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

[Aneesh V]

On Friday 12 August 2011 01:54 PM, 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;
> +}

Does memalign() take 0 as input and if so what is the output. The GNU C
library seems to mandate only that it's a power of 2. But the following
man page seems to says that "The value of alignment must be a power of
two and must be greater than or equal  to  the size of a word."

http://www.s-gms.ms.edus.si/cgi-bin/man-cgi?memalign+3C

Also, you seem to be using get_dcache_line_size() in MMC driver. Is
this function defined for all platforms. Maybe, you must implement a
weakly linked default function for all platforms?

best regards,
Aneesh