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Timer: Slightly restructure timer updating (fixes #1087, reopens #1012)

This commit is contained in:
Vicki Pfau 2018-05-26 14:16:24 -07:00
parent c353e1254a
commit e2a5efeaf7
1 changed files with 19 additions and 13 deletions
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32
src/gba/timer.c
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@ -1,4 +1,4 @@
/* Copyright (c) 2013-2016 Jeffrey Pfau
/* Copyright (c) 2013-2018 Jeffrey Pfau
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
@ -12,6 +12,8 @@
#define TIMER_RELOAD_DELAY 0
#define TIMER_STARTUP_DELAY 2
#define REG_TMCNT_LO(X) (REG_TM0CNT_LO + (X << 2))
static void GBATimerIrq(struct GBA* gba, int timerId) {
struct GBATimer* timer = &gba->timers[timerId];
if (GBATimerFlagsIsIrqPending(timer->flags)) {
@ -46,11 +48,6 @@ static void GBATimerIrq3(struct mTiming* timing, void* context, uint32_t cyclesL
static void GBATimerUpdate(struct GBA* gba, int timerId, uint32_t cyclesLate) {
struct GBATimer* timer = &gba->timers[timerId];
gba->memory.io[(REG_TM0CNT_LO >> 1) + (timerId << 1)] = timer->reload;
int32_t currentTime = mTimingCurrentTime(&gba->timing) - cyclesLate;
int32_t tickMask = (1 << GBATimerFlagsGetPrescaleBits(timer->flags)) - 1;
currentTime &= ~tickMask;
timer->lastEvent = currentTime;
GBATimerUpdateRegister(gba, timerId, TIMER_RELOAD_DELAY + cyclesLate);
if (GBATimerFlagsIsDoIrq(timer->flags)) {
@ -143,20 +140,29 @@ void GBATimerUpdateRegister(struct GBA* gba, int timer, int32_t cyclesLate) {
return;
}
// Align timer
int prescaleBits = GBATimerFlagsGetPrescaleBits(currentTimer->flags);
int32_t currentTime = mTimingCurrentTime(&gba->timing) - cyclesLate;
int32_t tickMask = (1 << prescaleBits) - 1;
currentTime &= ~tickMask;
// Update register
int32_t tickIncrement = currentTime - currentTimer->lastEvent;
currentTimer->lastEvent = currentTime;
tickIncrement >>= prescaleBits;
tickIncrement += gba->memory.io[(REG_TM0CNT_LO + (timer << 2)) >> 1];
gba->memory.io[(REG_TM0CNT_LO + (timer << 2)) >> 1] = tickIncrement;
if (!mTimingIsScheduled(&gba->timing, &currentTimer->event)) {
tickIncrement = (0x10000 - tickIncrement) << prescaleBits;
currentTime -= mTimingCurrentTime(&gba->timing) - cyclesLate;
mTimingSchedule(&gba->timing, &currentTimer->event, tickIncrement + currentTime);
tickIncrement += gba->memory.io[REG_TMCNT_LO(timer) >> 1];
while (tickIncrement >= 0x10000) {
tickIncrement -= 0x10000 - currentTimer->reload;
}
gba->memory.io[REG_TMCNT_LO(timer) >> 1] = tickIncrement;
// Schedule next update
tickIncrement = (0x10000 - tickIncrement) << prescaleBits;
currentTime += tickIncrement;
currentTime &= ~tickMask;
currentTime -= mTimingCurrentTime(&gba->timing);
mTimingDeschedule(&gba->timing, &currentTimer->event);
mTimingSchedule(&gba->timing, &currentTimer->event, currentTime);
}
void GBATimerWriteTMCNT_LO(struct GBA* gba, int timer, uint16_t reload) {
@ -190,7 +196,7 @@ void GBATimerWriteTMCNT_HI(struct GBA* gba, int timer, uint16_t control) {
currentTimer->flags = GBATimerFlagsTestFillEnable(currentTimer->flags, control & 0x0080);
if (!wasEnabled && GBATimerFlagsIsEnable(currentTimer->flags)) {
mTimingDeschedule(&gba->timing, &currentTimer->event);
gba->memory.io[(REG_TM0CNT_LO + (timer << 2)) >> 1] = currentTimer->reload;
gba->memory.io[REG_TMCNT_LO(timer) >> 1] = currentTimer->reload;
int32_t tickMask = (1 << prescaleBits) - 1;
currentTimer->lastEvent = (mTimingCurrentTime(&gba->timing) - TIMER_STARTUP_DELAY) & ~tickMask;
GBATimerUpdateRegister(gba, timer, TIMER_STARTUP_DELAY);