ARM: 6859/1: Add writethrough dcache support for ARM926EJS processor

The ARM kernel supports writethrough data cache via the
CONFIG_CPU_DCACHE_WRITETHROUGH option.  However, that
functionality wasn't implemented in the arch/arm/boot/compressed
code.  It is now necessary due to a new ARM926EJS processor
that has an issue with writeback data cache.

Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index adf583cd0c3..ae7ecc286e7 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -447,7 +447,11 @@ __setup_mmu:	sub	r3, r4, #16384		@ Page directory size
                 orr     r1, r1, #3 << 10
                 add     r2, r3, #16384
 1:              cmp     r1, r9                  @ if virt > start of RAM
+#ifdef CONFIG_CPU_DCACHE_WRITETHROUGH
+                orrhs   r1, r1, #0x08           @ set cacheable
+#else
                 orrhs   r1, r1, #0x0c           @ set cacheable, bufferable
+#endif
                 cmp     r1, r10                 @ if virt > end of RAM
                 bichs   r1, r1, #0x0c           @ clear cacheable, bufferable
                 str     r1, [r0], #4            @ 1:1 mapping
@@ -472,6 +476,12 @@ __setup_mmu:	sub	r3, r4, #16384		@ Page directory size
                 mov     pc, lr
 ENDPROC(__setup_mmu)
 
+__arm926ejs_mmu_cache_on:
+#ifdef CONFIG_CPU_DCACHE_WRITETHROUGH
+                mov     r0, #4                  @ put dcache in WT mode
+                mcr     p15, 7, r0, c15, c0, 0
+#endif
+
 __armv4_mmu_cache_on:
                 mov     r12, lr
 #ifdef CONFIG_MMU
@@ -653,6 +663,12 @@ proc_types:
                 W(b)    __armv4_mpu_cache_off
                 W(b)    __armv4_mpu_cache_flush
 
+                .word   0x41069260              @ ARM926EJ-S (v5TEJ)
+                .word   0xff0ffff0
+                b       __arm926ejs_mmu_cache_on
+                b       __armv4_mmu_cache_off
+                b       __armv5tej_mmu_cache_flush
+
                 .word   0x00007000              @ ARM7 IDs
                 .word   0x0000f000
                 mov     pc, lr