Messages in this thread | | | Date | Thu, 29 Jul 2010 12:35:48 +0900 | Subject | Re: [PATCH 1/2] arm: msm: Add System MMU support. | From | FUJITA Tomonori <> |
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On Wed, 28 Jul 2010 17:58:50 -0700 (PDT) stepanm@codeaurora.org wrote:
> >> These are just SMMU APIs, and the DMA-mapping API is one layer above > >> this. > >> > >> We have our own SMMU API for the MSM SoCs because we have muliple > >> IOMMUs, > >> each one having multiple contexts, or even having multiple instances of > >> the same context. Our usage model is also quite a bit different from how > >> the DMA APIs are set up. I believe only two IOMMU drivers actually make > >> use of the DMA API (Intel and AMD) and the other ones (OMAP and other > >> SoCs) have their own APIs for their specific use cases. > > > > The DMA API is extremely flexible, it works just fine with all the > > IOMMUs that I've seen so far. Please take a look at > > include/asm-generic/dma-mapping-common.h and its users to see how > > to use multiple IOMMUs depending on the device. > > > > If the OMAP developers got this wrong, that's not your problem :-) > > > > Arnd > > Hi Arnd, > > From what I have been able to tell, the IOMMU interface was written by > AMD/Intel to allow the kvm code to work with a common IOMMU interface. To
Don't confuse the IOMMU interface with the DMA API that Arnd mentioned.
They are not related at all.
The DMA API is defined in Documentation/DMA-API.txt.
Arnd told you that include/asm-generic/dma-mapping-common.h is the library to support the DMA API with multiple IOMMUs. Lots of architectures (x86, powerpc, sh, alpha, ia64, microblaze, sparc) use it.
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