M CHANGES → CHANGES

@@ -40,6 +40,7 @@ - 3DS: Fix opening files in directory names with trailing slashes
  - GB MBC: Fix MBC2 saves (fixes mgba.io/i/954)
  - GBA Memory: Fix copy-on-write memory leak
  - Core: Fix ROM patches not being unloaded when disabled (fixes mgba.io/i/962)
+ - GBA I/O: Fix writing to DISPCNT CGB flag (fixes mgba.io/i/902)
 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/extra/proxy.c → src/gba/extra/proxy.c

@@ -171,11 +171,16 @@
 uint16_t GBAVideoProxyRendererWriteVideoRegister(struct GBAVideoRenderer* renderer, uint32_t address, uint16_t value) {
 	struct GBAVideoProxyRenderer* proxyRenderer = (struct GBAVideoProxyRenderer*) renderer;
 	switch (address) {
+	case REG_DISPCNT:
+		value &= 0xFFF7;
+		break;
 	case REG_BG0CNT:
 	case REG_BG1CNT:
+		value &= 0xDFFF;
+		break;
 	case REG_BG2CNT:
 	case REG_BG3CNT:
-		value &= 0xFFCF;
+		value &= 0xFFFF;
 		break;
 	case REG_BG0HOFS:
 	case REG_BG0VOFS:

M src/gba/renderers/video-software.c → src/gba/renderers/video-software.c

@@ -157,6 +157,7 @@ }
 
 	switch (address) {
 	case REG_DISPCNT:
+		value &= 0xFFF7;
 		softwareRenderer->dispcnt = value;
 		GBAVideoSoftwareRendererUpdateDISPCNT(softwareRenderer);
 		break;

M src/gba/video.c → src/gba/video.c

@@ -217,6 +217,9 @@ if (renderer->cache) {
 		GBAVideoCacheWriteVideoRegister(renderer->cache, address, value);
 	}
 	switch (address) {
+	case REG_DISPCNT:
+		value &= 0xFFF7;
+		break;
 	case REG_BG0CNT:
 	case REG_BG1CNT:
 		value &= 0xDFFF;