[PATCH v2 1/2] cyclic: Fix rollover every 72 min on 32 bits platforms

Patrice Chotard patrice.chotard at foss.st.com
Tue Jan 14 14:28:13 CET 2025


On 32 bits platforms, timer_get_us() returns an unsigned long which
is a 32 bits. timer_get_us() wraps around every 72 minutes
(2 ^ 32 / 1000000 =~ 4295 sec =~ 72 min).

So the test "if time_after_eq64(now, cyclic->next_call)" is no more
true when cyclic->next_call becomes above 32 bits max value (4294967295).

At this point after 72 min, no more cyclic function are
executed included watchdog one.

Instead of using timer_get_us(), use get_timer_us() which returns a
uint64_t, this allows a rollover every 584942 years.

Signed-off-by: Patrice Chotard <patrice.chotard at foss.st.com>

---

Changes in v2:
      _ Replace remaining timer_get_us() by get_timer_us(0)

 common/cyclic.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/common/cyclic.c b/common/cyclic.c
index 196797fd61e..fad071a39c6 100644
--- a/common/cyclic.c
+++ b/common/cyclic.c
@@ -36,7 +36,7 @@ void cyclic_register(struct cyclic_info *cyclic, cyclic_func_t func,
 	cyclic->func = func;
 	cyclic->name = name;
 	cyclic->delay_us = delay_us;
-	cyclic->start_time_us = timer_get_us();
+	cyclic->start_time_us = get_timer_us(0);
 	hlist_add_head(&cyclic->list, cyclic_get_list());
 }
 
@@ -61,13 +61,13 @@ static void cyclic_run(void)
 		 * Check if this cyclic function needs to get called, e.g.
 		 * do not call the cyclic func too often
 		 */
-		now = timer_get_us();
+		now = get_timer_us(0);
 		if (time_after_eq64(now, cyclic->next_call)) {
 			/* Call cyclic function and account it's cpu-time */
 			cyclic->next_call = now + cyclic->delay_us;
 			cyclic->func(cyclic);
 			cyclic->run_cnt++;
-			cpu_time = timer_get_us() - now;
+			cpu_time = get_timer_us(0) - now;
 			cyclic->cpu_time_us += cpu_time;
 
 			/* Check if cpu-time exceeds max allowed time */
-- 
2.25.1



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