Bridges having the DRM_BRIDGE_OP_HDMI flag set in drm_bridge->ops are
supposed to rely on drm_bridge->supported_formats bitmask to advertise
the supported colorspaces, including HDMI_COLORSPACE_YUV420.  Therefore,
the newly introduced drm_bridge->ycbcr_420_allowed flag becomes
redundant in this particular context.

Moreover, when drm_bridge_connector gets initialised, only
drm_bridge->ycbcr_420_allowed is considered in the process of adjusting
the equivalent property of the base drm_connector, which effectively
discards the formats advertised by the HDMI bridge.

Handle the inconsistency by ignoring ycbcr_420_allowed for HDMI bridges
and, instead, make use of the supported_formats bitmask when setting up
the bridge connector.

Fixes: 3ced1c687512 ("drm/display: bridge_connector: handle ycbcr_420_allowed")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
 drivers/gpu/drm/display/drm_bridge_connector.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index 320c297008aaa8b6ef5b1f4c71928849b202e8ac..b1bb937da85dbe1dcb1f5e5f621fb02647bcc793 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -414,7 +414,7 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 	drm_for_each_bridge_in_chain(encoder, bridge) {
 		if (!bridge->interlace_allowed)
 			connector->interlace_allowed = false;
-		if (!bridge->ycbcr_420_allowed)
+		if (!bridge->ycbcr_420_allowed && !(bridge->ops & DRM_BRIDGE_OP_HDMI))
 			connector->ycbcr_420_allowed = false;
 
 		if (bridge->ops & DRM_BRIDGE_OP_EDID)
@@ -436,6 +436,10 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 
 			if (bridge->supported_formats)
 				supported_formats = bridge->supported_formats;
+
+			if (!(bridge->supported_formats & HDMI_COLORSPACE_YUV420))
+				connector->ycbcr_420_allowed = false;
+
 			if (bridge->max_bpc)
 				max_bpc = bridge->max_bpc;
 		}

---
base-commit: f486c8aa16b8172f63bddc70116a0c897a7f3f02
change-id: 20241130-bridge-conn-fmt-prio-c517c1407ed5

On 11/30/24 1:13 AM, Cristian Ciocaltea wrote:
> Bridges having the DRM_BRIDGE_OP_HDMI flag set in drm_bridge->ops are
> supposed to rely on drm_bridge->supported_formats bitmask to advertise
> the supported colorspaces, including HDMI_COLORSPACE_YUV420.  Therefore,
> the newly introduced drm_bridge->ycbcr_420_allowed flag becomes
> redundant in this particular context.
> 
> Moreover, when drm_bridge_connector gets initialised, only
> drm_bridge->ycbcr_420_allowed is considered in the process of adjusting
> the equivalent property of the base drm_connector, which effectively
> discards the formats advertised by the HDMI bridge.
> 
> Handle the inconsistency by ignoring ycbcr_420_allowed for HDMI bridges
> and, instead, make use of the supported_formats bitmask when setting up
> the bridge connector.
> 
> Fixes: 3ced1c687512 ("drm/display: bridge_connector: handle ycbcr_420_allowed")

Please ignore this and check v2 instead:

https://lore.kernel.org/all/20241206-bridge-conn-fmt-prio-v2-1-85c817529b88@collabora.com/