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    SubjectRe: [PATCH 1/8] x86: add alloc_coherent dma_ops callback to GART driver
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    On Tue, 19 Aug 2008 16:32:39 +0200
    Joerg Roedel <joerg.roedel@amd.com> wrote:

    > Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
    > ---
    > arch/x86/kernel/pci-gart_64.c | 21 +++++++++++++++++++++
    > 1 files changed, 21 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
    > index 4d8efb0..44a75a6 100644
    > --- a/arch/x86/kernel/pci-gart_64.c
    > +++ b/arch/x86/kernel/pci-gart_64.c
    > @@ -506,6 +506,26 @@ error:
    > return 0;
    > }
    >
    > +/* allocate and map a coherent mapping */
    > +static void *
    > +gart_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_addr,
    > + gfp_t flag)
    > +{
    > + void *vaddr;
    > +
    > + vaddr = (void *)__get_free_pages(flag, get_order(size));
    > + if (!vaddr)
    > + return NULL;
    > +
    > + *dma_addr = gart_map_single(dev, __pa(vaddr), size, DMA_BIDIRECTIONAL);
    > + if (*dma_addr != bad_dma_address)
    > + return vaddr;

    I'm not sure a rule is documented or not, but I think that IOMMUs
    return zeroed memory wrt dma_alloc_coherent. The current pci-dma.c
    does, so I think that it would be better to keep the current behavior.


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