[PATCH] Revert "arm64: Make default dma_ops to be noncoherent"

[Dann Frazier]

On Thu, Nov 27, 2014 at 8:43 PM, Ming Lei <ming.lei at canonical.com> wrote:
> This reverts commit c7a4a7658d689f664050c45493d79adf053f226e.
>
> Conflicts:
>         arch/arm64/mm/dma-mapping.c
>
> On ARM64, Utopic kernel ships APM's PCI host controller driver
> which isn't upstreamed yet, and APM's ARM64 Soc is a coherent
> platform. On the other side, ARM64 maintainer[1] said the
> commit c7a4a7658 can be reverted safely if booting with ACPI
> which can be supported by APM's own kernel release too.
>
> So please revert the commit c7a4a7658 to avoid breaking
> PCI function on APM ARM64.

Thanks Ming.

One question I have (that I also mentioned in the bug), is what will
prevent us from having to carry this forward indefinitely?
The m400 cartridge does not provide ACPI tables (afaik), so we need a
device-tree based boot to continue to work. Reverting this for utopic
might be the right stop-gap, but what's plan for vivid and beyond?

 -dann

> BugLink: https://bugs.launchpad.net/bugs/1386490
>
> [1] http://marc.info/?l=linux-arm-kernel&m=141708838404470&w=2
>
> Cc: Dann Frazier <dann.frazier at canonical.com>
> Signed-off-by: Ming Lei <ming.lei at canonical.com>
> ---
>  arch/arm64/mm/dma-mapping.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index 4164c5a..acc807a 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -342,7 +342,7 @@ static int __init swiotlb_late_init(void)
>         bus_register_notifier(&platform_bus_type, &platform_bus_nb);
>         bus_register_notifier(&amba_bustype, &amba_bus_nb);
>
> -       dma_ops = &noncoherent_swiotlb_dma_ops;
> +       dma_ops = &coherent_swiotlb_dma_ops;
>
>         return swiotlb_late_init_with_default_size(swiotlb_size);
>  }
> --
> 1.9.1
>
>
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