Re: PROBLEM: Broken or delayed ethernet on Xilinx ZCU104 since 5.18 (regression)

[Robert Hancock <robert.hancock@calian.com>]

On Fri, 2023-08-04 at 17:45 +0200, Linux regression tracking (Thorsten
Leemhuis) wrote:
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> [TLDR: I'm adding this report to the list of tracked Linux kernel
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> On 04.08.23 17:26, Nick Bowler wrote:
> > Hi,
> > 
> > With recent kernels (5.18 and newer) the ethernet is all wonky on
> > my
> > ZCU104 board.
> > 
> > There is some behaviour inconsistency between kernel versions
> > identified
> > during bisection, so maybe there is more than one issue with the
> > ethernet?
> > 
> >   6.5-rc4: after 10 seconds, the following message is printed:
> > 
> >     [   10.761808] platform ff0e0000.ethernet: deferred probe
> > pending
> > 
> >   but the network device seemingly never appears (I waited about a
> > minute).
> > 
> >   6.1 and 6.4: after 10 seconds, the device suddenly appears and
> > starts
> >   working (but this is way too late).
> > 
> >   5.18: the device never appears and no unusual messages are
> > printed
> >   (I waited ten minutes).
> > 
> > With 5.17 and earlier versions, the eth0 device appears without any
> > delay.
> > 
> > Unfortunately, as bisection closed on the problematic section, all
> > the
> > built kernels became untestable as they appear to crash during
> > early
> > boot.  Nevertheless, I manually selected a commit that sounded
> > relevant:
> > 
> >   commit e461bd6f43f4e568f7436a8b6bc21c4ce6914c36
> >   Author: Robert Hancock <robert.hancock@calian.com>
> >   Date:   Thu Jan 27 10:37:36 2022 -0600
> > 
> >       arm64: dts: zynqmp: Added GEM reset definitions
> > 
> > Reverting this fixes the problem on 5.18.  Reverting this fixes the
> > problem on 6.1.  Reverting this fixes the problem on 6.4.  In all
> > of
> > these versions, with this change reverted, the network device
> > appears
> > without delay.

Hi Nick,

If this change triggered the problem, then I would suspect there's an
issue with either the zynqmp_reset driver itself, or something it's
dependent on, somehow not being enabled in your kernel configuration.
If the device tree has a reference to that reset device node as
providing a reset but the driver for that device hasn't loaded yet,
then the probe will keep being deferred in the hope that eventually
that driver will be ready, but if it's somehow disabled or has
unsatisfied dependencies, it never will be.

I'm not sure why you're seeing it start working after 10 seconds in
some versions and not at all in others, however.

Can you provide the kernel .config you are using?

> > 
> > Unfortunately, it seems this is not sufficient to correct the
> > problem on
> > 6.5-rc4 -- there is no apparent change in behaviour, so maybe there
> > is
> > a new, different problem?
> > 
> > I guess I can kick off another bisection to find out when this
> > revert
> > stops fixing things...
> > 
> > Let me know if you need any more info!
> 
> Thanks for the report. To be sure the issue doesn't fall through the
> cracks unnoticed, I'm adding it to regzbot, the Linux kernel
> regression
> tracking bot:
> 
> #regzbot ^introduced e461bd6f43f4e5
> #regzbot title net/arm64: dts: Broken or delayed ethernet on Xilinx
> ZCU104
> #regzbot ignore-activity
> 
> This isn't a regression? This issue or a fix for it are already
> discussed somewhere else? It was fixed already? You want to clarify
> when
> the regression started to happen? Or point out I got the title or
> something else totally wrong? Then just reply and tell me -- ideally
> while also telling regzbot about it, as explained by the page listed
> in
> the footer of this mail.
> 
> Developers: When fixing the issue, remember to add 'Link:' tags
> pointing
> to the report (the parent of this mail). See page linked in footer
> for
> details.
> 
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker'
> hat)
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-- 
Robert Hancock <robert.hancock@calian.com>
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