[PATCH] hwrng: stm32: fix usage_count leak when autosuspend_delay is negative

[Guangshuo Li]

Hi Daniel,

Thanks for the suggestion.

On Mon, 10 Aug 2026 at 18:24, Daniel Thompson <danielt at kernel.org> wrote:
>
> On Sat, Aug 08, 2026 at 03:45:10PM +0800, Guangshuo Li wrote:
> > stm32_rng_probe() calls pm_runtime_use_autosuspend(), but neither the
> > probe failure path nor stm32_rng_remove() calls the matching
> > pm_runtime_dont_use_autosuspend() before disabling runtime PM.
> >
> > If the autosuspend delay is set to a negative value while autosuspend
> > is enabled, the runtime PM core increments usage_count to prevent
> > runtime suspend. Without calling pm_runtime_dont_use_autosuspend()
> > during teardown, this reference is not dropped and usage_count remains
> > unbalanced.
>
> If calls to pm_runtime_use_autosuspend() must be paired with
> pm_runtime_dont_use_autosuspend() then I wonder if having a
> devm_pm_runtime_use_autosuspend() would be worthwhile?
>
> That way stm32_rng_remove() could be entirely replaced with devres
> cleanup.
>
>
> Daniel.

There is already devm_pm_runtime_enable(), whose devres cleanup calls
pm_runtime_dont_use_autosuspend() followed by pm_runtime_disable().

So I think this driver can simply switch from pm_runtime_enable() to
devm_pm_runtime_enable(), and stm32_rng_remove() can then be removed
entirely.

I'll rework the patch accordingly.

Thanks,
Guangshuo