Re: [Intel-gfx] [PATCH 1/2] drm/i915: Check lane count when determining FEC support

[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>
>
> ICL doesn't support FEC with a x1 DP link. Make sure
> we don't try to enable FEC in such cases.

The question is, should we rather require x2 link for FEC?

I suppose x1 link with DSC+FEC is an unlikely scenario with our current
link bandwidth policy, so probably not a big deal.

BR,
Jani.

>
> Requires a bit of reordering to make sure we've computed lane_count
> before checking it.
>
> 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 | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 55ba6eeaa810..2cde8ac513bb 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1363,7 +1363,8 @@ static bool intel_dp_source_supports_fec(struct intel_dp *intel_dp,
>  	if (DISPLAY_VER(dev_priv) >= 12)
>  		return true;
>  
> -	if (DISPLAY_VER(dev_priv) == 11 && encoder->port != PORT_A)
> +	if (DISPLAY_VER(dev_priv) == 11 &&
> +	    encoder->port != PORT_A && pipe_config->lane_count != 1)
>  		return true;
>  
>  	return false;
> @@ -2105,15 +2106,6 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
>  		&pipe_config->hw.adjusted_mode;
>  	int ret;
>  
> -	pipe_config->fec_enable = !intel_dp_is_edp(intel_dp) &&
> -		intel_dp_supports_fec(intel_dp, pipe_config);
> -
> -	if (!intel_dp_supports_dsc(intel_dp, pipe_config))
> -		return -EINVAL;
> -
> -	if (!intel_dp_dsc_supports_format(intel_dp, pipe_config->output_format))
> -		return -EINVAL;
> -
>  	/*
>  	 * compute pipe bpp is set to false for DP MST DSC case
>  	 * and compressed_bpp is calculated same time once
> @@ -2134,6 +2126,15 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
>  		}
>  	}
>  
> +	pipe_config->fec_enable = !intel_dp_is_edp(intel_dp) &&
> +		intel_dp_supports_fec(intel_dp, pipe_config);
> +
> +	if (!intel_dp_supports_dsc(intel_dp, pipe_config))
> +		return -EINVAL;
> +
> +	if (!intel_dp_dsc_supports_format(intel_dp, pipe_config->output_format))
> +		return -EINVAL;
> +
>  	/* Calculate Slice count */
>  	if (intel_dp_is_edp(intel_dp)) {
>  		pipe_config->dsc.slice_count =

-- 
Jani Nikula, Intel