On Thu, Jan 20, 2022 at 04:16:11PM +0100, Maxime Ripard wrote:
> The current code, when parsing the EDID Deep Color depths, that the
> YUV422 cannot be used, referring to the HDMI 1.3 Specification.
>
> This specification, in its section 6.2.4, indeed states:
>
> For each supported Deep Color mode, RGB 4:4:4 shall be supported and
> optionally YCBCR 4:4:4 may be supported.
>
> YCBCR 4:2:2 is not permitted for any Deep Color mode.
>
> This indeed can be interpreted like the code does, but the HDMI 1.4
> specification further clarifies that statement in its section 6.2.4:
>
> For each supported Deep Color mode, RGB 4:4:4 shall be supported and
> optionally YCBCR 4:4:4 may be supported.
>
> YCBCR 4:2:2 is also 36-bit mode but does not require the further use
> of the Deep Color modes described in section 6.5.2 and 6.5.3.
>
> This means that, even though YUV422 can be used with 12 bit per color,
> it shouldn't be treated as a deep color mode.
>
> This is also broken with YUV444 if it's supported by the display, but
> DRM_EDID_HDMI_DC_Y444 isn't set. In such a case, the code will clear
> color_formats of the YUV444 support set previously in
> drm_parse_cea_ext(), but will not set it back.
>
> Since the formats supported are already setup properly in
> drm_parse_cea_ext(), let's just remove the code modifying the formats in
> drm_parse_hdmi_deep_color_info()
>
> Fixes: d0c94692e0a3 ("drm/edid: Parse and handle HDMI deep color modes.")
> Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_edid.c | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 13644dd579b4..5085ef08c22d 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -5104,16 +5104,8 @@ static void drm_parse_hdmi_deep_color_info(struct drm_connector *connector,
> connector->name, dc_bpc);
> info->bpc = dc_bpc;
>
> - /*
> - * Deep color support mandates RGB444 support for all video
> - * modes and forbids YCRCB422 support for all video modes per
> - * HDMI 1.3 spec.
> - */
> - info->color_formats = DRM_COLOR_FORMAT_RGB444;
> -
> /* YCRCB444 is optional according to spec. */
> if (hdmi[6] & DRM_EDID_HDMI_DC_Y444) {
> - info->color_formats |= DRM_COLOR_FORMAT_YCRCB444;
> DRM_DEBUG("%s: HDMI sink does YCRCB444 in deep color.\n",
> connector->name);
> }
> --
> 2.34.1
--
Ville Syrjälä
Intel
