netdev - Re: [PATCH 28/44] sparc: remove arch specific dma

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Date:   Fri, 9 Jun 2017 00:22:48 +1000
From:   Julian Calaby <julian.calaby@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     x86@...nel.org,
        "Mailing List, Arm" <linux-arm-kernel@...ts.infradead.org>,
        xen-devel@...ts.xenproject.org, linux-c6x-dev@...ux-c6x.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-mips@...ux-mips.org, openrisc@...ts.librecores.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux <sparclinux@...r.kernel.org>,
        linux-xtensa@...ux-xtensa.org, dmaengine@...r.kernel.org,
        linux-tegra@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-samsung-soc@...r.kernel.org,
        iommu@...ts.linux-foundation.org, netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 28/44] sparc: remove arch specific dma_supported implementations

Hi Christoph,

On Thu, Jun 8, 2017 at 11:25 PM, Christoph Hellwig <hch@....de> wrote:
> Usually dma_supported decisions are done by the dma_map_ops instance.
> Switch sparc to that model by providing a ->dma_supported instance for
> sbus that always returns false, and implementations tailored to the sun4u
> and sun4v cases for sparc64, and leave it unimplemented for PCI on
> sparc32, which means always supported.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/sparc/include/asm/dma-mapping.h |  3 ---
>  arch/sparc/kernel/iommu.c            | 40 +++++++++++++++---------------------
>  arch/sparc/kernel/ioport.c           | 22 ++++++--------------
>  arch/sparc/kernel/pci_sun4v.c        | 17 +++++++++++++++
>  4 files changed, 39 insertions(+), 43 deletions(-)
>
> diff --git a/arch/sparc/kernel/ioport.c b/arch/sparc/kernel/ioport.c
> index dd081d557609..12894f259bea 100644
> --- a/arch/sparc/kernel/ioport.c
> +++ b/arch/sparc/kernel/ioport.c
> @@ -401,6 +401,11 @@ static void sbus_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
>         BUG();
>  }
>
> +static int sbus_dma_supported(struct device *dev, u64 mask)
> +{
> +       return 0;
> +}
> +

I'm guessing there's a few places that have DMA ops but DMA isn't
actually supported. Why not have a common method for this, maybe
"dma_not_supported"?

>  static const struct dma_map_ops sbus_dma_ops = {
>         .alloc                  = sbus_alloc_coherent,
>         .free                   = sbus_free_coherent,
> @@ -410,6 +415,7 @@ static const struct dma_map_ops sbus_dma_ops = {
>         .unmap_sg               = sbus_unmap_sg,
>         .sync_sg_for_cpu        = sbus_sync_sg_for_cpu,
>         .sync_sg_for_device     = sbus_sync_sg_for_device,
> +       .dma_supported          = sbus_dma_supported,
>  };
>
>  static int __init sparc_register_ioport(void)

Thanks,

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/