Subject: Re: Regression: mv88e6xxx packet loss after 4.18's PHYLINK merge

From: Andrew Lunn <[email-masked]>
Date: Mon, 14 Jan 2019 15:23:58 +0100

On Mon, Jan 14, 2019 at 01:34:44PM +0200, Samu Nuutamo wrote:
> Hi,
> 
> We have an imx6q-b450v3 board that has one of the switch ports configured as a
> fixed link. After upgrading the kernel to version 4.18 the link has experienced
> a small amount of packet loss, around 0.15%.
> 
> The issue was bisected to a commit: aab9c4067d23 net: dsa: Plug in PHYLINK support
> 
> After enabling debug we could see that the new phylink code causes the link to
> reset once every second:
> 
> [  309.992368] mv88e6085 gpio-0:00 enembc: phylink_mac_config: mode=fixed//100Mbps/Full adv=00000,00000208 pause=10 link=1 an=1
> [  309.998451] mv88e6085 gpio-0:00: p5: Force link down
> [  309.998869] mv88e6085 gpio-0:00: p5: Speed set to 100 Mbps
> [  309.999280] mv88e6085 gpio-0:00: p5: Force full duplex
> [  309.999895] mv88e6085 gpio-0:00: p5: Force link up
> [  311.032400] mv88e6085 gpio-0:00 enembc: phylink_mac_config: mode=fixed//100Mbps/Full adv=00000,00000208 pause=10 link=1 an=1
> [  311.038248] mv88e6085 gpio-0:00: p5: Force link down
> [  311.038660] mv88e6085 gpio-0:00: p5: Speed set to 100 Mbps
> [  311.039069] mv88e6085 gpio-0:00: p5: Force full duplex
> [  311.039678] mv88e6085 gpio-0:00: p5: Force link up
> [  312.072328] mv88e6085 gpio-0:00 enembc: phylink_mac_config: mode=fixed//100Mbps/Full adv=00000,00000208 pause=10 link=1 an=1
> [  312.077603] mv88e6085 gpio-0:00: p5: Force link down
> [  312.078010] mv88e6085 gpio-0:00: p5: Speed set to 100 Mbps
> [  312.078417] mv88e6085 gpio-0:00: p5: Force full duplex
> [  312.079026] mv88e6085 gpio-0:00: p5: Force link up

Hi Samu

Thanks for the report.

I think we should be fixing this from the other end. Why does PHYLINK
reset the link once per second? If you have time, please could you
investigate that.

	    Thanks
		Andrew