M CHANGES → CHANGES

@@ -31,6 +31,7 @@ - Qt: Fix timezone issues with time overrides
  - Qt: Fix sprite export pausing game indefinitely (fixes mgba.io/i/841)
  - ARM: Fix MSR when T bit is set
  - GB Video: Fix potential hang when ending mode 0
+ - GB Memory: Fix HDMA count starting in mode 0 (fixes mgba.io/i/855)
 Misc:
  - GBA Timer: Use global cycles for timers
  - GBA: Extend oddly-sized ROMs to full address space (fixes mgba.io/i/722)

M src/gb/memory.c → src/gb/memory.c

@@ -469,10 +469,13 @@ gb->memory.hdmaDest |= 0x8000;
 	bool wasHdma = gb->memory.isHdma;
 	gb->memory.isHdma = value & 0x80;
 	if ((!wasHdma && !gb->memory.isHdma) || gb->video.mode == 0) {
-		gb->memory.hdmaRemaining = ((value & 0x7F) + 1) * 0x10;
+		if (gb->memory.isHdma) {
+			gb->memory.hdmaRemaining = 0x10;
+		} else {
+			gb->memory.hdmaRemaining = ((value & 0x7F) + 1) * 0x10;
+		}
 		gb->cpuBlocked = true;
 		mTimingSchedule(&gb->timing, &gb->memory.hdmaEvent, 0);
-		gb->cpu->nextEvent = gb->cpu->cycles;
 	}
 }
 

M src/gb/video.c → src/gb/video.c

@@ -304,6 +304,7 @@ struct GBVideo* video = context;
 	GBVideoProcessDots(video);
 	if (video->ly < GB_VIDEO_VERTICAL_PIXELS && video->p->memory.isHdma && video->p->memory.io[REG_HDMA5] != 0xFF) {
 		video->p->memory.hdmaRemaining = 0x10;
+		video->p->cpuBlocked = true;
 		mTimingDeschedule(timing, &video->p->memory.hdmaEvent);
 		mTimingSchedule(timing, &video->p->memory.hdmaEvent, 0);
 	}