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GB Timer: Batch timer updates as needed

This commit is contained in:
Jeffrey Pfau 2016-08-28 10:32:47 -07:00
parent 4c5ba8d8c1
commit c9b69bba44
1 changed files with 13 additions and 2 deletions
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15
src/gb/timer.c
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@ -29,12 +29,11 @@ int32_t GBTimerProcessEvents(struct GBTimer* timer, int32_t cycles) {
timer->irqPending = false; timer->irqPending = false;
timer->nextEvent += timer->nextDiv; timer->nextEvent += timer->nextDiv;
} }
if (timer->nextDiv <= 0) { while (timer->nextDiv <= 0) {
if ((timer->internalDiv & 15) == 15) { if ((timer->internalDiv & 15) == 15) {
++timer->p->memory.io[REG_DIV]; ++timer->p->memory.io[REG_DIV];
} }
timer->nextDiv += GB_DMG_DIV_PERIOD; timer->nextDiv += GB_DMG_DIV_PERIOD;
timer->nextEvent += GB_DMG_DIV_PERIOD;
// Make sure to trigger when the correct bit is a falling edge // Make sure to trigger when the correct bit is a falling edge
if (timer->timaPeriod > 0 && (timer->internalDiv & (timer->timaPeriod - 1)) == timer->timaPeriod - 1) { if (timer->timaPeriod > 0 && (timer->internalDiv & (timer->timaPeriod - 1)) == timer->timaPeriod - 1) {
@ -46,6 +45,18 @@ int32_t GBTimerProcessEvents(struct GBTimer* timer, int32_t cycles) {
} }
++timer->internalDiv; ++timer->internalDiv;
} }
if (timer->nextEvent <= 0) {
// Batch div increments
int divsToGo = 16 - (timer->internalDiv & 15);
int timaToGo = INT_MAX;
if (timer->timaPeriod) {
timaToGo = timer->timaPeriod - (timer->internalDiv & (timer->timaPeriod - 1));
}
if (timaToGo < divsToGo) {
divsToGo = timaToGo;
}
timer->nextEvent += GB_DMG_DIV_PERIOD * divsToGo;
}
timer->eventDiff = 0; timer->eventDiff = 0;
} }
return timer->nextEvent; return timer->nextEvent;