[PATCH v2] hwrng: stm32: fix usage_count leak when autosuspend_delay is negative

[Linus Walleij]

On Tue, Aug 11, 2026 at 8:35 AM Guangshuo Li <lgs201920130244 at gmail.com> wrote:

> stm32_rng_probe() calls pm_runtime_use_autosuspend(), but runtime PM is
> enabled with pm_runtime_enable() and the matching
> pm_runtime_dont_use_autosuspend() is not called on driver teardown.
>
> 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.
>
> Use devm_pm_runtime_enable() so that pm_runtime_dont_use_autosuspend()
> and pm_runtime_disable() are automatically called on probe failure and
> driver teardown. With runtime PM cleanup handled by devres,
> stm32_rng_remove() is no longer needed.
>
> This issue was found by manual code inspection.
>
> Fixes: c6a97c42e399 ("hwrng: stm32 - add support for STM32 HW RNG")
> Cc: stable at vger.kernel.org
> Signed-off-by: Guangshuo Li <lgs201920130244 at gmail.com>

Reviewed-by: Linus Walleij <linusw at kernel.org>

Yours,
Linus Walleij