[RFC PATCH 2/7] dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops

[arnd@arndb.de (Arnd Bergmann)]

On Friday 29 August 2014 16:54:25 Will Deacon wrote:
> set_arch_dma_coherent_ops is called from of_dma_configure in order to
> swizzle the architectural dma-mapping functions over to a cache-coherent
> implementation. This is currently implemented only for ARM.
> 
> In anticipation of re-using this mechanism for IOMMU-backed dma-mapping
> ops too, this patch replaces the function with a broader
> arch_setup_dma_ops callback which is also responsible for setting the
> DMA mask and offset as well as selecting the correct mapping functions.
> 
> A further advantage of this split is that it nicely isolates the
> of-specific code from the dma-mapping code, allowing potential reuse by
> other buses (e.g. PCI) in the future.
> 
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Looks good, just one tiny comment

> ---
>  arch/arm/include/asm/dma-mapping.h | 20 ++++++++++++++----
>  drivers/of/platform.c              | 42 ++++++++++----------------------------
>  include/linux/dma-mapping.h        |  8 +++-----
>  3 files changed, 30 insertions(+), 40 deletions(-)
> 
> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> index c45b61a4b4a5..936125ef3f3f 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -121,12 +121,24 @@ static inline unsigned long dma_max_pfn(struct device *dev)
>  }
>  #define dma_max_pfn(dev) dma_max_pfn(dev)
>  
> -static inline int set_arch_dma_coherent_ops(struct device *dev)
> +static inline void arch_setup_dma_ops(struct device *dev, u64 mask,
> +                                     unsigned long offset, bool coherent)
>  {
> -       set_dma_ops(dev, &arm_coherent_dma_ops);
> -       return 0;
> +       dev->coherent_dma_mask = mask;
> +
> +       /*
> +        * Set dma_mask to coherent_dma_mask by default if the architecture
> +        * code has not set it.
> +        */
> +       if (!dev->dma_mask)
> +               dev->dma_mask = &dev->coherent_dma_mask;
> +

We are in architecture specific code here, and we know that this
architecture has not set up the dev->dma_mask pointer, so we can
remove the 'if (!dev->dma_mask)'

	Arnd