Re: [Intel-gfx] [PATCH 15/20] drm/i915/fbc: Disable FBC fully on FIFO underrun

["Kahola, Mika" <mika.kahola@intel.com>]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces@lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: Wednesday, November 24, 2021 1:37 PM
> To: intel-gfx@lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH 15/20] drm/i915/fbc: Disable FBC fully on FIFO
> underrun
> 
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Currently a FIFO underrun just causes FBC to be deactivated, and later checks
> then prevent it from being reactivated. We can simpify our lives a bit by logically
> disabling FBC on FIFO underruna. This avoids the funny intermediate state where
> FBC is logically enabled but can't actually be activated.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Mika Kahola <mika.kahola@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_fbc.c | 29 +++++++-----------------
>  1 file changed, 8 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c
> b/drivers/gpu/drm/i915/display/intel_fbc.c
> index 616ab95766b2..74ba54d70e57 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> @@ -994,16 +994,6 @@ static bool intel_fbc_cfb_size_changed(struct intel_fbc
> *fbc)
>  	return fbc->state_cache.cfb_size > fbc->compressed_fb.size * fbc-
> >limit;  }
> 
> -static bool intel_fbc_can_enable(struct intel_fbc *fbc) -{
> -	if (fbc->underrun_detected) {
> -		fbc->no_fbc_reason = "underrun detected";
> -		return false;
> -	}
> -
> -	return true;
> -}
> -
>  static int intel_fbc_check_plane(struct intel_atomic_state *state,
>  				 struct intel_plane *plane)
>  {
> @@ -1123,22 +1113,11 @@ static bool intel_fbc_can_activate(struct intel_fbc
> *fbc)
>  	struct drm_i915_private *i915 = fbc->i915;
>  	struct intel_fbc_state *cache = &fbc->state_cache;
> 
> -	if (!intel_fbc_can_enable(fbc))
> -		return false;
> -
>  	if (cache->no_fbc_reason) {
>  		fbc->no_fbc_reason = cache->no_fbc_reason;
>  		return false;
>  	}
> 
> -	/* We don't need to use a state cache here since this information is
> -	 * global for all CRTC.
> -	 */
> -	if (fbc->underrun_detected) {
> -		fbc->no_fbc_reason = "underrun detected";
> -		return false;
> -	}
> -
>  	/* The use of a CPU fence is one of two ways to detect writes by the
>  	 * CPU to the scanout and trigger updates to the FBC.
>  	 *
> @@ -1467,6 +1446,11 @@ static void __intel_fbc_enable(struct
> intel_atomic_state *state,
>  	if (cache->no_fbc_reason)
>  		return;
> 
> +	if (fbc->underrun_detected) {
> +		fbc->no_fbc_reason = "FIFO underrun";
> +		return;
> +	}
> +
>  	if (intel_fbc_alloc_cfb(fbc, intel_fbc_cfb_size(plane_state), min_limit)) {
>  		fbc->no_fbc_reason = "not enough stolen memory";
>  		return;
> @@ -1567,6 +1551,9 @@ static void intel_fbc_underrun_work_fn(struct
> work_struct *work)
>  	fbc->underrun_detected = true;
> 
>  	intel_fbc_deactivate(fbc, "FIFO underrun");
> +	if (!fbc->flip_pending)
> +		intel_wait_for_vblank(i915, fbc->plane->pipe);
> +	__intel_fbc_disable(fbc);
>  out:
>  	mutex_unlock(&fbc->lock);
>  }
> --
> 2.32.0