drm/i915/dp: Configure PCON for conversion of output_format to YCbCr444

Handle the case with DP to HDMI PCON, where sink_format is set to YCbCr444.
In that case PCON is required to be configured to convert from given
output_format to YCbCR444.

v2: Drop drm_WARN for invalid case, let MISSING_CASE catch it. (Ville)
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230427125605.487769-4-ankit.k.nautiyal@intel.com

drivers/gpu/drm/i915/display/intel_dp.c

@@ -2923,6 +2923,17 @@ void intel_dp_configure_protocol_converter(struct intel_dp *intel_dp,
 			MISSING_CASE(crtc_state->output_format);
 			break;
 		}
+	} else if (crtc_state->sink_format == INTEL_OUTPUT_FORMAT_YCBCR444) {
+		switch (crtc_state->output_format) {
+		case INTEL_OUTPUT_FORMAT_YCBCR444:
+			break;
+		case INTEL_OUTPUT_FORMAT_RGB:
+			rgb_to_ycbcr = true;
+			break;
+		default:
+			MISSING_CASE(crtc_state->output_format);
+			break;
+		}
 	}
 
 	tmp = ycbcr444_to_420 ? DP_CONVERSION_TO_YCBCR420_ENABLE : 0;