Re: [PATCH v4 01/18] drm/panthor: Disable reset work before unplug

[Adrian Larumbe <adrian.larumbe@collabora.com>]

Reviewed-by: Adrián Larumbe <adrian.larumbe@collabora.com>

On 26.08.2026 16:56, Boris Brezillon wrote:
> Unplug is supposed to be the end of the road, so we need to make sure
> reset works won't execute while we're cleaning up everything as part
> of the unplug, otherwise it would mess up the internal state.
> 
> In order to be able to call disable_work_sync() in the unplug
> path, we need to defer the unplug triggered by the reset logic,
> otherwise we would deadlock.
> 
> Fixes: 5fe909cae118 ("drm/panthor: Add the device logical block")
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_device.c | 21 ++++++++++++++++++++-
>  drivers/gpu/drm/panthor/panthor_device.h |  3 +++
>  2 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
> index 0b25abebb803..7c55d0c45cfd 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.c
> +++ b/drivers/gpu/drm/panthor/panthor_device.c
> @@ -79,6 +79,9 @@ void panthor_device_unplug(struct panthor_device *ptdev)
>  		return;
>  	}
>  
> +	/* Make sure we're not interrupted by resets while we're unplugging. */
> +	disable_work_sync(&ptdev->reset.work);
> +
>  	drm_WARN_ON(&ptdev->base, pm_runtime_get_sync(ptdev->base.dev) < 0);
>  
>  	/* Call drm_dev_unplug() so any access to HW blocks happening after
> @@ -91,6 +94,13 @@ void panthor_device_unplug(struct panthor_device *ptdev)
>  	 */
>  	mutex_unlock(&ptdev->unplug.lock);
>  
> +	/* Unplug triggered by a device removal might race with the deferred
> +	 * one queued by the reset work. The function covers this concurrent
> +	 * unplug situation, but if we can disable the work before its
> +	 * execution, that's still better.
> +	 */
> +	disable_work(&ptdev->unplug.work);
> +
>  	/* Now, try to cleanly shutdown the GPU before the device resources
>  	 * get reclaimed.
>  	 */
> @@ -114,6 +124,13 @@ void panthor_device_unplug(struct panthor_device *ptdev)
>  	complete_all(&ptdev->unplug.done);
>  }
>  
> +static void panthor_device_unplug_work(struct work_struct *work)
> +{
> +	struct panthor_device *ptdev = container_of(work, struct panthor_device, unplug.work);
> +
> +	panthor_device_unplug(ptdev);
> +}
> +
>  static void panthor_device_reset_cleanup(struct drm_device *ddev, void *data)
>  {
>  	struct panthor_device *ptdev = container_of(ddev, struct panthor_device, base);
> @@ -148,8 +165,9 @@ static void panthor_device_reset_work(struct work_struct *work)
>  	drm_dev_exit(cookie);
>  
>  	if (ret) {
> -		panthor_device_unplug(ptdev);
> +		disable_work(&ptdev->reset.work);
>  		drm_err(&ptdev->base, "Failed to boot MCU after reset, making device unusable.");
> +		queue_work(ptdev->reset.wq, &ptdev->unplug.work);
>  	}
>  }
>  
> @@ -206,6 +224,7 @@ int panthor_device_init(struct panthor_device *ptdev)
>  	 */
>  	*dummy_page_virt = 1;
>  
> +	INIT_WORK(&ptdev->unplug.work, panthor_device_unplug_work);
>  	INIT_WORK(&ptdev->reset.work, panthor_device_reset_work);
>  	disable_work(&ptdev->reset.work);
>  	ptdev->reset.wq = alloc_ordered_workqueue("panthor-reset-wq", 0);
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index b55a3f9edd41..6529e01e838d 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -268,6 +268,9 @@ struct panthor_device {
>  		 * operation is done.
>  		 */
>  		struct completion done;
> +
> +		/** @work: Unplug work. */
> +		struct work_struct work;
>  	} unplug;
>  
>  	/** @reset: Reset related fields. */
> 
> -- 
> 2.55.0
 
Adrian Larumbe