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Sender: Salvatore Bonaccorso <salvatore.bonaccorso@gmail.com>
Date:   Tue, 20 Sep 2022 13:59:33 +0200
From:   Salvatore Bonaccorso <carnil@debian.org>
To:     Karol Herbst <kherbst@redhat.com>
Cc:     linux-kernel@vger.kernel.org, Ben Skeggs <bskeggs@redhat.com>,
        Lyude Paul <lyude@redhat.com>, dri-devel@lists.freedesktop.org,
        nouveau@lists.freedesktop.org, stable@vger.kernel.org,
        Computer Enthusiastic <computer.enthusiastic@gmail.com>
Subject: Re: [PATCH] nouveau: explicitly wait on the fence in
 nouveau_bo_move_m2mf
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Hi,

On Tue, Sep 20, 2022 at 01:36:32PM +0200, Karol Herbst wrote:
> On Tue, Sep 20, 2022 at 12:42 PM Salvatore Bonaccorso <carnil@debian.org> wrote:
> >
> > Hi,
> >
> > On Fri, Aug 19, 2022 at 10:09:28PM +0200, Karol Herbst wrote:
> > > It is a bit unlcear to us why that's helping, but it does and unbreaks
> > > suspend/resume on a lot of GPUs without any known drawbacks.
> > >
> > > Cc: stable@vger.kernel.org # v5.15+
> > > Closes: https://gitlab.freedesktop.org/drm/nouveau/-/issues/156
> > > Signed-off-by: Karol Herbst <kherbst@redhat.com>
> > > ---
> > >  drivers/gpu/drm/nouveau/nouveau_bo.c | 9 +++++++++
> > >  1 file changed, 9 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > index 35bb0bb3fe61..126b3c6e12f9 100644
> > > --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > @@ -822,6 +822,15 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict,
> > >               if (ret == 0) {
> > >                       ret = nouveau_fence_new(chan, false, &fence);
> > >                       if (ret == 0) {
> > > +                             /* TODO: figure out a better solution here
> > > +                              *
> > > +                              * wait on the fence here explicitly as going through
> > > +                              * ttm_bo_move_accel_cleanup somehow doesn't seem to do it.
> > > +                              *
> > > +                              * Without this the operation can timeout and we'll fallback to a
> > > +                              * software copy, which might take several minutes to finish.
> > > +                              */
> > > +                             nouveau_fence_wait(fence, false, false);
> > >                               ret = ttm_bo_move_accel_cleanup(bo,
> > >                                                               &fence->base,
> > >                                                               evict, false,
> > > --
> > > 2.37.1
> > >
> > >
> >
> > While this is marked for 5.15+ only, a user in Debian was seeing the
> > suspend issue as well on 5.10.y and did confirm the commit fixes the
> > issue as well in the 5.10.y series:
> >
> > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=989705#69
> >
> > Karol, Lyude, should that as well be picked for 5.10.y?
> >
> 
> mhh from the original report 5.10 was fine, but maybe something got
> backported and it broke it? I'll try to do some testing on my machine
> and see what I can figure out, but it could also be a debian only
> issue at this point.

Right, this is a possiblity, thanks for looking into it!

Computer Enthusiastic, can you verify the problem as well in a
non-Debian patched upstream kernel directly from the 5.10.y series
(latest 5.10.144) and verify the fix there?

Regards,
Salvatore