Re: [PATCH v8 10/16] drm/panfrost: Add debugfs knob for manually triggering a GPU reset

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Incorrect error handling of pm_runtime_get_if_active() leads to unsafe hardware access when runtime PM is disabled.
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commit 8d990169095e4c032a10ab3f7f2aa29eb0345717
Author: Adrián Larumbe <adrian.larumbe@collabora.com>

drm/panfrost: Add debugfs knob for manually triggering a GPU reset

This commit introduces a new debugfs file to manually schedule a GPU reset.
It is intended to help test potential race conditions between the reset
sequence and other hardware register accesses.

> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index f0fae6fa1e248..f171abe26f80d 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
[ ... ]
> +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) {

[Severity: High]
Can this cause a kernel panic if runtime PM is disabled?

pm_runtime_get_if_active() returns a negative error code (like -EINVAL)
when runtime PM is disabled, such as during system suspend. Because this
condition checks if (ret) instead of if (ret > 0), a negative error return
evaluates to true.

This would cause panfrost_device_schedule_reset() to execute and flush the
work queue while the device is potentially powered down, which may lead to
unclocked register accesses and a synchronous external abort (bus fault).

Should this condition be if (ret > 0) to ensure the device is genuinely
active before proceeding with the hardware reset?

> +		panfrost_device_schedule_reset(pfdev);
> +		flush_work(&pfdev->reset.work);
> +		if (ret > 0)
> +			pm_runtime_put(pfdev->base.dev);
> +	}
> +
> +	return 0;
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260907-claude-fixes-v8-0-c2bcb5e82184@collabora.com?part=10