GB MBC: Sachen MMC2 support

CHANGES

@@ -13,7 +13,7 @@ Features:
  - Additional scaling shaders
  - Support for GameShark Advance SP (.gsv) save file importing
  - Support for multiple saves per game using .sa2, .sa3, etc.
- - New unlicensed GB mappers: NT (newer type), Sachen (MMC1)
+ - New unlicensed GB mappers: NT (newer type), Sachen (MMC1, MMC2)
 Emulation fixes:
  - ARM7: Fix unsigned multiply timing
  - GB: Copy logo from ROM if not running the BIOS intro (fixes mgba.io/i/2378)

include/mgba/internal/gb/memory.h

@@ -248,6 +248,11 @@ struct GBMemory {
 	uint8_t* wramBank;
 	int wramCurrentBank;
 
+	bool mbcReadBank0;
+	bool mbcReadBank1;
+	bool mbcReadHigh;
+	bool mbcWriteHigh;
+
 	bool sramAccess;
 	bool directSramAccess;
 	uint8_t* sram;

src/gb/gb.c

@@ -636,6 +636,10 @@ void GBSkipBIOS(struct GB* gb) {
 		}
 	}
 
+	if (gb->memory.mbcType == GB_UNL_SACHEN_MMC2) {
+		gb->memory.mbcState.sachen.locked = GB_SACHEN_UNLOCKED;
+	}
+
 	cpu->sp = 0xFFFE;
 	cpu->pc = 0x100;
 
@@ -660,7 +664,7 @@ void GBMapBIOS(struct GB* gb) {
 	if (gb->memory.rom) {
 		memcpy(&gb->memory.romBase[size], &gb->memory.rom[size], GB_SIZE_CART_BANK0 - size);
 		if (size > 0x100) {
-			memcpy(&gb->memory.romBase[0x100], &gb->memory.rom[0x100], sizeof(struct GBCartridge));
+			memcpy(&gb->memory.romBase[0x100], &gb->memory.rom[0x100], 0x100);
 		}
 	}
 }

src/gb/mbc.c

@@ -54,6 +54,7 @@ static uint8_t _GBPKJDRead(struct GBMemory*, uint16_t address);
 static uint8_t _GBBBDRead(struct GBMemory*, uint16_t address);
 static uint8_t _GBHitekRead(struct GBMemory*, uint16_t address);
 static uint8_t _GBSachenMMC1Read(struct GBMemory*, uint16_t address);
+static uint8_t _GBSachenMMC2Read(struct GBMemory*, uint16_t address);
 
 static uint8_t _GBPocketCamRead(struct GBMemory*, uint16_t address);
 static void _GBPocketCamCapture(struct GBMemory*);
@@ -204,6 +205,10 @@ static enum GBMemoryBankControllerType _detectUnlMBC(const uint8_t* mem, size_t
 		return GB_UNL_SACHEN_MMC1;
 	}
 
+	if (mem[0x184] == 0xCE && mem[0x1C4] == 0xED && mem[0x194] == 0x66) {
+		return GB_UNL_SACHEN_MMC2;
+	}
+
 	return GB_MBC_AUTODETECT;
 }
 
@@ -423,16 +428,31 @@ void GBMBCInit(struct GB* gb) {
 	case GB_UNL_BBD:
 		gb->memory.mbcWrite = _GBBBD;
 		gb->memory.mbcRead = _GBBBDRead;
+		gb->memory.mbcReadBank1 = true;
 		break;
 	case GB_UNL_HITEK:
 		gb->memory.mbcWrite = _GBHitek;
 		gb->memory.mbcRead = _GBHitekRead;
 		gb->memory.mbcState.bbd.dataSwapMode = 7;
 		gb->memory.mbcState.bbd.bankSwapMode = 7;
+		gb->memory.mbcReadBank1 = true;
 		break;
 	case GB_UNL_SACHEN_MMC1:
 		gb->memory.mbcWrite = _GBSachen;
 		gb->memory.mbcRead = _GBSachenMMC1Read;
+		gb->memory.mbcReadBank0 = true;
+		gb->memory.mbcReadBank1 = true;
+		break;
+	case GB_UNL_SACHEN_MMC2:
+		gb->memory.mbcWrite = _GBSachen;
+		gb->memory.mbcRead = _GBSachenMMC2Read;
+		gb->memory.mbcReadBank0 = true;
+		gb->memory.mbcReadBank1 = true;
+		gb->memory.mbcReadHigh = true;
+		gb->memory.mbcWriteHigh = true;
+		if (gb->sramSize) {
+			gb->memory.sramAccess = true;
+		}
 		break;
 	}
 
@@ -1760,6 +1780,12 @@ void _GBSachen(struct GB* gb, uint16_t address, uint8_t value) {
 			GBMBCSwitchBank0(gb, state->baseBank & state->mask);
 		}
 		break;
+	case 6:
+		if (gb->memory.mbcType == GB_UNL_SACHEN_MMC2 && state->locked == GB_SACHEN_LOCKED_DMG) {
+			state->locked = GB_SACHEN_LOCKED_CGB;
+			state->transition = 0;
+		}
+		break;
 	}
 }
 
@@ -1774,12 +1800,13 @@ static uint16_t _unscrambleSachen(uint16_t address) {
 
 uint8_t _GBSachenMMC1Read(struct GBMemory* memory, uint16_t address) {
 	struct GBSachenState* state = &memory->mbcState.sachen;
-	if (state->locked != GB_SACHEN_UNLOCKED) {
+	if (state->locked != GB_SACHEN_UNLOCKED && (address & 0xFF00) == 0x100) {
 		++state->transition;
 		if (state->transition == 0x31) {
 			state->locked = GB_SACHEN_UNLOCKED;
+		} else {
+			address |= 0x80;
 		}
-		address |= 0x80;
 	}
 
 	if ((address & 0xFF00) == 0x0100) {
@@ -1795,6 +1822,37 @@ uint8_t _GBSachenMMC1Read(struct GBMemory* memory, uint16_t address) {
 	}
 }
 
+uint8_t _GBSachenMMC2Read(struct GBMemory* memory, uint16_t address) {
+	struct GBSachenState* state = &memory->mbcState.sachen;
+	if (address >= 0xC000 && state->locked == GB_SACHEN_LOCKED_DMG) {
+		state->transition = 0;
+		state->locked = GB_SACHEN_LOCKED_CGB;
+	}
+
+	if (state->locked != GB_SACHEN_UNLOCKED && (address & 0x8700) == 0x0100) {
+		++state->transition;
+		if (state->transition == 0x31) {
+			++state->locked;
+			state->transition = 0;
+		}
+	}
+
+	if ((address & 0xFF00) == 0x0100) {
+		if (state->locked == GB_SACHEN_LOCKED_CGB) {
+			address |= 0x80;
+		}
+		address = _unscrambleSachen(address);
+	}
+
+	if (address < GB_BASE_CART_BANK1) {
+		return memory->romBase[address];
+	} else if (address < GB_BASE_VRAM) {
+		return memory->romBank[address & (GB_SIZE_CART_BANK0 - 1)];
+	} else {
+		return 0xFF;
+	}
+}
+
 static void _appendSaveSuffix(struct GB* gb, const void* buffer, size_t size) {
 	struct VFile* vf = gb->sramVf;
 	if ((size_t) vf->size(vf) < gb->sramSize + size) {

src/gb/memory.c

@@ -73,7 +73,7 @@ static void GBSetActiveRegion(struct SM83Core* cpu, uint16_t address) {
 	case GB_REGION_CART_BANK0 + 1:
 	case GB_REGION_CART_BANK0 + 2:
 	case GB_REGION_CART_BANK0 + 3:
-		if ((gb->memory.mbcType & GB_UNL_SACHEN_MMC1) == GB_UNL_SACHEN_MMC1) {
+		if (gb->memory.mbcReadBank0) {
 			cpu->memory.cpuLoad8 = GBLoad8;
 			break;
 		}
@@ -94,7 +94,7 @@ static void GBSetActiveRegion(struct SM83Core* cpu, uint16_t address) {
 	case GB_REGION_CART_BANK1 + 1:
 	case GB_REGION_CART_BANK1 + 2:
 	case GB_REGION_CART_BANK1 + 3:
-		if ((gb->memory.mbcType & GB_UNL_BBD) == GB_UNL_BBD) {
+		if (gb->memory.mbcReadBank1) {
 			cpu->memory.cpuLoad8 = GBLoad8;
 			break;
 		}
@@ -249,7 +249,7 @@ uint8_t GBLoad8(struct SM83Core* cpu, uint16_t address) {
 	case GB_REGION_CART_BANK0 + 3:
 		if (address >= memory->romSize) {
 			memory->cartBus = 0xFF;
-		} else if ((memory->mbcType & GB_UNL_SACHEN_MMC1) == GB_UNL_SACHEN_MMC1) {
+		} else if (gb->memory.mbcReadBank0) {
 			memory->cartBus = memory->mbcRead(memory, address);
 		} else {
 			memory->cartBus = memory->romBase[address & (GB_SIZE_CART_BANK0 - 1)];
@@ -268,7 +268,7 @@ uint8_t GBLoad8(struct SM83Core* cpu, uint16_t address) {
 	case GB_REGION_CART_BANK1 + 1:
 		if (address >= memory->romSize) {
 			memory->cartBus = 0xFF;
-		} else if ((memory->mbcType & GB_UNL_BBD) == GB_UNL_BBD) {
+		} else if (gb->memory.mbcReadBank1) {
 			memory->cartBus = memory->mbcRead(memory, address);
 		} else {
 			memory->cartBus = memory->romBank[address & (GB_SIZE_CART_BANK0 - 1)];
@@ -298,8 +298,14 @@ uint8_t GBLoad8(struct SM83Core* cpu, uint16_t address) {
 		return memory->cartBus;
 	case GB_REGION_WORKING_RAM_BANK0:
 	case GB_REGION_WORKING_RAM_BANK0 + 2:
+		if (gb->memory.mbcReadHigh) {
+			memory->mbcRead(memory, address);
+		}
 		return memory->wram[address & (GB_SIZE_WORKING_RAM_BANK0 - 1)];
 	case GB_REGION_WORKING_RAM_BANK1:
+		if (gb->memory.mbcReadHigh) {
+			memory->mbcRead(memory, address);
+		}
 		return memory->wramBank[address & (GB_SIZE_WORKING_RAM_BANK0 - 1)];
 	default:
 		if (address < GB_BASE_OAM) {
@@ -373,9 +379,15 @@ void GBStore8(struct SM83Core* cpu, uint16_t address, int8_t value) {
 		return;
 	case GB_REGION_WORKING_RAM_BANK0:
 	case GB_REGION_WORKING_RAM_BANK0 + 2:
+		if (memory->mbcWriteHigh) {
+			memory->mbcWrite(gb, address, value);
+		}
 		memory->wram[address & (GB_SIZE_WORKING_RAM_BANK0 - 1)] = value;
 		return;
 	case GB_REGION_WORKING_RAM_BANK1:
+		if (memory->mbcWriteHigh) {
+			memory->mbcWrite(gb, address, value);
+		}
 		memory->wramBank[address & (GB_SIZE_WORKING_RAM_BANK0 - 1)] = value;
 		return;
 	default: