Re: [Intel-gfx] [PATCH v3] drm/i915/display: Exit PSR when doing async flips

["Souza, Jose" <jose.souza@intel.com>]

On Thu, 2021-11-04 at 16:10 +0200, Ville Syrjälä wrote:
> On Tue, Nov 02, 2021 at 12:32:14PM -0700, José Roberto de Souza wrote:
> > Changing the buffer in the middle of the scanout then entering an
> > period of flip idleness will cause part of the previous buffer being
> > diplayed to user when PSR is enabled.
> > 
> > So here disabling PSR and scheduling activation during the next
> > sync flip.
> > 
> > The async flip check that we had in PSR compute is not executed at
> > every flip so it was not doing anything useful and is also being
> > dropped here.
> > 
> > v2:
> > - scheduling the PSR work in _intel_psr_post_plane_update()
> > 
> > v3:
> > - only re enabling PSR when doing a sync flip
> > 
> > Cc: Karthik B S <karthik.b.s@intel.com>
> > Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_psr.c | 37 ++++++++++++++----------
> >  1 file changed, 21 insertions(+), 16 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> > index 9d589d471e335..b8fac53d57df1 100644
> > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > @@ -731,12 +731,6 @@ static bool intel_psr2_sel_fetch_config_valid(struct intel_dp *intel_dp,
> >  		return false;
> >  	}
> >  
> > -	if (crtc_state->uapi.async_flip) {
> > -		drm_dbg_kms(&dev_priv->drm,
> > -			    "PSR2 sel fetch not enabled, async flip enabled\n");
> > -		return false;
> > -	}
> > -
> >  	/* Wa_14010254185 Wa_14010103792 */
> >  	if (IS_TGL_DISPLAY_STEP(dev_priv, STEP_A0, STEP_C0)) {
> >  		drm_dbg_kms(&dev_priv->drm,
> > @@ -1780,36 +1774,47 @@ void intel_psr_pre_plane_update(struct intel_atomic_state *state,
> >  		if (psr->enabled && needs_to_disable)
> >  			intel_psr_disable_locked(intel_dp);
> >  
> > +		if (psr->enabled && crtc_state->uapi.async_flip)
> > +			intel_psr_exit(intel_dp);
> > +
> >  		mutex_unlock(&psr->lock);
> >  	}
> >  }
> >  
> >  static void _intel_psr_post_plane_update(const struct intel_atomic_state *state,
> > -					 const struct intel_crtc_state *crtc_state)
> > +					 const struct intel_crtc_state *old_crtc_state,
> > +					 const struct intel_crtc_state *new_crtc_state)
> 
> Might make sense to change this to match how psr_pre_plane_update()
> works these days.

Will do as follow up.

> 
> >  {
> >  	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> >  	struct intel_encoder *encoder;
> >  
> > -	if (!crtc_state->has_psr)
> > +	if (!new_crtc_state->has_psr)
> >  		return;
> >  
> >  	for_each_intel_encoder_mask_with_psr(state->base.dev, encoder,
> > -					     crtc_state->uapi.encoder_mask) {
> > +					     new_crtc_state->uapi.encoder_mask) {
> >  		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> >  		struct intel_psr *psr = &intel_dp->psr;
> >  
> >  		mutex_lock(&psr->lock);
> >  
> > -		drm_WARN_ON(&dev_priv->drm, psr->enabled && !crtc_state->active_planes);
> > +		drm_WARN_ON(&dev_priv->drm, psr->enabled &&
> > +			    !new_crtc_state->active_planes);
> >  
> >  		/* Only enable if there is active planes */
> > -		if (!psr->enabled && crtc_state->active_planes)
> > -			intel_psr_enable_locked(intel_dp, crtc_state);
> > +		if (!psr->enabled && new_crtc_state->active_planes)
> > +			intel_psr_enable_locked(intel_dp, new_crtc_state);
> 
> What prevents this guy from activating PSR while we're doing
> an async flip?

enabled != active, when doing a async flip it will set active = false but enabled will be kept on.

And to change the number of active_planes it will need to do a sync flip, so we are safe.

> 
> >  
> >  		/* Force a PSR exit when enabling CRC to avoid CRC timeouts */
> > -		if (crtc_state->crc_enabled && psr->enabled)
> > +		if (new_crtc_state->crc_enabled && psr->enabled)
> >  			psr_force_hw_tracking_exit(intel_dp);
> >  
> > +		/* Only re enabling PSR when doing a sync flip */
> > +		if (psr->enabled && !psr->active &&
> > +		    old_crtc_state->uapi.async_flip &&
> > +		    !new_crtc_state->uapi.async_flip)
> > +			schedule_work(&intel_dp->psr.work);
> > +
> >  		mutex_unlock(&psr->lock);
> >  	}
> >  }
> > @@ -1817,15 +1822,15 @@ static void _intel_psr_post_plane_update(const struct intel_atomic_state *state,
> >  void intel_psr_post_plane_update(const struct intel_atomic_state *state)
> >  {
> >  	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> > -	struct intel_crtc_state *crtc_state;
> > +	struct intel_crtc_state *old_crtc_state, *new_crtc_state;
> >  	struct intel_crtc *crtc;
> >  	int i;
> >  
> >  	if (!HAS_PSR(dev_priv))
> >  		return;
> >  
> > -	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i)
> > -		_intel_psr_post_plane_update(state, crtc_state);
> > +	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i)
> > +		_intel_psr_post_plane_update(state, old_crtc_state, new_crtc_state);
> >  }
> >  
> >  static int _psr2_ready_for_pipe_update_locked(struct intel_dp *intel_dp)
> > -- 
> > 2.33.1
>