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    SubjectRe: [PATCH] pci: print out DMA mask info
    On Thu, Oct 9, 2008 at 7:40 PM, FUJITA Tomonori
    <fujita.tomonori@lab.ntt.co.jp> wrote:
    > On Thu, 09 Oct 2008 16:05:57 -0700
    > Yinghai Lu <yinghai@kernel.org> wrote:
    >
    >> Grant Grundler wrote:
    >> > On Thu, Oct 09, 2008 at 02:51:32PM -0700, Yinghai Lu wrote:
    >> >> On Thu, Oct 9, 2008 at 2:35 PM, Matthew Wilcox <matthew@wil.cx> wrote:
    >> >>> Why's that interesting to the sysadmin of the machine? To the driver
    >> >>> writer, certainly. But what's the use of it to the people using the
    >> >>> machine?
    >> > ...
    >> >> make linux kernel act like black box as other os?
    >> >
    >> > I don't understand your reply.
    >> > If someone thinks linux is a black box, printing this message won't help them.
    >> >
    >> could find out easily why some driver doesn't set dma mask correctly.
    >> like why
    >> qlogic qla2xxx only set consistent to 64bit,
    >> emulex lpfc not set consistent to 64bit
    >
    > IIRC, except for one SGI architecture, coherent_dma_mask is
    > meaningless, dma_mask is always equal to coherent_dma_mask. Lots of
    > IOMMU implementations ignore coherent_dma_mask and use dma_mask for
    > alloc_coherent(). Some drivers doesn't set up coherent_dma_mask.

    ehci_hcd 0000:00:02.1: using 31bit consistent DMA mask
    ==> ck804 ehci, is using 31bit for consistent dma mask, at still use
    32 bit for dma mask.

    qlogic qla2xxx and emulex lpfc dma mask and consistent_dma_mask is different...
    could have some story for them

    at least gart iommu is honoring the consistent dma mask.
    by calling dma_alloc_coherent_mask(dev, flag)

    if device could use 64 bit coherent dma mask, that is driver problem...
    print it out could put them in focus.

    YH


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