nouveau regression with 5.7 caused by "PCI/PM: Assume ports without DLL Link Active train links in 100 ms"

[Sasha Levin]

On Fri, Jul 17, 2020 at 02:43:52AM +0200, Karol Herbst wrote:
>On Fri, Jul 17, 2020 at 1:54 AM Bjorn Helgaas <helgaas at kernel.org> wrote:
>>
>> [+cc Sasha -- stable kernel regression]
>> [+cc Patrick, Kai-Heng, LKML]
>>
>> On Fri, Jul 17, 2020 at 12:10:39AM +0200, Karol Herbst wrote:
>> > On Tue, Jul 7, 2020 at 9:30 PM Karol Herbst <kherbst at redhat.com> wrote:
>> > >
>> > > Hi everybody,
>> > >
>> > > with the mentioned commit Nouveau isn't able to load firmware onto the
>> > > GPU on one of my systems here. Even though the issue doesn't always
>> > > happen I am quite confident this is the commit breaking it.
>> > >
>> > > I am still digging into the issue and trying to figure out what
>> > > exactly breaks, but it shows up in different ways. Either we are not
>> > > able to boot the engines on the GPU or the GPU becomes unresponsive.
>> > > Btw, this is also a system where our runtime power management issue
>> > > shows up, so maybe there is indeed something funky with the bridge
>> > > controller.
>> > >
>> > > Just pinging you in case you have an idea on how this could break Nouveau
>> > >
>> > > most of the times it shows up like this:
>> > > nouveau 0000:01:00.0: acr: AHESASC binary failed
>> > >
>> > > Sometimes it works at boot and fails at runtime resuming with random
>> > > faults. So I will be investigating a bit more, but yeah... I am super
>> > > sure the commit triggered this issue, no idea if it actually causes
>> > > it.
>> >
>> > so yeah.. I reverted that locally and never ran into issues again.
>> > Still valid on latest 5.7. So can we get this reverted or properly
>> > fixed? This breaks runtime pm for us on at least some hardware.
>>
>> Yeah, that stinks.  We had another similar report from Patrick:
>>
>>   https://lore.kernel.org/r/CAErSpo5sTeK_my1dEhWp7aHD0xOp87+oHYWkTjbL7ALgDbXo-Q@mail.gmail.com
>>
>> Apparently the problem is ec411e02b7a2 ("PCI/PM: Assume ports without
>> DLL Link Active train links in 100 ms"), which Patrick found was
>> backported to v5.4.49 as 828b192c57e8, and you found was backported to
>> v5.7.6 as afaff825e3a4.
>>
>> Oddly, Patrick reported that v5.7.7 worked correctly, even though it
>> still contains afaff825e3a4.
>>
>> I guess in the absence of any other clues we'll have to revert it.
>> I hate to do that because that means we'll have slow resume of
>> Thunderbolt-connected devices again, but that's better than having
>> GPUs completely broken.
>>
>> Could you and Patrick open bugzilla.kernel.org reports, attach dmesg
>> logs and "sudo lspci -vv" output, and add the URLs to Kai-Heng's
>> original report at https://bugzilla.kernel.org/show_bug.cgi?id=206837
>> and to this thread?
>>
>> There must be a way to fix the slow resume problem without breaking
>> the GPUs.
>>
>
>I wouldn't be surprised if this is related to the Intel bridge we
>check against for Nouveau.. I still have to check on another laptop
>with the same bridge our workaround was required as well but wouldn't
>be surprised if it shows the same problem. Will get you the
>information from both systems tomorrow then.

I take it that ec411e02b7a2 will be reverted upstream?

-- 
Thanks,
Sasha