Re: [PATCH v9 10/16] drm/panfrost: Add debugfs knob for manually triggering a GPU reset

[Boris Brezillon <boris.brezillon@collabora.com>]

On Sat, 12 Sep 2026 00:28:11 +0100
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> This will be of great help when testing potential races between the GPU
> reset sequence and other parts of the code accessing HW registers.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

One comment below.

> ---
>  drivers/gpu/drm/panfrost/panfrost_device.c | 37 ++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index d75566a45392..0aee1d87a7ab 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -2,6 +2,7 @@
>  /* Copyright 2018 Marty E. Plummer <hanetzer@startmail.com> */
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  
> +#include <linux/debugfs.h>
>  #include <linux/clk.h>
>  #include <linux/reset.h>
>  #include <linux/platform_device.h>
> @@ -583,9 +584,45 @@ EXPORT_GPL_DEV_PM_OPS(panfrost_pm_ops) = {
>  };
>  
>  #ifdef CONFIG_DEBUG_FS
> +static int reset_get(void *data, u64 *val)
> +{
> +	struct panfrost_device *pfdev =
> +		container_of(data, struct panfrost_device, base);
> +
> +	*val = atomic_read(&pfdev->reset.pending);
> +	return 0;
> +}
> +
> +static int reset_set(void *data, u64 val)
> +{
> +	struct panfrost_device *pfdev =
> +		container_of(data, struct panfrost_device, base);
> +	int ret = pm_runtime_get_if_active(pfdev->base.dev);
> +
> +	if (ret) {
> +		panfrost_device_schedule_reset(pfdev);

It feels weird to schedule a reset if the device is suspended, because
a suspend/resume cycle already acts as a reset. Any particular reason
you'd want to do that? If not, I'd suggest going for:

	if (ret <= 0)
		return ret;

	panfrost_device_schedule_reset(pfdev);
	pm_runtime_put(pfdev->base.dev);
	return 0;

> +		flush_work(&pfdev->reset.work);
> +		if (ret > 0)
> +			pm_runtime_put(pfdev->base.dev);
> +	}
> +
> +	return 0;
> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(panfrost_reset_debugfs_fops,
> +			 reset_get, reset_set,
> +			 "0x%08llx\n");
> +
> +static void panfrost_reset_debugfs_init(struct drm_minor *minor)
> +{
> +	debugfs_create_file("reset", 0600, minor->debugfs_root,
> +			    minor->dev, &panfrost_reset_debugfs_fops);
> +}
> +
>  void panfrost_device_debugfs_init(struct drm_minor *minor)
>  {
>  	panfrost_gem_debugfs_init(minor);
>  	panfrost_sched_debugfs_init(minor);
> +	panfrost_reset_debugfs_init(minor);
>  }
>  #endif // CONFIG_DEBUG_FS
>