Re: [PATCH v1 3/3] msm: skip the atomic commit of self refresh while PSR running

[Dmitry Baryshkov]

On 03/04/2023 19:11, Dmitry Baryshkov wrote:
> On Mon, 3 Apr 2023 at 15:01, Vinod Polimera <vpolimer@xxxxxxxxxxxxxxxx> wrote:
> > > On Fri, 31 Mar 2023 at 16:59, Vinod Polimera <quic_vpolimer@xxxxxxxxxxx>
> > > wrote:
> > > > In certain CPU stress conditions, there can be a delay in scheduling commit
> > > > work and it was observed that PSR commit from a different work queue
> > > was
> > > > scheduled. Avoid these commits as display is already in PSR mode.
> > > >
> > > > Signed-off-by: Vinod Polimera <quic_vpolimer@xxxxxxxxxxx>
> > > > ---
> > > >   drivers/gpu/drm/msm/msm_atomic.c | 3 +++
> > > >   1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/msm/msm_atomic.c
> > > b/drivers/gpu/drm/msm/msm_atomic.c
> > > > index 645fe53..f8141bb 100644
> > > > --- a/drivers/gpu/drm/msm/msm_atomic.c
> > > > +++ b/drivers/gpu/drm/msm/msm_atomic.c
> > > > @@ -192,6 +192,9 @@ int msm_atomic_check(struct drm_device *dev,
> > > struct drm_atomic_state *state)
> > > >                          new_crtc_state->mode_changed = true;
> > > >                          state->allow_modeset = true;
> > > >                  }
> > > > +
> > > > +               if (old_crtc_state->self_refresh_active && new_crtc_state-
> > > > self_refresh_active)
> > > > +                       return -EINVAL;
> > >
> > > EINVAL here means that atomic_check will fail if both old and new
> > > states are in SR mode. For example, there might be a mode set for
> > > another CRTC (while keeping this one in SR mode). I don't think this
> > > is correct. We should skip/shortcut the commit, that's true. But I
> > > doubt that returning an error here is a proper way to do this. Please
> > > correct me if I'm wrong.
> >
> > If there is a modeset on same crtc with a different connector. The new_crtc_state will not have self_refresh_active set.
> > Self_refresh_active is set from the helper library, which will duplicate the old_state and just adds self_refresh_active to true and active to false.
> > so we can be confident that if we are checking for self_refresh_active status then it should be coming from the library call.
> >
> > Also the EINVAL is returned to the self_refresh library API and the function will be retired.
>
> Maybe I misunderstand you here. However, in this way EINVAL is
> returned to drm_atomic_check_only() and not to the SR code.

Unless anybody objects, I'm going to drop this patch now. The issue 
should be solved in the framework itself.

> > And self_refresh_active is cleared on every commit : https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/drm/drm_atomic_state_helper.c#n158
>
> And this means that this check will not trigger at all, if I'm not
> mistaken. You've added code to msm_atomic_check(), so
> drm_self_refresh_helper_alter_state() was not called (yet) and thus
> new_crtc_state->self_refresh_active is set to false, fresh after
> crtc's duplicate_state.
>
> --
> With best wishes
> Dmitry

--
With best wishes
Dmitry