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drivers/timer: Fixing issue in nRF RTC driver when RTC handler is blocked.

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Fixes an unlikely issue that could arise if the RTC handler in the nRF RTC
driver was blocked for more than one sys tick interval. This could lead to
_sys_clock_tick_announce() being called with more than one sys tick when the
kernel did not expect it.

Jira: ZEP-1763

Change-ID: I5608fca6f0ac97a17c1ce452c1c5c67696a49a9a
Signed-off-by: Øyvind Hovdsveen <oyvind.hovdsveen@nordicsemi.no>
This commit is contained in:
Øyvind Hovdsveen 2017-02-20 18:15:30 +01:00 • committed by Anas Nashif
commit d787099c90
1 changed files with 14 additions and 10 deletions
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24
drivers/timer/nrf_rtc_timer.c
View file

@ -47,7 +47,7 @@ static uint32_t rtc_past;
* Holds the maximum sys ticks the kernel expects to see in the next
* _sys_clock_tick_announce().
*/
static uint32_t allowed_idle_sys_ticks;
static uint32_t expected_sys_ticks;
#endif /* CONFIG_TICKLESS_IDLE */
/*
@ -111,21 +111,25 @@ static void rtc_announce_set_next(void)
* counters or announcing it.
*/
if (rtc_elapsed >= RTC_TICKS_PER_SYS_TICK) {
#ifdef CONFIG_TICKLESS_IDLE
/* Calculate how many sys ticks elapsed since the last sys tick
* and notify the kernel if necessary.
*/
sys_elapsed = rtc_elapsed / RTC_TICKS_PER_SYS_TICK;
#ifdef CONFIG_TICKLESS_IDLE
if (sys_elapsed > allowed_idle_sys_ticks) {
if (sys_elapsed > expected_sys_ticks) {
/* Never announce more sys ticks than the kernel asked
* to be idle for. The remainder will be announced when
* the RTC ISR runs after rtc_compare_set() is called
* after the first announcement.
*/
sys_elapsed = allowed_idle_sys_ticks;
sys_elapsed = expected_sys_ticks;
}
#else
/* Never announce more than one sys tick if tickless idle is not
* configured.
*/
sys_elapsed = 1;
#endif /* CONFIG_TICKLESS_IDLE */
/* Store RTC_COUNTER floored to the last sys tick. This is
@ -179,7 +183,7 @@ void _timer_idle_enter(int32_t sys_ticks)
sys_ticks = RTC_HALF / RTC_TICKS_PER_SYS_TICK;
}
allowed_idle_sys_ticks = sys_ticks;
expected_sys_ticks = sys_ticks;
/* If ticks is 0, the RTC interrupt handler will be set pending
* immediately, meaning that we will not go to sleep.
@ -224,10 +228,10 @@ void _timer_idle_exit(void)
rtc_announce_set_next();
/* After exiting idle, the kernel no longer expects a maximum amount of
* sys ticks to have passed when _sys_clock_tick_announce() is called.
/* After exiting idle, the kernel no longer expects more than one sys
* ticks to have passed when _sys_clock_tick_announce() is called.
*/
allowed_idle_sys_ticks = RTC_HALF;
expected_sys_ticks = 1;
}
#endif /* CONFIG_TICKLESS_IDLE */
@ -279,7 +283,7 @@ int _sys_clock_driver_init(struct device *device)
rtc_past = 0;
#ifdef CONFIG_TICKLESS_IDLE
allowed_idle_sys_ticks = RTC_HALF;
expected_sys_ticks = 1;
#endif /* CONFIG_TICKLESS_IDLE */
/* TODO: replace with counter driver to access RTC */