[MIPS] ret_from_irq adjustment

Make sure that RA on top of interrupt stack is an address of ret_from_irq,
so that dump_stack etc. can trace info interrupted context.

Also this patch fixes except_vec_vi_handler and __smtc_ipi_vector which
seems broken.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/dec/int-handler.S

@@ -266,10 +266,8 @@
 handle_it:
 		LONG_L	s0, TI_REGS($28)
 		LONG_S	sp, TI_REGS($28)
-		jal	do_IRQ
-		LONG_S	s0, TI_REGS($28)
-
-		j	ret_from_irq
+		PTR_LA	ra, ret_from_irq
+		j	do_IRQ
 		 nop
 
 #ifdef CONFIG_32BIT
@@ -279,9 +277,8 @@ fpu:
 #endif
 
 spurious:
-		jal	spurious_interrupt
-		 nop
-		j	ret_from_irq
+		PTR_LA	ra, _ret_from_irq
+		j	spurious_interrupt
 		 nop
 		END(plat_irq_dispatch)
 

arch/mips/kernel/entry.S

@@ -20,10 +20,7 @@
 #include <asm/mipsmtregs.h>
 #endif
 
-#ifdef CONFIG_PREEMPT
-	.macro	preempt_stop
-	.endm
-#else
+#ifndef CONFIG_PREEMPT
 	.macro	preempt_stop
 	local_irq_disable
 	.endm
@@ -32,9 +29,16 @@
 
 	.text
 	.align	5
+FEXPORT(ret_from_irq)
+	LONG_S	s0, TI_REGS($28)
+#ifdef CONFIG_PREEMPT
+FEXPORT(ret_from_exception)
+#else
+	b	_ret_from_irq
 FEXPORT(ret_from_exception)
 	preempt_stop
-FEXPORT(ret_from_irq)
+#endif
+FEXPORT(_ret_from_irq)
 	LONG_L	t0, PT_STATUS(sp)		# returning to kernel mode?
 	andi	t0, t0, KU_USER
 	beqz	t0, resume_kernel

arch/mips/kernel/genex.S

@@ -133,9 +133,8 @@ NESTED(handle_int, PT_SIZE, sp)
 
 	LONG_L	s0, TI_REGS($28)
 	LONG_S	sp, TI_REGS($28)
-	jal	plat_irq_dispatch
-	LONG_S	s0, TI_REGS($28)
-	j	ret_from_irq
+	PTR_LA	ra, ret_from_irq
+	j	plat_irq_dispatch
 	END(handle_int)
 
 	__INIT
@@ -224,9 +223,8 @@ NESTED(except_vec_vi_handler, 0, sp)
 
 	LONG_L	s0, TI_REGS($28)
 	LONG_S	sp, TI_REGS($28)
-	jalr	v0
-	LONG_S	s0, TI_REGS($28)
 	PTR_LA	ra, ret_from_irq
+	jr	v0
 	END(except_vec_vi_handler)
 
 /*

arch/mips/kernel/smtc-asm.S

@@ -97,15 +97,12 @@ FEXPORT(__smtc_ipi_vector)
 	SAVE_ALL
 	CLI
 	TRACE_IRQS_OFF
-	move	a0,sp
 	/* Function to be invoked passed stack pad slot 5 */
 	lw	t0,PT_PADSLOT5(sp)
 	/* Argument from sender passed in stack pad slot 4 */
-	lw	a1,PT_PADSLOT4(sp)
-	jalr	t0
-	nop
-	j	ret_from_irq
-	nop
+	lw	a0,PT_PADSLOT4(sp)
+	PTR_LA	ra, _ret_from_irq
+	jr	t0
 
 /*
  * Called from idle loop to provoke processing of queued IPIs