[PATCH v2 1/2] accel/rocket: release the shared device's devres on teardown

rocket_device_init() attaches its allocations to the shared "rknn"
platform device via devres: devm_drm_dev_alloc(), devm_kcalloc() for
the cores array and devm_mutex_init(). That device is registered at
module init, never binds to a driver, and is only unregistered at
module exit - so its devres list is not released for as long as the
module is loaded.

rocket_device_fini() only calls drm_dev_unregister(): it does not run
the drm_dev_put() devres action or free any of the other entries.
Every fini/re-init cycle therefore leaks the previous rocket_device
(with its embedded drm_device and all drmm state, including the accel
minor number), the cores array and the mutex devres node. The cycle is
easy to trigger: unbind the last bound core and bind one again, or
fail the first core's probe (-EPROBE_DEFER retries included).

Observable symptom, RK3588 (Orange Pi 5 Plus): each unbind/rebind
cycle of all three cores moves the accel node forward -
/dev/accel/accel0 comes back as accel1, then accel2 - because every
leaked drm_device keeps its minor pinned.

Wrap the initialization in a devres group and release exactly that
group wherever the device is torn down: on the rocket_device_init()
error path, when the first core's rocket_core_init() fails, and when
the last core is removed. Each fini now frees what the matching init
allocated, and the accel minor is reusable again.

Fixes: ed98261b4168 ("accel/rocket: Add a new driver for Rockchip's NPU")
Signed-off-by: Igor Paunovic <[email protected]>
---
v2: unchanged.
v1: https://lore.kernel.org/dri-devel/[email protected]/

This applies on top of Guangshuo Li's pending fix, which it depends on:
"accel/rocket: clear rdev on device init failure"
https://lore.kernel.org/dri-devel/[email protected]/

Verified on RK3588 (Orange Pi 5 Plus): with the patch, repeated
unbind/rebind cycles keep /dev/accel/accel0 stable (previously the
minor incremented on every cycle); normal three-core probe, runtime PM
and a MobileNetV1 inference run via the Teflon TFLite delegate are
unaffected.

 drivers/accel/rocket/rocket_drv.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/accel/rocket/rocket_drv.c b/drivers/accel/rocket/rocket_drv.c
index 67e7f54..d29c5ee 100644
--- a/drivers/accel/rocket/rocket_drv.c
+++ b/drivers/accel/rocket/rocket_drv.c
@@ -24,6 +24,7 @@
  */
 static struct platform_device *drm_dev;
 static struct rocket_device *rdev;
+static void *rdev_group;
 
 static void
 rocket_iommu_domain_destroy(struct kref *kref)
@@ -163,14 +164,19 @@ static int rocket_probe(struct platform_device *pdev)
 
 	if (rdev == NULL) {
 		/* First core probing, initialize DRM device. */
+		rdev_group = devres_open_group(&drm_dev->dev, NULL, GFP_KERNEL);
+		if (!rdev_group)
+			return -ENOMEM;
 		rdev = rocket_device_init(drm_dev, &rocket_drm_driver);
 		if (IS_ERR(rdev)) {
 			int err = PTR_ERR(rdev);
 
 			dev_err(&pdev->dev, "failed to initialize rocket device\n");
 			rdev = NULL;
+			devres_release_group(&drm_dev->dev, rdev_group);
 			return err;
 		}
+		devres_close_group(&drm_dev->dev, rdev_group);
 	}
 
 	unsigned int core = rdev->num_cores;
@@ -190,6 +196,7 @@ static int rocket_probe(struct platform_device *pdev)
 		if (rdev->num_cores == 0) {
 			rocket_device_fini(rdev);
 			rdev = NULL;
+			devres_release_group(&drm_dev->dev, rdev_group);
 		}
 	}
 
@@ -213,6 +220,7 @@ static void rocket_remove(struct platform_device *pdev)
 		/* Last core removed, deinitialize DRM device. */
 		rocket_device_fini(rdev);
 		rdev = NULL;
+		devres_release_group(&drm_dev->dev, rdev_group);
 	}
 }