[RFC PATCH v1 01/12] Revert "drm/sysfs: Link DRM connectors to corresponding Type-C connectors"

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

The kdev->fwnode pointer is never set in drm_sysfs_connector_add(), so
dev_fwnode() checks never succeed, making the respective commit NOP.

And if drm_sysfs_connector_add() is modified to set kdev->fwnode, it
breaks drivers already using components (as it was pointed at [1]),
resulting in a deadlock. Lockdep trace is provided below.

Granted these two issues, it seems impractical to fix this commit in any
sane way. Revert it instead.

[1] https://lore.kernel.org/dri-devel/Y24bcYJKGy%2Fgd5fV@phenom.ffwll.local/

============================================
WARNING: possible recursive locking detected
6.5.0-rc6-next-20230816-10542-g090e2ca9feae-dirty #713 Tainted: G        W
--------------------------------------------
kworker/u16:0/11 is trying to acquire lock:
ffffce0f54bea490 (component_mutex){+.+.}-{3:3}, at: __component_add+0x64/0x170

but task is already holding lock:
ffffce0f54bea490 (component_mutex){+.+.}-{3:3}, at: __component_add+0x64/0x170

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(component_mutex);
  lock(component_mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

6 locks held by kworker/u16:0/11:
 #0: ffff5b7680008d38 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x14c/0x51c
 #1: ffff8000800abde0 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x14c/0x51c
 #2: ffff5b76837a2908 (&dev->mutex){....}-{3:3}, at: __device_attach+0x38/0x188
 #3: ffffce0f54bea490 (component_mutex){+.+.}-{3:3}, at: __component_add+0x64/0x170
 #4: ffffce0f54bdeb40 (drm_connector_list_iter){.+.+}-{0:0}, at: drm_modeset_register_all+0x80/0x9c
 #5: ffff5b76866ad0d0 (&connector->mutex){+.+.}-{3:3}, at: drm_connector_register.part.0+0x28/0x104

stack backtrace:
CPU: 6 PID: 11 Comm: kworker/u16:0 Tainted: G        W          6.5.0-rc6-next-20230816-10542-g090e2ca9feae-dirty #713
Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
Workqueue: events_unbound deferred_probe_work_func
Call trace:
 dump_backtrace+0x98/0xf0
 show_stack+0x18/0x24
 dump_stack_lvl+0x60/0xac
 dump_stack+0x18/0x24
 print_deadlock_bug+0x254/0x340
 __lock_acquire+0x105c/0x1ebc
 lock_acquire+0x1ec/0x314
 __lock_acquire+0x105c/0x1ebc
 lock_acquire+0x1ec/0x314
 __mutex_lock+0xa0/0x77c
 mutex_lock_nested+0x24/0x30
 __component_add+0x64/0x170
 component_add+0x14/0x20
 drm_sysfs_connector_add+0x144/0x1a0
 drm_connector_register.part.0+0x5c/0x104
 drm_connector_register_all+0x84/0x160
 drm_modeset_register_all+0x80/0x9c
 drm_dev_register+0x120/0x238
 msm_drm_bind+0x550/0x6e0
 try_to_bring_up_aggregate_device+0x164/0x1d0
 __component_add+0xa8/0x170
 component_add+0x14/0x20
 dsi_dev_attach+0x20/0x2c
 dsi_host_attach+0x9c/0x144
 devm_mipi_dsi_attach+0x34/0xb4
 lt9611uxc_attach_dsi.isra.0+0x84/0xfc
 lt9611uxc_probe+0x5ac/0x66c
 i2c_device_probe+0x148/0x290
 really_probe+0x148/0x2ac
 __driver_probe_device+0x78/0x12c
 driver_probe_device+0x3c/0x160
 __device_attach_driver+0xb8/0x138
 bus_for_each_drv+0x80/0xdc
 __device_attach+0x9c/0x188
 device_initial_probe+0x14/0x20
 bus_probe_device+0xac/0xb0
 deferred_probe_work_func+0x8c/0xc8
 process_one_work+0x1ec/0x51c
 worker_thread+0x1ec/0x3e4
 kthread+0x120/0x124
 ret_from_fork+0x10/0x20

Fixes: c5c51b242062 ("drm/sysfs: Link DRM connectors to corresponding Type-C connectors")
Cc: Won Chung <wonchung@google.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/drm_sysfs.c | 40 -------------------------------------
 1 file changed, 40 deletions(-)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index b169b3e44a92..06662cc8d3f4 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -11,14 +11,12 @@
  */
 
 #include <linux/acpi.h>
-#include <linux/component.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
 #include <linux/i2c.h>
 #include <linux/kdev_t.h>
-#include <linux/property.h>
 #include <linux/slab.h>
 
 #include <drm/drm_accel.h>
@@ -98,34 +96,6 @@ static char *drm_devnode(const struct device *dev, umode_t *mode)
 	return kasprintf(GFP_KERNEL, "dri/%s", dev_name(dev));
 }
 
-static int typec_connector_bind(struct device *dev,
-				struct device *typec_connector, void *data)
-{
-	int ret;
-
-	ret = sysfs_create_link(&dev->kobj, &typec_connector->kobj, "typec_connector");
-	if (ret)
-		return ret;
-
-	ret = sysfs_create_link(&typec_connector->kobj, &dev->kobj, "drm_connector");
-	if (ret)
-		sysfs_remove_link(&dev->kobj, "typec_connector");
-
-	return ret;
-}
-
-static void typec_connector_unbind(struct device *dev,
-				   struct device *typec_connector, void *data)
-{
-	sysfs_remove_link(&typec_connector->kobj, "drm_connector");
-	sysfs_remove_link(&dev->kobj, "typec_connector");
-}
-
-static const struct component_ops typec_connector_ops = {
-	.bind = typec_connector_bind,
-	.unbind = typec_connector_unbind,
-};
-
 static CLASS_ATTR_STRING(version, S_IRUGO, "drm 1.1.0 20060810");
 
 /**
@@ -394,16 +364,9 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
 
 	connector->kdev = kdev;
 
-	if (dev_fwnode(kdev)) {
-		r = component_add(kdev, &typec_connector_ops);
-		if (r)
-			drm_err(dev, "failed to add component to create link to typec connector\n");
-	}
-
 	if (connector->ddc)
 		return sysfs_create_link(&connector->kdev->kobj,
 				 &connector->ddc->dev.kobj, "ddc");
-
 	return 0;
 
 err_free:
@@ -419,9 +382,6 @@ void drm_sysfs_connector_remove(struct drm_connector *connector)
 	if (connector->ddc)
 		sysfs_remove_link(&connector->kdev->kobj, "ddc");
 
-	if (dev_fwnode(connector->kdev))
-		component_del(connector->kdev, &typec_connector_ops);
-
 	DRM_DEBUG("removing \"%s\" from sysfs\n",
 		  connector->name);
 
-- 
2.39.2