drm/bridge-connector: reset the HDMI connector state

On HDMI connectors which use drm_bridge_connector and DRM_BRIDGE_OP_HDMI
IGT chokes on the max_bpc property in several kms_properties tests due
to the drm_bridge_connector failing to reset HDMI-related
properties.

Call __drm_atomic_helper_connector_hdmi_reset() if the
drm_bridge_connector has bridge_hdmi.

It is impossible to call this function from HDMI bridges, none of the
bridge callbacks correspond to the drm_connector_funcs::reset().

Fixes: 6b4468b ("drm/bridge-connector: implement glue code for HDMI connector")
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240903-drm-bridge-connector-fix-hdmi-reset-v5-3-daebde6d9857@linaro.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

drivers/gpu/drm/display/Kconfig

@@ -15,6 +15,7 @@ if DRM_DISPLAY_HELPER
 
 config DRM_BRIDGE_CONNECTOR
 	bool
+	select DRM_DISPLAY_HDMI_STATE_HELPER
 	help
 	  DRM connector implementation terminating DRM bridge chains.
 

drivers/gpu/drm/display/drm_bridge_connector.c

@@ -216,8 +216,19 @@ static void drm_bridge_connector_debugfs_init(struct drm_connector *connector,
 	}
 }
 
+static void drm_bridge_connector_reset(struct drm_connector *connector)
+{
+	struct drm_bridge_connector *bridge_connector =
+		to_drm_bridge_connector(connector);
+
+	drm_atomic_helper_connector_reset(connector);
+	if (bridge_connector->bridge_hdmi)
+		__drm_atomic_helper_connector_hdmi_reset(connector,
+							 connector->state);
+}
+
 static const struct drm_connector_funcs drm_bridge_connector_funcs = {
-	.reset = drm_atomic_helper_connector_reset,
+	.reset = drm_bridge_connector_reset,
 	.detect = drm_bridge_connector_detect,
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,