Re: [Freedreno] [PATCH v2 3/7] drm/msm: Fix cx collapse issue during recovery

[Akhil P Oommen]

On 7/12/2022 4:52 AM, Doug Anderson wrote:
> Hi,
>
> On Fri, Jul 8, 2022 at 11:00 PM Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx> wrote:
> > There are some hardware logic under CX domain. For a successful
> > recovery, we should ensure cx headswitch collapses to ensure all the
> > stale states are cleard out. This is especially true to for a6xx family
> > where we can GMU co-processor.
> >
> > Currently, cx doesn't collapse due to a devlink between gpu and its
> > smmu. So the *struct gpu device* needs to be runtime suspended to ensure
> > that the iommu driver removes its vote on cx gdsc.
> >
> > Signed-off-by: Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx>
> > ---
> >
> > (no changes since v1)
> >
> >   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 16 ++++++++++++++--
> >   drivers/gpu/drm/msm/msm_gpu.c         |  2 --
> >   2 files changed, 14 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > index 4d50110..7ed347c 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > @@ -1278,8 +1278,20 @@ static void a6xx_recover(struct msm_gpu *gpu)
> >           */
> >          gmu_write(&a6xx_gpu->gmu, REG_A6XX_GMU_GMU_PWR_COL_KEEPALIVE, 0);
> >
> > -       gpu->funcs->pm_suspend(gpu);
> > -       gpu->funcs->pm_resume(gpu);
> > +       /*
> > +        * Now drop all the pm_runtime usage count to allow cx gdsc to collapse.
> > +        * First drop the usage count from all active submits
> > +        */
> > +       for (i = gpu->active_submits; i > 0; i--)
> > +               pm_runtime_put(&gpu->pdev->dev);
> > +
> > +       /* And the final one from recover worker */
> > +       pm_runtime_put_sync(&gpu->pdev->dev);
> > +
> > +       for (i = gpu->active_submits; i > 0; i--)
> > +               pm_runtime_get(&gpu->pdev->dev);
> > +
> > +       pm_runtime_get_sync(&gpu->pdev->dev);
> In response to v1, Rob suggested pm_runtime_force_suspend/resume().
> Those seem like they would work to me, too. Why not use them?
Quoting my previous response which I seem to have sent only to Freedreno 
list:

"I believe it is supposed to be used only during system sleep state 
transitions. Btw, we don't want pm_runtime_get() calls from elsewhere to 
fail by disabling RPM here."

-Akhil