Re: [Freedreno] [PATCH v2 2/3] drm: msm: a6xx: Add support for A618

[Rob Clark]

On Mon, Feb 3, 2020 at 4:21 PM John Stultz <john.stultz@xxxxxxxxxx> wrote:
>
> On Wed, Jan 22, 2020 at 11:19 PM Sharat Masetty <smasetty@xxxxxxxxxxxxxx> wrote:
> >
> > This patch adds support for enabling Graphics Bus Interface(GBIF)
> > used in multiple A6xx series chipets. Also makes changes to the
> > PDC/RSC sequencing specifically required for A618. This is needed
> > for proper interfacing with RPMH.
> >
> > Signed-off-by: Sharat Masetty <smasetty@xxxxxxxxxxxxxx>
> > ---
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > index dc8ec2c..2ac9a51 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > @@ -378,6 +378,18 @@ static int a6xx_hw_init(struct msm_gpu *gpu)
> >         struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> >         int ret;
> >
> > +       /*
> > +        * During a previous slumber, GBIF halt is asserted to ensure
> > +        * no further transaction can go through GPU before GPU
> > +        * headswitch is turned off.
> > +        *
> > +        * This halt is deasserted once headswitch goes off but
> > +        * incase headswitch doesn't goes off clear GBIF halt
> > +        * here to ensure GPU wake-up doesn't fail because of
> > +        * halted GPU transactions.
> > +        */
> > +       gpu_write(gpu, REG_A6XX_GBIF_HALT, 0x0);
> > +
> >         /* Make sure the GMU keeps the GPU on while we set it up */
> >         a6xx_gmu_set_oob(&a6xx_gpu->gmu, GMU_OOB_GPU_SET);
> >
>
> So I already brought this up on #freedreno but figured I'd follow up
> on the list.
>
> With linus/master, I'm seeing hard crashes (into usb crash mode) with
> the db845c, which I isolated down to this patch, and then to the chunk
> above.

(repeating my speculation from #freedreno for benefit of those not on IRC)

I'm suspecting, that like the registers to take the GPU out of secure
mode, this register is being blocked on LA devices (like db845c),
which is why we didn't see this on cheza.

Maybe we can make this write conditional on whether we have a zap shader?

BR,
-R

> Dropping the gpu_write line above gets things booting again for me.
>
> Let me know if there are any follow on patches I can help validate.
>
> thanks
> -john
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