From: Kiran Kumar <kkokkilagadda@caviumnetworks.com>
Date: Wed, 11 Jul 2018 08:24:36 +0000 (+0530)
Subject: net/thunderx: avoid sq door bell write on zero packet
X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=47636efe878dd8885bb47b142765c9ccae6babe3;p=dpdk.git

net/thunderx: avoid sq door bell write on zero packet

Avoid sq door bell write on zero packet case to reduce additional
traffic on register bus.

Fixes: 1c421f18e0 ("net/thunderx: add single and multi-segment Tx")
Cc: stable@dpdk.org

Signed-off-by: Kiran Kumar <kkokkilagadda@caviumnetworks.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
---

diff --git a/drivers/net/thunderx/nicvf_rxtx.c b/drivers/net/thunderx/nicvf_rxtx.c
index 72305d9d2a..6e075e23cb 100644
--- a/drivers/net/thunderx/nicvf_rxtx.c
+++ b/drivers/net/thunderx/nicvf_rxtx.c
@@ -162,12 +162,14 @@ nicvf_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 		free_desc -= TX_DESC_PER_PKT;
 	}
 
-	sq->tail = tail;
-	sq->xmit_bufs += i;
-	rte_wmb();
+	if (likely(i)) {
+		sq->tail = tail;
+		sq->xmit_bufs += i;
+		rte_wmb();
 
-	/* Inform HW to xmit the packets */
-	nicvf_addr_write(sq->sq_door, i * TX_DESC_PER_PKT);
+		/* Inform HW to xmit the packets */
+		nicvf_addr_write(sq->sq_door, i * TX_DESC_PER_PKT);
+	}
 	return i;
 }
 
@@ -218,12 +220,14 @@ nicvf_xmit_pkts_multiseg(void *tx_queue, struct rte_mbuf **tx_pkts,
 		}
 	}
 
-	sq->tail = tail;
-	sq->xmit_bufs += used_bufs;
-	rte_wmb();
+	if (likely(used_desc)) {
+		sq->tail = tail;
+		sq->xmit_bufs += used_bufs;
+		rte_wmb();
 
-	/* Inform HW to xmit the packets */
-	nicvf_addr_write(sq->sq_door, used_desc);
+		/* Inform HW to xmit the packets */
+		nicvf_addr_write(sq->sq_door, used_desc);
+	}
 	return i;
 }