Revert "drm/bridge: panel: Add a device link between drm device and panel device"

This reverts commit 199cf07.

This patch creates bugs on devices where the DRM device is
the ancestor of the panel devices.

Attempts to fix this have failed because it leads to using
device core functionality which is questionable.

Reported-by: Linus Walleij <[email protected]>
Link: https://lore.kernel.org/lkml/CACRpkdaGzXD6HbiX7mVUNJAJtMEPG00Pp6+nJ1P0JrfJ-ArMvQ@mail.gmail.com/T/
Signed-off-by: Linus Walleij <[email protected]>
Acked-by: Neil Armstrong <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Neil Armstrong <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: linusw

drivers/gpu/drm/bridge/panel.c

@@ -4,8 +4,6 @@
  * Copyright (C) 2017 Broadcom
  */
 
-#include <linux/device.h>
-
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_connector.h>
@@ -21,7 +19,6 @@ struct panel_bridge {
 	struct drm_bridge bridge;
 	struct drm_connector connector;
 	struct drm_panel *panel;
-	struct device_link *link;
 	u32 connector_type;
 };
 
@@ -63,24 +60,13 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
 {
 	struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
 	struct drm_connector *connector = &panel_bridge->connector;
-	struct drm_panel *panel = panel_bridge->panel;
-	struct drm_device *drm_dev = bridge->dev;
 	int ret;
 
-	panel_bridge->link = device_link_add(drm_dev->dev, panel->dev,
-					     DL_FLAG_STATELESS);
-	if (!panel_bridge->link) {
-		DRM_ERROR("Failed to add device link between %s and %s\n",
-			  dev_name(drm_dev->dev), dev_name(panel->dev));
-		return -EINVAL;
-	}
-
 	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
 		return 0;
 
 	if (!bridge->encoder) {
 		DRM_ERROR("Missing encoder\n");
-		device_link_del(panel_bridge->link);
 		return -ENODEV;
 	}
 
@@ -92,7 +78,6 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
 				 panel_bridge->connector_type);
 	if (ret) {
 		DRM_ERROR("Failed to initialize connector\n");
-		device_link_del(panel_bridge->link);
 		return ret;
 	}
 
@@ -115,8 +100,6 @@ static void panel_bridge_detach(struct drm_bridge *bridge)
 	struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
 	struct drm_connector *connector = &panel_bridge->connector;
 
-	device_link_del(panel_bridge->link);
-
 	/*
 	 * Cleanup the connector if we know it was initialized.
 	 *