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@mcrowe.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 7562ccb..19efa88 100644 (file)
--- 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) {