GBA I/O: Redo internal key input, enabling edge-based key IRQs

CHANGES

@@ -16,6 +16,7 @@ Emulation fixes:
  - GB Memory: Add cursory cartridge open bus emulation (fixes mgba.io/i/2032)
  - GB Video: Render SGB border when unmasking with ATTR/PAL_SET (fixes mgba.io/i/2261)
  - GBA: Improve timing when not booting from BIOS
+ - GBA I/O: Redo internal key input, enabling edge-based key IRQs
  - GBA Memory: Fix misaligned 32-bit I/O loads (fixes mgba.io/i/2307)
  - GBA SIO: Fix SI value for unattached MULTI mode
  - GBA Video: Fix backdrop color if DISPCNT is first set to 0 (fixes mgba.io/i/2260)

include/mgba/internal/gba/gba.h

@@ -85,7 +85,8 @@ struct GBA {
 	struct mTimingEvent irqEvent;
 
 	uint32_t biosChecksum;
-	int* keySource;
+	uint16_t keysActive;
+	uint16_t keysLast;
 	struct mRotationSource* rotationSource;
 	struct GBALuminanceSource* luminanceSource;
 	struct mRTCSource* rtcSource;

src/gba/core.c

@@ -146,7 +146,6 @@ struct GBACore {
 #ifndef DISABLE_THREADING
 	struct mVideoThreadProxy threadProxy;
 #endif
-	int keys;
 	struct mCPUComponent* components[CPU_COMPONENT_MAX];
 	const struct Configuration* overrides;
 	struct mDebuggerPlatform* debuggerPlatform;
@@ -205,9 +204,6 @@ static bool _GBACoreInit(struct mCore* core) {
 	gbacore->proxyRenderer.logger = NULL;
 #endif
 
-	gbacore->keys = 0;
-	gba->keySource = &gbacore->keys;
-
 #if !defined(MINIMAL_CORE) || MINIMAL_CORE < 2
 	mDirectorySetInit(&core->dirs);
 #endif
@@ -707,20 +703,20 @@ static bool _GBACoreSaveState(struct mCore* core, void* state) {
 }
 
 static void _GBACoreSetKeys(struct mCore* core, uint32_t keys) {
-	struct GBACore* gbacore = (struct GBACore*) core;
-	gbacore->keys = keys;
-	GBATestKeypadIRQ(core->board);
+	struct GBA* gba = core->board;
+	gba->keysActive = keys;
+	GBATestKeypadIRQ(gba);
 }
 
 static void _GBACoreAddKeys(struct mCore* core, uint32_t keys) {
-	struct GBACore* gbacore = (struct GBACore*) core;
-	gbacore->keys |= keys;
-	GBATestKeypadIRQ(core->board);
+	struct GBA* gba = core->board;
+	gba->keysActive |= keys;
+	GBATestKeypadIRQ(gba);
 }
 
 static void _GBACoreClearKeys(struct mCore* core, uint32_t keys) {
-	struct GBACore* gbacore = (struct GBACore*) core;
-	gbacore->keys &= ~keys;
+	struct GBA* gba = core->board;
+	gba->keysActive &= ~keys;
 }
 
 static int32_t _GBACoreFrameCounter(const struct mCore* core) {

src/gba/gba.c

@@ -90,7 +90,8 @@ static void GBAInit(void* cpu, struct mCPUComponent* component) {
 
 	GBAHardwareInit(&gba->memory.hw, NULL);
 
-	gba->keySource = 0;
+	gba->keysActive = 0;
+	gba->keysLast = 0;
 	gba->rotationSource = 0;
 	gba->luminanceSource = 0;
 	gba->rtcSource = 0;
@@ -877,18 +878,22 @@ void GBAFrameEnded(struct GBA* gba) {
 }
 
 void GBATestKeypadIRQ(struct GBA* gba) {
+	if (gba->keysActive == gba->keysLast) {
+		return;
+	}
 	uint16_t keycnt = gba->memory.io[REG_KEYCNT >> 1];
 	if (!(keycnt & 0x4000)) {
 		return;
 	}
 	int isAnd = keycnt & 0x8000;
-	if (!gba->keySource) {
-		// TODO?
-		return;
-	}
 
 	keycnt &= 0x3FF;
-	uint16_t keyInput = *gba->keySource & keycnt;
+	uint16_t keyInput = gba->keysActive & keycnt;
+	uint16_t lastInput = gba->keysLast & keycnt;
+	gba->keysLast = gba->keysActive;
+	if (keyInput == lastInput) {
+		return;
+	}
 
 	if (isAnd && keycnt == keyInput) {
 		GBARaiseIRQ(gba, IRQ_KEYPAD, 0);

src/gba/io.c

@@ -743,24 +743,19 @@ uint16_t GBAIORead(struct GBA* gba, uint32_t address) {
 					callbacks->keysRead(callbacks->context);
 				}
 			}
-			uint16_t input = 0;
 			if (gba->keyCallback) {
-				input = gba->keyCallback->readKeys(gba->keyCallback);
-				if (gba->keySource) {
-					*gba->keySource = input;
+				gba->keysActive = gba->keyCallback->readKeys(gba->keyCallback);
+			}
+			uint16_t input = gba->keysActive;
+			if (!gba->allowOpposingDirections) {
+				unsigned rl = input & 0x030;
+				unsigned ud = input & 0x0C0;
+				input &= 0x30F;
+				if (rl != 0x030) {
+					input |= rl;
 				}
-			} else if (gba->keySource) {
-				input = *gba->keySource;
-				if (!gba->allowOpposingDirections) {
-					unsigned rl = input & 0x030;
-					unsigned ud = input & 0x0C0;
-					input &= 0x30F;
-					if (rl != 0x030) {
-						input |= rl;
-					}
-					if (ud != 0x0C0) {
-						input |= ud;
-					}
+				if (ud != 0x0C0) {
+					input |= ud;
 				}
 			}
 			gba->memory.io[address >> 1] = 0x3FF ^ input;