Re: [Freedreno] [v1] drm/msm/dpu: Fix reservation failures in modeset

[Rob Clark]

On Thu, Aug 6, 2020 at 7:46 AM <kalyan_t@xxxxxxxxxxxxxx> wrote:
>
> On 2020-08-05 21:18, Rob Clark wrote:
> > On Wed, Aug 5, 2020 at 6:34 AM Kalyan Thota <kalyan_t@xxxxxxxxxxxxxx>
> > wrote:
> >>
> >> In TEST_ONLY commit, rm global_state will duplicate the
> >> object and request for new reservations, once they pass
> >> then the new state will be swapped with the old and will
> >> be available for the Atomic Commit.
> >>
> >> This patch fixes some of missing links in the resource
> >> reservation sequence mentioned above.
> >>
> >> 1) Creation of a duplicate state in test_only commit (Rob)
> >> 2) Allow resource release only during crtc_active false.
> >>
> >> For #2
> >> In a modeset operation, swap state happens well before disable.
> >> Hence clearing reservations in disable will cause failures
> >> in modeset enable.
> >>
> >> Sequence:
> >>     Swap state --> old, new
> >>     modeset disables --> virt disable
> >>     modeset enable --> virt modeset
> >>
> >> Allow reservations to be cleared only when crtc active is false
> >> as in that case there wont be any modeset enable after disable.
> >>
> >> Signed-off-by: Kalyan Thota <kalyan_t@xxxxxxxxxxxxxx>
> >> ---
> >>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 7 +++++--
> >>  1 file changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> >> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> >> index 63976dc..b85a576 100644
> >> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> >> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> >> @@ -582,7 +582,7 @@ static int dpu_encoder_virt_atomic_check(
> >>         dpu_kms = to_dpu_kms(priv->kms);
> >>         mode = &crtc_state->mode;
> >>         adj_mode = &crtc_state->adjusted_mode;
> >> -       global_state = dpu_kms_get_existing_global_state(dpu_kms);
> >> +       global_state = dpu_kms_get_global_state(crtc_state->state);
> >>         trace_dpu_enc_atomic_check(DRMID(drm_enc));
> >>
> >>         /*
> >> @@ -1172,6 +1172,7 @@ static void dpu_encoder_virt_disable(struct
> >> drm_encoder *drm_enc)
> >>         struct msm_drm_private *priv;
> >>         struct dpu_kms *dpu_kms;
> >>         struct dpu_global_state *global_state;
> >> +       struct drm_crtc_state *crtc_state;
> >>         int i = 0;
> >>
> >>         if (!drm_enc) {
> >> @@ -1191,6 +1192,7 @@ static void dpu_encoder_virt_disable(struct
> >> drm_encoder *drm_enc)
> >>         priv = drm_enc->dev->dev_private;
> >>         dpu_kms = to_dpu_kms(priv->kms);
> >>         global_state = dpu_kms_get_existing_global_state(dpu_kms);
> >> +       crtc_state = drm_enc->crtc->state;
> >>
> >>         trace_dpu_enc_disable(DRMID(drm_enc));
> >>
> >> @@ -1220,7 +1222,8 @@ static void dpu_encoder_virt_disable(struct
> >> drm_encoder *drm_enc)
> >>
> >>         DPU_DEBUG_ENC(dpu_enc, "encoder disabled\n");
> >>
> >> -       dpu_rm_release(global_state, drm_enc);
> >> +       if (crtc_state->active_changed && !crtc_state->active)
> >> +               dpu_rm_release(global_state, drm_enc);
> >
> > I still think releasing the state in the atomic_commit() path is the
> > wrong thing to do.  In the commit path, the various state objects
> > should be immutable.. ie. in the atomic_test() path you derive the new
> > hw state (including assignment/release of resources), and
> > atomic_commit() is simply pushing the state down to the hw.
> >
> > Otherwise, this looks better than v1.
> >
> > BR,
> > -R
> >
> okay. Should we avoid reservation all together if active=0 on that crtc
> and trigger rm_release on the enc during atomic_check ?
> how do you see the approach ?

Yeah, I suppose something like:

   if (drm_atomic_crtc_needs_modeset()) {
      reserve()
   } else if (active_changed && !active) {
      release()
   }

I think it could happen (at least with atomic api) that you get a
modeset without active_changed, so we might need to release() and then
reserve() in that case?  (This is probably where starting to run more
IGT tests would be useful)

BR,
-R

> -Kalyan
> >>
> >>         mutex_unlock(&dpu_enc->enc_lock);
> >>  }
> >> --
> >> 1.9.1
> >>
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