[Intel-gfx] [PATCH v2] drm/i915: Fix inconsistance between pfit.enable and scaler freeing

[Ville Syrjälä]

On Fri, Jan 24, 2020 at 04:42:16PM +0200, Stanislav Lisovskiy wrote:
> Despite that during hw readout we seem to have scalers assigned
> to pipes, then call atomic_setup_scalers, at the commit stage in
> skl_update_scaler there is a check, that if we have fb src and
> dest of same size, we stage freeing of that scaler.
> 
> However we don't update pfit.enabled flag then, which makes
> the state inconsistent, which in turn triggers a WARN_ON
> in skl_pfit_enable, because we have pfit enabled,
> but no assigned scaler.
> 
> To me this looks weird that we kind of do the decision
> to use or not use the scaler at skl_update_scaler stage
> but not in intel_atomic_setup_scalers, moreover
> not updating the whole state consistently.
> 
> This fix is to not free the scaler if we have pfit.enabled
> flag set, so that the state is now consistent
> and the warnings are gone.
> 
> Bugzilla: https://gitlab.freedesktop.org/drm/intel/issues/577
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 5768cfcf71c4..23221b8d244d 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -5953,7 +5953,7 @@ skl_update_scaler(struct intel_crtc_state *crtc_state, bool force_detach,
>  	 * the 90/270 degree plane rotation cases (to match the
>  	 * GTT mapping), hence no need to account for rotation here.
>  	 */
> -	if (src_w != dst_w || src_h != dst_h)
> +	if (src_w != dst_w || src_h != dst_h || crtc_state->pch_pfit.enabled)

This is called for both pfit and planes. So you need to put
that pfit check into the pfit specific function.

>  		need_scaler = true;
>  
>  	/*
> -- 
> 2.24.1.485.gad05a3d8e5

-- 
Ville Syrjälä
Intel