[PATCH v3] sh: avoid using IRQ0 on SH3/4

[Sergey Shtylyov <s.shtylyov@omp.ru>]

Using IRQ0 by the platform devices is going to be disallowed soon (see [1])
and even now, when IRQ0 is about to be returned by platfrom_get_irq(), you
see a big warning.  The code supporting SH3/4 SoCs maps the IRQ #s starting
at 0 -- modify that code to start the IRQ #s from 16 instead.

The patch should mostly affect the AP-SH4A-3A/AP-SH4AD-0A boards as they
indeed use IRQ0 for the SMSC911x compatible Ethernet chip...

[1] https://lore.kernel.org/all/025679e1-1f0a-ae4b-4369-01164f691511@omp.ru/

Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>

---
The patch is against Linus Torvalds' 'linux.git' repo.

Changes in version 3:
- added an appropriate Fixes: tag and added a passage about it to the patch
  description;
- added actual cases of the boards using IRQ0 to the patch description;
- added Geert Uytterhoeven's and John Paul Adrian Glaubitz's tags;
- updated the link to point to the version 2 of the patch.

Changes in version 2:
- changed cmp/ge to cmp/hs in the assembly code.

 arch/sh/kernel/cpu/sh3/entry.S |    4 ++--
 include/linux/sh_intc.h        |    6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

Index: linux/arch/sh/kernel/cpu/sh3/entry.S
===================================================================
--- linux.orig/arch/sh/kernel/cpu/sh3/entry.S
+++ linux/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
 
 	/*
Index: linux/include/linux/sh_intc.h
===================================================================
--- linux.orig/include/linux/sh_intc.h
+++ linux/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)