netdev - [PATCH net] r8169: disable default rx interrupt coalescing on RTL8168

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Date:   Sat, 30 Mar 2019 17:13:24 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     David Miller <davem@...emloft.net>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Mike Crowe <mac@...owe.com>
Subject: [PATCH net] r8169: disable default rx interrupt coalescing on RTL8168

It was reported that re-introducing ASPM, in combination with RX
interrupt coalescing, results in significantly increased packet
latency, see [0]. Disabling ASPM or RX interrupt coalescing fixes
the issue. Therefore change the driver's default to disable RX
interrupt coalescing. Users still have the option to enable RX
coalescing via ethtool.

[0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=925496

Fixes: a99790bf5c7f ("r8169: Reinstate ASPM Support")
Reported-by: Mike Crowe <mac@...owe.com>
Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 drivers/net/ethernet/realtek/r8169.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index c9ee1c8eb..8a8a4f70d 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -5460,7 +5460,7 @@ static void rtl_hw_start_8168(struct rtl8169_private *tp)
 	tp->cp_cmd |= PktCntrDisable | INTT_1;
 	RTL_W16(tp, CPlusCmd, tp->cp_cmd);
 
-	RTL_W16(tp, IntrMitigate, 0x5151);
+	RTL_W16(tp, IntrMitigate, 0x5100);
 
 	/* Work around for RxFIFO overflow. */
 	if (tp->mac_version == RTL_GIGA_MAC_VER_11) {
-- 
2.21.0