Re: [Intel-gfx] [PATCH 4/6] drm/i915: Enable VRR later during fastsets

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Aug 28, 2023 at 11:47:49AM -0700, Manasi Navare wrote:
> On Sun, Aug 27, 2023 at 10:41 PM Ville Syrjala
> <ville.syrjala@linux.intel.com> wrote:
> >
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > In order to reconcile seamless M/N updates with VRR we'll
> > need to defer the fastset VRR enable to happen after the
> > seamless M/N update (which happens during the vblank evade
> > critical section). So just push the VRR enable to be the last
> > thing during the update.
> >
> > This will also affect the vblank evasion as the transcoder
> > will now still be running with the old VRR state during
> > the vblank evasion. So just grab the timings always from the
> > old crtc state during any non-modeset commit, and also grab
> > the current state of VRR from the active timings (as we disable
> > VRR before vblank evasion during fastsets).
> >
> > This also fixes vblank evasion for seamless M/N updates as
> > we now properly account for the fact that the M/N update
> > happens after vblank evasion.
> >
> > Cc: Manasi Navare <navaremanasi@chromium.org>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_crtc.c    | 35 ++++++++++++--------
> >  drivers/gpu/drm/i915/display/intel_display.c | 21 ++++++++----
> >  2 files changed, 36 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c b/drivers/gpu/drm/i915/display/intel_crtc.c
> > index e46a15d59d79..1992e7060263 100644
> > --- a/drivers/gpu/drm/i915/display/intel_crtc.c
> > +++ b/drivers/gpu/drm/i915/display/intel_crtc.c
> > @@ -472,15 +472,31 @@ static void intel_crtc_vblank_evade_scanlines(struct intel_atomic_state *state,
> >                                               struct intel_crtc *crtc,
> >                                               int *min, int *max, int *vblank_start)
> >  {
> > +       const struct intel_crtc_state *old_crtc_state =
> > +               intel_atomic_get_old_crtc_state(state, crtc);
> >         const struct intel_crtc_state *new_crtc_state =
> >                 intel_atomic_get_new_crtc_state(state, crtc);
> > -       const struct drm_display_mode *adjusted_mode = &new_crtc_state->hw.adjusted_mode;
> > +       const struct intel_crtc_state *crtc_state;
> > +       const struct drm_display_mode *adjusted_mode;
> >
> > -       if (new_crtc_state->vrr.enable) {
> > -               if (intel_vrr_is_push_sent(new_crtc_state))
> > -                       *vblank_start = intel_vrr_vmin_vblank_start(new_crtc_state);
> > +       /*
> > +        * During fastsets/etc. the transcoder is still
> > +        * running with the old timings at this point.
> > +        *
> > +        * TODO: maybe just use the active timings here?
> > +        */
> > +       if (intel_crtc_needs_modeset(new_crtc_state))
> > +               crtc_state = new_crtc_state;
> > +       else
> > +               crtc_state = old_crtc_state;
> > +
> > +       adjusted_mode = &crtc_state->hw.adjusted_mode;
> > +
> > +       if (crtc->mode_flags & I915_MODE_FLAG_VRR) {
> > +               if (intel_vrr_is_push_sent(crtc_state))
> > +                       *vblank_start = intel_vrr_vmin_vblank_start(crtc_state);
> >                 else
> > -                       *vblank_start = intel_vrr_vmax_vblank_start(new_crtc_state);
> > +                       *vblank_start = intel_vrr_vmax_vblank_start(crtc_state);
> >         } else {
> >                 *vblank_start = intel_mode_vblank_start(adjusted_mode);
> >         }
> > @@ -710,15 +726,6 @@ void intel_pipe_update_end(struct intel_atomic_state *state,
> >          */
> >         intel_vrr_send_push(new_crtc_state);
> >
> > -       /*
> > -        * Seamless M/N update may need to update frame timings.
> > -        *
> > -        * FIXME Should be synchronized with the start of vblank somehow...
> > -        */
> > -       if (new_crtc_state->seamless_m_n && intel_crtc_needs_fastset(new_crtc_state))
> > -               intel_crtc_update_active_timings(new_crtc_state,
> > -                                                new_crtc_state->vrr.enable);
> > -
> >         local_irq_enable();
> >
> >         if (intel_vgpu_active(dev_priv))
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> > index cfad967b5684..632f1f58df9e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -6476,6 +6476,8 @@ static void commit_pipe_post_planes(struct intel_atomic_state *state,
> >                                     struct intel_crtc *crtc)
> >  {
> >         struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> > +       const struct intel_crtc_state *old_crtc_state =
> > +               intel_atomic_get_old_crtc_state(state, crtc);
> >         const struct intel_crtc_state *new_crtc_state =
> >                 intel_atomic_get_new_crtc_state(state, crtc);
> >
> > @@ -6487,6 +6489,9 @@ static void commit_pipe_post_planes(struct intel_atomic_state *state,
> >         if (DISPLAY_VER(dev_priv) >= 9 &&
> >             !intel_crtc_needs_modeset(new_crtc_state))
> >                 skl_detach_scalers(new_crtc_state);
> > +
> > +       if (vrr_enabling(old_crtc_state, new_crtc_state))
> > +               intel_vrr_enable(new_crtc_state);
> 
> Wouldnt we also need the condition here:
> new_crtc_state->seamless_m_n && intel_crtc_needs_fastset(new_crtc_state))

That is handled elsewhere already.

> 
> So that we update VRR enable bit in the seamless_m_n fastset case as well.
> This will be needed later once we start updating the VRR params regs
> in fastset, since
> that otherwise ends up resetting VRR enable bit.
> 
> 
> 
> >  }
> >
> >  static void intel_enable_crtc(struct intel_atomic_state *state,
> > @@ -6527,12 +6532,6 @@ static void intel_update_crtc(struct intel_atomic_state *state,
> >                         intel_dpt_configure(crtc);
> >         }
> >
> > -       if (vrr_enabling(old_crtc_state, new_crtc_state)) {
> > -               intel_vrr_enable(new_crtc_state);
> > -               intel_crtc_update_active_timings(new_crtc_state,
> > -                                                new_crtc_state->vrr.enable);
> > -       }
> > -
> >         if (!modeset) {
> >                 if (new_crtc_state->preload_luts &&
> >                     intel_crtc_needs_color_update(new_crtc_state))
> > @@ -6569,6 +6568,16 @@ static void intel_update_crtc(struct intel_atomic_state *state,
> >
> >         intel_pipe_update_end(state, crtc);
> >
> > +       /*
> > +        * VRR/Seamless M/N update may need to update frame timings.
> > +        *
> > +        * FIXME Should be synchronized with the start of vblank somehow...
> > +        */
> > +       if (vrr_enabling(old_crtc_state, new_crtc_state) ||
> > +           (new_crtc_state->seamless_m_n && intel_crtc_needs_fastset(new_crtc_state)))
> > +               intel_crtc_update_active_timings(new_crtc_state,
> > +                                                new_crtc_state->vrr.enable);
> > +
> 
> So would the VRR min/max, flipline values also be updated here
> eventually for the fastset in seamless_m_n case?

No, it would be done earlier. Should be OK to do anywhere
between the VRR disable and enable really. Doesn't even need
to be inside the vblank evade critical section since VRR will
already have been disabled when we change these.

> 
> Manasi
> 
> 
> >         /*
> >          * We usually enable FIFO underrun interrupts as part of the
> >          * CRTC enable sequence during modesets.  But when we inherit a
> > --
> > 2.41.0
> >

-- 
Ville Syrjälä
Intel