r8169: disable default rx interrupt coalescing on RTL8168

BugLink: https://bugs.launchpad.net/bugs/1838116
[ Upstream commit 288ac524cf70a8e7ed851a61ed2a9744039dae8d ]

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@mcrowe.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index c454cc414d42ddf3d9c4935748a52976e9a5cc10..f0f768a0fd8dbb3adabc8a6ecb795fff3cd83ff5 100644 (file)
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -6554,7 +6554,7 @@ static void rtl_hw_start_8168(struct net_device *dev)
 
        RTL_W16(CPlusCmd, tp->cp_cmd);
 
-       RTL_W16(IntrMitigate, 0x5151);
+       RTL_W16(IntrMitigate, 0x5100);
 
        /* Work around for RxFIFO overflow. */
        if (tp->mac_version == RTL_GIGA_MAC_VER_11) {