lkml.org 
[lkml]   [2010]   [Jul]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH 1/2] arm: msm: Add System MMU support.
    From
    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.


    \
     
     \ /
      Last update: 2010-07-29 05:39    [W:0.022 / U:30.176 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site