Re: [PATCH] irqchip/stm32mp-exti: fix the unit of the hwspinlock timeout

[Radu Rendec <radu@rendec.net>]

On Wed, 2026-08-05 at 11:21 +0800, Ju Nan wrote:
> HWSPNLCK_TIMEOUT is passed to hwspin_lock_timeout_in_atomic(), whose
> timeout argument is in milliseconds, not microseconds:
> 
>   atomic_delay += HWSPINLOCK_RETRY_DELAY_US;
>   if (atomic_delay > to * 1000)
>           return -ETIMEDOUT;
> 
> So stm32mp_exti_set_type() asks for a 1 second timeout where the comment
> next to the macro says it wants 1 millisecond. The semaphore is polled
> with udelay() from a section that holds chip_data->rlock, a
> raw_spinlock_t, so preemption stays disabled for the whole wait on every
> configuration, PREEMPT_RT included.
> 
> The hwspinlock core documents this explicitly:
> 
>   If the mode is HWLOCK_IN_ATOMIC (called from an atomic context) the
>   timeout is handled with busy-waiting delays, hence shall not exceed
>   few msecs.
> 
> Pass the value the comment always described. The core retries every
> HWSPINLOCK_RETRY_DELAY_US (100 us), so the semaphore is still polled ten
> times before giving up, which is far longer than any plausible hold time
> on the coprocessor side. A timeout is reported with pr_err() and fails
> the trigger type configuration, so shortening it degrades gracefully.
> 
> Signed-off-by: Ju Nan <junan76@163.com>
> ---
>  drivers/irqchip/irq-stm32mp-exti.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-stm32mp-exti.c b/drivers/irqchip/irq-stm32mp-exti.c
> index a24f4f1a4..f5f0109bf 100644
> --- a/drivers/irqchip/irq-stm32mp-exti.c
> +++ b/drivers/irqchip/irq-stm32mp-exti.c
> @@ -23,7 +23,7 @@
>  
>  #define IRQS_PER_BANK			32
>  
> -#define HWSPNLCK_TIMEOUT		1000 /* usec */
> +#define HWSPNLCK_TIMEOUT		1 /* msec */
>  
>  #define EXTI_EnCIDCFGR(n)		(0x180 + (n) * 4)
>  #define EXTI_HWCFGR1			0x3f0

Reviewed-by: Radu Rendec <radu@rendec.net>