IDLE))
        goto err_unlock;

    /* check if sequence is within the BA window */
    if (unlikely(!BAW_WITHIN(agg->bsn, CARL9170_BAW_BITS, seq)))
        goto err_unlock;

    if (WARN_ON_ONCE(!BAW_WITHIN(agg->snx, CARL9170_BAW_BITS, seq)))
        goto err_unlock;

    off = SEQ_DIFF(seq, agg->bsn);
    if (WARN_ON_ONCE(test_and_set_bit(off, agg->bitmap)))
        goto err_unlock;

    if (likely(BAW_WITHIN(agg->hsn, CARL9170_BAW_BITS, seq))) {
        __skb_queue_tail(&agg->queue, skb);
        agg->hsn = seq;
        goto queued;
    }

    skb_queue_reverse_walk(&agg->queue, iter) {
        qseq = carl9170_get_seq(iter);

        if (BAW_WITHIN(qseq, CARL9170_BAW_BITS, seq)) {
            __skb_queue_after(&agg->queue, iter, skb);
            goto queued;
        }
    }

    __skb_queue_head(&agg->queue, skb);
queued:

    if (unlikely(agg->state != CARL9170_TID_STATE_XMIT)) {
        if (agg->snx == carl9170_get_seq(skb_peek(&agg->queue))) {
            agg->state = CARL9170_TID_STATE_XMIT;
            run = true;
        }
    }

    spin_unlock_bh(&agg->lock);
    rcu_read_unlock();

    return run;

err_unlock:
    spin_unlock_bh(&agg->lock);

err_unlock_rcu:
    rcu_read_unlock();
    super->f.mac_control &= ~cpu_to_le16(AR9170_TX_MAC_AGGR);
    carl9170_tx_status(ar, skb, false);
    ar->tx_dropped++;
    return false;
}

void carl9170_op_tx(struct ieee80211_hw *hw,
            struct ieee80211_tx_control *control,
            struct sk_buff *skb)
{
    struct ar9170 *ar = hw->priv;
    struct ieee80211_tx_info *info;
    struct ieee80211_sta *sta = control->sta;
    bool run;

    if (unlikely(!IS_STARTED(ar)))
        goto err_free;

    info = IEEE80211_SKB_CB(skb);

    if (unlikely(carl9170_tx_prepare(ar, sta, skb)))
        goto err_free;

    carl9170_tx_accounting(ar, skb);
    /*
     * from now on, one has to use carl9170_tx_status to free
     * all ressouces which are associated with the frame.
     */

    if (sta) {
        struct carl9170_sta_info *stai = (void *) sta->drv_priv;
        atomic_inc(&stai->pending_frames);
    }

    if (info->flags & IEEE80211_TX_CTL_AMPDU) {
        run = carl9170_tx_ampdu_queue(ar, sta, skb);
        if (run)
            carl9170_tx_ampdu(ar);

    } else {
        unsigned int queue = skb_get_queue_mapping(skb);

        skb_queue_tail(&ar->tx_pending[queue], skb);
    }

    carl9170_tx(ar);
    return;

err_free:
    ar->tx_dropped++;
    ieee80211_free_txskb(ar->hw, skb);
}

void carl9170_tx_scheduler(struct ar9170 *ar)
{

    if (ar->tx_ampdu_schedule)
        carl9170_tx_ampdu(ar);

    if (ar->tx_schedule)
        carl9170_tx(ar);
}

int carl9170_update_beacon(struct ar9170 *ar, const bool submit)
{
    struct sk_buff *skb = NULL;
    struct carl9170_vif_info *cvif;
    struct ieee80211_tx_info *txinfo;
    struct ieee80211_tx_rate *rate;
    __le32 *data, *old = NULL;
    unsigned int plcp, power, chains;
    u32 word, ht1, off, addr, len;
    int i = 0, err = 0;

    rcu_read_lock();
    cvif = rcu_dereference(ar->beacon_iter);
retry:
    if (ar->vifs == 0 || !cvif)
        goto out_unlock;

    list_for_each_entry_continue_rcu(cvif, &ar->vif_list, list) {
        if (cvif->active && cvif->enable_beacon)
            goto found;
    }

    if (!ar->beacon_enabled || i++)
        goto out_unlock;

    goto retry;

found:
    rcu_assign_pointer(ar->beacon_iter, cvif);

    skb = ieee80211_beacon_get_tim(ar->hw, carl9170_get_vif(cvif),
        NULL, NULL);

    if (!skb) {
        err = -ENOMEM;
        goto err_free;
    }

    txinfo = IEEE80211_SKB_CB(skb);
    spin_lock_bh(&ar->beacon_lock);
    data = (__le32 *)skb->data;
    if (cvif->beacon)
        old = (__le32 *)cvif->beacon->data;

    off = cvif->id * AR9170_MAC_BCN_LENGTH_MAX;
    addr = ar->fw.beacon_addr + off;
    len = roundup(skb->len + FCS_LEN, 4);

    if ((off + len) > ar->fw.beacon_max_len) {
        if (net_ratelimit()) {
            wiphy_err(ar->hw->wiphy, "beacon does not "
                  "fit into device memory!\n");
        }
        err = -EINVAL;
        goto err_unlock;
    }

    if (len > AR9170_MAC_BCN_LENGTH_MAX) {
        if (net_ratelimit()) {
            wiphy_err(ar->hw->wiphy, "no support for beacons "
                "bigger than %d (yours:%d).\n",
                 AR9170_MAC_BCN_LENGTH_MAX, len);
        }

        err = -EMSGSIZE;
        goto err_unlock;
    }

    ht1 = AR9170_MAC_BCN_HT1_TX_ANT0;
    rate = &txinfo->control.rates[0];
    carl9170_tx_rate_tpc_chains(ar, txinfo, rate, &plcp, &power, &chains);
    if (!(txinfo->control.rates[0].flags & IEEE80211_TX_RC_MCS)) {
        if (plcp <= AR9170_TX_PHY_RATE_CCK_11M)
            plcp |= ((skb->len + FCS_LEN) << (3 + 16)) + 0x0400;
        else
            plcp |= ((skb->len + FCS_LEN) << 16) + 0x0010;
    } else {
        ht1 |= AR9170_MAC_BCN_HT1_HT_EN;
        if (rate->flags & IEEE80211_TX_RC_SHORT_GI)
            plcp |= AR9170_MAC_BCN_HT2_SGI;

        if (rate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH) {
            ht1 |= AR9170_MAC_BCN_HT1_BWC_40M_SHARED;
            plcp |= AR9170_MAC_BCN_HT2_BW40;
        }
        if (rate->flags & IEEE80211_TX_RC_DUP_DATA) {
            ht1 |= AR9170_MAC_BCN_HT1_BWC_40M_DUP;
            plcp |= AR9170_MAC_BCN_HT2_BW40;
        }

        SET_VAL(AR9170_MAC_BCN_HT2_LEN, plcp, skb->len + FCS_LEN);
    }

    SET_VAL(AR9170_MAC_BCN_HT1_PWR_CTRL, ht1, 7);
    SET_VAL(AR9170_MAC_BCN_HT1_TPC, ht1, power);
    SET_VAL(AR9170_MAC_BCN_HT1_CHAIN_MASK, ht1, chains);
    if (chains == AR9170_TX_PHY_TXCHAIN_2)
        ht1 |= AR9170_MAC_BCN_HT1_TX_ANT1;

    carl9170_async_regwrite_begin(ar);
    carl9170_async_regwrite(AR9170_MAC_REG_BCN_HT1, ht1);
    if (!(txinfo->control.rates[0].flags & IEEE80211_TX_RC_MCS))
        carl9170_async_regwrite(AR9170_MAC_REG_BCN_PLCP, plcp);
    else
        carl9170_async_regwrite(AR9170_MAC_REG_BCN_HT2, plcp);

    for (i = 0; i < DIV_ROUND_UP(skb->len, 4); i++) {
        /*
         * XXX: This accesses beyond skb data for up
         *  to the last 3 bytes!!
         */

        if (old && (data[i] == old[i]))
            continue;

        word = le32_to_cpu(data[i]);
        carl9170_async_regwrite(addr + 4 * i, word);
    }
    carl9170_async_regwrite_finish();

    dev_kfree_skb_any(cvif->beacon);
    cvif->beacon = NULL;

    err = carl9170_async_regwrite_result();
    if (!err)
        cvif->beacon = skb;
    spin_unlock_bh(&ar->beacon_lock);
    if (err)
        goto err_free;

    if (submit) {
        err = carl9170_bcn_ctrl(ar, cvif->id,
                    CARL9170_BCN_CTRL_CAB_TRIGGER,
                    addr, skb->len + FCS_LEN);

        if (err)
            goto err_free;
    }
out_unlock:
    rcu_read_unlock();
    return 0;

err_unlock:
    spin_unlock_bh(&ar->beacon_lock);

err_free:
    rcu_read_unlock();
    dev_kfree_skb_any(skb);
    return err;
}