mt76: check return value of mt76_txq_send_burst in mt76_txq_schedule_list

Since mt76_txq_send_burst routine can report a negative error code,
check the returned value before incrementing the number of transmitted
frames in mt76_txq_schedule_list routine.
Return -EBUSY directly if the device is in reset or in power management.

Fixes: 90fdc171 ("mt76: use mac80211 txq scheduling")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/tx.c

@@ -461,11 +461,11 @@ mt76_txq_schedule_list(struct mt76_phy *phy, enum mt76_txq_id qid)
 	int ret = 0;
 
 	while (1) {
+		int n_frames = 0;
+
 		if (test_bit(MT76_STATE_PM, &phy->state) ||
-		    test_bit(MT76_RESET, &phy->state)) {
-			ret = -EBUSY;
-			break;
-		}
+		    test_bit(MT76_RESET, &phy->state))
+			return -EBUSY;
 
 		if (dev->queue_ops->tx_cleanup &&
 		    q->queued + 2 * MT_TXQ_FREE_THR >= q->ndesc) {
@@ -497,11 +497,16 @@ mt76_txq_schedule_list(struct mt76_phy *phy, enum mt76_txq_id qid)
 		}
 
 		if (!mt76_txq_stopped(q))
-			ret += mt76_txq_send_burst(phy, q, mtxq);
+			n_frames = mt76_txq_send_burst(phy, q, mtxq);
 
 		spin_unlock_bh(&q->lock);
 
 		ieee80211_return_txq(phy->hw, txq, false);
+
+		if (unlikely(n_frames < 0))
+			return n_frames;
+
+		ret += n_frames;
 	}
 
 	return ret;