ath9k: use software queues for un-aggregated data packets

This is a first step for improving fairness between legacy and 802.11n
traffic, and it should also improve reliability of resets and channel
changes by keeping the hardware queue depth very short.

When an aggregation session is torn down, all packets in the retry queue
will be removed from the BAW and freed.

For all subframes that have not been transmitted yet, the A-MPDU flag
will be cleared, and a sequence number allocated. This ensures that the
next A-MPDU session will get the correct initial sequence number.
This happens both on aggregation session start and stop.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ath9k.h

@@ -137,6 +137,8 @@ int ath_descdma_setup(struct ath_softc *sc, struct ath_descdma *dd,
 #define ATH_AGGR_ENCRYPTDELIM      10
 /* minimum h/w qdepth to be sustained to maximize aggregation */
 #define ATH_AGGR_MIN_QDEPTH        2
+/* minimum h/w qdepth for non-aggregated traffic */
+#define ATH_NON_AGGR_MIN_QDEPTH    8
 
 #define IEEE80211_SEQ_SEQ_SHIFT    4
 #define IEEE80211_SEQ_MAX          4096
@@ -173,12 +175,6 @@ int ath_descdma_setup(struct ath_softc *sc, struct ath_descdma *dd,
 
 #define ATH_TX_COMPLETE_POLL_INT	1000
 
-enum ATH_AGGR_STATUS {
-	ATH_AGGR_DONE,
-	ATH_AGGR_BAW_CLOSED,
-	ATH_AGGR_LIMITED,
-};
-
 #define ATH_TXFIFO_DEPTH 8
 struct ath_txq {
 	int mac80211_qnum; /* mac80211 queue number, -1 means not mac80211 Q */

drivers/net/wireless/ath/ath9k/xmit.c

@@ -198,6 +198,41 @@ static struct sk_buff *ath_tid_dequeue(struct ath_atx_tid *tid)
 	return skb;
 }
 
+/*
+ * ath_tx_tid_change_state:
+ * - clears a-mpdu flag of previous session
+ * - force sequence number allocation to fix next BlockAck Window
+ */
+static void
+ath_tx_tid_change_state(struct ath_softc *sc, struct ath_atx_tid *tid)
+{
+	struct ath_txq *txq = tid->ac->txq;
+	struct ieee80211_tx_info *tx_info;
+	struct sk_buff *skb, *tskb;
+	struct ath_buf *bf;
+	struct ath_frame_info *fi;
+
+	skb_queue_walk_safe(&tid->buf_q, skb, tskb) {
+		fi = get_frame_info(skb);
+		bf = fi->bf;
+
+		tx_info = IEEE80211_SKB_CB(skb);
+		tx_info->flags &= ~IEEE80211_TX_CTL_AMPDU;
+
+		if (bf)
+			continue;
+
+		bf = ath_tx_setup_buffer(sc, txq, tid, skb);
+		if (!bf) {
+			__skb_unlink(skb, &tid->buf_q);
+			ath_txq_skb_done(sc, txq, skb);
+			ieee80211_free_txskb(sc->hw, skb);
+			continue;
+		}
+	}
+
+}
+
 static void ath_tx_flush_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
 {
 	struct ath_txq *txq = tid->ac->txq;
@@ -212,28 +247,22 @@ static void ath_tx_flush_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
 
 	memset(&ts, 0, sizeof(ts));
 
-	while ((skb = ath_tid_dequeue(tid))) {
+	while ((skb = __skb_dequeue(&tid->retry_q))) {
 		fi = get_frame_info(skb);
 		bf = fi->bf;
-
 		if (!bf) {
-			bf = ath_tx_setup_buffer(sc, txq, tid, skb);
-			if (!bf) {
-				ath_txq_skb_done(sc, txq, skb);
-				ieee80211_free_txskb(sc->hw, skb);
-				continue;
-			}
+			ath_txq_skb_done(sc, txq, skb);
+			ieee80211_free_txskb(sc->hw, skb);
+			continue;
 		}
 
 		if (fi->baw_tracked) {
-			list_add_tail(&bf->list, &bf_head);
 			ath_tx_update_baw(sc, tid, bf->bf_state.seqno);
-			ath_tx_complete_buf(sc, bf, txq, &bf_head, &ts, 0);
 			sendbar = true;
-		} else {
-			ath_set_rates(tid->an->vif, tid->an->sta, bf);
-			ath_tx_send_normal(sc, txq, NULL, skb);
 		}
+
+		list_add_tail(&bf->list, &bf_head);
+		ath_tx_complete_buf(sc, bf, txq, &bf_head, &ts, 0);
 	}
 
 	if (sendbar) {
@@ -911,50 +940,39 @@ ath_tx_get_tid_subframe(struct ath_softc *sc, struct ath_txq *txq,
 	return NULL;
 }
 
-static enum ATH_AGGR_STATUS ath_tx_form_aggr(struct ath_softc *sc,
-					     struct ath_txq *txq,
-					     struct ath_atx_tid *tid,
-					     struct list_head *bf_q,
-					     int *aggr_len)
+static bool
+ath_tx_form_aggr(struct ath_softc *sc, struct ath_txq *txq,
+		 struct ath_atx_tid *tid, struct list_head *bf_q,
+		 struct ath_buf *bf_first, struct sk_buff_head *tid_q,
+		 int *aggr_len)
 {
 #define PADBYTES(_len) ((4 - ((_len) % 4)) % 4)
-	struct ath_buf *bf, *bf_first = NULL, *bf_prev = NULL;
+	struct ath_buf *bf = bf_first, *bf_prev = NULL;
 	int nframes = 0, ndelim;
 	u16 aggr_limit = 0, al = 0, bpad = 0,
 	    al_delta, h_baw = tid->baw_size / 2;
-	enum ATH_AGGR_STATUS status = ATH_AGGR_DONE;
 	struct ieee80211_tx_info *tx_info;
 	struct ath_frame_info *fi;
 	struct sk_buff *skb;
-	struct sk_buff_head *tid_q;
+	bool closed = false;
 
-	do {
-		bf = ath_tx_get_tid_subframe(sc, txq, tid, &tid_q);
-		if (!bf) {
-			status = ATH_AGGR_BAW_CLOSED;
-			break;
-		}
+	bf = bf_first;
+	aggr_limit = ath_lookup_rate(sc, bf, tid);
 
+	do {
 		skb = bf->bf_mpdu;
 		fi = get_frame_info(skb);
 
-		if (!bf_first) {
-			bf_first = bf;
-			ath_set_rates(tid->an->vif, tid->an->sta, bf);
-			aggr_limit = ath_lookup_rate(sc, bf, tid);
-		}
-
 		/* do not exceed aggregation limit */
 		al_delta = ATH_AGGR_DELIM_SZ + fi->framelen;
 		if (nframes) {
 			if (aggr_limit < al + bpad + al_delta ||
-			    ath_lookup_legacy(bf) || nframes >= h_baw) {
-				status = ATH_AGGR_LIMITED;
+			    ath_lookup_legacy(bf) || nframes >= h_baw)
 				break;
-			}
 
 			tx_info = IEEE80211_SKB_CB(bf->bf_mpdu);
-			if (tx_info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
+			if ((tx_info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) ||
+			    !(tx_info->flags & IEEE80211_TX_CTL_AMPDU))
 				break;
 		}
 
@@ -984,11 +1002,26 @@ static enum ATH_AGGR_STATUS ath_tx_form_aggr(struct ath_softc *sc,
 
 		bf_prev = bf;
 
+		bf = ath_tx_get_tid_subframe(sc, txq, tid, &tid_q);
+		if (!bf) {
+			closed = true;
+			break;
+		}
 	} while (ath_tid_has_buffered(tid));
 
+	bf = bf_first;
+	bf->bf_lastbf = bf_prev;
+
+	if (bf == bf_prev) {
+		al = get_frame_info(bf->bf_mpdu)->framelen;
+		bf->bf_state.bf_type = BUF_AMPDU;
+	} else {
+		TX_STAT_INC(txq->axq_qnum, a_aggr);
+	}
+
 	*aggr_len = al;
 
-	return status;
+	return closed;
 #undef PADBYTES
 }
 
@@ -1277,14 +1310,50 @@ static void ath_tx_fill_desc(struct ath_softc *sc, struct ath_buf *bf,
 	}
 }
 
+static void
+ath_tx_form_burst(struct ath_softc *sc, struct ath_txq *txq,
+		  struct ath_atx_tid *tid, struct list_head *bf_q,
+		  struct ath_buf *bf_first, struct sk_buff_head *tid_q)
+{
+	struct ath_buf *bf = bf_first, *bf_prev = NULL;
+	struct sk_buff *skb;
+	int nframes = 0;
+
+	do {
+		struct ieee80211_tx_info *tx_info;
+		skb = bf->bf_mpdu;
+
+		nframes++;
+		__skb_unlink(skb, tid_q);
+		list_add_tail(&bf->list, bf_q);
+		if (bf_prev)
+			bf_prev->bf_next = bf;
+		bf_prev = bf;
+
+		if (nframes >= 2)
+			break;
+
+		bf = ath_tx_get_tid_subframe(sc, txq, tid, &tid_q);
+		if (!bf)
+			break;
+
+		tx_info = IEEE80211_SKB_CB(bf->bf_mpdu);
+		if (tx_info->flags & IEEE80211_TX_CTL_AMPDU)
+			break;
+
+		ath_set_rates(tid->an->vif, tid->an->sta, bf);
+	} while (1);
+}
+
 static void ath_tx_sched_aggr(struct ath_softc *sc, struct ath_txq *txq,
 			      struct ath_atx_tid *tid)
 {
 	struct ath_buf *bf;
-	enum ATH_AGGR_STATUS status;
 	struct ieee80211_tx_info *tx_info;
+	struct sk_buff_head *tid_q;
 	struct list_head bf_q;
-	int aggr_len;
+	int aggr_len = 0;
+	bool aggr, last = true;
 
 	do {
 		if (!ath_tid_has_buffered(tid))
@@ -1292,38 +1361,34 @@ static void ath_tx_sched_aggr(struct ath_softc *sc, struct ath_txq *txq,
 
 		INIT_LIST_HEAD(&bf_q);
 
-		status = ath_tx_form_aggr(sc, txq, tid, &bf_q, &aggr_len);
-
-		/*
-		 * no frames picked up to be aggregated;
-		 * block-ack window is not open.
-		 */
-		if (list_empty(&bf_q))
+		bf = ath_tx_get_tid_subframe(sc, txq, tid, &tid_q);
+		if (!bf)
 			break;
 
-		bf = list_first_entry(&bf_q, struct ath_buf, list);
-		bf->bf_lastbf = list_entry(bf_q.prev, struct ath_buf, list);
 		tx_info = IEEE80211_SKB_CB(bf->bf_mpdu);
+		aggr = !!(tx_info->flags & IEEE80211_TX_CTL_AMPDU);
+		if ((aggr && txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH) ||
+		    (!aggr && txq->axq_depth >= ATH_NON_AGGR_MIN_QDEPTH))
+			break;
+
+		ath_set_rates(tid->an->vif, tid->an->sta, bf);
+		if (aggr)
+			last = ath_tx_form_aggr(sc, txq, tid, &bf_q, bf,
+						tid_q, &aggr_len);
+		else
+			ath_tx_form_burst(sc, txq, tid, &bf_q, bf, tid_q);
+
+		if (list_empty(&bf_q))
+			return;
 
 		if (tid->ac->clear_ps_filter) {
 			tid->ac->clear_ps_filter = false;
 			tx_info->flags |= IEEE80211_TX_CTL_CLEAR_PS_FILT;
-		} else {
-			tx_info->flags &= ~IEEE80211_TX_CTL_CLEAR_PS_FILT;
-		}
-
-		/* if only one frame, send as non-aggregate */
-		if (bf == bf->bf_lastbf) {
-			aggr_len = get_frame_info(bf->bf_mpdu)->framelen;
-			bf->bf_state.bf_type = BUF_AMPDU;
-		} else {
-			TX_STAT_INC(txq->axq_qnum, a_aggr);
 		}
 
 		ath_tx_fill_desc(sc, bf, txq, aggr_len);
 		ath_tx_txqaddbuf(sc, txq, &bf_q, false);
-	} while (txq->axq_ampdu_depth < ATH_AGGR_MIN_QDEPTH &&
-		 status != ATH_AGGR_BAW_CLOSED);
+	} while (!last);
 }
 
 int ath_tx_aggr_start(struct ath_softc *sc, struct ieee80211_sta *sta,
@@ -1347,6 +1412,9 @@ int ath_tx_aggr_start(struct ath_softc *sc, struct ieee80211_sta *sta,
 		an->mpdudensity = density;
 	}
 
+	/* force sequence number allocation for pending frames */
+	ath_tx_tid_change_state(sc, txtid);
+
 	txtid->active = true;
 	txtid->paused = true;
 	*ssn = txtid->seq_start = txtid->seq_next;
@@ -1368,6 +1436,7 @@ void ath_tx_aggr_stop(struct ath_softc *sc, struct ieee80211_sta *sta, u16 tid)
 	txtid->active = false;
 	txtid->paused = false;
 	ath_tx_flush_tid(sc, txtid);
+	ath_tx_tid_change_state(sc, txtid);
 	ath_txq_unlock_complete(sc, txq);
 }
 
@@ -1882,58 +1951,6 @@ static void ath_tx_txqaddbuf(struct ath_softc *sc, struct ath_txq *txq,
 	}
 }
 
-static void ath_tx_send_ampdu(struct ath_softc *sc, struct ath_txq *txq,
-			      struct ath_atx_tid *tid, struct sk_buff *skb,
-			      struct ath_tx_control *txctl)
-{
-	struct ath_frame_info *fi = get_frame_info(skb);
-	struct list_head bf_head;
-	struct ath_buf *bf;
-
-	/*
-	 * Do not queue to h/w when any of the following conditions is true:
-	 * - there are pending frames in software queue
-	 * - the TID is currently paused for ADDBA/BAR request
-	 * - seqno is not within block-ack window
-	 * - h/w queue depth exceeds low water mark
-	 */
-	if ((ath_tid_has_buffered(tid) || tid->paused ||
-	     !BAW_WITHIN(tid->seq_start, tid->baw_size, tid->seq_next) ||
-	     txq->axq_ampdu_depth >= ATH_AGGR_MIN_QDEPTH) &&
-	    txq != sc->tx.uapsdq) {
-		/*
-		 * Add this frame to software queue for scheduling later
-		 * for aggregation.
-		 */
-		TX_STAT_INC(txq->axq_qnum, a_queued_sw);
-		__skb_queue_tail(&tid->buf_q, skb);
-		if (!txctl->an || !txctl->an->sleeping)
-			ath_tx_queue_tid(txq, tid);
-		return;
-	}
-
-	bf = ath_tx_setup_buffer(sc, txq, tid, skb);
-	if (!bf) {
-		ath_txq_skb_done(sc, txq, skb);
-		ieee80211_free_txskb(sc->hw, skb);
-		return;
-	}
-
-	ath_set_rates(tid->an->vif, tid->an->sta, bf);
-	bf->bf_state.bf_type = BUF_AMPDU;
-	INIT_LIST_HEAD(&bf_head);
-	list_add(&bf->list, &bf_head);
-
-	/* Add sub-frame to BAW */
-	ath_tx_addto_baw(sc, tid, bf);
-
-	/* Queue to h/w without aggregation */
-	TX_STAT_INC(txq->axq_qnum, a_queued_hw);
-	bf->bf_lastbf = bf;
-	ath_tx_fill_desc(sc, bf, txq, fi->framelen);
-	ath_tx_txqaddbuf(sc, txq, &bf_head, false);
-}
-
 static void ath_tx_send_normal(struct ath_softc *sc, struct ath_txq *txq,
 			       struct ath_atx_tid *tid, struct sk_buff *skb)
 {
@@ -2159,20 +2176,25 @@ int ath_tx_start(struct ieee80211_hw *hw, struct sk_buff *skb,
 		ath_txq_unlock(sc, txq);
 		txq = sc->tx.uapsdq;
 		ath_txq_lock(sc, txq);
-	}
-
-	if (txctl->an && ieee80211_is_data_qos(hdr->frame_control)) {
+	} else if (txctl->an &&
+		   ieee80211_is_data_present(hdr->frame_control)) {
 		tid = ath_get_skb_tid(sc, txctl->an, skb);
 
 		WARN_ON(tid->ac->txq != txctl->txq);
-	}
 
-	if ((info->flags & IEEE80211_TX_CTL_AMPDU) && tid) {
+		if (info->flags & IEEE80211_TX_CTL_CLEAR_PS_FILT)
+			tid->ac->clear_ps_filter = true;
+
 		/*
-		 * Try aggregation if it's a unicast data frame
-		 * and the destination is HT capable.
+		 * Add this frame to software queue for scheduling later
+		 * for aggregation.
 		 */
-		ath_tx_send_ampdu(sc, txq, tid, skb, txctl);
+		TX_STAT_INC(txq->axq_qnum, a_queued_sw);
+		__skb_queue_tail(&tid->buf_q, skb);
+		if (!txctl->an->sleeping)
+			ath_tx_queue_tid(txq, tid);
+
+		ath_txq_schedule(sc, txq);
 		goto out;
 	}