On Thu, Apr 24, 2014 at 11:30:05AM -0400, Santosh Shilimkar wrote:
> diff --git a/arch/arm/include/asm/dma-mapping.h 
> b/arch/arm/include/asm/dma-mapping.h
> index e701a4d..424fda9 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -58,22 +58,35 @@ static inline int dma_set_mask(struct device *dev, u64 
> mask)
>  #ifndef __arch_pfn_to_dma
>  static inline dma_addr_t pfn_to_dma(struct device *dev, unsigned long pfn)
>  {
> -     return (dma_addr_t)__pfn_to_bus(pfn);
> +     if (!dev)
> +             return (dma_addr_t)__pfn_to_bus(pfn);
> +     else
> +             return (dma_addr_t)__pfn_to_bus(pfn - dev->dma_pfn_offset);

I really don't trust gcc to do this right, so I think it would be better
to make life easier on the compiler:

        if (dev)
                pfn -= dev->dma_pfn_offset;
        return (dma_addr_t)__pfn_to_bus(pfn);

>  static inline unsigned long dma_to_pfn(struct device *dev, dma_addr_t addr)
>  {
> -     return __bus_to_pfn(addr);
> +     if (!dev)
> +             return __bus_to_pfn(addr);
> +     else
> +             return __bus_to_pfn(addr) + dev->dma_pfn_offset;

and:

        unsigned long pfn = __bus_to_pfn(addr);

        if (dev)
                pfn += dev->dma_pfn_offset;

        return pfn;

>  }
>  
>  static inline void *dma_to_virt(struct device *dev, dma_addr_t addr)
>  {
> -     return (void *)__bus_to_virt((unsigned long)addr);
> +     if (!dev)
> +             return (void *)__bus_to_virt((unsigned long)addr);
> +     else
> +             return (void *)__bus_to_virt(__pfn_to_bus(dma_to_pfn(dev, 
> addr)));

This is quite horrendous.  There's easier ways to do this...  I assume
you haven't looked at the assembler resulting from this at all with
stuff like the p2v patching enabled?

>  }
>  
>  static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
>  {
> -     return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
> +     if (!dev)
> +             return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
> +     else
> +             return pfn_to_dma(dev,
> +                             __bus_to_pfn(__virt_to_bus((unsigned 
> long)(addr))));

Same here.

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