[PATCH] drm/amd/display: Use pixel encoding 444 for dongle usb-c to hdmi

[Julien Isorce]

Fix pinkish color issue around grey areas. This also happens
when not using any dongle so directly with a usb-c to Display
Port cable. Meaning there is something wrong when using pixel
encoding RGB with amd driver in the general case. In the meantime
just use the same pixel encoding as when using HDMI without dongle.
This way users will see the same thing on 2 identical screens when
one is connected with hdmi-to-hdmi and the other is connected with
usb-c-to-hdmi.

Signed-off-by: Julien Isorce <jisorce at oblong.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index d3f404f097eb..8139dcc0bfba 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3313,6 +3313,7 @@ static void fill_stream_properties_from_drm_display_mode(
 {
 	struct dc_crtc_timing *timing_out = &stream->timing;
 	const struct drm_display_info *info = &connector->display_info;
+	const struct dc_link *link = stream->sink->link;
 
 	memset(timing_out, 0, sizeof(struct dc_crtc_timing));
 
@@ -3327,6 +3328,10 @@ static void fill_stream_properties_from_drm_display_mode(
 	else if ((connector->display_info.color_formats & DRM_COLOR_FORMAT_YCRCB444)
 			&& stream->signal == SIGNAL_TYPE_HDMI_TYPE_A)
 		timing_out->pixel_encoding = PIXEL_ENCODING_YCBCR444;
+	else if ((connector->display_info.color_formats & DRM_COLOR_FORMAT_YCRCB444)
+			&& stream->sink->sink_signal == SIGNAL_TYPE_DISPLAY_PORT
+			&& link->dpcd_caps.dongle_type == DISPLAY_DONGLE_DP_HDMI_CONVERTER)
+		timing_out->pixel_encoding = PIXEL_ENCODING_YCBCR444;
 	else
 		timing_out->pixel_encoding = PIXEL_ENCODING_RGB;
 
-- 
2.17.1