Re: [PATCH v3 1/8] drm/msm: Remove unnecessary pm_runtime_get/put

[Akhil P Oommen]

On 7/31/2022 9:25 PM, Rob Clark wrote:
> On Sat, Jul 30, 2022 at 2:41 AM Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx> wrote:
> > We already enable gpu power from msm_gpu_submit(), so avoid a duplicate
> > pm_runtime_get/put from msm_job_run().
> >
> > Signed-off-by: Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx>
> > ---
> >
> > (no changes since v1)
> >
> >   drivers/gpu/drm/msm/msm_ringbuffer.c | 4 ----
> >   1 file changed, 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
> > index 56eecb4..cad4c35 100644
> > --- a/drivers/gpu/drm/msm/msm_ringbuffer.c
> > +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
> > @@ -29,8 +29,6 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
> >                  msm_gem_unlock(obj);
> >          }
> >
> > -       pm_runtime_get_sync(&gpu->pdev->dev);
> > -
> This is removing a _get_sync() and simply relying on a _get() (async)
> in msm_gpu_submit().. that seems pretty likely to go badly?  I think
> it should probably replace the _get() in msm_gpu_submit() with
> _get_sync() (but also since this is changing position of
> resume/suspend vs active_lock, please make sure you test with lockdep
> enabled)
>
> BR,
> -R
As discussed in the other patch, this is correctly handled in 
msm_gpu_submit(). And from active_lock perspective, there is no change 
actually. GPU is ON by the time we touch active_lock in both cases.

-Akhil.
> >          /* TODO move submit path over to using a per-ring lock.. */
> >          mutex_lock(&gpu->lock);
> >
> > @@ -38,8 +36,6 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
> >
> >          mutex_unlock(&gpu->lock);
> >
> > -       pm_runtime_put(&gpu->pdev->dev);
> > -
> >          return dma_fence_get(submit->hw_fence);
> >   }
> >
> > --
> > 2.7.4