[v3] irqchip/stm32mp-exti: fix the unit of the hwspinlock timeout

[PATCH v3] irqchip/stm32mp-exti: fix the unit of the hwspinlock timeout

Posted by Ju Nan 3 days, 1 hour ago

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.

Fixes: 5257169ade8c ("irqchip/stm32-exti: Use the hwspin_lock_timeout_in_atomic() API")
Reviewed-by: Radu Rendec <radu@rendec.net>
Signed-off-by: Ju Nan <junan76@163.com>
---
changelog:

v3: redefine the timeout macro with time unit on it
v2: add "Fixes" tag suggested by Radu Rendec
v1: https://lore.kernel.org/all/20260805032139.35420-2-junan76@163.com/
---
 drivers/irqchip/irq-stm32mp-exti.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-stm32mp-exti.c b/drivers/irqchip/irq-stm32mp-exti.c
index a24f4f1a4..ce4e03ee1 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_MS		1
 
 #define EXTI_EnCIDCFGR(n)		(0x180 + (n) * 4)
 #define EXTI_HWCFGR1			0x3f0
@@ -377,7 +377,7 @@ static int stm32mp_exti_set_type(struct irq_data *d, unsigned int type)
 	raw_spin_lock(&chip_data->rlock);
 
 	if (hwlock) {
-		err = hwspin_lock_timeout_in_atomic(hwlock, HWSPNLCK_TIMEOUT);
+		err = hwspin_lock_timeout_in_atomic(hwlock, HWSPNLCK_TIMEOUT_MS);
 		if (err) {
 			pr_err("%s can't get hwspinlock (%d)\n", __func__, err);
 			goto unlock;
-- 
2.55.0

Re: [Linux-stm32] [PATCH v3] irqchip/stm32mp-exti: fix the unit of the hwspinlock timeout

Posted by Antonio Borneo 2 days, 20 hours ago

On Fri, 2026-08-21 at 10:47 +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.
> 
> Fixes: 5257169ade8c ("irqchip/stm32-exti: Use the hwspin_lock_timeout_in_atomic() API")
> Reviewed-by: Radu Rendec <radu@rendec.net>
> Signed-off-by: Ju Nan <junan76@163.com>
> ---
> changelog:
> 
> v3: redefine the timeout macro with time unit on it
> v2: add "Fixes" tag suggested by Radu Rendec
> v1: https://lore.kernel.org/all/20260805032139.35420-2-junan76@163.com/
> ---
>  drivers/irqchip/irq-stm32mp-exti.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-stm32mp-exti.c b/drivers/irqchip/irq-stm32mp-exti.c
> index a24f4f1a4..ce4e03ee1 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_MS            1
>  
>  #define EXTI_EnCIDCFGR(n)              (0x180 + (n) * 4)
>  #define EXTI_HWCFGR1                   0x3f0
> @@ -377,7 +377,7 @@ static int stm32mp_exti_set_type(struct irq_data *d, unsigned int type)
>         raw_spin_lock(&chip_data->rlock);
>  
>         if (hwlock) {
> -               err = hwspin_lock_timeout_in_atomic(hwlock, HWSPNLCK_TIMEOUT);
> +               err = hwspin_lock_timeout_in_atomic(hwlock, HWSPNLCK_TIMEOUT_MS);
>                 if (err) {
>                         pr_err("%s can't get hwspinlock (%d)\n", __func__, err);
>                         goto unlock;

Thanks!

Reviewed-by: Antonio Borneo <antonio.borneo@foss.st.com>