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avr: Implement internal avr specific timer to handle 16bit overflows

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Don't rely on the generic scheduler code to always have a timer no
more than 1ms in the future.  Instead, create an avr specific timer
that will be called every 0x8000 ticks.  This simplifies the generic
code and it reduces the amount of code that needs to be run every
millisecond.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2017-08-06 19:21:16 -04:00
parent 6a63c27542
commit 78982ebb51
5 changed files with 31 additions and 26 deletions
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32
src/avr/timer.c
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@ -85,6 +85,15 @@ timer_kick(void)
TIFR1 = 1<<OCF1A;
}
static struct timer wrap_timer;
void
timer_reset(void)
{
sched_add_timer(&wrap_timer);
}
DECL_SHUTDOWN(timer_reset);
void
timer_init(void)
{
@ -96,6 +105,7 @@ timer_init(void)
irqstatus_t flag = irq_save();
timer_kick();
timer_repeat_set(timer_get() + 50);
timer_reset();
TIFR1 = 1<<TOV1;
// enable interrupt
TIMSK1 = 1<<OCIE1A;
@ -115,25 +125,33 @@ uint32_t
timer_read_time(void)
{
irqstatus_t flag = irq_save();
union u32_u calc;
calc.val = timer_get();
union u32_u calc = { .val = timer_get() };
calc.hi = timer_high;
if (TIFR1 & (1<<TOV1) && calc.lo < 0x8000)
calc.hi++;
if (unlikely(TIFR1 & (1<<TOV1))) {
irq_restore(flag);
if (calc.b1 < 0xff)
calc.hi++;
return calc.val;
}
irq_restore(flag);
return calc.val;
}
// Called by main code once every millisecond. (IRQs disabled.)
void
timer_periodic(void)
// Timer that runs every ~2ms - allows 16bit comparison optimizations
static uint_fast8_t
timer_event(struct timer *t)
{
if (TIFR1 & (1<<TOV1)) {
// Hardware timer has overflowed - update overflow counter
TIFR1 = 1<<TOV1;
timer_high++;
}
wrap_timer.waketime += 0x8000;
return SF_RESCHEDULE;
}
static struct timer wrap_timer = {
.func = timer_event,
};
#define TIMER_IDLE_REPEAT_TICKS 8000
#define TIMER_REPEAT_TICKS 3000