[U-Boot] [PATCH v2 35/40] ARM: Implement non-cached memory support

[Stephen Warren]

On 08/26/2014 09:34 AM, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
>
> Implement an API that can be used by drivers to allocate memory from a
> pool that is mapped uncached. This is useful if drivers would otherwise
> need to do extensive cache maintenance (or explicitly maintaining the
> cache isn't safe).
>
> The API is protected using the new CONFIG_SYS_NONCACHED_MEMORY setting.
> Boards can set this to the size to be used for the non-cached area. The
> area will typically be right below the malloc() area, but architectures
> should take care of aligning the beginning and end of the area to honor
> any mapping restrictions. Architectures must also ensure that mappings
> established for this area do not overlap with the malloc() area (which
> should remain cached for improved performance).
>
> While the API is currently only implemented for ARM v7, it should be
> generic enough to allow other architectures to implement it as well.

> diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c

> +void noncached_init(void)
...
> +	mmu_set_region_dcache_behaviour(noncached_start, size, DCACHE_OFF);
> +}

If I build with:

#define CONFIG_SYS_DCACHE_OFF
#define CONFIG_SYS_ICACHE_OFF

... then mmu_set_region_dcache_behaviour() doesn't exist (or at least 
isn't linked in) on Jetson TK1 at least.