On Fri, Feb 26, 2010 at 04:25:21PM +0000, Catalin Marinas wrote:

For mmap'ed pages (and present in the page cache), is it guaranteed that
the HCD driver won't write to it once it has been mapped into user
space? If that's the case, it may solve the problem by just reversing
the meaning of PG_arch_1 on ARM and assume that a newly allocated page
has dirty D-cache by default.

I guess we could also set PG_arch_1 in the DMA API as well, to avoid the
unnecessary D cache flushing when clean pages get mapped into userspace.