[Intel-gfx] [PATCH 20/20] drm/i915/dp: Disable DFP RGB->YCbCr conversion for now

[Nautiyal, Ankit K]

On 10/15/2021 7:09 PM, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> We lack sufficient state tracking to figure out whether
> we want the DFP to perform the RGB->YCbCr conversion for us
> or not. So currently we are blindly just enabling that all the
> time when supported by the DFP. That is nonsense. So until
> we imporve our state tracking for this just disable the feature.
>
> Cc: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> Cc: Uma Shankar <uma.shankar at intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_dp.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 29b12456c461..3e2a29b589a9 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1107,6 +1107,7 @@ static bool intel_dp_supports_dsc(struct intel_dp *intel_dp,
>   static bool intel_dp_is_ycbcr420(struct intel_dp *intel_dp,
>   				 const struct intel_crtc_state *crtc_state)
>   {
> +	/* FIXME see intel_dp_update_420() regarding rgb_to_ycbcr */
>   	return crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420 ||
>   		(crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444 &&
>   		 intel_dp->dfp.ycbcr_444_to_420);
> @@ -2456,6 +2457,7 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
>   			    "Failed to %s protocol converter YCbCr 4:2:0 conversion mode\n",
>   			    enabledisable(intel_dp->dfp.ycbcr_444_to_420));
>   
> +	/* FIXME see intel_dp_update_420() regarding rgb_to_ycbcr */
>   	tmp = intel_dp->dfp.rgb_to_ycbcr ?
>   		DP_CONVERSION_BT709_RGB_YCBCR_ENABLE : 0;
>   
> @@ -4261,6 +4263,14 @@ intel_dp_update_420(struct intel_dp *intel_dp)
>   	rgb_to_ycbcr = drm_dp_downstream_rgb_to_ycbcr_conversion(intel_dp->dpcd,
>   								 intel_dp->downstream_ports,
>   								 DP_DS_HDMI_BT709_RGB_YCBCR_CONV);
> +	/*
> +	 * FIXME need to actually track whether we're really
> +	 * going to be doing the RGB->YCbCr connversion or not.
> +	 * We can't tell by simply looking at intel_dp->dfp.rgb_to_ycbcr.
> +	 * Readout is going to annoying due to having to read that
> +	 * state from external hardware that may vanish at any time :(
> +	 */


Hmm right. Do you have any suggestion what should be the better place 
for defining the policy for using DFPs CSC or use our own HW, in case of 
YCbCr 420 output?

Also, IIUC, this might need consideration for higher modes with DSC1.1 
H/w that do not support compression for YCbCr420.

In that case we might need to either use RGB compressed output and ask 
for DFPs CSC for conversion to 444 and then down sampling to 420.

Regards,

Ankit

> +	rgb_to_ycbcr = false;
>   
>   	if (DISPLAY_VER(i915) >= 11) {
>   		/* Let PCON convert from RGB->YCbCr if possible */