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 <redacted>
---
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
--
2.55.0