carl9170 firmware: extract tx and rx code from wlan.c into separate files
[carl9170fw.git] / carlfw / src / wlantx.c
diff --git a/carlfw/src/wlantx.c b/carlfw/src/wlantx.c
new file mode 100644 (file)
index 0000000..9f2f51b
--- /dev/null
@@ -0,0 +1,679 @@
+/*
+ * carl9170 firmware - used by the ar9170 wireless device
+ *
+ * WLAN transmit and tx status
+ *
+ * Copyright (c) 2000-2005 ZyDAS Technology Corporation
+ * Copyright (c) 2007-2009 Atheros Communications, Inc.
+ * Copyright   2009    Johannes Berg <johannes@sipsolutions.net>
+ * Copyright 2009-2012 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; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "carl9170.h"
+#include "shared/phy.h"
+#include "hostif.h"
+#include "timer.h"
+#include "wl.h"
+#include "printf.h"
+#include "rf.h"
+#include "linux/ieee80211.h"
+#include "wol.h"
+
+static void wlan_txunstuck(unsigned int queue)
+{
+       set_wlan_txq_dma_addr(queue, ((uint32_t) fw.wlan.tx_queue[queue].head) | 1);
+}
+
+#ifdef CONFIG_CARL9170FW_DMA_QUEUE_BUMP
+static void wlan_txupdate(unsigned int queue)
+{
+       set_wlan_txq_dma_addr(queue, ((uint32_t) fw.wlan.tx_queue[queue].head));
+}
+
+void wlan_dma_bump(unsigned int qidx)
+{
+       unsigned int offset = qidx;
+       uint32_t status, trigger;
+
+       status = get(AR9170_MAC_REG_DMA_STATUS) >> 12;
+       trigger = get(AR9170_MAC_REG_DMA_TRIGGER) >> 12;
+
+       while (offset != 0) {
+               status >>= 4;
+               trigger >>= 4;
+               offset--;
+       }
+
+       status &= 0xf;
+       trigger &= 0xf;
+
+       if ((trigger == 0xa) && (status == 0x8)) {
+               DBG("UNSTUCK");
+               wlan_txunstuck(qidx);
+       } else {
+               DBG("UPDATE");
+               wlan_txupdate(qidx);
+       }
+}
+#else
+void wlan_dma_bump(unsigned int __unused qidx)
+{
+}
+#endif /* CONFIG_CARL9170FW_DMA_QUEUE_BUMP */
+
+void wlan_send_buffered_tx_status(void)
+{
+       unsigned int len;
+
+       while (fw.wlan.tx_status_pending) {
+               len = min((unsigned int)fw.wlan.tx_status_pending,
+                         CARL9170_RSP_TX_STATUS_NUM);
+               len = min(len, CARL9170_TX_STATUS_NUM - fw.wlan.tx_status_head_idx);
+
+               /*
+                * rather than memcpy each individual request into a large buffer,
+                * we _splice_ them all together.
+                *
+                * The only downside is however that we have to be careful around
+                * the edges of the tx_status_cache.
+                *
+                * Note:
+                * Each tx_status is about 2 bytes. However every command package
+                * must have a size which is a multiple of 4.
+                */
+
+               send_cmd_to_host((len * sizeof(struct carl9170_tx_status) + 3) & ~3,
+                                CARL9170_RSP_TXCOMP, len, (void *)
+                                &fw.wlan.tx_status_cache[fw.wlan.tx_status_head_idx]);
+
+               fw.wlan.tx_status_pending -= len;
+               fw.wlan.tx_status_head_idx += len;
+               fw.wlan.tx_status_head_idx %= CARL9170_TX_STATUS_NUM;
+       }
+}
+
+static struct carl9170_tx_status *wlan_get_tx_status_buffer(void)
+{
+       struct carl9170_tx_status *tmp;
+
+       tmp = &fw.wlan.tx_status_cache[fw.wlan.tx_status_tail_idx++];
+       fw.wlan.tx_status_tail_idx %= CARL9170_TX_STATUS_NUM;
+
+       if (fw.wlan.tx_status_pending == CARL9170_TX_STATUS_NUM)
+               wlan_send_buffered_tx_status();
+
+       fw.wlan.tx_status_pending++;
+
+       return tmp;
+}
+
+/* generate _aggregated_ tx_status for the host */
+void wlan_tx_complete(struct carl9170_tx_superframe *super,
+                     bool txs)
+{
+       struct carl9170_tx_status *status;
+
+       status = wlan_get_tx_status_buffer();
+
+       /*
+        * The *unique* cookie and AC_ID is used by the driver for
+        * frame lookup.
+        */
+       status->cookie = super->s.cookie;
+       status->queue = super->s.queue;
+       super->s.cookie = 0;
+
+       /*
+        * This field holds the number of tries of the rate in
+        * the rate index field (rix).
+        */
+       status->rix = super->s.rix;
+       status->tries = super->s.cnt;
+       status->success = (txs) ? 1 : 0;
+}
+
+static bool wlan_tx_consume_retry(struct carl9170_tx_superframe *super)
+{
+       /* check if this was the last possible retry with this rate */
+       if (unlikely(super->s.cnt >= super->s.ri[super->s.rix].tries)) {
+               /* end of the road - indicate tx failure */
+               if (unlikely(super->s.rix == CARL9170_TX_MAX_RETRY_RATES))
+                       return false;
+
+               /* check if there are alternative rates available */
+               if (!super->s.rr[super->s.rix].set)
+                       return false;
+
+               /* try next retry rate */
+               super->f.hdr.phy.set = super->s.rr[super->s.rix].set;
+
+               /* finally - mark the old rate as USED */
+               super->s.rix++;
+
+               /* update MAC flags */
+               super->f.hdr.mac.erp_prot = super->s.ri[super->s.rix].erp_prot;
+               super->f.hdr.mac.ampdu = super->s.ri[super->s.rix].ampdu;
+
+               /* reinitialize try counter */
+               super->s.cnt = 1;
+       } else {
+               /* just increase retry counter */
+               super->s.cnt++;
+       }
+
+       return true;
+}
+
+static inline u16 get_tid(struct ieee80211_hdr *hdr)
+{
+       return (ieee80211_get_qos_ctl(hdr))[0] & IEEE80211_QOS_CTL_TID_MASK;
+}
+
+/* This function will only work on uint32_t-aligned pointers! */
+static bool same_hdr(const void *_d0, const void *_d1)
+{
+       const uint32_t *d0 = _d0;
+       const uint32_t *d1 = _d1;
+
+       /* BUG_ON((unsigned long)d0 & 3 || (unsigned long)d1 & 3)) */
+       return !((d0[0] ^ d1[0]) |                      /* FC + DU */
+                (d0[1] ^ d1[1]) |                      /* addr1 */
+                (d0[2] ^ d1[2]) | (d0[3] ^ d1[3]) |    /* addr2 + addr3 */
+                (d0[4] ^ d1[4]));                      /* addr3 */
+}
+
+static inline bool same_aggr(struct ieee80211_hdr *a, struct ieee80211_hdr *b)
+{
+       return (get_tid(a) == get_tid(b)) || same_hdr(a, b);
+}
+
+static void wlan_tx_ampdu_reset(unsigned int qidx)
+{
+       fw.wlan.ampdu_prev[qidx] = NULL;
+}
+
+static void wlan_tx_ampdu_end(unsigned int qidx)
+{
+       struct carl9170_tx_superframe *ht_prev = fw.wlan.ampdu_prev[qidx];
+
+       if (ht_prev)
+               ht_prev->f.hdr.mac.ba_end = 1;
+
+       wlan_tx_ampdu_reset(qidx);
+}
+
+static void wlan_tx_ampdu(struct carl9170_tx_superframe *super)
+{
+       unsigned int qidx = super->s.queue;
+       struct carl9170_tx_superframe *ht_prev = fw.wlan.ampdu_prev[qidx];
+
+       if (super->f.hdr.mac.ampdu) {
+               if (ht_prev &&
+                   !same_aggr(&super->f.data.i3e, &ht_prev->f.data.i3e))
+                       ht_prev->f.hdr.mac.ba_end = 1;
+               else
+                       super->f.hdr.mac.ba_end = 0;
+
+               fw.wlan.ampdu_prev[qidx] = super;
+       } else {
+               wlan_tx_ampdu_end(qidx);
+       }
+}
+
+/* for all tries */
+static void __wlan_tx(struct dma_desc *desc)
+{
+       struct carl9170_tx_superframe *super = get_super(desc);
+
+       if (unlikely(super->s.fill_in_tsf)) {
+               struct ieee80211_mgmt *mgmt = (void *) &super->f.data.i3e;
+               uint32_t *tsf = (uint32_t *) &mgmt->u.probe_resp.timestamp;
+
+               /*
+                * Truth be told: this is a hack.
+                *
+                * The *real* TSF is definitely going to be higher/older.
+                * But this hardware emulation code is head and shoulders
+                * above anything a driver can possibly do.
+                *
+                * (even, if it's got an accurate atomic clock source).
+                */
+
+               read_tsf(tsf);
+       }
+
+       wlan_tx_ampdu(super);
+
+#ifdef CONFIG_CARL9170FW_DEBUG
+       BUG_ON(fw.phy.psm.state != CARL9170_PSM_WAKE);
+#endif /* CONFIG_CARL9170FW_DEBUG */
+
+       /* insert desc into the right queue */
+       dma_put(&fw.wlan.tx_queue[super->s.queue], desc);
+}
+
+static void wlan_assign_seq(struct ieee80211_hdr *hdr, unsigned int vif)
+{
+       hdr->seq_ctrl &= cpu_to_le16(~IEEE80211_SCTL_SEQ);
+       hdr->seq_ctrl |= cpu_to_le16(fw.wlan.sequence[vif]);
+
+       if (ieee80211_is_first_frag(hdr->seq_ctrl))
+               fw.wlan.sequence[vif] += 0x10;
+}
+
+/* prepares frame for the first transmission */
+static void _wlan_tx(struct dma_desc *desc)
+{
+       struct carl9170_tx_superframe *super = get_super(desc);
+
+       if (unlikely(super->s.assign_seq))
+               wlan_assign_seq(&super->f.data.i3e, super->s.vif_id);
+
+       if (unlikely(super->s.ampdu_commit_density)) {
+               set(AR9170_MAC_REG_AMPDU_DENSITY,
+                   MOD_VAL(AR9170_MAC_AMPDU_DENSITY,
+                           get(AR9170_MAC_REG_AMPDU_DENSITY),
+                           super->s.ampdu_density));
+       }
+
+       if (unlikely(super->s.ampdu_commit_factor)) {
+               set(AR9170_MAC_REG_AMPDU_FACTOR,
+                   MOD_VAL(AR9170_MAC_AMPDU_FACTOR,
+                           get(AR9170_MAC_REG_AMPDU_FACTOR),
+                           8 << super->s.ampdu_factor));
+       }
+}
+
+/* propagate transmission status back to the driver */
+static bool wlan_tx_status(struct dma_queue *queue,
+                          struct dma_desc *desc)
+{
+       struct carl9170_tx_superframe *super = get_super(desc);
+       unsigned int qidx = super->s.queue;
+       bool txfail = false, success;
+
+       success = true;
+
+       /* update hangcheck */
+       fw.wlan.last_super_num[qidx] = 0;
+
+       /*
+        * Note:
+        * There could be a corner case when the TXFAIL is set
+        * even though the frame was properly ACKed by the peer:
+        *   a BlockAckReq with the immediate policy will cause
+        *   the receiving peer to produce a BlockACK unfortunately
+        *   the MAC in this chip seems to be expecting a legacy
+        *   ACK and marks the BAR as failed!
+        */
+
+       if (!!(desc->ctrl & AR9170_CTRL_FAIL)) {
+               txfail = !!(desc->ctrl & AR9170_CTRL_TXFAIL);
+
+               /* reset retry indicator flags */
+               desc->ctrl &= ~(AR9170_CTRL_TXFAIL | AR9170_CTRL_BAFAIL);
+
+               /*
+                * Note: wlan_tx_consume_retry will override the old
+                * phy [CCK,OFDM, HT, BW20/40, MCS...] and mac vectors
+                * [AMPDU,RTS/CTS,...] therefore be careful when they
+                * are used.
+                */
+               if (wlan_tx_consume_retry(super)) {
+                       /*
+                        * retry for simple and aggregated 802.11 frames.
+                        *
+                        * Note: We must not mess up the original frame
+                        * order.
+                        */
+
+                       if (!super->f.hdr.mac.ampdu) {
+                               /*
+                                * 802.11 - 7.1.3.1.5.
+                                * set "Retry Field" for consecutive attempts
+                                *
+                                * Note: For AMPDU see:
+                                * 802.11n 9.9.1.6 "Retransmit Procedures"
+                                */
+                               super->f.data.i3e.frame_control |=
+                                       cpu_to_le16(IEEE80211_FCTL_RETRY);
+                       }
+
+                       if (txfail) {
+                               /* Normal TX Failure */
+
+                               /* demise descriptor ownership back to the hardware */
+                               dma_rearm(desc);
+
+                               /*
+                                * And this will get the queue going again.
+                                * To understand why: you have to get the HW
+                                * specs... But sadly I never saw them.
+                                */
+                               wlan_txunstuck(qidx);
+
+                               /* abort cycle - this is necessary due to HW design */
+                               return false;
+                       } else {
+                               /* (HT-) BlockACK failure */
+
+                               /*
+                                * Unlink the failed attempt and put it into
+                                * the retry queue. The caller routine must
+                                * be aware of this so the frames don't get lost.
+                                */
+
+#ifndef CONFIG_CARL9170FW_DEBUG
+                               dma_unlink_head(queue);
+#else /* CONFIG_CARL9170FW_DEBUG */
+                               BUG_ON(dma_unlink_head(queue) != desc);
+#endif /* CONFIG_CARL9170FW_DEBUG */
+                               dma_put(&fw.wlan.tx_retry, desc);
+                               return true;
+                       }
+               } else {
+                       /* out of frame attempts - discard frame */
+                       success = false;
+               }
+       }
+
+#ifndef CONFIG_CARL9170FW_DEBUG
+       dma_unlink_head(queue);
+#else /* CONFIG_CARL9170FW_DEBUG */
+       BUG_ON(dma_unlink_head(queue) != desc);
+#endif /* CONFIG_CARL9170FW_DEBUG */
+       if (txfail) {
+               /*
+                * Issue the queue bump,
+                * We need to do this in case this was the frame's last
+                * possible retry attempt and it unfortunately: it failed.
+                */
+
+               wlan_txunstuck(qidx);
+       }
+
+       unhide_super(desc);
+
+       if (unlikely(super == fw.wlan.fw_desc_data)) {
+               fw.wlan.fw_desc = desc;
+               fw.wlan.fw_desc_available = 1;
+
+               if (fw.wlan.fw_desc_callback)
+                       fw.wlan.fw_desc_callback(super, success);
+
+               return true;
+       }
+
+       if (unlikely(super->s.cab))
+               fw.wlan.cab_queue_len[super->s.vif_id]--;
+
+       wlan_tx_complete(super, success);
+
+       if (ieee80211_is_back_req(super->f.data.i3e.frame_control)) {
+               fw.wlan.queued_bar--;
+       }
+
+       /* recycle freed descriptors */
+       dma_reclaim(&fw.pta.down_queue, desc);
+       down_trigger();
+       return true;
+}
+
+void handle_wlan_tx_completion(void)
+{
+       struct dma_desc *desc;
+       int i;
+
+       for (i = AR9170_TXQ_SPECIAL; i >= AR9170_TXQ0; i--) {
+               __while_desc_bits(desc, &fw.wlan.tx_queue[i], AR9170_OWN_BITS_SW) {
+                       if (!wlan_tx_status(&fw.wlan.tx_queue[i], desc)) {
+                               /* termination requested. */
+                               break;
+                       }
+               }
+
+               wlan_tx_ampdu_reset(i);
+
+               for_each_desc(desc, &fw.wlan.tx_retry)
+                       __wlan_tx(desc);
+
+               wlan_tx_ampdu_end(i);
+               if (!queue_empty(&fw.wlan.tx_queue[i]))
+                       wlan_trigger(BIT(i));
+       }
+}
+
+void __hot wlan_tx(struct dma_desc *desc)
+{
+       struct carl9170_tx_superframe *super = DESC_PAYLOAD(desc);
+
+       if (ieee80211_is_back_req(super->f.data.i3e.frame_control)) {
+               fw.wlan.queued_bar++;
+       }
+
+       /* initialize rate control struct */
+       super->s.rix = 0;
+       super->s.cnt = 1;
+       hide_super(desc);
+
+       if (unlikely(super->s.cab)) {
+               fw.wlan.cab_queue_len[super->s.vif_id]++;
+               dma_put(&fw.wlan.cab_queue[super->s.vif_id], desc);
+               return;
+       }
+
+       _wlan_tx(desc);
+       __wlan_tx(desc);
+       wlan_trigger(BIT(super->s.queue));
+}
+
+void wlan_tx_fw(struct carl9170_tx_superdesc *super, fw_desc_callback_t cb)
+{
+       if (!fw.wlan.fw_desc_available)
+               return;
+
+       fw.wlan.fw_desc_available = 0;
+
+       /* Format BlockAck */
+       fw.wlan.fw_desc->ctrl = AR9170_CTRL_FS_BIT | AR9170_CTRL_LS_BIT;
+       fw.wlan.fw_desc->status = AR9170_OWN_BITS_SW;
+
+       fw.wlan.fw_desc->totalLen = fw.wlan.fw_desc->dataSize = super->len;
+       fw.wlan.fw_desc_data = fw.wlan.fw_desc->dataAddr = super;
+       fw.wlan.fw_desc->nextAddr = fw.wlan.fw_desc->lastAddr =
+               fw.wlan.fw_desc;
+       fw.wlan.fw_desc_callback = cb;
+       wlan_tx(fw.wlan.fw_desc);
+}
+
+void wlan_send_buffered_ba(void)
+{
+       struct carl9170_tx_ba_superframe *baf = &dma_mem.reserved.ba.ba;
+       struct ieee80211_ba *ba = (struct ieee80211_ba *) &baf->f.ba;
+       struct carl9170_bar_ctx *ctx;
+
+       if (likely(!fw.wlan.queued_ba))
+               return;
+
+       /* there's no point to continue when the ba_desc is not available. */
+       if (!fw.wlan.fw_desc_available)
+               return;
+
+       ctx = &fw.wlan.ba_cache[fw.wlan.ba_head_idx];
+       fw.wlan.ba_head_idx++;
+       fw.wlan.ba_head_idx %= CONFIG_CARL9170FW_BACK_REQS_NUM;
+       fw.wlan.queued_ba--;
+
+       baf->s.len = sizeof(struct carl9170_tx_superdesc) +
+                    sizeof(struct ar9170_tx_hwdesc) +
+                    sizeof(struct ieee80211_ba);
+       baf->s.ri[0].tries = 1;
+       baf->s.cookie = 0;
+       baf->s.queue = AR9170_TXQ_VO;
+       baf->f.hdr.length = sizeof(struct ieee80211_ba) + FCS_LEN;
+
+       baf->f.hdr.mac.no_ack = 1;
+
+       baf->f.hdr.phy.modulation = 1; /* OFDM */
+       baf->f.hdr.phy.tx_power = 34; /* 17 dBm */
+       baf->f.hdr.phy.chains = 1;
+       baf->f.hdr.phy.mcs = AR9170_TXRX_PHY_RATE_OFDM_6M;
+
+       /* format outgoing BA */
+       ba->frame_control = cpu_to_le16(IEEE80211_FTYPE_CTL | IEEE80211_STYPE_BACK);
+       ba->duration = cpu_to_le16(0);
+
+       /* the BAR contains all necessary MACs. All we need is to swap them */
+       memcpy(ba->ra, ctx->ta, 6);
+       memcpy(ba->ta, ctx->ra, 6);
+
+       /*
+        * Unfortunately, we cannot look into the hardware's scoreboard.
+        * Therefore we have to proceed as described in 802.11n 9.10.7.5
+        * and send a null BlockAck.
+        */
+       memset(ba->bitmap, 0x0, sizeof(ba->bitmap));
+
+       /*
+        * Both, the original firmare and ath9k set the NO ACK flag in
+        * the BA Ack Policy subfield.
+        */
+       ba->control = ctx->control | cpu_to_le16(1);
+       ba->start_seq_num = ctx->start_seq_num;
+       wlan_tx_fw(&baf->s, NULL);
+}
+
+void wlan_cab_flush_queue(const unsigned int vif)
+{
+       struct dma_queue *cab_queue = &fw.wlan.cab_queue[vif];
+       struct dma_desc *desc;
+
+       /* move queued frames into the main tx queues */
+       for_each_desc(desc, cab_queue) {
+               struct carl9170_tx_superframe *super = get_super(desc);
+               if (!queue_empty(cab_queue)) {
+                       /*
+                        * Set MOREDATA flag for all,
+                        * but the last queued frame.
+                        * see: 802.11-2007 11.2.1.5 f)
+                        *
+                        * This is actually the reason to why
+                        * we need to prevent the reentry.
+                        */
+
+                       super->f.data.i3e.frame_control |=
+                               cpu_to_le16(IEEE80211_FCTL_MOREDATA);
+               } else {
+                       super->f.data.i3e.frame_control &=
+                               cpu_to_le16(~IEEE80211_FCTL_MOREDATA);
+               }
+
+               /* ready to roll! */
+               _wlan_tx(desc);
+               __wlan_tx(desc);
+               wlan_trigger(BIT(super->s.queue));
+       }
+}
+
+static uint8_t *beacon_find_ie(uint8_t ie, void *addr,
+                              const unsigned int len)
+{
+       struct ieee80211_mgmt *mgmt = addr;
+       uint8_t *pos, *end;
+
+       pos = mgmt->u.beacon.variable;
+       end = (uint8_t *) ((unsigned long)mgmt + (len - FCS_LEN));
+       while (pos < end) {
+               if (pos + 2 + pos[1] > end)
+                       return NULL;
+
+               if (pos[0] == ie)
+                       return pos;
+
+               pos += pos[1] + 2;
+       }
+
+       return NULL;
+}
+
+void wlan_modify_beacon(const unsigned int vif,
+       const unsigned int addr, const unsigned int len)
+{
+       uint8_t *_ie;
+       struct ieee80211_tim_ie *ie;
+
+       _ie = beacon_find_ie(WLAN_EID_TIM, (void *)addr, len);
+       if (likely(_ie)) {
+               ie = (struct ieee80211_tim_ie *) &_ie[2];
+
+               if (!queue_empty(&fw.wlan.cab_queue[vif]) && (ie->dtim_count == 0)) {
+                       /* schedule DTIM transfer */
+                       fw.wlan.cab_flush_trigger[vif] = CARL9170_CAB_TRIGGER_ARMED;
+               } else if ((fw.wlan.cab_queue_len[vif] == 0) && (fw.wlan.cab_flush_trigger[vif])) {
+                       /* undo all chances to the beacon structure */
+                       ie->bitmap_ctrl &= ~0x1;
+                       fw.wlan.cab_flush_trigger[vif] = CARL9170_CAB_TRIGGER_EMPTY;
+               }
+
+               /* Triggered by CARL9170_CAB_TRIGGER_ARMED || CARL9170_CAB_TRIGGER_DEFER */
+               if (fw.wlan.cab_flush_trigger[vif]) {
+                       /* Set the almighty Multicast Traffic Indication Bit. */
+                       ie->bitmap_ctrl |= 0x1;
+               }
+       }
+
+       /*
+        * Ideally, the sequence number should be assigned by the TX arbiter
+        * hardware. But AFAIK that's not possible, so we have to go for the
+        * next best thing and write it into the beacon fifo during the open
+        * beacon update window.
+        */
+
+       wlan_assign_seq((struct ieee80211_hdr *)addr, vif);
+}
+
+void wlan_send_buffered_cab(void)
+{
+       unsigned int i;
+
+       for (i = 0; i < CARL9170_INTF_NUM; i++) {
+               if (unlikely(fw.wlan.cab_flush_trigger[i] == CARL9170_CAB_TRIGGER_ARMED)) {
+                       /*
+                        * This is hardcoded into carl9170usb driver.
+                        *
+                        * The driver must set the PRETBTT event to beacon_interval -
+                        * CARL9170_PRETBTT_KUS (usually 6) Kus.
+                        *
+                        * But still, we can only do so much about 802.11-2007 9.3.2.1 &
+                        * 11.2.1.6. Let's hope the current solution is adequate enough.
+                        */
+
+                       if (is_after_msecs(fw.wlan.cab_flush_time, (CARL9170_TBTT_DELTA))) {
+                               wlan_cab_flush_queue(i);
+
+                               /*
+                                * This prevents the code from sending new BC/MC frames
+                                * which were queued after the previous buffered traffic
+                                * has been sent out... They will have to wait until the
+                                * next DTIM beacon comes along.
+                                */
+                               fw.wlan.cab_flush_trigger[i] = CARL9170_CAB_TRIGGER_DEFER;
+                       }
+               }
+
+       }
+}