mac80211: fix aggregation for hardware with ampdu queues

Hardware with AMPDU queues currently has broken aggregation.

This patch fixes it by making all A-MPDUs go over the regular AC queues,
but keeping track of the hardware queues in mac80211. As a first rough
version, it actually stops the AC queue for extended periods of time,
which can be removed by adding buffering internal to mac80211, but is
currently not a huge problem because people rarely use multiple TIDs
that are in the same AC (and iwlwifi currently doesn't operate as AP).

This is a short-term fix, my current medium-term plan, which I hope to
execute soon as well, but am not sure can finish before .30, looks like
this:
 1) rework the internal queuing layer in mac80211 that we use for
    fragments if the driver stopped queue in the middle of a fragmented
    frame to be able to queue more frames at once (rather than just a
    single frame with its fragments)
 2) instead of stopping the entire AC queue, queue up the frames in a
    per-station/per-TID queue during aggregation session initiation,
    when the session has come up take all those frames and put them
    onto the queue from 1)
 3) push the ampdu queue layer abstraction this patch introduces in
    mac80211 into the driver, and remove the virtual queue stuff from
    mac80211 again

This plan will probably also affect ath9k in that mac80211 queues the
frames instead of passing them down, even when there are no ampdu queues.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 126 insertions, 60 deletions

diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index 1232d9f01ca9..0217b68c47ca 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -132,9 +132,24 @@ static int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
 
 	state = &sta->ampdu_mlme.tid_state_tx[tid];
 
-	if (local->hw.ampdu_queues)
-		ieee80211_stop_queue(&local->hw, sta->tid_to_tx_q[tid]);
+	if (local->hw.ampdu_queues) {
+		if (initiator) {
+			/*
+			 * Stop the AC queue to avoid issues where we send
+			 * unaggregated frames already before the delba.
+			 */
+			ieee80211_stop_queue_by_reason(&local->hw,
+				local->hw.queues + sta->tid_to_tx_q[tid],
+				IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+		}
 
+		/*
+		 * Pretend the driver woke the queue, just in case
+		 * it disabled it before the session was stopped.
+		 */
+		ieee80211_wake_queue(
+			&local->hw, local->hw.queues + sta->tid_to_tx_q[tid]);
+	}
 	*state = HT_AGG_STATE_REQ_STOP_BA_MSK |
 		(initiator << HT_AGG_STATE_INITIATOR_SHIFT);
 
@@ -144,8 +159,6 @@ static int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
 	/* HW shall not deny going back to legacy */
 	if (WARN_ON(ret)) {
 		*state = HT_AGG_STATE_OPERATIONAL;
-		if (local->hw.ampdu_queues)
-			ieee80211_wake_queue(&local->hw, sta->tid_to_tx_q[tid]);
 	}
 
 	return ret;
@@ -189,14 +202,19 @@ static void sta_addba_resp_timer_expired(unsigned long data)
 	spin_unlock_bh(&sta->lock);
 }
 
+static inline int ieee80211_ac_from_tid(int tid)
+{
+	return ieee802_1d_to_ac[tid & 7];
+}
+
 int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct sta_info *sta;
 	struct ieee80211_sub_if_data *sdata;
-	u16 start_seq_num;
 	u8 *state;
-	int ret = 0;
+	int i, qn = -1, ret = 0;
+	u16 start_seq_num;
 
 	if (WARN_ON(!local->ops->ampdu_action))
 		return -EINVAL;
@@ -209,6 +227,13 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 	       ra, tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
 
+	if (hw->ampdu_queues && ieee80211_ac_from_tid(tid) == 0) {
+#ifdef CONFIG_MAC80211_HT_DEBUG
+		printk(KERN_DEBUG "rejecting on voice AC\n");
+#endif
+		return -EINVAL;
+	}
+
 	rcu_read_lock();
 
 	sta = sta_info_get(local, ra);
@@ -217,7 +242,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 		printk(KERN_DEBUG "Could not find the station\n");
 #endif
 		ret = -ENOENT;
-		goto exit;
+		goto unlock;
 	}
 
 	/*
@@ -230,11 +255,13 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 	    sta->sdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
 	    sta->sdata->vif.type != NL80211_IFTYPE_AP) {
 		ret = -EINVAL;
-		goto exit;
+		goto unlock;
 	}
 
 	spin_lock_bh(&sta->lock);
 
+	sdata = sta->sdata;
+
 	/* we have tried too many times, receiver does not want A-MPDU */
 	if (sta->ampdu_mlme.addba_req_num[tid] > HT_AGG_MAX_RETRIES) {
 		ret = -EBUSY;
@@ -252,6 +279,42 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 		goto err_unlock_sta;
 	}
 
+	if (hw->ampdu_queues) {
+		spin_lock(&local->queue_stop_reason_lock);
+		/* reserve a new queue for this session */
+		for (i = 0; i < local->hw.ampdu_queues; i++) {
+			if (local->ampdu_ac_queue[i] < 0) {
+				qn = i;
+				local->ampdu_ac_queue[qn] =
+					ieee80211_ac_from_tid(tid);
+				break;
+			}
+		}
+		spin_unlock(&local->queue_stop_reason_lock);
+
+		if (qn < 0) {
+#ifdef CONFIG_MAC80211_HT_DEBUG
+			printk(KERN_DEBUG "BA request denied - "
+			       "queue unavailable for tid %d\n", tid);
+#endif /* CONFIG_MAC80211_HT_DEBUG */
+			ret = -ENOSPC;
+			goto err_unlock_sta;
+		}
+
+		/*
+		 * If we successfully allocate the session, we can't have
+		 * anything going on on the queue this TID maps into, so
+		 * stop it for now. This is a "virtual" stop using the same
+		 * mechanism that drivers will use.
+		 *
+		 * XXX: queue up frames for this session in the sta_info
+		 *	struct instead to avoid hitting all other STAs.
+		 */
+		ieee80211_stop_queue_by_reason(
+			&local->hw, hw->queues + qn,
+			IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+	}
+
 	/* prepare A-MPDU MLME for Tx aggregation */
 	sta->ampdu_mlme.tid_tx[tid] =
 			kmalloc(sizeof(struct tid_ampdu_tx), GFP_ATOMIC);
@@ -262,8 +325,9 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 					tid);
 #endif
 		ret = -ENOMEM;
-		goto err_unlock_sta;
+		goto err_return_queue;
 	}
+
 	/* Tx timer */
 	sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer.function =
 			sta_addba_resp_timer_expired;
@@ -271,49 +335,25 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 			(unsigned long)&sta->timer_to_tid[tid];
 	init_timer(&sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer);
 
-	if (hw->ampdu_queues) {
-		/* create a new queue for this aggregation */
-		ret = ieee80211_ht_agg_queue_add(local, sta, tid);
-
-		/* case no queue is available to aggregation
-		 * don't switch to aggregation */
-		if (ret) {
-#ifdef CONFIG_MAC80211_HT_DEBUG
-			printk(KERN_DEBUG "BA request denied - "
-			       "queue unavailable for tid %d\n", tid);
-#endif /* CONFIG_MAC80211_HT_DEBUG */
-			goto err_unlock_queue;
-		}
-	}
-	sdata = sta->sdata;
-
 	/* Ok, the Addba frame hasn't been sent yet, but if the driver calls the
 	 * call back right away, it must see that the flow has begun */
 	*state |= HT_ADDBA_REQUESTED_MSK;
 
-	/* This is slightly racy because the queue isn't stopped */
 	start_seq_num = sta->tid_seq[tid];
 
 	ret = local->ops->ampdu_action(hw, IEEE80211_AMPDU_TX_START,
 				       &sta->sta, tid, &start_seq_num);
 
 	if (ret) {
-		/* No need to requeue the packets in the agg queue, since we
-		 * held the tx lock: no packet could be enqueued to the newly
-		 * allocated queue */
-		if (hw->ampdu_queues)
-			ieee80211_ht_agg_queue_remove(local, sta, tid, 0);
 #ifdef CONFIG_MAC80211_HT_DEBUG
 		printk(KERN_DEBUG "BA request denied - HW unavailable for"
 					" tid %d\n", tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
 		*state = HT_AGG_STATE_IDLE;
-		goto err_unlock_queue;
+		goto err_free;
 	}
+	sta->tid_to_tx_q[tid] = qn;
 
-	/* Will put all the packets in the new SW queue */
-	if (hw->ampdu_queues)
-		ieee80211_requeue(local, ieee802_1d_to_ac[tid]);
 	spin_unlock_bh(&sta->lock);
 
 	/* send an addBA request */
@@ -322,7 +362,6 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 			sta->ampdu_mlme.dialog_token_allocator;
 	sta->ampdu_mlme.tid_tx[tid]->ssn = start_seq_num;
 
-
 	ieee80211_send_addba_request(sta->sdata, ra, tid,
 			 sta->ampdu_mlme.tid_tx[tid]->dialog_token,
 			 sta->ampdu_mlme.tid_tx[tid]->ssn,
@@ -334,15 +373,24 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 #ifdef CONFIG_MAC80211_HT_DEBUG
 	printk(KERN_DEBUG "activated addBA response timer on tid %d\n", tid);
 #endif
-	goto exit;
+	goto unlock;
 
-err_unlock_queue:
+ err_free:
 	kfree(sta->ampdu_mlme.tid_tx[tid]);
 	sta->ampdu_mlme.tid_tx[tid] = NULL;
-	ret = -EBUSY;
-err_unlock_sta:
+ err_return_queue:
+	if (qn >= 0) {
+		/* We failed, so start queue again right away. */
+		ieee80211_wake_queue_by_reason(hw, hw->queues + qn,
+			IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+		/* give queue back to pool */
+		spin_lock(&local->queue_stop_reason_lock);
+		local->ampdu_ac_queue[qn] = -1;
+		spin_unlock(&local->queue_stop_reason_lock);
+	}
+ err_unlock_sta:
 	spin_unlock_bh(&sta->lock);
-exit:
+ unlock:
 	rcu_read_unlock();
 	return ret;
 }
@@ -375,7 +423,7 @@ void ieee80211_start_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 	state = &sta->ampdu_mlme.tid_state_tx[tid];
 	spin_lock_bh(&sta->lock);
 
-	if (!(*state & HT_ADDBA_REQUESTED_MSK)) {
+	if (WARN_ON(!(*state & HT_ADDBA_REQUESTED_MSK))) {
 #ifdef CONFIG_MAC80211_HT_DEBUG
 		printk(KERN_DEBUG "addBA was not requested yet, state is %d\n",
 				*state);
@@ -385,7 +433,8 @@ void ieee80211_start_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 		return;
 	}
 
-	WARN_ON_ONCE(*state & HT_ADDBA_DRV_READY_MSK);
+	if (WARN_ON(*state & HT_ADDBA_DRV_READY_MSK))
+		goto out;
 
 	*state |= HT_ADDBA_DRV_READY_MSK;
 
@@ -393,9 +442,18 @@ void ieee80211_start_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 #ifdef CONFIG_MAC80211_HT_DEBUG
 		printk(KERN_DEBUG "Aggregation is on for tid %d \n", tid);
 #endif
-		if (hw->ampdu_queues)
-			ieee80211_wake_queue(hw, sta->tid_to_tx_q[tid]);
+		if (hw->ampdu_queues) {
+			/*
+			 * Wake up this queue, we stopped it earlier,
+			 * this will in turn wake the entire AC.
+			 */
+			ieee80211_wake_queue_by_reason(hw,
+				hw->queues + sta->tid_to_tx_q[tid],
+				IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+		}
 	}
+
+ out:
 	spin_unlock_bh(&sta->lock);
 	rcu_read_unlock();
 }
@@ -485,7 +543,6 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct sta_info *sta;
 	u8 *state;
-	int agg_queue;
 
 	if (tid >= STA_TID_NUM) {
 #ifdef CONFIG_MAC80211_HT_DEBUG
@@ -527,19 +584,19 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
 		ieee80211_send_delba(sta->sdata, ra, tid,
 			WLAN_BACK_INITIATOR, WLAN_REASON_QSTA_NOT_USE);
 
-	if (hw->ampdu_queues) {
-		agg_queue = sta->tid_to_tx_q[tid];
-		ieee80211_ht_agg_queue_remove(local, sta, tid, 1);
+	spin_lock_bh(&sta->lock);
 
-		/* We just requeued the all the frames that were in the
-		 * removed queue, and since we might miss a softirq we do
-		 * netif_schedule_queue.  ieee80211_wake_queue is not used
-		 * here as this queue is not necessarily stopped
+	if (*state & HT_AGG_STATE_INITIATOR_MSK &&
+	    hw->ampdu_queues) {
+		/*
+		 * Wake up this queue, we stopped it earlier,
+		 * this will in turn wake the entire AC.
 		 */
-		netif_schedule_queue(netdev_get_tx_queue(local->mdev,
-							 agg_queue));
+		ieee80211_wake_queue_by_reason(hw,
+			hw->queues + sta->tid_to_tx_q[tid],
+			IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
 	}
-	spin_lock_bh(&sta->lock);
+
 	*state = HT_AGG_STATE_IDLE;
 	sta->ampdu_mlme.addba_req_num[tid] = 0;
 	kfree(sta->ampdu_mlme.tid_tx[tid]);
@@ -613,12 +670,21 @@ void ieee80211_process_addba_resp(struct ieee80211_local *local,
 #endif /* CONFIG_MAC80211_HT_DEBUG */
 	if (le16_to_cpu(mgmt->u.action.u.addba_resp.status)
 			== WLAN_STATUS_SUCCESS) {
+		u8 curstate = *state;
+
 		*state |= HT_ADDBA_RECEIVED_MSK;
-		sta->ampdu_mlme.addba_req_num[tid] = 0;
 
-		if (*state == HT_AGG_STATE_OPERATIONAL &&
-		    local->hw.ampdu_queues)
-			ieee80211_wake_queue(hw, sta->tid_to_tx_q[tid]);
+		if (hw->ampdu_queues && *state != curstate &&
+		    *state == HT_AGG_STATE_OPERATIONAL) {
+			/*
+			 * Wake up this queue, we stopped it earlier,
+			 * this will in turn wake the entire AC.
+			 */
+			ieee80211_wake_queue_by_reason(hw,
+				hw->queues + sta->tid_to_tx_q[tid],
+				IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+		}
+		sta->ampdu_mlme.addba_req_num[tid] = 0;
 
 		if (local->ops->ampdu_action) {
 			(void)local->ops->ampdu_action(hw,