[U-Boot] [PATCH] armv7:cache: D cache line size read method

[Albert ARIBAUD]

Hi Lukasz,

On 12/08/2011 10:24, Lukasz Majewski wrote:
> This commit adds support for reading the D cache line size for armv7
> architecture.
>
> The get_dcache_line_size() function is supposed to work in conjunction
> with memalign call to provide D cache aligned DMA buffers.
>
> Signed-off-by: Lukasz Majewski<l.majewski at samsung.com>
> Signed-off-by: Kyungmin Park<kyungmin.park at samsung.com>
> CC: Aneesh V<aneesh at ti.com>
> CC: Albert ARIBAUD<albert.u.boot at aribaud.net>
> ---
>   arch/arm/cpu/armv7/cache_v7.c |   25 +++++++++++++++++++++++++
>   include/common.h              |    1 +
>   2 files changed, 26 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/cpu/armv7/cache_v7.c b/arch/arm/cpu/armv7/cache_v7.c
> index 3e1e1bf..bd0b1a8 100644
> --- a/arch/arm/cpu/armv7/cache_v7.c
> +++ b/arch/arm/cpu/armv7/cache_v7.c
> @@ -246,6 +246,21 @@ static void v7_inval_tlb(void)
>   	CP15ISB;
>   }
>
> +/* Read the cache line size (bytes) */
> +static int v7_dcache_line_size(void)
> +{
> +	u32 ccsidr, log2_line_len;
> +
> +	ccsidr = get_ccsidr();
> +
> +	log2_line_len = ((ccsidr&  CCSIDR_LINE_SIZE_MASK)>>
> +				CCSIDR_LINE_SIZE_OFFSET) + 2;
> +	/* Converting from words to bytes */
> +	log2_line_len += 2;
> +
> +	return 1<<  log2_line_len;
> +}
> +
>   void invalidate_dcache_all(void)
>   {
>   	v7_maint_dcache_all(ARMV7_DCACHE_INVAL_ALL);
> @@ -303,6 +318,11 @@ void  flush_cache(unsigned long start, unsigned long size)
>   {
>   	flush_dcache_range(start, start + size);
>   }
> +
> +int get_dcache_line_size(void)
> +{
> +	return v7_dcache_line_size();
> +}
>   #else /* #ifndef CONFIG_SYS_DCACHE_OFF */
>   void invalidate_dcache_all(void)
>   {
> @@ -327,6 +347,11 @@ void arm_init_before_mmu(void)
>   void  flush_cache(unsigned long start, unsigned long size)
>   {
>   }
> +
> +int get_dcache_line_size(void)
> +{
> +	return 0;
> +}
>   #endif /* #ifndef CONFIG_SYS_DCACHE_OFF */
>
>   #ifndef CONFIG_SYS_ICACHE_OFF
> diff --git a/include/common.h b/include/common.h
> index 12a1074..b535300 100644
> --- a/include/common.h
> +++ b/include/common.h
> @@ -622,6 +622,7 @@ void	flush_dcache_range(unsigned long start, unsigned long stop);
>   void	invalidate_dcache_range(unsigned long start, unsigned long stop);
>   void	invalidate_dcache_all(void);
>   void	invalidate_icache_all(void);
> +int     get_dcache_line_size(void);
>
>   /* arch/$(ARCH)/lib/ticks.S */
>   unsigned long long get_ticks(void);

I like the idea of a global cache line accessor, but:

1) Does it have to be a function? I don't know cache implementations 
where line size is not a constant, and a function might be overkill.

2) If it has to be a function, then I'd rather have the function 
introduced in arch/arm/lib/cache.c as a weak function returning 32, with 
armv7 providing a replacement.

Aneesh, that patch could affect your patch series as the magic 32 could 
then come from this weak function rather than be hard-coded.

Amicalement,
-- 
Albert.