[U-Boot] [PATCH v2] ARM926ejs: Add routines to invalidate D-Cache

[Reinhard Meyer]

Dear Hong Xu,
> After DMA operation, we need to maintain D-Cache coherency.
> We need to clean cache (write back the dirty lines) and then
> make the cache invalidate as well(hence CPU will fetch data
> written by DMA controller from RAM).
>
> Tested on AT91SAM9261EK with Peripheral DMA controller.
>
> Signed-off-by: Hong Xu<hong.xu at atmel.com>
> Tested-by: Elen Song<elen.song at atmel.com>
> CC: Albert Aribaud<albert.aribaud at free.fr>
> CC: Heiko Schocher<hs at denx.de>
> ---
> Changes since v1
> ~ Per Albert's suggestion, add invalidate_dcache_range originally defined
>    in include/common.h
>
>   arch/arm/lib/cache.c |   46 ++++++++++++++++++++++++++++++++++++++++++++++
>   1 files changed, 46 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c
> index 92b61a2..0436443 100644
> --- a/arch/arm/lib/cache.c
> +++ b/arch/arm/lib/cache.c
> @@ -53,3 +53,49 @@ void	__flush_dcache_all(void)
>   }
>   void	flush_dcache_all(void)
>   	__attribute__((weak, alias("__flush_dcache_all")));
> +
> +void __invalidate_dcache_range(unsigned long start, unsigned long stop)
> +{
> +	int cache_line_len;
> +	unsigned long mva;
> +
> +#ifdef CONFIG_ARM926EJS
> +
> +#ifdef CONFIG_SYS_CACHELINE_SIZE
> +	cache_line_len = CONFIG_SYS_CACHELINE_SIZE;
> +#else
> +	cache_line_len = 32;
> +#endif
> +	/*
> +	 * If start and stop are not aligned to cache-line,
> +	 * the adjacent lines will be cleaned
> +	 */
> +	if ((start&  (cache_line_len - 1)) != 0)
> +		asm("mcr p15, 0, %0, c7, c10, 1" : : "r" (start));
> +	if ((stop&  (cache_line_len - 1)) != 0)
> +		asm("mcr p15, 0, %0, c7, c10, 1" : : "r" (stop));

Why so complicated?
How about:
	/* round down to the start of the cache line */
	start &= (cache_line_len - 1);
	/* round up to the end of the cache line */
note: if, what I assume, the range to be invalidated is
[start, stop) - that means stop is the first address not to be
invalidated, the next statement is not necessary
	stop |= (cache_line_len - 1);
	while (start < stop) {
		asm("mcr p15, 0, %0, c7, c6, 1" : : "r"(start));
		start += cache_line_len;
	}
	/* Drain the WB */
	asm("mcr p15, 0, %0, c7, c10, 4" : : "r" (0));
> +#endif

Best Regards,
Reinhard