From 1402593855729beaca177d43700eb462bd8c123d Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Tue, 16 Jun 2020 20:49:07 -0700
Subject: [PATCH] GB MBC: Fix MBC2 bit selection

---
 CHANGES                                           |   1 +
 .../mbc2/bits_ramg/baseline_0000.png              | Bin 0 -> 528 bytes
 .../emulator-only/mbc2/bits_ramg/config.ini       |   2 +-
 .../mbc2/bits_romb/baseline_0000.png              | Bin 0 -> 528 bytes
 .../emulator-only/mbc2/bits_romb/config.ini       |   2 +-
 src/gb/mbc.c                                      |  14 ++++++++++----
 6 files changed, 13 insertions(+), 6 deletions(-)
 create mode 100644 cinema/gb/mooneye-gb/emulator-only/mbc2/bits_ramg/baseline_0000.png
 create mode 100644 cinema/gb/mooneye-gb/emulator-only/mbc2/bits_romb/baseline_0000.png

diff --git a/CHANGES b/CHANGES
index 0cb5eaafa..b4b1cccf3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -7,6 +7,7 @@ Emulation fixes:
  - ARM: Fix STR storing PC after address calculation
  - GB MBC: Fix MBC1 mode changing behavior
  - GB MBC: Fix MBC1 RAM enable bit selection
+ - GB MBC: Fix MBC2 bit selection
  - GB Video: Fix state after skipping BIOS (fixes mgba.io/i/1715 and mgba.io/i/1716)
  - GBA: Fix timing advancing too quickly in rare cases
  - GBA BIOS: Implement dummy sound driver calls
diff --git a/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_ramg/baseline_0000.png b/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_ramg/baseline_0000.png
new file mode 100644
index 0000000000000000000000000000000000000000..f9e5e47b50a4d548ddbc988a8e76364d30f505cf
GIT binary patch
literal 528
zcmeAS@N?(olHy`uVBq!ia0vp^3xIe62NRHFxc>b*0|VoAPZ!6KiaBquU(7mWz~FE(
z<;Va1cWgxt&B%VfEU&=!xnok3TT$lH;@jICuivi!&oIyXfkoqEmOfz%KM+GNxySPP
z*F*Dd<=5Z6-dB81|M;InsWNlk%!+)xc<Jk(w<pip9`e0z`sA(t&#O<jZVkU5|2}8&
zJLfs9a_r^r4UcWhjSsu?{5^m17Jd7#z7Hmc{Ju1K-R9+WKfNuv_vl^zTGreDui^Tu
z-bA~+!oL&U@AAjZeBAw6Mn=70&VfRv<D8=m?1Au|?;2;WuxQJTNKj0By85}Sb4q9e
E0Q;uho&W#<

literal 0
HcmV?d00001

diff --git a/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_ramg/config.ini b/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_ramg/config.ini
index 7ddee425b..7f44b56a9 100644
--- a/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_ramg/config.ini
+++ b/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_ramg/config.ini
@@ -1,2 +1,2 @@
 [testinfo]
-fail=1
+skip=360
diff --git a/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_romb/baseline_0000.png b/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_romb/baseline_0000.png
new file mode 100644
index 0000000000000000000000000000000000000000..f9e5e47b50a4d548ddbc988a8e76364d30f505cf
GIT binary patch
literal 528
zcmeAS@N?(olHy`uVBq!ia0vp^3xIe62NRHFxc>b*0|VoAPZ!6KiaBquU(7mWz~FE(
z<;Va1cWgxt&B%VfEU&=!xnok3TT$lH;@jICuivi!&oIyXfkoqEmOfz%KM+GNxySPP
z*F*Dd<=5Z6-dB81|M;InsWNlk%!+)xc<Jk(w<pip9`e0z`sA(t&#O<jZVkU5|2}8&
zJLfs9a_r^r4UcWhjSsu?{5^m17Jd7#z7Hmc{Ju1K-R9+WKfNuv_vl^zTGreDui^Tu
z-bA~+!oL&U@AAjZeBAw6Mn=70&VfRv<D8=m?1Au|?;2;WuxQJTNKj0By85}Sb4q9e
E0Q;uho&W#<

literal 0
HcmV?d00001

diff --git a/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_romb/config.ini b/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_romb/config.ini
index 7ddee425b..7f44b56a9 100644
--- a/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_romb/config.ini
+++ b/cinema/gb/mooneye-gb/emulator-only/mbc2/bits_romb/config.ini
@@ -1,2 +1,2 @@
 [testinfo]
-fail=1
+skip=360
diff --git a/src/gb/mbc.c b/src/gb/mbc.c
index 8417c2102..ca94cb534 100644
--- a/src/gb/mbc.c
+++ b/src/gb/mbc.c
@@ -480,9 +480,9 @@ void _GBMBC2(struct GB* gb, uint16_t address, uint8_t value) {
 	struct GBMemory* memory = &gb->memory;
 	int shift = (address & 1) * 4;
 	int bank = value & 0xF;
-	switch (address >> 13) {
+	switch ((address & 0xC100) >> 8) {
 	case 0x0:
-		switch (value) {
+		switch (value & 0x0F) {
 		case 0:
 			memory->sramAccess = false;
 			break;
@@ -491,7 +491,7 @@ void _GBMBC2(struct GB* gb, uint16_t address, uint8_t value) {
 			break;
 		default:
 			// TODO
-			mLOG(GB_MBC, STUB, "MBC1 unknown value %02X", value);
+			mLOG(GB_MBC, STUB, "MBC2 unknown value %02X", value);
 			break;
 		}
 		break;
@@ -501,7 +501,10 @@ void _GBMBC2(struct GB* gb, uint16_t address, uint8_t value) {
 		}
 		GBMBCSwitchBank(gb, bank);
 		break;
-	case 0x5:
+	case 0x80:
+	case 0x81:
+	case 0x82:
+	case 0x83:
 		if (!memory->sramAccess) {
 			return;
 		}
@@ -517,6 +520,9 @@ void _GBMBC2(struct GB* gb, uint16_t address, uint8_t value) {
 }
 
 static uint8_t _GBMBC2Read(struct GBMemory* memory, uint16_t address) {
+	if (!memory->sramAccess) {
+		return 0xFF;
+	}
 	address &= 0x1FF;
 	int shift = (address & 1) * 4;
 	return (memory->sramBank[(address >> 1)] >> shift) | 0xF0;