WIP FPC-III support

[linux/fpc-iii.git] / drivers / net / wireless / ath / carl9170 / tx.c

/*
 * Atheros CARL9170 driver
 *
 * 802.11 xmit & status routines
 *
 * Copyright 2008, Johannes Berg <johannes@sipsolutions.net>
 * Copyright 2009, 2010, Christian Lamparter <chunkeey@googlemail.com>
 *
 * 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/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 (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)
                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 = iter->sta;
                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 == NL80211_BAND_2GHZ)
                                txpower = ar->power_2G_ht40;
                        else
                                txpower = ar->power_5G_ht40;
                } else {
                        if (info->band == NL80211_BAND_2GHZ)
                                txpower = ar->power_2G_ht20;
                        else
                                txpower = ar->power_5G_ht20;
                }

                *phyrate = txrate->idx;
                *tpc += txpower[idx & 7];
        } else {
                if (info->band == NL80211_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 == NL80211_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;
                fallthrough;

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

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

        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;
                fallthrough;

        case CARL9170_ERP_CTS:
                return true;

        default:
                break;
        }

        return false;
}

static void carl9170_tx_get_rates(struct ar9170 *ar,
                                  struct ieee80211_vif *vif,
                                  struct ieee80211_sta *sta,
                                  struct sk_buff *skb)
{
        struct ieee80211_tx_info *info;

        BUILD_BUG_ON(IEEE80211_TX_MAX_RATES < CARL9170_TX_MAX_RATES);
        BUILD_BUG_ON(IEEE80211_TX_MAX_RATES > IEEE80211_TX_RATE_TABLE_SIZE);

        info = IEEE80211_SKB_CB(skb);

        ieee80211_get_tx_rates(vif, sta, skb,
                               info->control.rates,
                               IEEE80211_TX_MAX_RATES);
}

static void carl9170_tx_apply_rateset(struct ar9170 *ar,
                                      struct ieee80211_tx_info *sinfo,
                                      struct sk_buff *skb)
{
        struct ieee80211_tx_rate *txrate;
        struct ieee80211_tx_info *info;
        struct _carl9170_tx_superframe *txc = (void *) skb->data;
        int i;
        bool ampdu;
        bool no_ack;

        info = IEEE80211_SKB_CB(skb);
        ampdu = !!(info->flags & IEEE80211_TX_CTL_AMPDU);
        no_ack = !!(info->flags & IEEE80211_TX_CTL_NO_ACK);

        /* Set the rate control probe flag for all (sub-) frames.
         * This is because the TX_STATS_AMPDU flag is only set on
         * the last frame, so it has to be inherited.
         */
        info->flags |= (sinfo->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE);

        /* 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 = 0; i < CARL9170_TX_MAX_RATES; i++) {
                __le32 phy_set;

                txrate = &sinfo->control.rates[i];
                if (txrate->idx < 0)
                        break;

                phy_set = carl9170_tx_physet(ar, info, txrate);
                if (i == 0) {
                        __le16 mac_tmp = cpu_to_le16(0);

                        /* first rate - part of the hw's frame header */
                        txc->f.phy_control = phy_set;

                        if (ampdu && txrate->flags & IEEE80211_TX_RC_MCS)
                                mac_tmp |= cpu_to_le16(AR9170_TX_MAC_AGGR);

                        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->f.mac_control |= mac_tmp;
                } else {
                        /* fallback rates are stored in the firmware's
                         * retry rate set array.
                         */
                        txc->s.rr[i - 1] = phy_set;
                }

                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);

                if (ampdu && (txrate->flags & IEEE80211_TX_RC_MCS))
                        txc->s.ri[i] |= CARL9170_TX_SUPER_RI_AMPDU;
        }
}

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 carl9170_tx_info *arinfo;
        unsigned int hw_queue;
        __le16 mac_tmp;
        u16 len;

        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(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 = 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);

        if (unlikely(info->flags & IEEE80211_TX_CTL_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;
                }
        }

        if (info->flags & IEEE80211_TX_CTL_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);
        }

        txc->s.len = cpu_to_le16(skb->len);
        txc->f.length = cpu_to_le16(len + FCS_LEN);
        txc->f.mac_control = mac_tmp;

        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 void carl9170_tx_ampdu(struct ar9170 *ar)
{
        struct sk_buff_head agg;
        struct carl9170_sta_tid *tid_info;
        struct sk_buff *skb, *first;
        struct ieee80211_tx_info *tx_info_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;
                }

                tx_info_first = NULL;
                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 (!tx_info_first) {
                                carl9170_tx_get_rates(ar, tid_info->vif,
                                                      tid_info->sta, first);
                                tx_info_first = IEEE80211_SKB_CB(first);
                        }

                        carl9170_tx_apply_rateset(ar, tx_info_first, skb);

                        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 ieee80211_tx_info *txinfo)
{
        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();
        txinfo->flags &= ~IEEE80211_TX_CTL_AMPDU;
        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;
        struct ieee80211_vif *vif;
        bool run;

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

        info = IEEE80211_SKB_CB(skb);
        vif = info->control.vif;

        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) {
                /* to static code analyzers and reviewers:
                 * mac80211 guarantees that a valid "sta"
                 * reference is present, if a frame is to
                 * be part of an ampdu. Hence any extra
                 * sta == NULL checks are redundant in this
                 * special case.
                 */
                run = carl9170_tx_ampdu_queue(ar, sta, skb, info);
                if (run)
                        carl9170_tx_ampdu(ar);

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

                carl9170_tx_get_rates(ar, vif, sta, skb);
                carl9170_tx_apply_rateset(ar, info, 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);
}

/* caller has to take rcu_read_lock */
static struct carl9170_vif_info *carl9170_pick_beaconing_vif(struct ar9170 *ar)
{
        struct carl9170_vif_info *cvif;
        int i = 1;

        /* The AR9170 hardware has no fancy beacon queue or some
         * other scheduling mechanism. So, the driver has to make
         * due by setting the two beacon timers (pretbtt and tbtt)
         * once and then swapping the beacon address in the HW's
         * register file each time the pretbtt fires.
         */

        cvif = rcu_dereference(ar->beacon_iter);
        if (ar->vifs > 0 && cvif) {
                do {
                        list_for_each_entry_continue_rcu(cvif, &ar->vif_list,
                                                         list) {
                                if (cvif->active && cvif->enable_beacon)
                                        goto out;
                        }
                } while (ar->beacon_enabled && i--);
        }

out:
        RCU_INIT_POINTER(ar->beacon_iter, cvif);
        return cvif;
}

static bool carl9170_tx_beacon_physet(struct ar9170 *ar, struct sk_buff *skb,
                                      u32 *ht1, u32 *plcp)
{
        struct ieee80211_tx_info *txinfo;
        struct ieee80211_tx_rate *rate;
        unsigned int power, chains;
        bool ht_rate;

        txinfo = IEEE80211_SKB_CB(skb);
        rate = &txinfo->control.rates[0];
        ht_rate = !!(txinfo->control.rates[0].flags & IEEE80211_TX_RC_MCS);
        carl9170_tx_rate_tpc_chains(ar, txinfo, rate, plcp, &power, &chains);

        *ht1 = AR9170_MAC_BCN_HT1_TX_ANT0;
        if (chains == AR9170_TX_PHY_TXCHAIN_2)
                *ht1 |= AR9170_MAC_BCN_HT1_TX_ANT1;
        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 (ht_rate) {
                *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;
                } else 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);
        } else {
                if (*plcp <= AR9170_TX_PHY_RATE_CCK_11M)
                        *plcp |= ((skb->len + FCS_LEN) << (3 + 16)) + 0x0400;
                else
                        *plcp |= ((skb->len + FCS_LEN) << 16) + 0x0010;
        }

        return ht_rate;
}

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

        rcu_read_lock();
        cvif = carl9170_pick_beaconing_vif(ar);
        if (!cvif)
                goto out_unlock;

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

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

        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;
        }

        ht_rate = carl9170_tx_beacon_physet(ar, skb, &ht1, &plcp);

        carl9170_async_regwrite_begin(ar);
        carl9170_async_regwrite(AR9170_MAC_REG_BCN_HT1, ht1);
        if (ht_rate)
                carl9170_async_regwrite(AR9170_MAC_REG_BCN_HT2, plcp);
        else
                carl9170_async_regwrite(AR9170_MAC_REG_BCN_PLCP, 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;
}