[PATCH net] ionic: use netif_txq_maybe_stop() in ionic_tx()

[PATCH net] ionic: use netif_txq_maybe_stop() in ionic_tx()

[Nikhil P. Rao]

Commit 061b9bedbef1 ("ionic: Rework Tx start/stop flow") replaced
ionic_maybe_stop_tx() with netif_txq_maybe_stop() to get the memory
barriers around the stop/start bits right, but did not cover the stop
in ionic_tx() added by commit 138506ab249b ("ionic: Check stop no
restart"). Convert the remaining site.

netif_txq_maybe_stop() requires the ring indexes to be updated before
it is invoked, so the post has to come first. But ring_dbell comes
from __netdev_tx_sent_queue(), which runs after that and reads the
stop bit, so it is not known in time to pass to ionic_txq_post(). Post
without the doorbell and ring it separately.

The stop condition is unchanged. The re-check only clears the stop bit
when space has become available, so the doorbell starvation fixed by
commit 138506ab249b ("ionic: Check stop no restart") cannot recur.

Fixes: 138506ab249b ("ionic: Check stop no restart")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Nikhil P. Rao <nikhil.rao@amd.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
---
 drivers/net/ethernet/pensando/ionic/ionic_txrx.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
index e436e3231e86..2543a8ff8547 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
@@ -1672,15 +1672,22 @@ static int ionic_tx(struct net_device *netdev, struct ionic_queue *q,
 	stats->pkts++;
 	stats->bytes += skb->len;
 
+	ionic_txq_post(q, false);
+
 	if (likely(!ionic_txq_hwstamp_enabled(q))) {
 		struct netdev_queue *ndq = q_to_ndq(netdev, q);
 
-		if (unlikely(!ionic_q_has_space(q, MAX_SKB_FRAGS + 1)))
-			netif_tx_stop_queue(ndq);
+		netif_txq_maybe_stop(ndq, ionic_q_space_avail(q),
+				     MAX_SKB_FRAGS + 1, MAX_SKB_FRAGS + 1);
 		ring_dbell = __netdev_tx_sent_queue(ndq, skb->len,
 						    netdev_xmit_more());
 	}
-	ionic_txq_post(q, ring_dbell);
+
+	if (ring_dbell) {
+		ionic_dbell_ring(q->lif->kern_dbpage, q->hw_type,
+				 q->dbval | q->head_idx);
+		q->dbell_jiffies = jiffies;
+	}
 
 	return 0;
 }
-- 
2.43.0