drm/panel: Add an API to allow drm to set orientation from panel

Panels usually call drm_connector_set_panel_orientation(), which is
later than drm/kms driver calling drm_dev_register(). This leads to a
WARN().

The orientation property is known earlier. For example, some panels
parse the property through device tree during probe.

Add an API to return the property from panel to drm/kms driver, so the
drivers are able to call drm_connector_set_orientation_from_panel() before
drm_dev_register().
Suggested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
[dianders: removed space before tab]
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220609072722.3488207-2-hsinyi@chromium.org

drivers/gpu/drm/drm_connector.c

@@ -24,6 +24,7 @@
 #include <drm/drm_connector.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_encoder.h>
+#include <drm/drm_panel.h>
 #include <drm/drm_utils.h>
 #include <drm/drm_print.h>
 #include <drm/drm_drv.h>
@@ -2320,6 +2321,9 @@ EXPORT_SYMBOL(drm_connector_set_vrr_capable_property);
  * It is allowed to call this function with a panel_orientation of
  * DRM_MODE_PANEL_ORIENTATION_UNKNOWN, in which case it is a no-op.
  *
+ * The function shouldn't be called in panel after drm is registered (i.e.
+ * drm_dev_register() is called in drm).
+ *
  * Returns:
  * Zero on success, negative errno on failure.
  */
@@ -2389,6 +2393,33 @@ int drm_connector_set_panel_orientation_with_quirk(
 }
 EXPORT_SYMBOL(drm_connector_set_panel_orientation_with_quirk);
 
+/**
+ * drm_connector_set_orientation_from_panel -
+ *	set the connector's panel_orientation from panel's callback.
+ * @connector: connector for which to init the panel-orientation property.
+ * @panel: panel that can provide orientation information.
+ *
+ * Drm drivers should call this function before drm_dev_register().
+ * Orientation is obtained from panel's .get_orientation() callback.
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_connector_set_orientation_from_panel(
+	struct drm_connector *connector,
+	struct drm_panel *panel)
+{
+	enum drm_panel_orientation orientation;
+
+	if (panel && panel->funcs && panel->funcs->get_orientation)
+		orientation = panel->funcs->get_orientation(panel);
+	else
+		orientation = DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
+
+	return drm_connector_set_panel_orientation(connector, orientation);
+}
+EXPORT_SYMBOL(drm_connector_set_orientation_from_panel);
+
 static const struct drm_prop_enum_list privacy_screen_enum[] = {
 	{ PRIVACY_SCREEN_DISABLED,		"Disabled" },
 	{ PRIVACY_SCREEN_ENABLED,		"Enabled" },

include/drm/drm_connector.h

@@ -38,6 +38,7 @@ struct drm_modeset_acquire_ctx;
 struct drm_device;
 struct drm_crtc;
 struct drm_encoder;
+struct drm_panel;
 struct drm_property;
 struct drm_property_blob;
 struct drm_printer;
@@ -1802,6 +1803,9 @@ int drm_connector_set_panel_orientation_with_quirk(
 	struct drm_connector *connector,
 	enum drm_panel_orientation panel_orientation,
 	int width, int height);
+int drm_connector_set_orientation_from_panel(
+	struct drm_connector *connector,
+	struct drm_panel *panel);
 int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
 					  int min, int max);
 void drm_connector_create_privacy_screen_properties(struct drm_connector *conn);

include/drm/drm_panel.h

@@ -116,6 +116,15 @@ struct drm_panel_funcs {
 	int (*get_modes)(struct drm_panel *panel,
 			 struct drm_connector *connector);
 
+	/**
+	 * @get_orientation:
+	 *
+	 * Return the panel orientation set by device tree or EDID.
+	 *
+	 * This function is optional.
+	 */
+	enum drm_panel_orientation (*get_orientation)(struct drm_panel *panel);
+
 	/**
 	 * @get_timings:
 	 *