ARM: cache: add an empty stub function for invalidate/flush dcache

Since some driver like ohci, lcd used dcache functions. But some ARM
cpu don't implement the invalidate_dcache_range()/flush_dcache_range()
functions.

To avoid compiling errors this patch adds an weak empty stub function
for all ARM cpu in arch/arm/lib/cache.c.
And ARM cpu still can implemnt its own cache functions on the cpu folder.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Reviewed-by: York Sun <yorksun@freescale.com>

arch/arm/cpu/arm11/cpu.c

@@ -124,14 +124,6 @@ void flush_dcache_all(void)
 {
 }
 
-void invalidate_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
-void flush_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
 void flush_cache(unsigned long start, unsigned long size)
 {
 }

arch/arm/cpu/arm926ejs/cache.c

@@ -83,14 +83,6 @@ void flush_dcache_all(void)
 {
 }
 
-void invalidate_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
-void flush_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
 void flush_cache(unsigned long start, unsigned long size)
 {
 }

arch/arm/cpu/armv7/cache_v7.c

@@ -304,14 +304,6 @@ void flush_dcache_all(void)
 {
 }
 
-void invalidate_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
-void flush_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
 void arm_init_before_mmu(void)
 {
 }

arch/arm/cpu/armv8/cache_v8.c

@@ -180,14 +180,6 @@ void flush_dcache_all(void)
 {
 }
 
-void invalidate_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
-void flush_dcache_range(unsigned long start, unsigned long stop)
-{
-}
-
 void dcache_enable(void)
 {
 }

arch/arm/lib/cache.c

@@ -53,6 +53,15 @@ __weak void enable_caches(void)
 	puts("WARNING: Caches not enabled\n");
 }
 
+__weak void invalidate_dcache_range(unsigned long start, unsigned long stop)
+{
+	/* An empty stub, real implementation should be in platform code */
+}
+__weak void flush_dcache_range(unsigned long start, unsigned long stop)
+{
+	/* An empty stub, real implementation should be in platform code */
+}
+
 #ifdef CONFIG_SYS_NONCACHED_MEMORY
 /*
  * Reserve one MMU section worth of address space below the malloc() area that