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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Fri, 1 Dec 2023 11:55:36 -0500
Message-ID: <CADnq5_Oy6RMyJ52TbsxVjZ=0p=wYJHduE4X8B3DiYnqHYJUAvw@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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Phillip,

Can you test this patch?  I was not able to repro the issue on the
navi2x card I had handy, but I think it should fix it.

Thanks,

Alex

On Wed, Nov 29, 2023 at 3:49=E2=80=AFPM Alex Deucher <alexdeucher@gmail.com=
> wrote:
>
> On Wed, Nov 29, 2023 at 3:10=E2=80=AFPM Alex Deucher <alexdeucher@gmail.c=
om> wrote:
> >
> > Actually I think I see the problem.  I'll try and send out a patch
> > later today to test.
>
> Does the attached patch fix it?
>
> Alex
>
> >
> > 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@gmai=
l.com> wrote:
> > > >
> > > > On 2023-11-29 10:22, Alex Deucher wrote:
> > > > > On Wed, Nov 29, 2023 at 8:50=E2=80=AFAM Alex Deucher <alexdeucher=
@gmail.com> wrote:
> > > > >>
> > > > >> On Tue, Nov 28, 2023 at 11:45=E2=80=AFPM Luben Tuikov <ltuikov89=
@gmail.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@th=
esusis.net> wrote:
> > > > >>>>>
> > > > >>>>> Alex Deucher <alexdeucher@gmail.com> writes:
> > > > >>>>>
> > > > >>>>>>> In that case those are the already known problems with the =
scheduler
> > > > >>>>>>> changes, aren't they?
> > > > >>>>>>
> > > > >>>>>> Yes.  Those changes went into 6.7 though, not 6.6 AFAIK.  Ma=
ybe I'm
> > > > >>>>>> misunderstanding what the original report was actually testi=
ng.  If it
> > > > >>>>>> was 6.7, then try reverting:
> > > > >>>>>> 56e449603f0ac580700621a356d35d5716a62ce5
> > > > >>>>>> b70438004a14f4d0f9890b3297cd66248728546c
> > > > >>>>>
> > > > >>>>> At some point it was suggested that I file a gitlab issue, bu=
t 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 co=
uld track?
> > > > >>>>>
> > > > >>>>
> > > > >>>> At this point, unless there are any objections, I think we sho=
uld 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=
 number of run-queues
> > > > >>> *does not* mitigate the failed suspend. (Furthermore, this comm=
it doesn't really change
> > > > >>> anything operational, other than using an allocated array, inst=
ead of a static one, in DRM,
> > > > >>> while the 2nd patch is solely contained within the amdgpu drive=
r code.)
> > > > >>>
> > > > >>> 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 =
above shows.
> > > > >>>
> > > > >>> The conclusion is that only b70438004a14f4 needs reverting.
> > > > >>
> > > > >> b70438004a14f4 was a fix for 56e449603f0ac5.  Without b70438004a=
14f4,
> > > > >> 56e449603f0ac5 breaks amdgpu.
> > > > >
> > > > > We can try and re-enable it in the next kernel.  I'm just not sur=
e
> > > > > we'll be able to fix this in time for 6.7 with the holidays and a=
ll
> > > > > 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 lik=
e the
> > > > > best short term solution.
> > > >
> > > > A lot of subsequent code has come in since commit 56e449603f0ac5, a=
s it opened
> > > > the opportunity for a 1-to-1 relationship between an entity and a s=
cheduler.
> > > > (Should've always been the case, from the outset. Not sure why it w=
as coded 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=
, there is
> > > > no reason to have to "churn", i.e. go back and forth in DRM, only t=
o cover 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@gmai=
l.com
> > > >
> > > > And it's not like this issue is unknown. I first posted about it on=
 2023-10-16.
> > > >
> > > > 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