[dpdk-stable] patch 'net/thunderx: avoid sq door bell write on zero packet' has been queued to LTS release 17.11.4

[Yongseok Koh <yskoh@mellanox.com>]

Hi,

FYI, your patch has been queued to LTS release 17.11.4

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 07/28/18. So please
shout if anyone has objections.

Thanks.

Yongseok

---
>From 998da59e9e3cc06f565c648e9e870a93d0a7ad37 Mon Sep 17 00:00:00 2001
From: Kiran Kumar <kkokkilagadda@caviumnetworks.com>
Date: Wed, 11 Jul 2018 13:54:36 +0530
Subject: [PATCH] net/thunderx: avoid sq door bell write on zero packet

[ upstream commit 47636efe878dd8885bb47b142765c9ccae6babe3 ]

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")

Signed-off-by: Kiran Kumar <kkokkilagadda@caviumnetworks.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
---
 drivers/net/thunderx/nicvf_rxtx.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/net/thunderx/nicvf_rxtx.c b/drivers/net/thunderx/nicvf_rxtx.c
index 9d69cf4e2..06cbc4635 100644
--- a/drivers/net/thunderx/nicvf_rxtx.c
+++ b/drivers/net/thunderx/nicvf_rxtx.c
@@ -190,12 +190,14 @@ 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;
 }
 
@@ -246,12 +248,14 @@ 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;
 }
 
-- 
2.11.0