[PATCH] ARM: relax conditions required for enabling Contiguous Memory Allocator

On Monday 20 August 2012, Marek Szyprowski wrote:

Contiguous Memory Allocator requires only paging and MMU enabled not
particular CPU architectures, so there is no need for strict dependency
on CPU type. This enables to use CMA on some older ARM v5 systems which
also might need large contiguous blocks for the multimedia processing hw
modules.

Reported-by: Prabhakar Lad <prabhakar.csengg@gmail.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

The patch looks simple, but I want a better explanation for it.
When we went through all possible cases, we decided that:

* ARMv6+ need CMA to avoid the double mapping problem.
* ARMv4/v5 cannot generally use CMA because it doesn't work
  together with DMABOUNCE. I don't remember if it was the
  only problem, but I definitely remember this was intentional.
* We want a common kernel for all ARMv6+ eventually, and a
  separate kernel for all ARMv4/v5 ones.

If the reasoning has changed, please try to explain the full
situation. On a related topic, what happened to the idea that
ARMv6+ is broken without CMA? I noticed that it's optional
now.

	Arnd