drm/amd/display: Filter out YCbCr420 timing if VSC SDP not supported

[Why]
Per DP specification, YCbCr420 shall use VSC SDP.

[How]
For YCbCr420 timings, fail DP mode timing validation
if DPCD caps do not indicate VSC SDP colorimetry
support.
Signed-off-by: George Shen <george.shen@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Wayne Lin <Wayne.Lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -2411,6 +2411,12 @@ bool dp_validate_mode_timing(
 
 	const struct dc_link_settings *link_setting;
 
+	/* According to spec, VSC SDP should be used if pixel format is YCbCr420 */
+	if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR420 &&
+			!link->dpcd_caps.dprx_feature.bits.VSC_SDP_COLORIMETRY_SUPPORTED &&
+			dal_graphics_object_id_get_connector_id(link->link_id) != CONNECTOR_ID_VIRTUAL)
+		return false;
+
 	/*always DP fail safe mode*/
 	if ((timing->pix_clk_100hz / 10) == (uint32_t) 25175 &&
 		timing->h_addressable == (uint32_t) 640 &&