Subject: Re: bug: net: dsa: mv88e6xxx: unable to tx or rx with Clearfog GT 8K (with git bisect)

From: Andrew Lunn <[email-masked]>
Date: Sat, 11 Jul 2020 18:23:49 +0200

On Sat, Jul 11, 2020 at 01:50:21PM +0000, Martin Rowe wrote:
> Hello,
> 
> I hope this is the right forum.
> 
> I have been troubleshooting an issue with my Clearfog GT 8Ks where I
> am unable to tx or rx on the switch interface, which uses the
> mv88e6xxx driver. Based on git bisect, I believe it is related to
> commit 34b5e6a33c1a8e466c3a73fd437f66fb16cb83ea from around the
> 5.7-rc2 era.

Hi Martin

Thanks for the bug report.

> Symptoms:
> The interface used to work, then it stopped and I didn't immediately
> notice because of life. Now the network never comes fully up. dmesg
> indicates no issues bringing the device up. Links are brought up and
> down with cable connects and disconnects. Negotiation seems to be
> working. But the interface rx counter never increases. While the tx
> counters do increase, tcpdumps on the other end of the cables never
> see any traffic. Basically, it doesn't look like any traffic is going
> out or in.

So i'm guessing it is the connection between the CPU and the switch.
Could you confirm this? Create a bridge, add two ports of the switch
to the bridge, and then see if packets can pass between switch ports.

If it is the connection between the CPU and the switch, i would then
be thinking about the comphy and the firmware. We have seen issues
where the firmware is too old. That is not something i've debugged
myself, so i don't know where the version information is, or what
version is required.

	Andrew