Re: [Xen-devel] [PATCH 28/44] sparc: remove arch specific dma_supported implementations

[Christoph Hellwig]

On Fri, Jun 09, 2017 at 12:22:48AM +1000, Julian Calaby wrote:
> 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"?

It's not common at all.  Except for sbus all dma API user first
call set_dma_mask which ends up in the dma_supported call.  sbus
is the weird outlier here.

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Re: [Xen-devel] [PATCH 28/44] sparc: remove arch specific dma_supported implementations

[David Miller]

From: Christoph Hellwig 
Date: Thu,  8 Jun 2017 15:25:53 +0200

> 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 

Acked-by: David S. Miller 

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Re: [Xen-devel] [PATCH 28/44] sparc: remove arch specific dma_supported implementations

[Julian Calaby]

Hi Christoph,

On Thu, Jun 8, 2017 at 11:25 PM, Christoph Hellwig  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 
> ---
>  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.cal...@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/

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