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    SubjectRe: [PATCH 1/2] arm: msm: Add System MMU support.
    On Wed, 28 Jul 2010 17:58:50 -0700 (PDT) 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

    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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      Last update: 2010-07-29 05:39    [W:0.022 / U:9.868 seconds]
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