Re: [Intel-gfx] [PATCH 2/2] drm/i915: Require FEC for DSC on DP-MST

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 13 Sep 2023, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The current check just asserts that we need FEC to use DSC
> with (non-eDP) DP-SST. But MST also needs FEC for DSC. Just
> check for !eDP instead to cover all the cases correctly.

128b/132b won't have crtc->fec_enable set, as it's part of channel
encoding. We don't need to explicitly enable it in hardware, the
128b/132b bandwidth computations take it into account in the equation,
but we can't skip DSC based on !crtc_state->fec_enable either.

BR,
Jani.


>
> Cc: Luca Coelho <luciano.coelho@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 2cde8ac513bb..41f180f2879e 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1380,7 +1380,7 @@ static bool intel_dp_supports_fec(struct intel_dp *intel_dp,
>  static bool intel_dp_supports_dsc(struct intel_dp *intel_dp,
>  				  const struct intel_crtc_state *crtc_state)
>  {
> -	if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP) && !crtc_state->fec_enable)
> +	if (!intel_dp_is_edp(intel_dp) && !crtc_state->fec_enable)
>  		return false;
>  
>  	return intel_dsc_source_support(crtc_state) &&

-- 
Jani Nikula, Intel