Re: [Intel-gfx] [PATCH] drm/i915/display: Ensure PSR gets disabled if no encoders in new state

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Mon, Jul 11, 2022 at 09:16:01AM +0300, Jouni Högander wrote:
> Currently PSR is left enabled when all planes are disabled if there
> is no attached encoder in new state. This seems to be causing FIFO
> underruns.
> 
> Fix this by checking if old and new crtc encoder masks are differing.
> PSR is disabled for encoders not in new crtc state encoder mask.
> 
> Cc: Mika Kahola <mika.kahola@intel.com>
> Reported-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_psr.c | 72 +++++++++++++++++-------
>  1 file changed, 51 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index e6a870641cd2..710cc31ace22 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -1863,36 +1863,66 @@ void intel_psr_pre_plane_update(struct intel_atomic_state *state,
>  				struct intel_crtc *crtc)
>  {
>  	struct drm_i915_private *i915 = to_i915(state->base.dev);
> -	const struct intel_crtc_state *crtc_state =
> -		intel_atomic_get_new_crtc_state(state, crtc);
> +	struct intel_crtc_state *new_crtc_state, *old_crtc_state;
>  	struct intel_encoder *encoder;
> +	struct intel_dp *intel_dp;
> +	struct intel_psr *psr;
> +	int i;
>  
>  	if (!HAS_PSR(i915))
>  		return;
>  
> -	for_each_intel_encoder_mask_with_psr(state->base.dev, encoder,
> -					     crtc_state->uapi.encoder_mask) {
> -		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> -		struct intel_psr *psr = &intel_dp->psr;
> -		bool needs_to_disable = false;
> -
> -		mutex_lock(&psr->lock);
> -
> +	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
> +					    new_crtc_state, i) {
>  		/*
> -		 * Reasons to disable:
> -		 * - PSR disabled in new state
> -		 * - All planes will go inactive
> -		 * - Changing between PSR versions
> +		 * Check if encoder exists in new state and disable
> +		 * psr if it doesn't. Otherwise we will end update
> +		 * having all planes disabled and psr enabled which
> +		 * seems to be causing problems.
>  		 */
> -		needs_to_disable |= intel_crtc_needs_modeset(crtc_state);
> -		needs_to_disable |= !crtc_state->has_psr;
> -		needs_to_disable |= !crtc_state->active_planes;
> -		needs_to_disable |= crtc_state->has_psr2 != psr->psr2_enabled;
> +		if (old_crtc_state->uapi.encoder_mask != new_crtc_state->uapi.encoder_mask) {
> +			for_each_intel_encoder_mask_with_psr(state->base.dev, encoder,
> +							     old_crtc_state->uapi.encoder_mask) {
> +				intel_dp = enc_to_intel_dp(encoder);
> +				psr = &intel_dp->psr;
>  
> -		if (psr->enabled && needs_to_disable)
> -			intel_psr_disable_locked(intel_dp);
> +				if (new_crtc_state->uapi.encoder_mask &
> +				    drm_encoder_mask(&(encoder)->base))
> +					continue;
>  
> -		mutex_unlock(&psr->lock);
> +				mutex_lock(&psr->lock);
> +
> +				if (psr->enabled)
> +					intel_psr_disable_locked(intel_dp);
> +
> +				mutex_unlock(&psr->lock);
> +			}
> +		}
> +		for_each_intel_encoder_mask_with_psr(state->base.dev, encoder,
> +						     new_crtc_state->uapi.encoder_mask) {
> +			bool needs_to_disable = false;
> +
> +			intel_dp = enc_to_intel_dp(encoder);
> +			psr = &intel_dp->psr;
> +
> +			mutex_lock(&psr->lock);
> +
> +			/*
> +			 * Reasons to disable:
> +			 * - PSR disabled in new state
> +			 * - All planes will go inactive
> +			 * - Changing between PSR versions
> +			 */
> +			needs_to_disable |= intel_crtc_needs_modeset(new_crtc_state);
> +			needs_to_disable |= !new_crtc_state->has_psr;
> +			needs_to_disable |= !new_crtc_state->active_planes;
> +			needs_to_disable |= new_crtc_state->has_psr2 != psr->psr2_enabled;
> +
> +			if (psr->enabled && needs_to_disable)
> +				intel_psr_disable_locked(intel_dp);
> +
> +			mutex_unlock(&psr->lock);
> +		}
>  	}
>  }

Looks correct to me, the only thing that we could probable unite both for_each_intel_encoder_mask_with_psr
cycles and also then get rid of if (old_crtc_state->uapi.encoder_mask != new_crtc_state->uapi.encoder_mask) check by
doing something like:

old_new_encoder_mask = old_crtc_state->uapi.encoder_mask |  new_crtc_state->uapi.encoder_mask;

for_each_intel_encoder_mask_with_psr(state->base.dev, encoder, old_new_encoder_mask) {
	bool needs_to_disable = false;

	intel_dp = enc_to_intel_dp(encoder);

	psr = &intel_dp->psr;

	mutex_lock(&psr->lock);

        needs_to_disable |= intel_crtc_needs_modeset(new_crtc_state);        
        needs_to_disable |= !new_crtc_state->has_psr;
        needs_to_disable |= !new_crtc_state->active_planes;
        needs_to_disable |= new_crtc_state->has_psr2 != psr->psr2_enabled;

	/* Check if this encoder isn't present in new mask */
        needs_to_disable |= !(new_crtc_state->uapi.encoder_mask & drm_encoder_mask(&(encoder)->base));

	if (psr->enabled && needs_to_disable)
		 intel_psr_disable_locked(intel_dp);

	mutex_unlock(&psr_lock);
}

So basically we make non-presence of the encoder in new mask to be just one more check
for needs_to_disable and have a single place where we turn it off..

Stan

>  
> -- 
> 2.25.1
>