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

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

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.

>  {
>  	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?

>  
>  		/* 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

-- 
Ville Syrjälä
Intel