drm/msm/dsi: Support NO_CONNECTOR bridges

For now, since we have a mix of bridges which support this flag, which
which do *not* support this flag, or work both ways, try it once with
NO_CONNECTOR and then fall back to the old way if that doesn't work.
Eventually we can drop the fallback path.

v2: Add missing drm_connector_attach_encoder() so display actually comes
    up when the bridge properly handles the NO_CONNECTOR flag
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210920225801.227211-2-robdclark@gmail.comSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/Kconfig

@@ -14,6 +14,8 @@ config DRM_MSM
 	select REGULATOR
 	select DRM_KMS_HELPER
 	select DRM_PANEL
+	select DRM_BRIDGE
+	select DRM_PANEL_BRIDGE
 	select DRM_SCHED
 	select SHMEM
 	select TMPFS

drivers/gpu/drm/msm/dsi/dsi_manager.c

@@ -3,6 +3,8 @@
  * Copyright (c) 2015, The Linux Foundation. All rights reserved.
  */
 
+#include "drm/drm_bridge_connector.h"
+
 #include "msm_kms.h"
 #include "dsi.h"
 
@@ -688,10 +690,10 @@ struct drm_connector *msm_dsi_manager_ext_bridge_init(u8 id)
 {
 	struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);
 	struct drm_device *dev = msm_dsi->dev;
+	struct drm_connector *connector;
 	struct drm_encoder *encoder;
 	struct drm_bridge *int_bridge, *ext_bridge;
-	struct drm_connector *connector;
-	struct list_head *connector_list;
+	int ret;
 
 	int_bridge = msm_dsi->bridge;
 	ext_bridge = msm_dsi->external_bridge =
@@ -699,22 +701,44 @@ struct drm_connector *msm_dsi_manager_ext_bridge_init(u8 id)
 
 	encoder = msm_dsi->encoder;
 
-	/* link the internal dsi bridge to the external bridge */
-	drm_bridge_attach(encoder, ext_bridge, int_bridge, 0);
-
 	/*
-	 * we need the drm_connector created by the external bridge
-	 * driver (or someone else) to feed it to our driver's
-	 * priv->connector[] list, mainly for msm_fbdev_init()
+	 * Try first to create the bridge without it creating its own
+	 * connector.. currently some bridges support this, and others
+	 * do not (and some support both modes)
 	 */
-	connector_list = &dev->mode_config.connector_list;
+	ret = drm_bridge_attach(encoder, ext_bridge, int_bridge,
+			DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+	if (ret == -EINVAL) {
+		struct drm_connector *connector;
+		struct list_head *connector_list;
+
+		/* link the internal dsi bridge to the external bridge */
+		drm_bridge_attach(encoder, ext_bridge, int_bridge, 0);
+
+		/*
+		 * we need the drm_connector created by the external bridge
+		 * driver (or someone else) to feed it to our driver's
+		 * priv->connector[] list, mainly for msm_fbdev_init()
+		 */
+		connector_list = &dev->mode_config.connector_list;
 
-	list_for_each_entry(connector, connector_list, head) {
-		if (drm_connector_has_possible_encoder(connector, encoder))
-			return connector;
+		list_for_each_entry(connector, connector_list, head) {
+			if (drm_connector_has_possible_encoder(connector, encoder))
+				return connector;
+		}
+
+		return ERR_PTR(-ENODEV);
+	}
+
+	connector = drm_bridge_connector_init(dev, encoder);
+	if (IS_ERR(connector)) {
+		DRM_ERROR("Unable to create bridge connector\n");
+		return ERR_CAST(connector);
 	}
 
-	return ERR_PTR(-ENODEV);
+	drm_connector_attach_encoder(connector, encoder);
+
+	return connector;
 }
 
 void msm_dsi_manager_bridge_destroy(struct drm_bridge *bridge)