[ARM] nommu: confirms the CR_V bit in nommu mode

In nommu mode, the exception vector location depends on the platforms.
Some of the implementations may have some special exception control
forwarding method in their ROM/flash and for some of them has its own
re-mapping mechanism by the h/w.

This patch introduces a special configuration CONFIG_CPU_HIGH_VECTOR which
turns on the CR_V bit in nommu mode. The CR_V bit is turned off by default.
This feature depends on CP15 and does not supported by ARM740.

Signed-off-by: Hyok S. Choi <hyok.choi@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -95,7 +95,7 @@ config ARCH_MTD_XIP
 
 config VECTORS_BASE
 	hex
-	default 0xffff0000 if MMU
+	default 0xffff0000 if MMU || CPU_HIGH_VECTOR
 	default DRAM_BASE if REMAP_VECTORS_TO_RAM
 	default 0x00000000
 	help

arch/arm/kernel/head-nommu.S

@@ -76,6 +76,11 @@ __after_proc_init:
 #endif
 #ifdef CONFIG_CPU_ICACHE_DISABLE
 	bic	r0, r0, #CR_I
+#endif
+#ifdef CONFIG_CPU_HIGH_VECTOR
+	orr	r0, r0, #CR_V
+#else
+	bic	r0, r0, #CR_V
 #endif
 	mcr	p15, 0, r0, c1, c0, 0		@ write control reg
 #endif /* CONFIG_CPU_CP15 */

arch/arm/mm/Kconfig

@@ -524,6 +524,18 @@ config CPU_BIG_ENDIAN
 	  port must properly enable any big-endian related features
 	  of your chipset/board/processor.
 
+config CPU_HIGH_VECTOR
+	depends !MMU && CPU_CP15 && !CPU_ARM740T
+	bool "Select the High exception vector"
+	default n
+	help
+	  Say Y here to select high exception vector(0xFFFF0000~).
+	  The exception vector can be vary depending on the platform
+	  design in nommu mode. If your platform needs to select
+	  high exception vector, say Y.
+	  Otherwise or if you are unsure, say N, and the low exception
+	  vector (0x00000000~) will be used.
+
 config CPU_ICACHE_DISABLE
 	bool "Disable I-Cache (I-bit)"
 	depends on CPU_CP15 && !(CPU_ARM610 || CPU_ARM710 || CPU_ARM720T || CPU_ARM740T || CPU_XSCALE || CPU_XSC3)