[PATCH 5.10 073/106] drm: bridge: dw_hdmi: fix preference of RGB modes over YUV420

Greg Kroah-Hartman
2022-12-12T13:16:27Z

From: Guillaume BRUN <the.cheaterman@gmail.com>

[ Upstream commit d3d6b1bf85aefe0ebc0624574b3bb62f0693914c ]

Cheap monitors sometimes advertise YUV modes they don't really have
(HDMI specification mandates YUV support so even monitors without actual
support will often wrongfully advertise it) which results in YUV matches
and user forum complaints of a red tint to light colour display areas in
common desktop environments.

Moving the default RGB fall-back before YUV selection results in RGB
mode matching in most cases, reducing complaints.

Fixes: 6c3c719936da ("drm/bridge: synopsys: dw-hdmi: add bus format negociation")
Signed-off-by: Guillaume BRUN <the.cheaterman@gmail.com>
Tested-by: Christian Hewitt <christianshewitt@gmail.com>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221116143523.2126-1-the.cheaterman@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 356c7d0bd035..2c3c743df950 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -2609,6 +2609,9 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
* if supported. In any case the default RGB888 format is added
*/

+ /* Default 8bit RGB fallback */
+ output_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
+
if (max_bpc >= 16 && info->bpc == 16) {
if (info->color_formats & DRM_COLOR_FORMAT_YCRCB444)
output_fmts[i++] = MEDIA_BUS_FMT_YUV16_1X48;
@@ -2642,9 +2645,6 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
if (info->color_formats & DRM_COLOR_FORMAT_YCRCB444)
output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;

- /* Default 8bit RGB fallback */
- output_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
-
*num_output_fmts = i;

return output_fmts;
--
2.35.1