ppc4xx: Clean up 440 exceptions handling

- Introduced dedicated switches for building 440 and 405 images required
  for 440-specific machine instructions like 'rfmci' etc.

- Exception vectors moved to the proper location (_start moved away from
  the critical exception handler space, which it occupied)

- CriticalInput now serviced (with default handler)

- MachineCheck properly serviced (added a dedicated handler and return
  subroutine)

- Overall cleanup of exceptions declared with STD_EXCEPTION macro (unused,
  unhandled and those not relevant for 4xx were eliminated)

- Eliminated Linux leftovers, removed dead code

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
Signed-off-by: Rafal Jaworowski <raj@semihalf.com>
Signed-off-by: Stefan Roese <sr@denx.de>

3 files changed, 242 insertions, 204 deletions

diff --git a/cpu/ppc4xx/config.mk b/cpu/ppc4xx/config.mk
index 119e061..e7fc3f63 100644
--- a/cpu/ppc4xx/config.mk
+++ b/cpu/ppc4xx/config.mk
@@ -22,5 +22,13 @@
 #
 
 PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi -fno-strict-aliasing
+PLATFORM_CPPFLAGS += -DCONFIG_4xx -ffixed-r2 -ffixed-r29 -mstring -msoft-float
 
-PLATFORM_CPPFLAGS += -DCONFIG_4xx -ffixed-r2 -ffixed-r29 -mstring -Wa,-m405 -mcpu=405 -msoft-float
+cfg=$(shell grep configs $(TOPDIR)/include/config.h | sed 's/.*<\(configs.*\)>/\1/')
+is440=$(shell grep CONFIG_440 $(TOPDIR)/include/$(cfg))
+
+ifneq (,$(findstring CONFIG_440,$(is440)))
+PLATFORM_CPPFLAGS += -Wa,-m440 -mcpu=440
+else
+PLATFORM_CPPFLAGS += -Wa,-m405 -mcpu=405
+endif
diff --git a/cpu/ppc4xx/start.S b/cpu/ppc4xx/start.S
index 78d0042..e135220 100644
--- a/cpu/ppc4xx/start.S
+++ b/cpu/ppc4xx/start.S
@@ -294,11 +294,13 @@ skip_debug_init:
 	mtspr	ivor7,r1	/* Floating point unavailable */
 	li	r1,0x0c00
 	mtspr	ivor8,r1	/* System call */
-	li	r1,0x1000
-	mtspr	ivor10,r1	/* Decrementer (PIT for 440) */
-	li	r1,0x1400
-	mtspr	ivor13,r1	/* Data TLB error */
+	li	r1,0x0a00
+	mtspr   ivor9,r1	/* Auxiliary Processor unavailable */
+	li	r1,0x0900
+	mtspr	ivor10,r1	/* Decrementer */
 	li	r1,0x1300
+	mtspr	ivor13,r1	/* Data TLB error */
+	li	r1,0x1400
 	mtspr	ivor14,r1	/* Instr TLB error */
 	li	r1,0x2000
 	mtspr	ivor15,r1	/* Debug */
@@ -503,11 +505,81 @@ version_string:
 	.ascii " (", __DATE__, " - ", __TIME__, ")"
 	.ascii CONFIG_IDENT_STRING, "\0"
 
-/*
- * Maybe this should be moved somewhere else because the current
- * location (0x100) is where the CriticalInput Execption should be.
- */
 	. = EXC_OFF_SYS_RESET
+	.globl	_start_of_vectors
+_start_of_vectors:
+
+/* Critical input. */
+	CRIT_EXCEPTION(0x100, CritcalInput, UnknownException)
+
+#ifdef CONFIG_440
+/* Machine check */
+        MCK_EXCEPTION(0x200, MachineCheck, MachineCheckException)
+#else
+        CRIT_EXCEPTION(0x200, MachineCheck, MachineCheckException)
+#endif /* CONFIG_440 */
+
+/* Data Storage exception. */
+	STD_EXCEPTION(0x300, DataStorage, UnknownException)
+
+/* Instruction Storage exception. */
+	STD_EXCEPTION(0x400, InstStorage, UnknownException)
+
+/* External Interrupt exception. */
+	STD_EXCEPTION(0x500, ExtInterrupt, external_interrupt)
+
+/* Alignment exception. */
+	. = 0x600
+Alignment:
+	EXCEPTION_PROLOG(SRR0, SRR1)
+	mfspr	r4,DAR
+	stw	r4,_DAR(r21)
+	mfspr	r5,DSISR
+	stw	r5,_DSISR(r21)
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	li	r20,MSR_KERNEL
+	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
+	lwz	r6,GOT(transfer_to_handler)
+	mtlr	r6
+	blrl
+.L_Alignment:
+	.long	AlignmentException - _start + _START_OFFSET
+	.long	int_return - _start + _START_OFFSET
+
+/* Program check exception */
+	. = 0x700
+ProgramCheck:
+	EXCEPTION_PROLOG(SRR0, SRR1)
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	li	r20,MSR_KERNEL
+	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
+	lwz	r6,GOT(transfer_to_handler)
+	mtlr	r6
+	blrl
+.L_ProgramCheck:
+	.long	ProgramCheckException - _start + _START_OFFSET
+	.long	int_return - _start + _START_OFFSET
+
+#ifdef CONFIG_440
+	STD_EXCEPTION(0x800, FPUnavailable, UnknownException)
+	STD_EXCEPTION(0x900, Decrementer, DecrementerPITException)
+	STD_EXCEPTION(0xa00, APU, UnknownException)
+#endif	
+	STD_EXCEPTION(0xc00, SystemCall, UnknownException)
+
+#ifdef CONFIG_440
+	STD_EXCEPTION(0x1300, DataTLBError, UnknownException)
+	STD_EXCEPTION(0x1400, InstructionTLBError, UnknownException)
+#else
+	STD_EXCEPTION(0x1000, PIT, DecrementerPITException)
+	STD_EXCEPTION(0x1100, InstructionTLBMiss, UnknownException)
+	STD_EXCEPTION(0x1200, DataTLBMiss, UnknownException)
+#endif
+	CRIT_EXCEPTION(0x2000, DebugBreakpoint, DebugException )
+
+	.globl	_end_of_vectors
+_end_of_vectors:
+	. = _START_OFFSET
 #endif
 	.globl	_start
 _start:
@@ -1017,107 +1089,6 @@ start_ram:
 
 
 #ifndef CONFIG_NAND_SPL
-/*****************************************************************************/
-	.globl	_start_of_vectors
-_start_of_vectors:
-
-#if 0
-/*TODO Fixup _start above so we can do this*/
-/* Critical input. */
-	CRIT_EXCEPTION(0x100, CritcalInput, CritcalInputException)
-#endif
-
-/* Machine check */
-	CRIT_EXCEPTION(0x200, MachineCheck, MachineCheckException)
-
-/* Data Storage exception. */
-	STD_EXCEPTION(0x300, DataStorage, UnknownException)
-
-/* Instruction Storage exception. */
-	STD_EXCEPTION(0x400, InstStorage, UnknownException)
-
-/* External Interrupt exception. */
-	STD_EXCEPTION(0x500, ExtInterrupt, external_interrupt)
-
-/* Alignment exception. */
-	. = 0x600
-Alignment:
-	EXCEPTION_PROLOG
-	mfspr	r4,DAR
-	stw	r4,_DAR(r21)
-	mfspr	r5,DSISR
-	stw	r5,_DSISR(r21)
-	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
-	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
-	lwz	r6,GOT(transfer_to_handler)
-	mtlr	r6
-	blrl
-.L_Alignment:
-	.long	AlignmentException - _start + EXC_OFF_SYS_RESET
-	.long	int_return - _start + EXC_OFF_SYS_RESET
-
-/* Program check exception */
-	. = 0x700
-ProgramCheck:
-	EXCEPTION_PROLOG
-	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
-	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
-	lwz	r6,GOT(transfer_to_handler)
-	mtlr	r6
-	blrl
-.L_ProgramCheck:
-	.long	ProgramCheckException - _start + EXC_OFF_SYS_RESET
-	.long	int_return - _start + EXC_OFF_SYS_RESET
-
-	/* No FPU on MPC8xx.  This exception is not supposed to happen.
-	*/
-	STD_EXCEPTION(0x800, FPUnavailable, UnknownException)
-
-	/* I guess we could implement decrementer, and may have
-	 * to someday for timekeeping.
-	 */
-	STD_EXCEPTION(0x900, Decrementer, timer_interrupt)
-	STD_EXCEPTION(0xa00, Trap_0a, UnknownException)
-	STD_EXCEPTION(0xb00, Trap_0b, UnknownException)
-	STD_EXCEPTION(0xc00, SystemCall, UnknownException)
-	STD_EXCEPTION(0xd00, SingleStep, UnknownException)
-
-	STD_EXCEPTION(0xe00, Trap_0e, UnknownException)
-	STD_EXCEPTION(0xf00, Trap_0f, UnknownException)
-
-	/* On the MPC8xx, this is a software emulation interrupt.  It occurs
-	 * for all unimplemented and illegal instructions.
-	 */
-	STD_EXCEPTION(0x1000, PIT, PITException)
-
-	STD_EXCEPTION(0x1100, InstructionTLBMiss, UnknownException)
-	STD_EXCEPTION(0x1200, DataTLBMiss, UnknownException)
-	STD_EXCEPTION(0x1300, InstructionTLBError, UnknownException)
-	STD_EXCEPTION(0x1400, DataTLBError, UnknownException)
-
-	STD_EXCEPTION(0x1500, Reserved5, UnknownException)
-	STD_EXCEPTION(0x1600, Reserved6, UnknownException)
-	STD_EXCEPTION(0x1700, Reserved7, UnknownException)
-	STD_EXCEPTION(0x1800, Reserved8, UnknownException)
-	STD_EXCEPTION(0x1900, Reserved9, UnknownException)
-	STD_EXCEPTION(0x1a00, ReservedA, UnknownException)
-	STD_EXCEPTION(0x1b00, ReservedB, UnknownException)
-
-	STD_EXCEPTION(0x1c00, DataBreakpoint, UnknownException)
-	STD_EXCEPTION(0x1d00, InstructionBreakpoint, UnknownException)
-	STD_EXCEPTION(0x1e00, PeripheralBreakpoint, UnknownException)
-	STD_EXCEPTION(0x1f00, DevPortBreakpoint, UnknownException)
-
-	CRIT_EXCEPTION(0x2000, DebugBreakpoint, DebugException )
-
-	.globl	_end_of_vectors
-_end_of_vectors:
-
-
-	. = 0x2100
-
 /*
  * This code finishes saving the registers to the exception frame
  * and jumps to the appropriate handler for the exception.
@@ -1133,28 +1104,12 @@ transfer_to_handler:
 	SAVE_4GPRS(8, r21)
 	SAVE_8GPRS(12, r21)
 	SAVE_8GPRS(24, r21)
-#if 0
-	andi.	r23,r23,MSR_PR
-	mfspr	r23,SPRG3		/* if from user, fix up tss.regs */
-	beq	2f
-	addi	r24,r1,STACK_FRAME_OVERHEAD
-	stw	r24,PT_REGS(r23)
-2:	addi	r2,r23,-TSS		/* set r2 to current */
-	tovirt(r2,r2,r23)
-#endif
 	mflr	r23
 	andi.	r24,r23,0x3f00		/* get vector offset */
 	stw	r24,TRAP(r21)
 	li	r22,0
 	stw	r22,RESULT(r21)
 	mtspr	SPRG2,r22		/* r1 is now kernel sp */
-#if 0
-	addi	r24,r2,TASK_STRUCT_SIZE /* check for kernel stack overflow */
-	cmplw	0,r1,r2
-	cmplw	1,r1,r24
-	crand	1,1,4
-	bgt	stack_ovf		/* if r2 < r1 < r2+TASK_STRUCT_SIZE */
-#endif
 	lwz	r24,0(r23)		/* virtual address of handler */
 	lwz	r23,4(r23)		/* where to go when done */
 	mtspr	SRR0,r24
@@ -1215,16 +1170,64 @@ crit_return:
 	REST_GPR(31, r1)
 	lwz	r2,_NIP(r1)	/* Restore environment */
 	lwz	r0,_MSR(r1)
-	mtspr	990,r2		/* SRR2 */
-	mtspr	991,r0		/* SRR3 */
+        mtspr   csrr0,r2
+        mtspr   csrr1,r0
 	lwz	r0,GPR0(r1)
 	lwz	r2,GPR2(r1)
 	lwz	r1,GPR1(r1)
 	SYNC
 	rfci
 
-/* Cache functions.
-*/
+#ifdef CONFIG_440
+mck_return:
+        mfmsr   r28             /* Disable interrupts */
+        li      r4,0
+        ori     r4,r4,MSR_EE
+        andc    r28,r28,r4
+        SYNC                    /* Some chip revs need this... */
+        mtmsr   r28
+        SYNC
+        lwz     r2,_CTR(r1)
+        lwz     r0,_LINK(r1)
+        mtctr   r2
+        mtlr    r0
+        lwz     r2,_XER(r1)
+        lwz     r0,_CCR(r1)
+        mtspr   XER,r2
+        mtcrf   0xFF,r0
+        REST_10GPRS(3, r1)
+        REST_10GPRS(13, r1)
+        REST_8GPRS(23, r1)
+        REST_GPR(31, r1)
+        lwz     r2,_NIP(r1)     /* Restore environment */
+        lwz     r0,_MSR(r1)
+        mtspr   mcsrr0,r2
+        mtspr   mcsrr1,r0
+        lwz     r0,GPR0(r1)
+        lwz     r2,GPR2(r1)
+        lwz     r1,GPR1(r1)
+        SYNC
+        rfmci
+#endif /* CONFIG_440 */
+
+
+/*
+ * Cache functions.
+ *
+ * NOTE: currently the 440s run with dcache _disabled_ once relocated to DRAM,
+ * although for some cache-ralated calls stubs have to be provided to satisfy
+ * symbols resolution.
+ *
+ */
+#ifdef CONFIG_440
+       .globl  dcache_disable
+dcache_disable:
+        blr
+
+        .globl  dcache_status
+dcache_status:
+        blr
+#else
 flush_dcache:
 	addis	r9,r0,0x0002		/* set mask for EE and CE msr bits */
 	ori	r9,r9,0x8000
@@ -1303,24 +1306,13 @@ dcache_status:
 	mfdccr	r3
 	srwi	r3, r3, 31	/* >>31 => select bit 0 */
 	blr
+#endif
 
 	.globl get_pvr
 get_pvr:
 	mfspr	r3, PVR
 	blr
 
-#if !defined(CONFIG_440)
-	.globl wr_pit
-wr_pit:
-	mtspr	pit, r3
-	blr
-#endif
-
-	.globl wr_tcr
-wr_tcr:
-	mtspr	tcr, r3
-	blr
-
 /*------------------------------------------------------------------------------- */
 /* Function:	 out16 */
 /* Description:	 Output 16 bits */
@@ -1518,7 +1510,7 @@ relocate_code:
  * initialization, now running from RAM.
  */
 
-	addi	r0, r10, in_ram - _start + EXC_OFF_SYS_RESET
+	addi	r0, r10, in_ram - _start + _START_OFFSET
 	mtlr	r0
 	blr				/* NEVER RETURNS! */
 
@@ -1588,7 +1580,7 @@ clear_bss:
 	 */
 	.globl	trap_init
 trap_init:
-	lwz	r7, GOT(_start)
+	lwz	r7, GOT(_start_of_vectors)
 	lwz	r8, GOT(_end_of_vectors)
 
 	li	r9, 0x100		/* reset vector always at 0x100 */
@@ -1608,35 +1600,48 @@ trap_init:
 	/*
 	 * relocate `hdlr' and `int_return' entries
 	 */
-	li	r7, .L_MachineCheck - _start + EXC_OFF_SYS_RESET
-	li	r8, Alignment - _start + EXC_OFF_SYS_RESET
+	li	r7, .L_MachineCheck - _start + _START_OFFSET
+	li	r8, Alignment - _start + _START_OFFSET
 2:
 	bl	trap_reloc
-	addi	r7, r7, 0x100		/* next exception vector	*/
+	addi	r7, r7, 0x100		/* next exception vector */
 	cmplw	0, r7, r8
 	blt	2b
 
-	li	r7, .L_Alignment - _start + EXC_OFF_SYS_RESET
+	li	r7, .L_Alignment - _start + _START_OFFSET
 	bl	trap_reloc
 
-	li	r7, .L_ProgramCheck - _start + EXC_OFF_SYS_RESET
+	li	r7, .L_ProgramCheck - _start + _START_OFFSET
 	bl	trap_reloc
 
-	li	r7, .L_FPUnavailable - _start + EXC_OFF_SYS_RESET
-	li	r8, SystemCall - _start + EXC_OFF_SYS_RESET
-3:
-	bl	trap_reloc
-	addi	r7, r7, 0x100		/* next exception vector	*/
-	cmplw	0, r7, r8
-	blt	3b
+#ifdef CONFIG_440
+	li	r7, .L_FPUnavailable - _start + _START_OFFSET
+        bl      trap_reloc
 
-	li	r7, .L_SingleStep - _start + EXC_OFF_SYS_RESET
-	li	r8, _end_of_vectors - _start + EXC_OFF_SYS_RESET
-4:
-	bl	trap_reloc
-	addi	r7, r7, 0x100		/* next exception vector	*/
-	cmplw	0, r7, r8
-	blt	4b
+	li	r7, .L_Decrementer - _start + _START_OFFSET
+        bl      trap_reloc
+
+	li	r7, .L_APU - _start + _START_OFFSET
+        bl      trap_reloc
+        
+	li      r7, .L_InstructionTLBError - _start + _START_OFFSET
+        bl      trap_reloc
+
+        li      r7, .L_DataTLBError - _start + _START_OFFSET
+        bl      trap_reloc
+#else /* CONFIG_440 */
+	li	r7, .L_PIT - _start + _START_OFFSET
+        bl      trap_reloc
+
+	li	r7, .L_InstructionTLBMiss - _start + _START_OFFSET
+        bl      trap_reloc
+
+	li	r7, .L_DataTLBMiss - _start + _START_OFFSET
+        bl      trap_reloc
+#endif /* CONFIG_440 */
+
+        li      r7, .L_DebugBreakpoint - _start + _START_OFFSET
+        bl      trap_reloc
 
 #if !defined(CONFIG_440)
 	addi	r7,r0,0x1000		/* set ME bit (Machine Exceptions) */
diff --git a/cpu/ppc4xx/traps.c b/cpu/ppc4xx/traps.c
index 6aecca2..54659d3 100644
--- a/cpu/ppc4xx/traps.c
+++ b/cpu/ppc4xx/traps.c
@@ -36,6 +36,8 @@
 #include <command.h>
 #include <asm/processor.h>
 
+DECLARE_GLOBAL_DATA_PTR;
+
 #if (CONFIG_COMMANDS & CFG_CMD_KGDB)
 int (*debugger_exception_handler)(struct pt_regs *) = 0;
 #endif
@@ -45,8 +47,7 @@ extern unsigned long search_exception_table(unsigned long);
 
 /* THIS NEEDS CHANGING to use the board info structure.
  */
-#define END_OF_MEM	0x00400000
-
+#define END_OF_MEM	(gd->bd->bi_memstart + gd->bd->bi_memsize)
 
 static __inline__ void set_tsr(unsigned long val)
 {
@@ -88,29 +89,29 @@ extern void do_bedbug_breakpoint(struct pt_regs *);
 void
 print_backtrace(unsigned long *sp)
 {
-	int cnt = 0;
-	unsigned long i;
-
-	printf("Call backtrace: ");
-	while (sp) {
-		if ((uint)sp > END_OF_MEM)
-			break;
-
-		i = sp[1];
-		if (cnt++ % 7 == 0)
-			printf("\n");
-		printf("%08lX ", i);
-		if (cnt > 32) break;
-		sp = (unsigned long *)*sp;
-	}
-	printf("\n");
+        int cnt = 0;
+        unsigned long i;
+
+        printf("Call backtrace: ");
+        while (sp) {
+                if ((uint)sp > END_OF_MEM)
+                        break;
+
+                i = sp[1];
+                if (cnt++ % 7 == 0)
+                        printf("\n");
+                printf("%08lX ", i);
+                if (cnt > 32) break;
+                sp = (unsigned long *)*sp;
+        }
+        printf("\n");
 }
 
 void show_regs(struct pt_regs * regs)
 {
 	int i;
 
-	printf("NIP: %08lX XER: %08lX LR: %08lX REGS: %p TRAP: %04lx DAR: %08lX\n",
+	printf("NIP: %08lX XER: %08lX LR: %08lX REGS: %p TRAP: %04lx DEAR: %08lX\n",
 	       regs->nip, regs->xer, regs->link, regs, regs->trap, regs->dar);
 	printf("MSR: %08lx EE: %01x PR: %01x FP: %01x ME: %01x IR/DR: %01x%01x\n",
 	       regs->msr, regs->msr&MSR_EE ? 1 : 0, regs->msr&MSR_PR ? 1 : 0,
@@ -139,14 +140,14 @@ _exception(int signr, struct pt_regs *regs)
 {
 	show_regs(regs);
 	print_backtrace((unsigned long *)regs->gpr[1]);
-	panic("Exception in kernel pc %lx signal %d",regs->nip,signr);
+	panic("Exception");
 }
 
 void
 MachineCheckException(struct pt_regs *regs)
 {
-	unsigned long fixup;
-
+	unsigned long fixup, val;
+	
 	/* Probing PCI using config cycles cause this exception
 	 * when a device is not present.  Catch it and return to
 	 * the PCI exception handler.
@@ -161,26 +162,50 @@ MachineCheckException(struct pt_regs *regs)
 		return;
 #endif
 
-	printf("Machine check in kernel mode.\n");
+	printf("Machine Check Exception.\n");
 	printf("Caused by (from msr): ");
-	printf("regs %p ",regs);
-	switch( regs->msr & 0x000F0000) {
-	case (0x80000000>>12):
-		printf("Machine check signal - probably due to mm fault\n"
-		       "with mmu off\n");
-		break;
-	case (0x80000000>>13):
-		printf("Transfer error ack signal\n");
-		break;
-	case (0x80000000>>14):
-		printf("Data parity signal\n");
-		break;
-	case (0x80000000>>15):
-		printf("Address parity signal\n");
-		break;
-	default:
-		printf("Unknown values in msr\n");
+	printf("regs %p ", regs);
+
+	val = get_esr();
+
+#if !defined(CONFIG_440)
+	if (val& ESR_IMCP) {
+		printf("Instruction");
+		mtspr(ESR, val & ~ESR_IMCP);
+	} else
+		printf("Data");
+	printf(" machine check.\n");
+
+#elif defined(CONFIG_440)
+	if (val& ESR_IMCP){
+		printf("Instruction Synchronous Machine Check exception\n");
+		mtspr(SPRN_ESR, val & ~ESR_IMCP);
 	}
+        else { 
+		val = mfspr(MCSR);
+		if (val & MCSR_IB)
+			printf("Instruction Read PLB Error\n");
+		if (val & MCSR_DRB)
+			printf("Data Read PLB Error\n");
+		if (val & MCSR_DWB)
+			printf("Data Write PLB Error\n");
+		if (val & MCSR_TLBP)
+			printf("TLB Parity Error\n");
+		if (val & MCSR_ICP){
+			/*flush_instruction_cache(); */
+			printf("I-Cache Parity Error\n");
+		}
+		if (val & MCSR_DCSP)
+			printf("D-Cache Search Parity Error\n");
+		if (val & MCSR_DCFP)
+			printf("D-Cache Flush Parity Error\n");
+		if (val & MCSR_IMPE)
+			printf("Machine Check exception is imprecise\n");
+
+		/* Clear MCSR */
+		mtspr(SPRN_MCSR, val);
+	}
+#endif
 	show_regs(regs);
 	print_backtrace((unsigned long *)regs->gpr[1]);
 	panic("machine check");
@@ -224,7 +249,7 @@ ProgramCheckException(struct pt_regs *regs)
 }
 
 void
-PITException(struct pt_regs *regs)
+DecrementerPITException(struct pt_regs *regs)
 {
 	/*
 	 * Reset PIT interrupt