[PATCH v2 18/21] drm/amd/display: Fallback to 2020_YCBCR if the pixel encoding is not RGB

[Sebastian Wick]

A new property to control YCC and subsampling would be the more
complete path here. If we actually want to fix this in the short-term
though, we should handle the YCC and RGB Colorspace values as
equivalent, everywhere. Technically we're breaking the user space API
here so it should be documented on the KMS property and other drivers
must be adjusted accordingly as well.

On Fri, Jan 13, 2023 at 5:26 PM Harry Wentland <harry.wentland at amd.com> wrote:
>
> From: Joshua Ashton <joshua at froggi.es>
>
> Userspace might not aware whether we're sending RGB or YCbCr
> data to the display. If COLOR_SPACE_2020_RGB_FULLRANGE is
> requested but the output encoding is YCbCr we should
> send COLOR_SPACE_2020_YCBCR.
>
> Signed-off-by: Joshua Ashton <joshua at froggi.es>
> Signed-off-by: Harry Wentland <harry.wentland at amd.com>
> Cc: Pekka Paalanen <ppaalanen at gmail.com>
> Cc: Sebastian Wick <sebastian.wick at redhat.com>
> Cc: Vitaly.Prosyak at amd.com
> Cc: Joshua Ashton <joshua at froggi.es>
> Cc: dri-devel at lists.freedesktop.org
> Cc: amd-gfx at lists.freedesktop.org
> Reviewed-by: Harry Wentland <harry.wentland at amd.com>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> 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 f74b125af31f..16940ea61b59 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -5184,7 +5184,10 @@ get_output_color_space(const struct dc_crtc_timing *dc_crtc_timing,
>                 color_space = COLOR_SPACE_ADOBERGB;
>                 break;
>         case DRM_MODE_COLORIMETRY_BT2020_RGB:
> -               color_space = COLOR_SPACE_2020_RGB_FULLRANGE;
> +               if (dc_crtc_timing->pixel_encoding == PIXEL_ENCODING_RGB)
> +                       color_space = COLOR_SPACE_2020_RGB_FULLRANGE;
> +               else
> +                       color_space = COLOR_SPACE_2020_YCBCR;
>                 break;
>         case DRM_MODE_COLORIMETRY_BT2020_YCC:
>                 color_space = COLOR_SPACE_2020_YCBCR;
> --
> 2.39.0
>