Fixed GBA mode switch.

* libnds's swiSwitchToGBAMode ASM function was broken. They used r0
instead of r2 so it didn't work. It must have been correct when GBA
Exploader was last compiled more then a decade ago, but now it's broken
so this ASM function had to be reimplemented. GBA Mode switch now
appears to function as intended.
* As I currently lack a compatible slot-2 flashcart (SuperCard Lite
doesn't work even after trying a few hardcoded card types in main.c)
further testing can't be done on the rest of the code. It appears to
work but I won't know for sure until someone with compatible hardware
tests it.

Makefile

@@ -46,7 +46,7 @@ checkarm9:
 $(TARGET).nds : arm7/$(TARGET).elf arm9/$(TARGET).elf
 	@ndstool	-c $@ -7 arm7/$(TARGET).elf -9 arm9/$(TARGET).elf \
 				-b $(CURDIR)/logo32.bmp "GBA ExpLoader;Version $(VERSTRING);By Rudolph;" \
-				-g GBEX 01 "GBAEXPLOADER" -z 80040000 -u 00030004 -a 00000138 -p 0001 \
+				-g #### 01 "GBAEXPLOADER" -z 80040000 -u 00030004 -a 00000138 -p 0001 \
 
 data:
 	@mkdir -p data

arm7/Makefile

@@ -34,9 +34,7 @@ CXXFLAGS	:=	$(CFLAGS) -fno-rtti -fno-exceptions
 
 
 ASFLAGS	:=	-g $(ARCH)
-LDFLAGS	=	-specs=ds_arm7.specs -g $(ARCH) -Wl,-Map,$(notdir $*).map
-# LDFLAGS	=	-specs=ds_arm7_iwram.specs -g $(ARCH) -Wl,-Map,$(notdir $*).map
-
+LDFLAGS	=	-specs=ds_arm7.specs -g $(ARCH) -Wl,-Map,$(notdir $*).map 
 
 LIBS	:=	-lnds7
 

arm7/source/biosCalls.s

@@ -0,0 +1,15 @@
+	.TEXT
+	.ARM
+
+@---------------------------------------------------------------------------------------
+.GLOBAL     swiSwitchToGBAModeFixed
+.func swiSwitchToGBAModeFixed
+@---------------------------------------------------------------------------------------
+swiSwitchToGBAModeFixed:
+	mov r2,#0x40
+	swi 0x1f0000
+
+.endfunc
+
+	.end
+

arm7/source/main.c

@@ -39,22 +39,22 @@ extern	void	ret_menu7_R4(void);
 extern	void	ret_menu7_Gen(void);
 extern	void	ret_menu7_mse(void);
 
+// libnds messed up the original SWI bios call ASM.
+// They used r0 instead of r2. This reimplementation fixes that issue for now.
+extern void swiSwitchToGBAModeFixed();
+
 void gbaMode() {
 	vu32	vr;
 
 	REG_IME = IME_DISABLE;
 	for(vr = 0; vr < 0x1000; vr++);	// Wait ARM9
 
-	if (((*(vu32*)0x027FFCE4 >> 3) & 0x01) == 0x01) {
-		writePowerManagement(0, PM_BACKLIGHT_BOTTOM | PM_SOUND_AMP);
-	} else { 
-		writePowerManagement(0, PM_BACKLIGHT_TOP | PM_SOUND_AMP);
+	if (PersonalData->gbaScreen) {
+		writePowerManagement(PM_CONTROL_REG, PM_BACKLIGHT_BOTTOM | PM_SOUND_AMP);
+	} else {
+		writePowerManagement(PM_CONTROL_REG, PM_BACKLIGHT_TOP | PM_SOUND_AMP);
 	}
-
-	swiSwitchToGBAMode();
-//	asm("mov    r2, #0x40");
-//	asm("swi    0x1F0000");
-
+	swiSwitchToGBAModeFixed();
 	while(1);
 }
 

arm9/source/main.c

@@ -197,32 +197,28 @@ static void resetToSlot2() {
 	swiSoftReset();
 }
 
-void gbaMode() {
+ITCM_CODE void gbaMode() {
 
-	/*if(strncmp(GBA_HEADER.gamecode, "PASS", 4) == 0) {
+	if(strncmp(GBA_HEADER.gamecode, "PASS", 4) == 0) {
 		resetARM9Memory();
 		resetToSlot2();
-	}*/
+	}
 
 	videoSetMode(0);
 	videoSetModeSub(0);
 
-	// vramSetMainBanks(VRAM_A_MAIN_BG, VRAM_B_MAIN_BG, VRAM_C_MAIN_BG, VRAM_D_MAIN_BG);
 	vramSetPrimaryBanks(VRAM_A_MAIN_BG, VRAM_B_MAIN_BG, VRAM_C_MAIN_BG, VRAM_D_MAIN_BG);
 //	vramSetMainBanks(VRAM_A_MAIN_BG, VRAM_B_MAIN_BG, VRAM_C_ARM7, VRAM_D_ARM7);
 
 	if(PersonalData->gbaScreen) { lcdMainOnBottom(); } else { lcdMainOnTop(); }
-
-//	FIFOSend(IPC_CMD_GBAMODE);
-	fifoSendValue32(FIFO_USER_01, 1);
 
 	gba_frame();
 
 	// FIFOSend(IPC_CMD_GBAMODE);
-	fifoSendValue32(FIFO_USER_01, 1);
 	sysSetBusOwners(ARM7_OWNS_CARD, ARM7_OWNS_ROM);
+	fifoSendValue32(FIFO_USER_01, 1);
 	REG_IME = 0;
-	while(1)swiWaitForVBlank();
+	while(1);
 }