[dpdk-stable] [PATCH 19.11] net/bnxt: fix doorbell write ordering

[dpdk-stable] [PATCH 19.11] net/bnxt: fix doorbell write ordering

[Lance Richardson]

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Write completion queue doorbell before receive descriptor
doorbell to avoid possibility of completion queue overflow
when completion queue size is equal to receive descriptor
ring size. Remove unnecessary compiler barriers (db write
functions have the necessary barriers.)

Fixes: 637e34befd9c ("net/bnxt: optimize Rx processing")
Cc: stable@dpdk.org

Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
---
 drivers/net/bnxt/bnxt_rxr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bnxt/bnxt_rxr.c b/drivers/net/bnxt/bnxt_rxr.c
index 5271d02366..0a8861c5a0 100644
--- a/drivers/net/bnxt/bnxt_rxr.c
+++ b/drivers/net/bnxt/bnxt_rxr.c
@@ -663,6 +663,10 @@ uint16_t bnxt_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 		goto done;
 	}
 
+	/* Ring the completion queue doorbell. */
+	bnxt_db_cq(cpr);
+
+	/* Ring the receive descriptor doorbell. */
 	if (prod != rxr->rx_prod)
 		bnxt_db_write(&rxr->rx_db, rxr->rx_prod);
 
@@ -670,8 +674,6 @@ uint16_t bnxt_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 	if (ag_prod != rxr->ag_prod)
 		bnxt_db_write(&rxr->ag_db, rxr->ag_prod);
 
-	bnxt_db_cq(cpr);
-
 	/* Attempt to alloc Rx buf in case of a previous allocation failure. */
 	if (rc == -ENOMEM) {
 		int i = RING_NEXT(rxr->rx_ring_struct, prod);
-- 
2.25.1