net/bnxt: enforce IO barrier for doorbell command

The doorbell ringing operation requires a rte_io_mb immediately to make
the command complete and visible to the device before reading the
response, otherwise it may read stale or invalid responses.

Fixes: ca241d9a09 ("net/bnxt: use I/O device memory read/write API")
Cc: stable@dpdk.org

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>

drivers/net/bnxt/bnxt_hwrm.c

@@ -146,6 +146,12 @@ static int bnxt_hwrm_send_message(struct bnxt *bp, void *msg,
 	/* Ring channel doorbell */
 	bar = (uint8_t *)bp->bar0 + mb_trigger_offset;
 	rte_write32(1, bar);
+	/*
+	 * Make sure the channel doorbell ring command complete before
+	 * reading the response to avoid getting stale or invalid
+	 * responses.
+	 */
+	rte_io_mb();
 
 	/* Poll for the valid bit */
 	for (i = 0; i < timeout; i++) {