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From:   Ben Skeggs <skeggsb@gmail.com>
Date:   Wed, 24 Feb 2021 19:50:21 +1000
Message-ID: <CACAvsv43MhF2JUUhLbxk+aaMkforpF1bvggyfJR=MOnv3wMCfA@mail.gmail.com>
Subject: Re: [PATCH v2] drm/nouveau/pmu: fix timeout on GP108
To:     Alexandre Courbot <gnurou@gmail.com>
Cc:     Diego Viola <diego.viola@gmail.com>,
        Roy Spliet <nouveau@spliet.org>,
        Ben Skeggs <bskeggs@redhat.com>,
        ML dri-devel <dri-devel@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, 17 Feb 2021 at 13:30, Alexandre Courbot <gnurou@gmail.com> wrote:
>
> On Wed, Feb 17, 2021 at 1:20 AM Diego Viola <diego.viola@gmail.com> wrote:
> >
> > This code times out on GP108, probably because the BIOS puts it into a
> > bad state.
> >
> > Since we reset the PMU on driver load anyway, we are at no risk from
> > missing a response from it since we are not waiting for one to begin
> > with.
>
> This looks safe to me, provided indeed that the PMU's reset is not
> called outside of initialization (which for GP108 is shouldn't be
> IIRC?).
ISTR that the PMU FW we use prior to GM200 might depend on that being there.

I've posted a proposed alternate fix here[1], as we probably shouldn't
have been touching PMU there anyway on those GPUs.

Ben.

[1] https://github.com/skeggsb/linux/commit/90224a17437b1f39dbecbb385567c1fce958f992

>
> >
> > Signed-off-by: Diego Viola <diego.viola@gmail.com>
> > ---
> >  drivers/gpu/drm/nouveau/nvkm/subdev/pmu/base.c | 6 +-----
> >  1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pmu/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/pmu/base.c
> > index a0fe607c9c07..5c802f2d00cb 100644
> > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/pmu/base.c
> > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pmu/base.c
> > @@ -102,12 +102,8 @@ nvkm_pmu_reset(struct nvkm_pmu *pmu)
> >         if (!pmu->func->enabled(pmu))
> >                 return 0;
> >
> > -       /* Inhibit interrupts, and wait for idle. */
> > +       /* Inhibit interrupts. */
> >         nvkm_wr32(device, 0x10a014, 0x0000ffff);
> > -       nvkm_msec(device, 2000,
> > -               if (!nvkm_rd32(device, 0x10a04c))
> > -                       break;
> > -       );
> >
> >         /* Reset. */
> >         if (pmu->func->reset)
> > --
> > 2.30.1
> >
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