On Fri, Aug 12, 2011 at 02:53:05PM +0200, Arnd Bergmann wrote:

On Friday 12 August 2011, Marek Szyprowski wrote:

quoted

From: Russell King <redacted>

Steal memory from the kernel to provide coherent DMA memory to drivers.
This avoids the problem with multiple mappings with differing attributes
on later CPUs.

Signed-off-by: Russell King <redacted>
[m.szyprowski: rebased onto 3.1-rc1]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

Hi Marek,

Is this the same patch that Russell had to revert because it didn't
work on some of the older machines, in particular those using
dmabounce?

I thought that our discussion ended with the plan to use this only
for ARMv6+ (which has a problem with double mapping) but not on ARMv5
and below (which don't have this problem but might need dmabounce).

I thought we'd decided to have a pool of available CMA memory on ARMv6K
to satisfy atomic allocations, which can grow and shrink in size, rather
than setting aside a fixed amount of contiguous system memory.

ARMv6 and ARMv7+ could use CMA directly, and <= ARMv5 can use the existing
allocation method.

Has something changed?