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GB Timer: Improve timer stepping when updating

This commit is contained in:
Vicki Pfau 2017-06-22 02:18:22 -07:00
parent d5c5173889
commit 4efd494cd7
1 changed files with 17 additions and 9 deletions
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26
src/gb/timer.c
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@ -19,22 +19,26 @@ void _GBTimerIRQ(struct mTiming* timing, void* context, uint32_t cyclesLate) {
GBUpdateIRQs(timer->p);
}
void _GBTimerIncrement(struct mTiming* timing, void* context, uint32_t cyclesLate) {
struct GBTimer* timer = context;
timer->nextDiv += cyclesLate;
while (timer->nextDiv > 0) {
static void _GBTimerDivIncrement(struct GBTimer* timer, uint32_t cyclesLate) {
while (timer->nextDiv >= GB_DMG_DIV_PERIOD) {
timer->nextDiv -= GB_DMG_DIV_PERIOD;
// Make sure to trigger when the correct bit is a falling edge
if (timer->timaPeriod > 0 && (timer->internalDiv & (timer->timaPeriod - 1)) == timer->timaPeriod - 1) {
++timer->p->memory.io[REG_TIMA];
if (!timer->p->memory.io[REG_TIMA]) {
mTimingSchedule(timing, &timer->irq, 4 - cyclesLate);
mTimingSchedule(&timer->p->timing, &timer->irq, 4 - cyclesLate);
}
}
++timer->internalDiv;
timer->p->memory.io[REG_DIV] = timer->internalDiv >> 4;
}
}
void _GBTimerUpdate(struct mTiming* timing, void* context, uint32_t cyclesLate) {
struct GBTimer* timer = context;
timer->nextDiv += cyclesLate;
_GBTimerDivIncrement(timer, cyclesLate);
// Batch div increments
int divsToGo = 16 - (timer->internalDiv & 15);
int timaToGo = INT_MAX;
@ -51,7 +55,7 @@ void _GBTimerIncrement(struct mTiming* timing, void* context, uint32_t cyclesLat
void GBTimerReset(struct GBTimer* timer) {
timer->event.context = timer;
timer->event.name = "GB Timer";
timer->event.callback = _GBTimerIncrement;
timer->event.callback = _GBTimerUpdate;
timer->event.priority = 0x20;
timer->irq.context = timer;
timer->irq.name = "GB Timer IRQ";
@ -64,16 +68,18 @@ void GBTimerReset(struct GBTimer* timer) {
}
void GBTimerDivReset(struct GBTimer* timer) {
timer->nextDiv -= mTimingUntil(&timer->p->timing, &timer->event);
mTimingDeschedule(&timer->p->timing, &timer->event);
_GBTimerDivIncrement(timer, (timer->p->cpu->executionState + 1) & 3);
if (timer->internalDiv & (timer->timaPeriod >> 1)) {
++timer->p->memory.io[REG_TIMA];
if (!timer->p->memory.io[REG_TIMA]) {
mTimingSchedule(&timer->p->timing, &timer->irq, 4 - ((timer->p->cpu->executionState + 1) & 3));
mTimingSchedule(&timer->p->timing, &timer->irq, 4 - (timer->p->cpu->executionState + 1) & 3);
}
}
timer->p->memory.io[REG_DIV] = 0;
timer->internalDiv = 0;
timer->nextDiv = GB_DMG_DIV_PERIOD;
mTimingDeschedule(&timer->p->timing, &timer->event);
mTimingSchedule(&timer->p->timing, &timer->event, timer->nextDiv - ((timer->p->cpu->executionState + 1) & 3));
}
@ -96,7 +102,9 @@ uint8_t GBTimerUpdateTAC(struct GBTimer* timer, GBRegisterTAC tac) {
timer->nextDiv -= mTimingUntil(&timer->p->timing, &timer->event);
mTimingDeschedule(&timer->p->timing, &timer->event);
mTimingSchedule(&timer->p->timing, &timer->event, 0);
_GBTimerDivIncrement(timer, (timer->p->cpu->executionState + 1) & 3);
timer->nextDiv += GB_DMG_DIV_PERIOD;
mTimingSchedule(&timer->p->timing, &timer->event, timer->nextDiv);
} else {
timer->timaPeriod = 0;
}