linux-kernel - [PATCH 4.18 029/197] Revert "net: stmmac: Do not keep rearming the coalesce timer in stmmac

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Message-Id: <20180913131842.734828401@linuxfoundation.org>
Date:   Thu, 13 Sep 2018 15:29:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jose Abreu <joabreu@...opsys.com>,
        Joao Pinto <jpinto@...opsys.com>,
        Vitor Soares <soares@...opsys.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Corentin Labbe <clabbe@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.18 029/197] Revert "net: stmmac: Do not keep rearming the coalesce timer in stmmac_xmit"

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jerome Brunet <jbrunet@...libre.com>

[ Upstream commit e5133f2f1261f8ab412e7fc5e3694c9f84328f89 ]

This reverts commit 4ae0169fd1b3c792b66be58995b7e6b629919ecf.

This change in the handling of the coalesce timer is causing regression on
(at least) amlogic platforms.

Network will break down very quickly (a few seconds) after starting
a download. This can easily be reproduced using iperf3 for example.

The problem has been reported on the S805, S905, S912 and A113 SoCs
(Realtek and Micrel PHYs) and it is likely impacting all Amlogics
platforms using Gbit ethernet

No problem was seen with the platform using 10/100 only PHYs (GXL internal)

Reverting change brings things back to normal and allows to use network
again until we better understand the problem with the coalesce timer.

Cc: Jose Abreu <joabreu@...opsys.com>
Cc: Joao Pinto <jpinto@...opsys.com>
Cc: Vitor Soares <soares@...opsys.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@...com>
Cc: Alexandre Torgue <alexandre.torgue@...com>
Cc: Corentin Labbe <clabbe@...libre.com>
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |    1 -
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |    5 +----
 2 files changed, 1 insertion(+), 5 deletions(-)

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -112,7 +112,6 @@ struct stmmac_priv {
 	u32 tx_count_frames;
 	u32 tx_coal_frames;
 	u32 tx_coal_timer;
-	bool tx_timer_armed;
 
 	int tx_coalesce;
 	int hwts_tx_en;
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3126,16 +3126,13 @@ static netdev_tx_t stmmac_xmit(struct sk
 	 * element in case of no SG.
 	 */
 	priv->tx_count_frames += nfrags + 1;
-	if (likely(priv->tx_coal_frames > priv->tx_count_frames) &&
-	    !priv->tx_timer_armed) {
+	if (likely(priv->tx_coal_frames > priv->tx_count_frames)) {
 		mod_timer(&priv->txtimer,
 			  STMMAC_COAL_TIMER(priv->tx_coal_timer));
-		priv->tx_timer_armed = true;
 	} else {
 		priv->tx_count_frames = 0;
 		stmmac_set_tx_ic(priv, desc);
 		priv->xstats.tx_set_ic_bit++;
-		priv->tx_timer_armed = false;
 	}
 
 	skb_tx_timestamp(skb);