From b867a40eb7680bdd99bfdd5e9a1416eb356e0ef0 Mon Sep 17 00:00:00 2001
From: zeromus <zeromus@users.sf.net>
Date: Fri, 1 Oct 2010 10:32:55 +0000
Subject: [PATCH] fix bugs in internal bios intrWaitARM after basic IRQ
 handling was rewritten

---
 desmume/src/armcpu.cpp |  1 +
 desmume/src/armcpu.h   |  1 +
 desmume/src/bios.cpp   | 66 +++++++++++++++++++++++++++---------------
 desmume/src/saves.cpp  |  2 ++
 4 files changed, 46 insertions(+), 24 deletions(-)

diff --git a/desmume/src/armcpu.cpp b/desmume/src/armcpu.cpp
index bff45cc58..3f0750744 100644
--- a/desmume/src/armcpu.cpp
+++ b/desmume/src/armcpu.cpp
@@ -221,6 +221,7 @@ void armcpu_init(armcpu_t *armcpu, u32 adr)
 	armcpu->intVector = 0xFFFF0000 * (armcpu->proc_ID==0);
 	armcpu->waitIRQ = FALSE;
 	armcpu->halt_IE_and_IF = FALSE;
+	armcpu->intrWaitARM_state = 0;
 
 //#ifdef GDB_STUB
 //    armcpu->irq_flag = 0;
diff --git a/desmume/src/armcpu.h b/desmume/src/armcpu.h
index 051c8d75d..1f9732316 100644
--- a/desmume/src/armcpu.h
+++ b/desmume/src/armcpu.h
@@ -206,6 +206,7 @@ struct armcpu_t
 	u8 LDTBit;  //1 : ARMv5 style 0 : non ARMv5
 	BOOL waitIRQ;
 	BOOL halt_IE_and_IF; //the cpu is halted, waiting for IE&IF to signal something
+	u8 intrWaitARM_state;
 
 	BOOL BIOS_loaded;
 
diff --git a/desmume/src/bios.cpp b/desmume/src/bios.cpp
index fad4af2ed..03891254f 100644
--- a/desmume/src/bios.cpp
+++ b/desmume/src/bios.cpp
@@ -216,40 +216,58 @@ TEMPLATE static u32 wait4IRQ()
 
 TEMPLATE u32 intrWaitARM()
 {
-	u32 intrFlagAdr = 0;
-	u32 intr = 0;
-	u32 intrFlag = 0;
+	//TODO - account for differences between arm7 and arm9 (according to gbatek, the "bug doesn't work")
 
-	//BOOL noDiscard = ((cpu->R[0] == 0) && (PROCNUM == ARMCPU_ARM7));
-
-	if(PROCNUM == ARMCPU_ARM7)
-		intrFlagAdr = 0x380FFF8;
-	else
-		intrFlagAdr = (((armcp15_t *)(cpu->coproc[15]))->DTCMRegion&0xFFFFF000)+0x3FF8;
-
-	intr = _MMU_read32<PROCNUM>(intrFlagAdr);
-	intrFlag = (cpu->R[1] & intr);
-
-	//INFO("ARM%c: wait for IRQ r0=0x%02X, r1=0x%08X - 0x%08X (flag 0x%08X)\n", PROCNUM?'7':'9', cpu->R[0], cpu->R[1], intr, intrFlag);
-	//if(!noDiscard)
-	//	intrFlag &= cpu->newIrqFlags;
+	const u32 intrFlagAdr = (PROCNUM == ARMCPU_ARM7)
+		? 0x380FFF8
+		: (((armcp15_t *)(cpu->coproc[15]))->DTCMRegion&0xFFFFF000)+0x3FF8;
 
 	//set IME=1
-	_MMU_write32<PROCNUM>(0x04000208, 1);			
+	//without this, no irq handlers can happen (even though IF&IE waits can happily happen)
+	//and so no bits in the OS irq flag variable can get set by the handlers
+	_MMU_write32<PROCNUM>(0x04000208, 1); 
 
-	if (intrFlag)
+	//analyze the OS irq flag variable
+	u32 intr = _MMU_read32<PROCNUM>(intrFlagAdr);
+	u32 intrFlag = (cpu->R[1] & intr);
+
+	//if the user requested us to discard flags, then clear the flag(s) we're going to be waiting on.
+	//(be sure to only do this only on the first run through. use a little state machine to control that)
+	if(cpu->intrWaitARM_state==0 && cpu->R[0]==1)
 	{
 		intr ^= intrFlag;
-		//if (intr)
-			_MMU_write32<PROCNUM>(intrFlagAdr, intr);
-		return wait4IRQ<PROCNUM>();
+		_MMU_write32<PROCNUM>(intrFlagAdr, intr);
+
+		//we want to make sure we wait at least once below
+		intrFlag = 0;
 	}
+
+	cpu->intrWaitARM_state = 1;
+
+	//now, if the condition is satisfied (and it won't be the first time through, no matter what, due to cares taken above)
+	if(intrFlag)
+	{
+		//write back the OS irq flags with the ones we were waiting for cleared
+		intr ^= intrFlag;
+		_MMU_write32<PROCNUM>(intrFlagAdr, intr);
+
+		//wait for an irq one last time. this is allegedly a bug.
+		cpu->waitIRQ = TRUE;
+		cpu->halt_IE_and_IF = TRUE;
+		
+		cpu->intrWaitARM_state = 0;
+		return 1;
+	}
+
+	//the condition wasn't satisfied. this means that we need to halt, wait for some enabled interrupt,
+	//and then ensure that we return to this opcode again to check the condition again
+	cpu->waitIRQ = TRUE;
+	cpu->halt_IE_and_IF = TRUE;
+
+	//(rewire PC to jump back to this opcode)
 	u32 instructAddr = cpu->instruct_adr;
 	cpu->R[15] = instructAddr;
 	cpu->next_instruction = instructAddr;
-	cpu->waitIRQ = TRUE;
-	cpu->halt_IE_and_IF = TRUE;
-	
 	return 1;
 }
 
diff --git a/desmume/src/saves.cpp b/desmume/src/saves.cpp
index b3fac2d25..349f17fd4 100644
--- a/desmume/src/saves.cpp
+++ b/desmume/src/saves.cpp
@@ -94,6 +94,7 @@ SFORMAT SF_ARM7[]={
 	{ "7LDT", 1, 1, &NDS_ARM7.LDTBit },
 	{ "7Wai", 4, 1, &NDS_ARM7.waitIRQ },
 	{ "7hef", 4, 1, &NDS_ARM7.halt_IE_and_IF },
+	{ "7iws", 1, 1, &NDS_ARM7.intrWaitARM_state },
 	{ 0 }
 };
 
@@ -130,6 +131,7 @@ SFORMAT SF_ARM9[]={
 	{ "9LDT", 1, 1, &NDS_ARM9.LDTBit},
 	{ "9Wai", 4, 1, &NDS_ARM9.waitIRQ},
 	{ "9hef", 4, 1, &NDS_ARM9.halt_IE_and_IF },
+	{ "9iws", 1, 1, &NDS_ARM7.intrWaitARM_state },
 	{ 0 }
 };