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arch/stm32f7: Fixes bug in tickless driver where the compare register is set to a value less than the current time.

This commit is contained in:
Anthony Merlino 2020-07-07 16:02:04 -04:00 committed by Xiang Xiao
parent ac7e5de5ae
commit e5be32ac21
1 changed files with 39 additions and 6 deletions
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45
arch/arm/src/stm32f7/stm32_tickless.c
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@ -139,7 +139,7 @@ struct stm32_tickless_s
volatile bool pending; /* True: pending task */
uint32_t period; /* Interval period */
uint32_t base;
#if CONFIG_SCHED_TICKLESS_ALARM
#ifdef CONFIG_SCHED_TICKLESS_ALARM
uint64_t last_alrm;
#endif
};
@ -393,6 +393,17 @@ static int stm32_tickless_handler(int irq, void *context, void *arg)
return OK;
}
/****************************************************************************
* Name: stm32_get_counter
*
****************************************************************************/
static uint64_t stm32_get_counter(void)
{
return ((uint64_t)g_tickless.overflow << 32) |
STM32_TIM_GETCOUNTER(g_tickless.tch);
}
/****************************************************************************
* Public Functions
****************************************************************************/
@ -988,22 +999,43 @@ int up_timer_start(FAR const struct timespec *ts)
}
#endif
#ifdef CONFIG_SCHED_TICKLESS_ALARM
int up_alarm_start(FAR const struct timespec *ts)
{
size_t offset = 1;
uint64_t tm = ((uint64_t)ts->tv_sec * NSEC_PER_SEC + ts->tv_nsec) /
NSEC_PER_TICK;
uint64_t counter = ((uint64_t)g_tickless.overflow << 32) |
STM32_TIM_GETCOUNTER(g_tickless.tch);
irqstate_t flags;
g_tickless.last_alrm = tm;
int32_t diff = tm / NSEC_PER_TICK + counter;
flags = enter_critical_section();
STM32_TIM_SETCOMPARE(g_tickless.tch, CONFIG_STM32F7_TICKLESS_CHANNEL, tm);
stm32_tickless_ackint(g_tickless.channel);
stm32_tickless_enableint(CONFIG_STM32F7_TICKLESS_CHANNEL);
g_tickless.pending = true;
/* We must protect for a race condition here with very small differences
* between the time of the alarm and the time now. We must ensure that the
* compare register is set, and interrupts are enabled BEFORE the rising edge
* of the clock when COUNT==COMPARE. Otherwise, we cannot be sure we are
* going to get the interrupt. If we didn't catch this case, we wouldn't
* interrupt until a full loop of the clock.
*
* Since we can't make assumptions about the clock speed and tick rate,
* we simply keep adding an offset to the current time, until we can leave
* certain that the interrupt is going to fire as soon as we leave the
* critical section.
*/
while (tm <= stm32_get_counter())
{
tm = stm32_get_counter() + offset++;
STM32_TIM_SETCOMPARE(g_tickless.tch, CONFIG_STM32F7_TICKLESS_CHANNEL, tm);
}
leave_critical_section(flags);
return OK;
}
@ -1019,5 +1051,6 @@ int up_alarm_cancel(FAR struct timespec *ts)
return 0;
}
#endif
#endif /* CONFIG_SCHED_TICKLESS */