ath9k: fix queue stop/start based on the number of pending frames

Because there is a limited number of tx buffers available, once the
queue has been filled to a certain point, ath9k needs to stop accepting
new frames from mac80211. In order to prevent a full WMM queue from
stopping another queue with fewer frames, this patch limits the number
of queued frames to a quarter of the total available tx buffers, minus
some reserved frames to be used for other purposes (e.g. beacons).

Because tx buffers are reserved for frames when they're staged in
software queues as well, the actual queue depth cannot be used for
this, so this patch stores a reference to the tx queue in the ath_buf
struct and keeps track of the total number of pending frames.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 18 insertions, 31 deletions

diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index f63f6a944d6..7547c8f9a58 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -984,32 +984,6 @@ int ath_tx_get_qnum(struct ath_softc *sc, int qtype, int haltype)
 	return qnum;
 }
 
-struct ath_txq *ath_test_get_txq(struct ath_softc *sc, struct sk_buff *skb)
-{
-	struct ath_txq *txq = NULL;
-	u16 skb_queue = skb_get_queue_mapping(skb);
-	int qnum;
-
-	qnum = ath_get_hal_qnum(skb_queue, sc);
-	txq = &sc->tx.txq[qnum];
-
-	spin_lock_bh(&txq->axq_lock);
-
-	if (txq->axq_depth >= (ATH_TXBUF - 20)) {
-		ath_print(ath9k_hw_common(sc->sc_ah), ATH_DBG_XMIT,
-			  "TX queue: %d is full, depth: %d\n",
-			  qnum, txq->axq_depth);
-		ath_mac80211_stop_queue(sc, skb_queue);
-		txq->stopped = 1;
-		spin_unlock_bh(&txq->axq_lock);
-		return NULL;
-	}
-
-	spin_unlock_bh(&txq->axq_lock);
-
-	return txq;
-}
-
 int ath_txq_update(struct ath_softc *sc, int qnum,
 		   struct ath9k_tx_queue_info *qinfo)
 {
@@ -1809,6 +1783,7 @@ int ath_tx_start(struct ieee80211_hw *hw, struct sk_buff *skb,
 	struct ath_wiphy *aphy = hw->priv;
 	struct ath_softc *sc = aphy->sc;
 	struct ath_common *common = ath9k_hw_common(sc->sc_ah);
+	struct ath_txq *txq = txctl->txq;
 	struct ath_buf *bf;
 	int r;
 
@@ -1818,10 +1793,16 @@ int ath_tx_start(struct ieee80211_hw *hw, struct sk_buff *skb,
 		return -1;
 	}
 
+	bf->txq = txctl->txq;
+	spin_lock_bh(&bf->txq->axq_lock);
+	if (++bf->txq->pending_frames > ATH_MAX_QDEPTH && !txq->stopped) {
+		ath_mac80211_stop_queue(sc, skb_get_queue_mapping(skb));
+		txq->stopped = 1;
+	}
+	spin_unlock_bh(&bf->txq->axq_lock);
+
 	r = ath_tx_setup_buffer(hw, bf, skb, txctl);
 	if (unlikely(r)) {
-		struct ath_txq *txq = txctl->txq;
-
 		ath_print(common, ATH_DBG_FATAL, "TX mem alloc failure\n");
 
 		/* upon ath_tx_processq() this TX queue will be resumed, we
@@ -1829,7 +1810,7 @@ int ath_tx_start(struct ieee80211_hw *hw, struct sk_buff *skb,
 		 * we will at least have to run TX completionon one buffer
 		 * on the queue */
 		spin_lock_bh(&txq->axq_lock);
-		if (sc->tx.txq[txq->axq_qnum].axq_depth > 1) {
+		if (!txq->stopped && txq->axq_depth > 1) {
 			ath_mac80211_stop_queue(sc, skb_get_queue_mapping(skb));
 			txq->stopped = 1;
 		}
@@ -1970,6 +1951,13 @@ static void ath_tx_complete_buf(struct ath_softc *sc, struct ath_buf *bf,
 			tx_flags |= ATH_TX_XRETRY;
 	}
 
+	if (bf->txq) {
+		spin_lock_bh(&bf->txq->axq_lock);
+		bf->txq->pending_frames--;
+		spin_unlock_bh(&bf->txq->axq_lock);
+		bf->txq = NULL;
+	}
+
 	dma_unmap_single(sc->dev, bf->bf_dmacontext, skb->len, DMA_TO_DEVICE);
 	ath_tx_complete(sc, skb, bf->aphy, tx_flags);
 	ath_debug_stat_tx(sc, txq, bf, ts);
@@ -2058,8 +2046,7 @@ static void ath_wake_mac80211_queue(struct ath_softc *sc, struct ath_txq *txq)
 	int qnum;
 
 	spin_lock_bh(&txq->axq_lock);
-	if (txq->stopped &&
-	    sc->tx.txq[txq->axq_qnum].axq_depth <= (ATH_TXBUF - 20)) {
+	if (txq->stopped && txq->pending_frames < ATH_MAX_QDEPTH) {
 		qnum = ath_get_mac80211_qnum(txq->axq_qnum, sc);
 		if (qnum != -1) {
 			ath_mac80211_start_queue(sc, qnum);