include/linux/pm_runtime.h pm_runtime_get_sync() description suggests to ... consider using pm_runtime_resume_and_get() instead of it, especially if its return value is checked by the caller, as this is likely to result in cleaner code. This is indeed better, switch to pm_runtime_resume_and_get() which correctly suspends the device again in case of failure. Also add error checking into the RNG driver in case pm_runtime_resume_and_get() does fail, which is currently not done, and it does detect sporadic -EACCES error return after resume, which would otherwise lead to a hang due to register access on un-resumed hardware. Now the read simply errors out and the system does not hang. Acked-by: Gatien Chevallier <gatien.chevallier@xxxxxxxxxxx> Signed-off-by: Marek Vasut <marex@xxxxxxx> --- Cc: "Uwe Kleine-König" <u.kleine-koenig@xxxxxxxxxxxxxx> Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx> Cc: Gatien Chevallier <gatien.chevallier@xxxxxxxxxxx> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Cc: Marek Vasut <marex@xxxxxxx> Cc: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx> Cc: Olivia Mackall <olivia@xxxxxxxxxxx> Cc: Rob Herring <robh@xxxxxxxxxx> Cc: Yang Yingliang <yangyingliang@xxxxxxxxxx> Cc: kernel@xxxxxxxxxxxxxxxxxx Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-crypto@xxxxxxxxxxxxxxx Cc: linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx --- V2: Add AB from Gatien --- drivers/char/hw_random/stm32-rng.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c index 0e903d6e22e30..6dec4adc49853 100644 --- a/drivers/char/hw_random/stm32-rng.c +++ b/drivers/char/hw_random/stm32-rng.c @@ -187,7 +187,9 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) int retval = 0, err = 0; u32 sr; - pm_runtime_get_sync((struct device *) priv->rng.priv); + retval = pm_runtime_resume_and_get((struct device *)priv->rng.priv); + if (retval) + return retval; if (readl_relaxed(priv->base + RNG_SR) & RNG_SR_SEIS) stm32_rng_conceal_seed_error(rng); -- 2.43.0
