arm, arm926ejs: Flush the data cache before disabling it

The current implementation invalidates the data cache before turning it
off and causes problems on the hawkboard. See the discussion in
http://lists.denx.de/pipermail/u-boot/2012-January/115212.html

According to the ARM926EJ-S Technical Reference Manual, the cache should
be flushed instead.

Also fix the comments to match code.

Signed-off-by: Sughosh Ganu <urwithsughosh@gmail.com>
Rebased and corrected commit message.

Signed-off-by: Christian Riesch <christian.riesch@omicron.at>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Acked-by: Heiko Schocher <hs@denx.de>
Tested-by: Heiko Schocher <hs@denx.de>

diff --git a/arch/arm/cpu/arm926ejs/start.S b/arch/arm/cpu/arm926ejs/start.S
index bb4d00bf3fd5b67d803ea89f150fdeb8213485a5..b39ed8a123779f2b6de7b61605bc1f7a24d81299 100644 (file)
--- a/arch/arm/cpu/arm926ejs/start.S
+++ b/arch/arm/cpu/arm926ejs/start.S
@@ -358,14 +358,18 @@ _dynsym_start_ofs:
 #ifndef CONFIG_SKIP_LOWLEVEL_INIT
 cpu_init_crit:
        /*
-        * flush v4 I/D caches
+        * flush D cache before disabling it
         */
        mov     r0, #0
-       mcr     p15, 0, r0, c7, c7, 0   /* flush v3/v4 cache */
-       mcr     p15, 0, r0, c8, c7, 0   /* flush v4 TLB */
+flush_dcache:
+       mrc     p15, 0, r15, c7, c10, 3
+       bne     flush_dcache
+
+       mcr     p15, 0, r0, c8, c7, 0   /* invalidate TLB */
+       mcr     p15, 0, r0, c7, c5, 0   /* invalidate I Cache */
 
        /*
-        * disable MMU stuff and caches
+        * disable MMU and D cache, and enable I cache
         */
        mrc     p15, 0, r0, c1, c0, 0
        bic     r0, r0, #0x00002300     /* clear bits 13, 9:8 (--V- --RS) */