mac80211: make ieee80211_schedule_txq schedule empty TXQs

Currently there is no way for the driver to signal to mac80211 that it should
schedule a TXQ even if there are no packets on the mac80211 part of that queue.
This is problematic if the driver has an internal retry queue to deal with
software A-MPDU retry.

This patch changes the behavior of ieee80211_schedule_txq to always schedule
the queue, as its only user (ath9k) seems to expect such behavior already:
it calls this function on tx status and on powersave wakeup whenever its
internal retry queue is not empty.

Also add an extra argument to ieee80211_return_txq to get the same behavior.

This fixes an issue on ath9k where tx queues with packets to retry (and no
new packets in mac80211) would not get serviced.

Fixes: 89cea749 ("ath9k: Switch to mac80211 TXQ scheduling and airtime APIs")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/ath/ath10k/htt_rx.c

@@ -2728,7 +2728,7 @@ static void ath10k_htt_rx_tx_fetch_ind(struct ath10k *ar, struct sk_buff *skb)
 			num_msdus++;
 			num_bytes += ret;
 		}
-		ieee80211_return_txq(hw, txq);
+		ieee80211_return_txq(hw, txq, false);
 		ieee80211_txq_schedule_end(hw, txq->ac);
 
 		record->num_msdus = cpu_to_le16(num_msdus);

drivers/net/wireless/ath/ath10k/mac.c

@@ -4089,7 +4089,7 @@ static int ath10k_mac_schedule_txq(struct ieee80211_hw *hw, u32 ac)
 			if (ret < 0)
 				break;
 		}
-		ieee80211_return_txq(hw, txq);
+		ieee80211_return_txq(hw, txq, false);
 		ath10k_htt_tx_txq_update(hw, txq);
 		if (ret == -EBUSY)
 			break;
@@ -4374,7 +4374,7 @@ static void ath10k_mac_op_wake_tx_queue(struct ieee80211_hw *hw,
 		if (ret < 0)
 			break;
 	}
-	ieee80211_return_txq(hw, txq);
+	ieee80211_return_txq(hw, txq, false);
 	ath10k_htt_tx_txq_update(hw, txq);
 out:
 	ieee80211_txq_schedule_end(hw, ac);

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

@@ -1938,12 +1938,15 @@ void ath_txq_schedule(struct ath_softc *sc, struct ath_txq *txq)
 		goto out;
 
 	while ((queue = ieee80211_next_txq(hw, txq->mac80211_qnum))) {
+		bool force;
+
 		tid = (struct ath_atx_tid *)queue->drv_priv;
 
 		ret = ath_tx_sched_aggr(sc, txq, tid);
 		ath_dbg(common, QUEUE, "ath_tx_sched_aggr returned %d\n", ret);
 
-		ieee80211_return_txq(hw, queue);
+		force = !skb_queue_empty(&tid->retry_q);
+		ieee80211_return_txq(hw, queue, force);
 	}
 
 out:

include/net/mac80211.h

@@ -6253,26 +6253,42 @@ static inline void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
 {
 }
 
+void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
+			      struct ieee80211_txq *txq, bool force);
+
 /**
  * ieee80211_schedule_txq - schedule a TXQ for transmission
  *
  * @hw: pointer as obtained from ieee80211_alloc_hw()
  * @txq: pointer obtained from station or virtual interface
  *
- * Schedules a TXQ for transmission if it is not already scheduled.
+ * Schedules a TXQ for transmission if it is not already scheduled,
+ * even if mac80211 does not have any packets buffered.
+ *
+ * The driver may call this function if it has buffered packets for
+ * this TXQ internally.
  */
-void ieee80211_schedule_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
+static inline void
+ieee80211_schedule_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
+{
+	__ieee80211_schedule_txq(hw, txq, true);
+}
 
 /**
  * ieee80211_return_txq - return a TXQ previously acquired by ieee80211_next_txq()
  *
  * @hw: pointer as obtained from ieee80211_alloc_hw()
  * @txq: pointer obtained from station or virtual interface
+ * @force: schedule txq even if mac80211 does not have any buffered packets.
+ *
+ * The driver may set force=true if it has buffered packets for this TXQ
+ * internally.
  */
 static inline void
-ieee80211_return_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
+ieee80211_return_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq,
+		     bool force)
 {
-	ieee80211_schedule_txq(hw, txq);
+	__ieee80211_schedule_txq(hw, txq, force);
 }
 
 /**

net/mac80211/tx.c

@@ -3688,8 +3688,9 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 }
 EXPORT_SYMBOL(ieee80211_next_txq);
 
-void ieee80211_schedule_txq(struct ieee80211_hw *hw,
-			    struct ieee80211_txq *txq)
+void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
+			      struct ieee80211_txq *txq,
+			      bool force)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct txq_info *txqi = to_txq_info(txq);
@@ -3697,7 +3698,8 @@ void ieee80211_schedule_txq(struct ieee80211_hw *hw,
 	spin_lock_bh(&local->active_txq_lock[txq->ac]);
 
 	if (list_empty(&txqi->schedule_order) &&
-	    (!skb_queue_empty(&txqi->frags) || txqi->tin.backlog_packets)) {
+	    (force || !skb_queue_empty(&txqi->frags) ||
+	     txqi->tin.backlog_packets)) {
 		/* If airtime accounting is active, always enqueue STAs at the
 		 * head of the list to ensure that they only get moved to the
 		 * back by the airtime DRR scheduler once they have a negative
@@ -3717,7 +3719,7 @@ void ieee80211_schedule_txq(struct ieee80211_hw *hw,
 
 	spin_unlock_bh(&local->active_txq_lock[txq->ac]);
 }
-EXPORT_SYMBOL(ieee80211_schedule_txq);
+EXPORT_SYMBOL(__ieee80211_schedule_txq);
 
 bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
 				struct ieee80211_txq *txq)