[PATCH] drm: bridge: dw_hdmi: fix preference of RGB modes over YUV420

[PATCH] drm: bridge: dw_hdmi: fix preference of RGB modes over YUV420

[Guillaume BRUN]

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>
---
 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 40d8ca37f5bc..aa51c61a78c7 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -2720,6 +2720,9 @@ 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_YCBCR444)
 			output_fmts[i++] = MEDIA_BUS_FMT_YUV16_1X48;
@@ -2753,9 +2756,6 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
 	if (info->color_formats & DRM_COLOR_FORMAT_YCBCR444)
 		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;
-- 
2.37.3


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Re: [PATCH] drm: bridge: dw_hdmi: fix preference of RGB modes over YUV420

[Robert Foss]

On Wed, 16 Nov 2022 at 15:35, Guillaume BRUN <the.cheaterman@gmail.com> wrote:
>
> 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>
> ---
>  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 40d8ca37f5bc..aa51c61a78c7 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -2720,6 +2720,9 @@ 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_YCBCR444)
>                         output_fmts[i++] = MEDIA_BUS_FMT_YUV16_1X48;
> @@ -2753,9 +2756,6 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
>         if (info->color_formats & DRM_COLOR_FORMAT_YCBCR444)
>                 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;
> --
> 2.37.3
>

Reviewed-by: Robert Foss <robert.foss@linaro.org>

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Re: [PATCH] drm: bridge: dw_hdmi: fix preference of RGB modes over YUV420

[Neil Armstrong]

Hi,

On Wed, 16 Nov 2022 15:35:23 +0100, Guillaume BRUN wrote:
> 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.
> 
> [...]

Thanks, Applied to https://anongit.freedesktop.org/git/drm/drm-misc.git (drm-misc-fixes)

[1/1] drm: bridge: dw_hdmi: fix preference of RGB modes over YUV420
      https://cgit.freedesktop.org/drm/drm-misc/commit/?id=d3d6b1bf85aefe0ebc0624574b3bb62f0693914c

-- 
Neil

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