ar71xx: ethernet: skip calls to netdev_completed_queue and netif_wake_queue if no tx cleanup was done

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 37758

target/linux/ar71xx/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c

@@ -847,6 +847,9 @@ static int ag71xx_tx_packets(struct ag71xx *ag)
 
 	DBG("%s: %d packets sent out\n", ag->dev->name, sent);
 
+	if (!sent)
+		return;
+
 	netdev_completed_queue(ag->dev, sent, bytes_compl);
 	if ((ring->curr - ring->dirty) < (ring->size * 3) / 4)
 		netif_wake_queue(ag->dev);