On 06/18/2013 08:50 AM, Catalin Marinas wrote:
On Tue, Jun 18, 2013 at 12:01:37PM +0100, Hiroshi Doyu wrote:
Arnd Bergmann<arnd@xxxxxxxx> wrote @ Tue, 18 Jun 2013 12:32:44 +0200:
On Tuesday 18 June 2013 11:19:14 Will Deacon wrote:
I've spoken briefly with Catalin about this and it seems like there might be
*some* scope for sharing common dma-mapping code between architectures.
There doesn't really need to be any architecture-specific details in
allocating iova space and the interface to the iommu drivers is
well-defined. The arch-specific stuff is bogged down in the non-coherent
buffer management, but that doesn't necessarily equate to lots of code.
So, the best bet would be to figure out how to split up what we have under
arch/arm/ so that it can be re-used by arm64 and potentially other
architectures (powerpc has some simple stuff for coherent mappings and some
less-simple stuff for non-coherent buffers).
I'm sure that other architectures are interested in sharing the code.
Best move it into the global mm/ directory, at least the version for
coherent mappings.
I'm guessing that this kind of unification usually takes some time
since we need to factor out the common code from the different
${ARCH}/mm/dma-mapping.c. Also some of ${ARCH} has IOMMU support in
it. So if we want to develop our 64-bit ARM with working DMA mapping
API during this transition, the step to take would be:
1, Copy arch/arm/mm/dma-mapping.c arch/arm64/mm/dma-mapping.c(+swiotlb)
2, Adapt arch/arm64/mm/dma-mapping.c(+swiotlb) to 64bit compatible.
3, Factor out the common code from them into mm/dma-mapping.c
Or add the relevant code to something like lib/iommu-helper.c, convert
arm64 to use that and we can work on converting arm and other
architectures afterwards.
why not in current drivers/iommu directory ?
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