Alignment Requirement for MT_MEMORY type

[Russell King - ARM Linux]

On Wed, Feb 17, 2010 at 04:33:00PM -0800, Henry Li wrote:
> Can someone tell me why there is a requirement for the virtual and physical
> addresses and size using MT_MEMORY memtype (where prot_l1=0) to be aligned
> to section boundary (1MB) in linux-2.6.32/arch/arm/mm/mmu.c/create_mapping
> during IO table init?

Because today SDRAM is always a whole number of MB, so its pointless
defining it in terms of 4K pages.  MT_MEMORY is not for general purpose
use, but only for setting up the initial kernel SDRAM mapping.