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timer: cortex_m_systick: handle cycle count overflow with idle timer

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When the idle timer is in use, we calculate number of cycles passed
since the sys_clock_set_timeout call.

The cycle counter can overflow easily, when the counter is 32-bit wide.
Handle that case.

Signed-off-by: Dawid Niedzwiecki <dawidn@google.com>
This commit is contained in:
Dawid Niedzwiecki 2023-11-23 09:35:17 +01:00 committed by Carles Cufí
parent b0b57dac72
commit 2ae09993ca
1 changed files with 13 additions and 2 deletions
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15
drivers/timer/cortex_m_systick.c
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@ -366,17 +366,28 @@ void sys_clock_idle_exit(void)
{
#ifdef CONFIG_CORTEX_M_SYSTICK_IDLE_TIMER
if (timeout_idle) {
cycle_t systick_diff, missed_cycles;
cycle_t cycle_post_idle, systick_diff, missed_cycles;
uint32_t idle_timer_diff, idle_timer_post, dcycles, dticks;
uint64_t systick_us, idle_timer_us, measurement_diff_us;
/* Get current values for both timers */
counter_get_value(idle_timer, &idle_timer_post);
systick_diff = cycle_count + elapsed() - cycle_pre_idle;
cycle_post_idle = cycle_count + elapsed();
/* Calculate has much time has pasted since last measurement for both timers */
idle_timer_diff = idle_timer_post - idle_timer_pre_idle;
idle_timer_us = counter_ticks_to_us(idle_timer, idle_timer_diff);
#ifndef CONFIG_CORTEX_M_SYSTICK_64BIT_CYCLE_COUNTER
/* Check cycle counter overflow when using uint32_t */
if (cycle_pre_idle > cycle_post_idle) {
systick_diff = (UINT32_MAX - cycle_pre_idle) + cycle_post_idle + 1;
} else {
systick_diff = cycle_post_idle - cycle_pre_idle;
}
#else
systick_diff = cycle_post_idle - cycle_pre_idle;
#endif /* !CONFIG_CORTEX_M_SYSTICK_64BIT_CYCLE_COUNTER */
systick_us =
((uint64_t)systick_diff * USEC_PER_SEC) / sys_clock_hw_cycles_per_sec();