netdev - Re: bug: net: dsa: mv88e6xxx: serdes Unable to communicate on fiber with vf610-zii-dev-rev-c

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Date:   Mon, 18 Jan 2021 18:47:10 +0100
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Chris Healy <cphealy@...il.com>, Marek Behun <marek.behun@....cz>,
        netdev <netdev@...r.kernel.org>
Subject: Re: bug: net: dsa: mv88e6xxx: serdes Unable to communicate on fiber with vf610-zii-dev-rev-c

On Mon, Jan 18, 2021 at 18:41, Andrew Lunn <andrew@...n.ch> wrote:
> On Mon, Jan 18, 2021 at 06:31:19PM +0100, Tobias Waldekranz wrote:
>> On Sun, Jul 19, 2020 at 14:43, Chris Healy <cphealy@...il.com> wrote:
>> > On Sat, Jul 18, 2020 at 8:22 AM Marek Behun <marek.behun@....cz> wrote:
>> >>
>> >> On Sat, 18 Jul 2020 17:05:14 +0200
>> >> Andrew Lunn <andrew@...n.ch> wrote:
>> >>
>> >> > > If the traces were broken between the fiber module and the SERDES, I
>> >> > > should not see these counters incrementing.
>> >> >
>> >> > Plus it is reproducible on multiple boards, of different designs.
>> >> >
>> >> > This is somehow specific to the 6390X ports 9 and 10.
>> >> >
>> >> >      Andrew
>> >>
>> >> Hmm.
>> >>
>> >> What about the errata setup?
>> >> It says:
>> >> /* The 6390 copper ports have an errata which require poking magic
>> >>  * values into undocumented hidden registers and then performing a
>> >>  * software reset.
>> >>  */
>> >> But then the port_hidden_write function is called for every port in the
>> >> function mv88e6390_setup_errata, not just for copper ports. Maybe Chris
>> >> should try to not write this hidden register for SerDes ports.
>> >
>> > I just disabled the mv88e6390_setup_errata all together and this did
>> > not result in any different behaviour on this broken fiber port.
>> 
>> Hi Chris,
>> 
>> Did you manage to track this down?
>> 
>> I am seeing the exact same issue. I have tried both a 1000base-x SFP and
>> a copper 1000base-T and get the same result on both - transmit is fine
>> but rx only works up to the SERDES, no rx MAC counters are moving.
>
> Hi Tobias
>
> We never tracked this down. I spent many hours bashing my head against
> this. I could not bisect it, which did not help.

Well that is disheartening :) "I could not bisect it", does that mean
that it did work at some point but your CPU platform was not supported
far enough back, or has it never worked?

> FYI: Chris has moved onto a new job, and is unlikely to be involved
> with Marvell switches any more.

Good to know, thanks.