[PATCH 3/3] swiotlb: Add support for CMA allocations

[Catalin Marinas]

On Tue, Dec 10, 2013 at 10:25:56AM +0000, Will Deacon wrote:
> On Tue, Dec 10, 2013 at 12:40:20AM +0000, Konrad Rzeszutek Wilk wrote:
> > Laura Abbott <lauraa at codeaurora.org> wrote:
> > >On 12/9/2013 4:29 PM, Konrad Rzeszutek Wilk wrote:
> > >> Laura Abbott <lauraa at codeaurora.org> wrote:
> > >>> Some architectures may implement the CMA APIs to allow allocation
> > >>> of larger contiguous blocks of memory. Add support in the swiotlb
> > >>> alloc/free functions to allocate from the CMA APIs instead of the
> > >>> basic page allocator.
> > >>>
> > >>> Cc: Will Deacon <will.deacon at arm.com>
> > >>> Cc: Catalin Marinas <catalin.marinas at arm.com>
> > >>> Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> > >>> Cc: Marek Szyprowski <m.szyprowski at samsung.com>
> > >>> Signed-off-by: Laura Abbott <lauraa at codeaurora.org>
> > >...
> > >>>
> > >>
> > >> Can this be done in the platform dma_ops functions instead?
> > >>
> > >
> > >I suppose it could but that seems like it would result in lots of 
> > >duplicated code if every architecture that uses swiotlb wants to use
> > >CMA.
> > >
> > >Thanks,
> > >Laura
> > 
> > Then let's do that it that way. Thank you.
> 
> Note that once arch/arm64 starts growing things like support for non-coherent
> DMA and IOMMU mappings, we'll probably want to factor out a bunch of the
> boilerplat from our dma-mapping.c file into places like lib/iommu-helper.c.

For coherency, we could build it on top of whatever dma (allocation) ops
are registered, whether swiotlb or iommu (see part of
https://git.kernel.org/cgit/linux/kernel/git/cmarinas/linux-aarch64.git/commit/?h=devel&id=c67fe405be6b55399c9e53dfeba5e2c6b930e429)

Regarding iommu, I don't think we need CMA on top, so it makes sense to
keep the CMA in the swiotlb code.

-- 
Catalin