[PATCH mt76] wifi: mt76: don't return TXQ when exceeding max non-AQL packets

[David Bauer <mail@david-bauer.net>]

mt76_txq_send_burst does check if the number of non-AQL frames exceeds
the maximum. In this case the queue is returned to ieee80211_return_txq
when iterating over the scheduled TXQs in mt76_txq_schedule_list.

This has the effect of inserting said TXQ at the head of the list. This
means the loop will get the same TXQ again, which will terminate the
scheduling round. TXQs following in the list thus never get scheduled
for transmission.

This can manifest in high latency low throughput or broken connections
for said STAs.

Check if the non-AQL packet count exceeds the limit and not return the
TXQ in this case.
Schedule all TXQs for the STA in case the non-AQL limit can be satisfied
again.

Signed-off-by: David Bauer <mail@david-bauer.net>
---
 drivers/net/wireless/mediatek/mt76/tx.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/tx.c b/drivers/net/wireless/mediatek/mt76/tx.c
index 9ec6d0b53a84a..0753acf2eccb8 100644
--- a/drivers/net/wireless/mediatek/mt76/tx.c
+++ b/drivers/net/wireless/mediatek/mt76/tx.c
@@ -227,7 +227,9 @@ mt76_tx_check_non_aql(struct mt76_dev *dev, struct mt76_wcid *wcid,
 		      struct sk_buff *skb)
 {
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_sta *sta;
 	int pending;
+	int i;
 
 	if (!wcid || info->tx_time_est)
 		return;
@@ -235,6 +237,17 @@ mt76_tx_check_non_aql(struct mt76_dev *dev, struct mt76_wcid *wcid,
 	pending = atomic_dec_return(&wcid->non_aql_packets);
 	if (pending < 0)
 		atomic_cmpxchg(&wcid->non_aql_packets, pending, 0);
+
+	sta = wcid_to_sta(wcid);
+	if (!sta || pending != MT_MAX_NON_AQL_PKT - 1)
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(sta->txq); i++) {
+		if (!sta->txq[i])
+			continue;
+
+		ieee80211_schedule_txq(dev->hw, sta->txq[i]);
+	}
 }
 
 void __mt76_tx_complete_skb(struct mt76_dev *dev, u16 wcid_idx, struct sk_buff *skb,
@@ -542,6 +555,9 @@ mt76_txq_schedule_list(struct mt76_phy *phy, enum mt76_txq_id qid)
 		if (!wcid || test_bit(MT_WCID_FLAG_PS, &wcid->flags))
 			continue;
 
+		if (atomic_read(&wcid->non_aql_packets) >= MT_MAX_NON_AQL_PKT)
+			continue;
+
 		phy = mt76_dev_phy(dev, wcid->phy_idx);
 		if (test_bit(MT76_RESET, &phy->state) || phy->offchannel)
 			continue;
-- 
2.51.0