[U-Boot] [PATCH] MIPS: Add CONFIG_SKIP_LOWLEVEL_INIT and flush dcache upon relocation

[Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>]

Hi Stefan,

Stefan Roese wrote:
> This patch adds the CONFIG_SKIP_LOWLEVEL_INIT option to start.S. This
> enables support for boards where the lowlevel initialization is
> already done when U-Boot runs (e.g. via OnChip ROM).
> 
> Also the data cache will be flushed upon relocation. This is missing
> in the current implementation.
> 
> All this will be used in the upcoming VCTH board support.
> 
> Signed-off-by: Stefan Roese <sr@denx.de>
> ---
>  cpu/mips/start.S |   19 ++++++++++++++++++-
>  1 files changed, 18 insertions(+), 1 deletions(-)

sorry for my late reply.  Please find the comments below.

> diff --git a/cpu/mips/start.S b/cpu/mips/start.S
> index 6a22302..5b71b00 100644
> --- a/cpu/mips/start.S
> +++ b/cpu/mips/start.S
> @@ -243,9 +243,11 @@ reset:
>  	mtc0	zero, CP0_COUNT
>  	mtc0	zero, CP0_COMPARE
>  
> +#if !defined(CONFIG_SKIP_LOWLEVEL_INIT)
>  	/* CONFIG0 register */
>  	li	t0, CONF_CM_UNCACHED
>  	mtc0	t0, CP0_CONFIG
> +#endif /* !CONFIG_SKIP_LOWLEVEL_INIT */
>  
>  	/* Initialize $gp.
>  	 */

It might be preferable to remove the /* CONFIG_SKIP_LOWLEVEL_INIT */
comment for better readability, IMHO.

> @@ -323,6 +327,14 @@ relocate_code:
>  	 * t1 = target address
>  	 * t2 = source end address
>  	 */
> +
> +	/*
> +	 * Save destination address and size for later usage in flush_cache()
> +	 */
> +	move	t7, a1		/* save gd in t7		*/
> +	move	a0, t1		/* a0 <-- destination addr	*/
> +	sub	a1, t2, t0	/* a1 <-- size			*/
> +
>  	/* On the purple board we copy the code earlier in a special way
>  	 * in order to solve flash problems
>  	 */
> @@ -338,6 +350,11 @@ relocate_code:
>  	/* If caches were enabled, we would have to flush them here.
>  	 */
>  
> +	/* a0 & a1 are already set up for flush_cache(start, size) */
> +	la	t9, flush_cache
> +	jalr	t9
> +	nop
> +
>  	/* Jump to where we've relocated ourselves.
>  	 */
>  	addi	t0, a2, in_ram - _start
> @@ -387,7 +404,7 @@ in_ram:
>  	bltl	t1, t2, 1b
>  	sw	zero, 0(t1)	/* delay slot			*/
>  
> -	move	a0, a1
> +	move	a0, t7		/* a0 <-- gd			*/
>  	la	t9, board_init_r
>  	jr	t9
>  	move	a1, a2		/* delay slot			*/

- Could we separate this flush_cache patch from this patch?

- Please use save register, s[0-7], instead of t7, since t7 register
  might be overwritten with another value in flush_cache().
  Furthermore, in this case, a2 should be saved as well.


Thanks,

  Shinya