drm/bridge: analogix_dp: Don't create useless connectors

If there is another bridge after analogix_dp, then the connector object
should not be created. This fixes following timeouts on Exynos5420-based
Chromebook2 Peach-PIT board during boot:

exynos-dp 145b0000.dp-controller: AUX CH cmd reply timeout!
exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
exynos-dp 145b0000.dp-controller: AUX CH enable timeout!
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180305085741.18896-4-m.szyprowski@samsung.com

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

@@ -1012,14 +1012,16 @@ static int analogix_dp_bridge_attach(struct drm_bridge *bridge)
 {
 	struct analogix_dp_device *dp = bridge->driver_private;
 	struct drm_encoder *encoder = dp->encoder;
-	struct drm_connector *connector = &dp->connector;
-	int ret;
+	struct drm_connector *connector = NULL;
+	int ret = 0;
 
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;
 	}
 
+	if (!dp->plat_data->skip_connector) {
+		connector = &dp->connector;
 		connector->polled = DRM_CONNECTOR_POLL_HPD;
 
 		ret = drm_connector_init(dp->drm_dev, connector,
@@ -1033,6 +1035,7 @@ static int analogix_dp_bridge_attach(struct drm_bridge *bridge)
 		drm_connector_helper_add(connector,
 					 &analogix_dp_connector_helper_funcs);
 		drm_mode_connector_attach_encoder(connector, encoder);
+	}
 
 	/*
 	 * NOTE: the connector registration is implemented in analogix

drivers/gpu/drm/exynos/exynos_dp.c

@@ -244,6 +244,7 @@ static int exynos_dp_probe(struct platform_device *pdev)
 
 	/* The remote port can be either a panel or a bridge */
 	dp->plat_data.panel = panel;
+	dp->plat_data.skip_connector = !!bridge;
 	dp->ptn_bridge = bridge;
 
 out:

include/drm/bridge/analogix_dp.h

@@ -31,6 +31,7 @@ struct analogix_dp_plat_data {
 	struct drm_panel *panel;
 	struct drm_encoder *encoder;
 	struct drm_connector *connector;
+	bool skip_connector;
 
 	int (*power_on)(struct analogix_dp_plat_data *);
 	int (*power_off)(struct analogix_dp_plat_data *);