On Fri, Aug 12, 2011 at 02:53:05PM +0200, Arnd Bergmann wrote:
On Friday 12 August 2011, Marek Szyprowski wrote:
From: Russell King rmk+kernel@arm.linux.org.uk
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 rmk+kernel@arm.linux.org.uk [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?