[U-Boot] [PATCH 1/2 V3] arm926: Flush the data cache before disabling it

[Sughosh Ganu]

The current implementation invalidates the cache instead of flushing
it. This causes problems on platforms where the spl/u-boot is already
loaded to the RAM, with caches enabled by a first stage bootloader.

The V bit of the cp15's control register c1 is set to the value of
VINITHI on reset. Do not clear this bit by default, as there are SOC's
with no valid memory region at 0x0.

Also fix the comments to match code.

Signed-off-by: Sughosh Ganu <urwithsughosh at gmail.com>
---

Changes since V2
* Added code to invalidate I cache, based on review comment by Aneesh.
* Fixed comments to match the code.

Changes since V1
* Added arm926 keyword to the subject line
* Removed the superfluous setting of r0.
* Fixed the comment to reflect the fact that V is not being cleared

 arch/arm/cpu/arm926ejs/start.S |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/start.S b/arch/arm/cpu/arm926ejs/start.S
index 6a09c02..91a9325 100644
--- a/arch/arm/cpu/arm926ejs/start.S
+++ b/arch/arm/cpu/arm926ejs/start.S
@@ -355,17 +355,21 @@ _dynsym_start_ofs:
  */
 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) */
+	bic	r0, r0, #0x00000300	/* clear bits 9:8 ( --RS) */
 	bic	r0, r0, #0x00000087	/* clear bits 7, 2:0 (B--- -CAM) */
 	orr	r0, r0, #0x00000002	/* set bit 2 (A) Align */
 	orr	r0, r0, #0x00001000	/* set bit 12 (I) I-Cache */
-- 
1.7.5.4