M CHANGES → CHANGES

@@ -17,6 +17,7 @@ - GBA Video: Fix scanline cache with scale factor change edge cases
  - GBA DMA: Fix DMA0-2 lengths (fixes mgba.io/i/1344)
  - GB Video: Fix window y changing mid-window (fixes mgba.io/i/1345)
  - GB Video: Fix more window edge cases (fixes mgba.io/i/1346)
+ - GB Timer: Fix timing adjustments when writing to TAC (fixes mgba.io/i/1340)
 Other fixes:
  - Qt: More app metadata fixes
  - Qt: Fix load recent from archive (fixes mgba.io/i/1325)

M src/gb/timer.c → src/gb/timer.c

@@ -92,6 +92,10 @@ }
 
 uint8_t GBTimerUpdateTAC(struct GBTimer* timer, GBRegisterTAC tac) {
 	if (GBRegisterTACIsRun(tac)) {
+		timer->nextDiv -= mTimingUntil(&timer->p->timing, &timer->event);
+		mTimingDeschedule(&timer->p->timing, &timer->event);
+		_GBTimerDivIncrement(timer, (timer->p->cpu->executionState + 2) & 3);
+
 		switch (GBRegisterTACGetClock(tac)) {
 		case 0:
 			timer->timaPeriod = 1024 >> 4;
@@ -107,9 +111,6 @@ timer->timaPeriod = 256 >> 4;
 			break;
 		}
 
-		timer->nextDiv -= mTimingUntil(&timer->p->timing, &timer->event);
-		mTimingDeschedule(&timer->p->timing, &timer->event);
-		_GBTimerDivIncrement(timer, (timer->p->cpu->executionState + 2) & 3);
 		timer->nextDiv += GB_DMG_DIV_PERIOD;
 		mTimingSchedule(&timer->p->timing, &timer->event, timer->nextDiv);
 	} else {