Re: [Intel-gfx] [v4 1/2] drm/i915/display/tgl: Disable FBC with PSR2

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

On Tue, 2020-12-01 at 20:00 +0530, Uma Shankar wrote:
> There are some corner cases wrt underrun when we enable
> FBC with PSR2 on TGL. Recommendation from hardware is to
> keep this combination disabled.
> 
> Bspec: 50422 HSD: 14010260002
> 
> v2: Added psr2 enabled check from crtc_state (Anshuman)
> Added Bspec link and HSD referneces (Jose)
> 
> v3: Moved the logic to disable fbc to intel_fbc_update_state_cache
> and removed the crtc->config usages, as per Ville's recommendation.
> 
> v4: Introduced a variable in fbc state_cache instead of the earlier
> plane.visible WA, as suggested by Jose.
> 
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_fbc.c | 29 ++++++++++++++++++++++++
>  drivers/gpu/drm/i915/i915_drv.h          |  1 +
>  2 files changed, 30 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
> index a5b072816a7b..ff2f2c00a10e 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> @@ -700,7 +700,21 @@ static void intel_fbc_update_state_cache(struct intel_crtc *crtc,
>  	struct intel_fbc_state_cache *cache = &fbc->state_cache;
>  	struct drm_framebuffer *fb = plane_state->hw.fb;
>  
> 
> 
> 
> +	if (crtc_state->has_psr2)
> +		cache->psr2_active = true;
> +	else
> +		cache->psr2_active = false;

cache->psr2_active = crtc_state->has_psr2;


> +
> +	/*
> +	 * Tigerlake is not supporting FBC with PSR2.
> +	 * Recommendation is to keep this combination disabled
> +	 * Bspec: 50422 HSD: 14010260002
> +	 */
> +	if (IS_TIGERLAKE(dev_priv) && cache->psr2_active)
> +		return;


Here you should only set psr2_active, add it to the bottom of intel_fbc_update_state_cache.
The check should only be done in intel_fbc_can_activate().

> +
>  	cache->plane.visible = plane_state->uapi.visible;
> +
>  	if (!cache->plane.visible)
>  		return;
>  
> 
> 
> 
> 
> 
> 
> 
> @@ -799,6 +813,16 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
>  	struct intel_fbc *fbc = &dev_priv->fbc;
>  	struct intel_fbc_state_cache *cache = &fbc->state_cache;
>  
> 
> 
> 
> 
> 
> 
> 
> +	/*
> +	 * Tigerlake is not supporting FBC with PSR2.
> +	 * Recommendation is to keep this combination disabled
> +	 * Bspec: 50422 HSD: 14010260002
> +	 */
> +	if (fbc->state_cache.psr2_active && IS_TIGERLAKE(dev_priv)) {
> +		fbc->no_fbc_reason = "not supported with PSR2";
> +		return false;
> +	}
> +
>  	if (!intel_fbc_can_enable(dev_priv))
>  		return false;
>  
> 
> 
> 
> 
> 
> 
> 
> @@ -1273,6 +1297,11 @@ void intel_fbc_enable(struct intel_atomic_state *state,
>  	if (!cache->plane.visible)
>  		goto out;
>  
> 
> 
> 
> 
> 
> 
> 
> +	if (fbc->state_cache.psr2_active && IS_TIGERLAKE(dev_priv)) {
> +		fbc->no_fbc_reason = "not supported with PSR2";
> +		goto out;
> +	}
> +
>  	if (intel_fbc_alloc_cfb(dev_priv,
>  				intel_fbc_calculate_cfb_size(dev_priv, cache),
>  				plane_state->hw.fb->format->cpp[0])) {
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 15be8debae54..f4e08c1a5867 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -416,6 +416,7 @@ struct intel_fbc {
>  		u16 gen9_wa_cfb_stride;
>  		u16 interval;
>  		s8 fence_id;
> +		bool psr2_active;
>  	} state_cache;
>  
> 
> 
> 
> 
> 
> 
> 
>  	/*

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