[U-Boot] [PATCH 1/2 V4] arm926: Flush the data cache before disabling it

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Sughosh,

Le 14/01/2012 15:02, Sughosh Ganu a ?crit :
> 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.
>
> Also fix the comments to match code.
>
> Signed-off-by: Sughosh Ganu<urwithsughosh@gmail.com>
> Cc: Albert Aribaud<albert.u.boot@aribaud.net>
> Cc: Tom Rini<trini@ti.com>
> ---
>
> Changes since V3
> * Removed tampering of the V bit setting. Would be done in a separate
>    patch on the lines of review comments by Albert.
>
> 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 |   12 ++++++++----
>   1 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm/cpu/arm926ejs/start.S b/arch/arm/cpu/arm926ejs/start.S
> index 6a09c02..d64165a 100644
> --- a/arch/arm/cpu/arm926ejs/start.S
> +++ b/arch/arm/cpu/arm926ejs/start.S
> @@ -355,14 +355,18 @@ _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 */

Please add a comment explaining what the loop is waiting for exactly:

> +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) */

Amicalement,
-- 
Albert.