diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/avr/timer.c | 73 |
1 files changed, 30 insertions, 43 deletions
diff --git a/src/avr/timer.c b/src/avr/timer.c index f8686998..ac7509ed 100644 --- a/src/avr/timer.c +++ b/src/avr/timer.c @@ -135,40 +135,40 @@ timer_periodic(void) #define TIMER_MIN_TRY_TICKS 60 // 40 ticks to exit irq; 20 ticks of progress #define TIMER_DEFER_REPEAT_TICKS 200 -// Set the next timer wake time (in absolute clock ticks) or return 1 -// if the next timer is too close to schedule. Caller must disable -// irqs. -static uint8_t -timer_try_set_next(unsigned int target) +// Hardware timer IRQ handler - dispatch software timers +ISR(TIMER1_COMPA_vect) { - uint16_t next = target; - int16_t diff = next - timer_get(); - if (likely(diff < 0)) { - // Another timer is pending - briefly allow irqs to fire - irq_enable(); - if (unlikely(TIFR1 & (1<<OCF1B))) - // Too many repeat timers - must exit irq handler - goto force_pause; - irq_disable(); - return 0; - } + uint16_t next; + for (;;) { + // Run the next software timer + next = sched_timer_dispatch(); - if (likely(diff > TIMER_MIN_TRY_TICKS)) - // Schedule next timer normally - goto done; + int16_t diff = next - timer_get(); + if (likely(diff < 0)) { + // Another timer is pending - briefly allow irqs to fire + irq_enable(); + if (unlikely(TIFR1 & (1<<OCF1B))) + // Too many repeat timers - must exit irq handler + goto force_defer; + irq_disable(); + continue; + } - // Next timer in very near future - wait for it to be ready - for (;;) { - irq_enable(); - if (unlikely(TIFR1 & (1<<OCF1B))) - break; - irq_disable(); - diff = next - timer_get(); - if (diff < 0) - return 0; + if (likely(diff > TIMER_MIN_TRY_TICKS)) + // Schedule next timer normally + goto done; + + // Next timer in very near future - wait for it to be ready + do { + irq_enable(); + if (unlikely(TIFR1 & (1<<OCF1B))) + goto force_defer; + irq_disable(); + diff = next - timer_get(); + } while (diff >= 0); } -force_pause: +force_defer: // Too many repeat timers - force a pause so tasks aren't starved irq_disable(); uint16_t now = timer_get(); @@ -179,24 +179,11 @@ force_pause: done: timer_set(next); - return 1; + return; fail: shutdown("Rescheduled timer in the past"); } -// Harware OCR1A interrupt handler -ISR(TIMER1_COMPA_vect) -{ - for (;;) { - uint16_t next_waketime = sched_timer_dispatch(); - - // Schedule next timer event (or run next timer if it's ready) - uint8_t res = timer_try_set_next(next_waketime); - if (res) - break; - } -} - // Periodic background task that temporarily boosts priority of // timers. This helps prioritize timers when tasks are idling. static void |