[PATCH v2 2/2] iommu/dma: Implement PCI allocation optimisation

Will Deacon will.deacon at arm.com
Mon Jan 23 09:39:58 PST 2017

On Mon, Jan 16, 2017 at 01:24:55PM +0000, Robin Murphy wrote:
> Whilst PCI devices may have 64-bit DMA masks, they still benefit from
> using 32-bit addresses wherever possible in order to avoid DAC (PCI) or
> longer address packets (PCIe), which may incur a performance overhead.
> Implement the same optimisation as other allocators by trying to get a
> 32-bit address first, only falling back to the full mask if that fails.
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---
>  drivers/iommu/dma-iommu.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)

Looks good to me, and has the added benefit of getting PCI ethernet
working on Juno when using the SMMU. Unintended side-effect, but:

Acked-by: Will Deacon <will.deacon at arm.com>


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