arm: cache: Add support for write-allocate D-Cache

Add configuration for the write-allocate mode of L1 D-Cache on ARM.
This is needed for D-Cache operation on Cortex-A9 on the SoCFPGA .

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@altera.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Pavel Machek <pavel@denx.de>
Acked-by: Pavel Machek <pavel@denx.de>

arch/arm/include/asm/system.h

@@ -185,6 +185,7 @@ enum dcache_option {
 	DCACHE_OFF = 0x12,
 	DCACHE_WRITETHROUGH = 0x1a,
 	DCACHE_WRITEBACK = 0x1e,
+	DCACHE_WRITEALLOC = 0x16,
 };
 
 /* Size of an MMU section */

arch/arm/lib/cache-cp15.c

@@ -73,6 +73,8 @@ __weak void dram_bank_mmu_setup(int bank)
 	     i++) {
 #if defined(CONFIG_SYS_ARM_CACHE_WRITETHROUGH)
 		set_section_dcache(i, DCACHE_WRITETHROUGH);
+#elif defined(CONFIG_SYS_ARM_CACHE_WRITEALLOC)
+		set_section_dcache(i, DCACHE_WRITEALLOC);
 #else
 		set_section_dcache(i, DCACHE_WRITEBACK);
 #endif