drm/bridge: analogix_dp: Improve panel on time

In order to reduce the time required to turn on the panel, this patch
makes 2 assumptions:
1- In detect(): if there's a panel, we're connected.
2- In get_modes(): if there's a panel, let the panel driver decide if
   it should prepare/unprepare in order to get the modes.

The first is straightforward, and shouldn't need further explanation. The
second should eliminate the prepare/unprepare delays from get_modes() in
most cases, since panels generally hardcode their modes in the driver as
opposed to reading EDID. If a panel does need to read EDID, it should be
responsible for ensuring it's in a state in which it can.
Signed-off-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/bridge/analogix/analogix_dp_core.c

@@ -924,15 +924,15 @@ int analogix_dp_get_modes(struct drm_connector *connector)
 	struct edid *edid;
 	int ret, num_modes = 0;
 
-	ret = analogix_dp_prepare_panel(dp, true, false);
-	if (ret) {
-		DRM_ERROR("Failed to prepare panel (%d)\n", ret);
-		return 0;
-	}
-
 	if (dp->plat_data->panel) {
 		num_modes += drm_panel_get_modes(dp->plat_data->panel);
 	} else {
+		ret = analogix_dp_prepare_panel(dp, true, false);
+		if (ret) {
+			DRM_ERROR("Failed to prepare panel (%d)\n", ret);
+			return 0;
+		}
+
 		edid = drm_get_edid(connector, &dp->aux.ddc);
 		if (edid) {
 			drm_mode_connector_update_edid_property(&dp->connector,
@@ -940,15 +940,15 @@ int analogix_dp_get_modes(struct drm_connector *connector)
 			num_modes += drm_add_edid_modes(&dp->connector, edid);
 			kfree(edid);
 		}
+
+		ret = analogix_dp_prepare_panel(dp, false, false);
+		if (ret)
+			DRM_ERROR("Failed to unprepare panel (%d)\n", ret);
 	}
 
 	if (dp->plat_data->get_modes)
 		num_modes += dp->plat_data->get_modes(dp->plat_data, connector);
 
-	ret = analogix_dp_prepare_panel(dp, false, false);
-	if (ret)
-		DRM_ERROR("Failed to unprepare panel (%d)\n", ret);
-
 	return num_modes;
 }
 
@@ -972,6 +972,9 @@ analogix_dp_detect(struct drm_connector *connector, bool force)
 	enum drm_connector_status status = connector_status_disconnected;
 	int ret;
 
+	if (dp->plat_data->panel)
+		return connector_status_connected;
+
 	ret = analogix_dp_prepare_panel(dp, true, false);
 	if (ret) {
 		DRM_ERROR("Failed to prepare panel (%d)\n", ret);