diff --git a/arch/sh/include/mach-common/mach/highlander.h b/arch/sh/include/mach-common/mach/highlander.h
index fb44c299d033..b12c79558422 100644
--- a/arch/sh/include/mach-common/mach/highlander.h
+++ b/arch/sh/include/mach-common/mach/highlander.h
@@ -176,7 +176,7 @@
 #define IVDR_CK_ON	4		/* iVDR Clock ON */
 #endif
 
-#define HL_FPGA_IRQ_BASE	200
+#define HL_FPGA_IRQ_BASE	(200 + 16)
 #define HL_NR_IRL		15
 
 #define IRQ_AX88796		(HL_FPGA_IRQ_BASE + 0)
diff --git a/arch/sh/include/mach-common/mach/r2d.h b/arch/sh/include/mach-common/mach/r2d.h
index 0d7e483c7d3f..69bc1907c563 100644
--- a/arch/sh/include/mach-common/mach/r2d.h
+++ b/arch/sh/include/mach-common/mach/r2d.h
@@ -47,7 +47,7 @@
 
 #define IRLCNTR1	(PA_BCR + 0)	/* Interrupt Control Register1 */
 
-#define R2D_FPGA_IRQ_BASE	100
+#define R2D_FPGA_IRQ_BASE	(100 + 16)
 
 #define IRQ_VOYAGER		(R2D_FPGA_IRQ_BASE + 0)
 #define IRQ_EXT			(R2D_FPGA_IRQ_BASE + 1)
diff --git a/arch/sh/include/mach-dreamcast/mach/sysasic.h b/arch/sh/include/mach-dreamcast/mach/sysasic.h
index ed69ce7f2030..3b27be9a527e 100644
--- a/arch/sh/include/mach-dreamcast/mach/sysasic.h
+++ b/arch/sh/include/mach-dreamcast/mach/sysasic.h
@@ -22,7 +22,7 @@
    takes.
 */
 
-#define HW_EVENT_IRQ_BASE  48
+#define HW_EVENT_IRQ_BASE  (48 + 16)
 
 /* IRQ 13 */
 #define HW_EVENT_VSYNC     (HW_EVENT_IRQ_BASE +  5) /* VSync */
diff --git a/arch/sh/include/mach-se/mach/se7724.h b/arch/sh/include/mach-se/mach/se7724.h
index 1fe28820dfa9..ea6c46633b33 100644
--- a/arch/sh/include/mach-se/mach/se7724.h
+++ b/arch/sh/include/mach-se/mach/se7724.h
@@ -37,7 +37,7 @@
 #define IRQ2_IRQ        evt2irq(0x640)
 
 /* Bits in IRQ012 registers */
-#define SE7724_FPGA_IRQ_BASE	220
+#define SE7724_FPGA_IRQ_BASE	(220 + 16)
 
 /* IRQ0 */
 #define IRQ0_BASE	SE7724_FPGA_IRQ_BASE
diff --git a/arch/sh/kernel/cpu/sh3/entry.S b/arch/sh/kernel/cpu/sh3/entry.S
index e48b3dd996f5..b1f5b3c58a01 100644
--- a/arch/sh/kernel/cpu/sh3/entry.S
+++ b/arch/sh/kernel/cpu/sh3/entry.S
@@ -470,9 +470,9 @@ ENTRY(handle_interrupt)
 	mov	r4, r0		! save vector->jmp table offset for later
 
 	shlr2	r4		! vector to IRQ# conversion
-	add	#-0x10, r4
 
-	cmp/pz	r4		! is it a valid IRQ?
+	mov	#0x10, r5
+	cmp/hs	r5, r4		! is it a valid IRQ?
 	bt	10f
 
 	/*
diff --git a/include/linux/sh_intc.h b/include/linux/sh_intc.h
index 37ad81058d6a..27ae79191bdc 100644
--- a/include/linux/sh_intc.h
+++ b/include/linux/sh_intc.h
@@ -13,9 +13,9 @@
 /*
  * Convert back and forth between INTEVT and IRQ values.
  */
-#ifdef CONFIG_CPU_HAS_INTEVT
-#define evt2irq(evt)		(((evt) >> 5) - 16)
-#define irq2evt(irq)		(((irq) + 16) << 5)
+#ifdef CONFIG_CPU_HAS_INTEVT	/* Avoid IRQ0 (invalid for platform devices) */
+#define evt2irq(evt)		((evt) >> 5)
+#define irq2evt(irq)		((irq) << 5)
 #else
 #define evt2irq(evt)		(evt)
 #define irq2evt(irq)		(irq)