[PATCH 2/2] drm/i915/dp: Add checking of YCBCR420 Pass-through to YCBCR420 outputs.

[Ville Syrjälä]

On Mon, Feb 03, 2020 at 02:04:21PM +0200, Gwan-gyeong Mun wrote:
> When a DP downstream uses a DP to HDMI active converter, the active
> converter needs to support YCbCr420 Pass-through to enable DP YCbCr 4:2:0
> outputs.
> 
> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 26 +++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index f4dede6253f8..824ed8096426 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2298,6 +2298,22 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  	return 0;
>  }
>  
> +static bool
> +intel_dp_downstream_is_hdmi_detailed_cap_info(struct intel_dp *intel_dp)
> +{
> +	int type = intel_dp->downstream_ports[0] & DP_DS_PORT_TYPE_MASK;
> +	bool detailed_cap_info = intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
> +				 DP_DETAILED_CAP_INFO_AVAILABLE;
> +
> +	return type == DP_DS_PORT_TYPE_HDMI && detailed_cap_info;

This looks a bit incomplete, and should really be in the core. I have a
bunch of stuff for DFPs sitting in a branch. I'll just post the whole
thing...

> +}
> +
> +static bool
> +intel_dp_downstream_supports_ycbcr_420_passthru(struct intel_dp *intel_dp)
> +{
> +	return intel_dp->downstream_ports[3] & DP_DS_YCBCR420_PASSTHRU_SUPPORT;
> +}
> +
>  static int
>  intel_dp_ycbcr420_config(struct intel_dp *intel_dp,
>  			 struct drm_connector *connector,
> @@ -2314,6 +2330,16 @@ intel_dp_ycbcr420_config(struct intel_dp *intel_dp,
>  	    !connector->ycbcr_420_allowed)
>  		return 0;
>  
> +	/*
> +	 * When a DP downstream uses a DP to HDMI active converter,
> +	 * the active converter needs to support YCbCr420 Pass-through.
> +	 */
> +	if (drm_dp_is_branch(intel_dp->dpcd)) {
> +		if (intel_dp_downstream_is_hdmi_detailed_cap_info(intel_dp) &&
> +		    !intel_dp_downstream_supports_ycbcr_420_passthru(intel_dp))
> +			return 0;
> +	}
> +
>  	crtc_state->output_format = INTEL_OUTPUT_FORMAT_YCBCR420;
>  
>  	/* YCBCR 420 output conversion needs a scaler */
> -- 
> 2.24.1
> 
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-- 
Ville Syrjälä
Intel