M CHANGES → CHANGES

@@ -55,6 +55,7 @@ - Qt: Fix opening in fullscreen (fixes mgba.io/i/993)
  - Python: Fix package directory
  - GB Memory: Fix OAM DMA blocking regions (fixes mgba.io/i/1013)
  - Wii: Fix various setup and teardown drawing issues (fixes mgba.io/i/988)
+ - GBA Timer: Fix timers sometimes being late (fixes mgba.io/i/1012)
 Misc:
  - GBA Timer: Use global cycles for timers
  - GBA: Extend oddly-sized ROMs to full address space (fixes mgba.io/i/722)

M src/gba/timer.c → src/gba/timer.c

@@ -51,7 +51,7 @@ int32_t currentTime = mTimingCurrentTime(&gba->timing) - cyclesLate;
 	int32_t tickMask = (1 << GBATimerFlagsGetPrescaleBits(timer->flags)) - 1;
 	currentTime &= ~tickMask;
 	timer->lastEvent = currentTime;
-	GBATimerUpdateRegister(gba, timerId, 0);
+	GBATimerUpdateRegister(gba, timerId, TIMER_RELOAD_DELAY + cyclesLate);
 
 	if (GBATimerFlagsIsDoIrq(timer->flags)) {
 		timer->flags = GBATimerFlagsFillIrqPending(timer->flags);
@@ -155,7 +155,7 @@ 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, TIMER_RELOAD_DELAY + tickIncrement + currentTime);
+		mTimingSchedule(&gba->timing, &currentTimer->event, tickIncrement + currentTime);
 	}
 }