ionic: Check stop no restart

If there is a lot of transmit traffic the driver can get into a
situation that the device is starved due to the doorbell never
being rung. This can happen if xmit_more is set constantly
and __netdev_tx_sent_queue() keeps returning false. Fix this
by checking if the queue needs to be stopped right before
calling __netdev_tx_sent_queue(). Use MAX_SKB_FRAGS + 1 as the
stop condition because that's the maximum number of frags
supported for non-TSO transmit.
Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/pensando/ionic/ionic_txrx.c

@@ -1665,9 +1665,14 @@ static int ionic_tx(struct ionic_queue *q, struct sk_buff *skb)
 	stats->pkts++;
 	stats->bytes += skb->len;
 
-	if (!ionic_txq_hwstamp_enabled(q))
-		ring_dbell = __netdev_tx_sent_queue(q_to_ndq(q), skb->len,
+	if (!ionic_txq_hwstamp_enabled(q)) {
+		struct netdev_queue *ndq = q_to_ndq(q);
+
+		if (unlikely(!ionic_q_has_space(q, MAX_SKB_FRAGS + 1)))
+			netif_tx_stop_queue(ndq);
+		ring_dbell = __netdev_tx_sent_queue(ndq, skb->len,
 						    netdev_xmit_more());
+	}
 	ionic_txq_post(q, ring_dbell, ionic_tx_clean, skb);
 
 	return 0;