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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Wed, 29 Nov 2023 15:10:14 -0500
Message-ID: <CADnq5_PgMxoW=4iabtgeHydwye-6DvwvCyETdfBToEpuYWocmA@mail.gmail.com>
Subject: Re: Radeon regression in 6.6 kernel
To:     Luben Tuikov <ltuikov89@gmail.com>
Cc:     Phillip Susi <phill@thesusis.net>,
        Linux regressions mailing list <regressions@lists.linux.dev>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <ckoenig.leichtzumerken@gmail.com>,
        linux-kernel@vger.kernel.org,
        "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
        dri-devel@lists.freedesktop.org,
        Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        Danilo Krummrich <dakr@redhat.com>
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Actually I think I see the problem.  I'll try and send out a patch
later today to test.

Alex

On Wed, Nov 29, 2023 at 1:52=E2=80=AFPM Alex Deucher <alexdeucher@gmail.com=
> wrote:
>
> On Wed, Nov 29, 2023 at 11:41=E2=80=AFAM Luben Tuikov <ltuikov89@gmail.co=
m> wrote:
> >
> > On 2023-11-29 10:22, Alex Deucher wrote:
> > > On Wed, Nov 29, 2023 at 8:50=E2=80=AFAM Alex Deucher <alexdeucher@gma=
il.com> wrote:
> > >>
> > >> On Tue, Nov 28, 2023 at 11:45=E2=80=AFPM Luben Tuikov <ltuikov89@gma=
il.com> wrote:
> > >>>
> > >>> On 2023-11-28 17:13, Alex Deucher wrote:
> > >>>> On Mon, Nov 27, 2023 at 6:24=E2=80=AFPM Phillip Susi <phill@thesus=
is.net> wrote:
> > >>>>>
> > >>>>> Alex Deucher <alexdeucher@gmail.com> writes:
> > >>>>>
> > >>>>>>> In that case those are the already known problems with the sche=
duler
> > >>>>>>> changes, aren't they?
> > >>>>>>
> > >>>>>> Yes.  Those changes went into 6.7 though, not 6.6 AFAIK.  Maybe =
I'm
> > >>>>>> misunderstanding what the original report was actually testing. =
 If it
> > >>>>>> was 6.7, then try reverting:
> > >>>>>> 56e449603f0ac580700621a356d35d5716a62ce5
> > >>>>>> b70438004a14f4d0f9890b3297cd66248728546c
> > >>>>>
> > >>>>> At some point it was suggested that I file a gitlab issue, but I =
took
> > >>>>> this to mean it was already known and being worked on.  -rc3 came=
 out
> > >>>>> today and still has the problem.  Is there a known issue I could =
track?
> > >>>>>
> > >>>>
> > >>>> At this point, unless there are any objections, I think we should =
just
> > >>>> revert the two patches
> > >>> Uhm, no.
> > >>>
> > >>> Why "the two" patches?
> > >>>
> > >>> This email, part of this thread,
> > >>>
> > >>> https://lore.kernel.org/all/87r0kircdo.fsf@vps.thesusis.net/
> > >>>
> > >>> clearly states that reverting *only* this commit,
> > >>> 56e449603f0ac5 drm/sched: Convert the GPU scheduler to variable num=
ber of run-queues
> > >>> *does not* mitigate the failed suspend. (Furthermore, this commit d=
oesn't really change
> > >>> anything operational, other than using an allocated array, instead =
of a static one, in DRM,
> > >>> while the 2nd patch is solely contained within the amdgpu driver co=
de.)
> > >>>
> > >>> Leaving us with only this change,
> > >>> b70438004a14f4 drm/amdgpu: move buffer funcs setting up a level
> > >>> to be at fault, as the kernel log attached in the linked email abov=
e shows.
> > >>>
> > >>> The conclusion is that only b70438004a14f4 needs reverting.
> > >>
> > >> b70438004a14f4 was a fix for 56e449603f0ac5.  Without b70438004a14f4=
,
> > >> 56e449603f0ac5 breaks amdgpu.
> > >
> > > We can try and re-enable it in the next kernel.  I'm just not sure
> > > we'll be able to fix this in time for 6.7 with the holidays and all
> > > and I don't want to cause a lot of scheduler churn at the end of the
> > > 6.7 cycle if we hold off and try and fix it.  Reverting seems like th=
e
> > > best short term solution.
> >
> > A lot of subsequent code has come in since commit 56e449603f0ac5, as it=
 opened
> > the opportunity for a 1-to-1 relationship between an entity and a sched=
uler.
> > (Should've always been the case, from the outset. Not sure why it was c=
oded as
> > a fixed-size array.)
> >
> > Given that commit 56e449603f0ac5 has nothing to do with amdgpu, and the=
 problem
> > is wholly contained in amdgpu, and no other driver has this problem, th=
ere is
> > no reason to have to "churn", i.e. go back and forth in DRM, only to co=
ver up
> > an init bug in amdgpu. See the response I just sent in @this thread:
> > https://lore.kernel.org/r/05007cb0-871e-4dc7-af58-1351f4ba43e2@gmail.co=
m
> >
> > And it's not like this issue is unknown. I first posted about it on 202=
3-10-16.
> >
> > Ideally, amdgpu would just fix their init code.
>
> You can't make changes to core code that break other drivers.
> Arguably 56e449603f0ac5 should not have gone in in the first place if
> it broke amdgpu.  b70438004a14f4 was the code to fix amdgpu's init
> code, but as a side effect it seems to have broken suspend for some
> users.
>
> Alex