GBA Memory: Fix DMA timing

src/core/timing.c

@@ -68,6 +68,10 @@ int32_t mTimingTick(struct mTiming* timing, int32_t cycles) {
 	return *timing->nextEvent;
 }
 
+int32_t mTimingCurrentTime(struct mTiming* timing) {
+	return timing->masterCycles + *timing->relativeCycles;
+}
+
 int32_t mTimingNextEvent(struct mTiming* timing) {
 	struct mTimingEvent* next = timing->root;
 	if (!next) {

src/core/timing.h

@@ -32,6 +32,7 @@ void mTimingClear(struct mTiming* timing);
 void mTimingSchedule(struct mTiming* timing, struct mTimingEvent*, int32_t when);
 void mTimingDeschedule(struct mTiming* timing, struct mTimingEvent*);
 int32_t mTimingTick(struct mTiming* timing, int32_t cycles);
+int32_t mTimingCurrentTime(struct mTiming* timing);
 int32_t mTimingNextEvent(struct mTiming* timing);
 
 #endif

src/gba/memory.c

@@ -1555,8 +1555,9 @@ void GBAMemoryScheduleDMA(struct GBA* gba, int number, struct GBADMA* info) {
 	info->hasStarted = 0;
 	switch (GBADMARegisterGetTiming(info->reg)) {
 	case DMA_TIMING_NOW:
-		info->nextEvent = 2;
+		info->nextEvent = 2 + 1; // XXX: Account for I cycle when writing
-		GBAMemoryUpdateDMAs(gba, -1);
+		info->scheduledAt = mTimingCurrentTime(&gba->timing);
+		GBAMemoryUpdateDMAs(gba, 0);
 		break;
 	case DMA_TIMING_HBLANK:
 		// Handled implicitly
@@ -1586,27 +1587,43 @@ void GBAMemoryScheduleDMA(struct GBA* gba, int number, struct GBADMA* info) {
 void GBAMemoryRunHblankDMAs(struct GBA* gba, int32_t cycles) {
 	struct GBAMemory* memory = &gba->memory;
 	struct GBADMA* dma;
+	bool dmaSeen = false;
+	if (memory->activeDMA >= 0) {
+		GBAMemoryUpdateDMAs(gba, mTimingCurrentTime(&gba->timing) - memory->dma[memory->activeDMA].scheduledAt);
+	}
 	int i;
 	for (i = 0; i < 4; ++i) {
 		dma = &memory->dma[i];
 		if (GBADMARegisterIsEnable(dma->reg) && GBADMARegisterGetTiming(dma->reg) == DMA_TIMING_HBLANK) {
 			dma->nextEvent = 2 + cycles;
+			dma->scheduledAt = mTimingCurrentTime(&gba->timing);
+			dmaSeen = true;
 		}
 	}
-	GBAMemoryUpdateDMAs(gba, 0);
+	if (dmaSeen) {
+		GBAMemoryUpdateDMAs(gba, 0);
+	}
 }
 
 void GBAMemoryRunVblankDMAs(struct GBA* gba, int32_t cycles) {
 	struct GBAMemory* memory = &gba->memory;
 	struct GBADMA* dma;
+	bool dmaSeen = false;
+	if (memory->activeDMA >= 0) {
+		GBAMemoryUpdateDMAs(gba, mTimingCurrentTime(&gba->timing) - memory->dma[memory->activeDMA].scheduledAt);
+	}
 	int i;
 	for (i = 0; i < 4; ++i) {
 		dma = &memory->dma[i];
 		if (GBADMARegisterIsEnable(dma->reg) && GBADMARegisterGetTiming(dma->reg) == DMA_TIMING_VBLANK) {
 			dma->nextEvent = 2 + cycles;
+			dma->scheduledAt = mTimingCurrentTime(&gba->timing);
+			dmaSeen = true;
 		}
 	}
-	GBAMemoryUpdateDMAs(gba, 0);
+	if (dmaSeen) {
+		GBAMemoryUpdateDMAs(gba, 0);
+	}
 }
 
 void _dmaEvent(struct mTiming* timing, void* context, uint32_t cyclesLate) {
@@ -1664,6 +1681,7 @@ void GBAMemoryServiceDMA(struct GBA* gba, int number, struct GBADMA* info) {
 		if (info->hasStarted < 1) {
 			info->hasStarted = wordsRemaining;
 			info->nextEvent = 0;
+			info->scheduledAt = mTimingCurrentTime(&gba->timing);
 			GBAMemoryUpdateDMAs(gba, -cycles);
 			return;
 		}
@@ -1729,6 +1747,7 @@ void GBAMemoryServiceDMA(struct GBA* gba, int number, struct GBADMA* info) {
 	} else {
 		info->nextDest = dest;
 		info->nextCount = wordsRemaining;
+		info->scheduledAt = mTimingCurrentTime(&gba->timing);
 	}
 	info->nextSource = source;
 	GBAMemoryUpdateDMAs(gba, 0);

src/gba/memory.h

@@ -109,6 +109,7 @@ struct GBADMA {
 	uint32_t nextDest;
 	int32_t nextCount;
 	int32_t nextEvent;
+	uint32_t scheduledAt;
 	int32_t hasStarted;
 };