linux-kernel - Re: [PATCH v8 01/17] arm: make SWIOTLB available

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Date:	Thu, 10 Oct 2013 10:43:08 +0100
From:	Will Deacon <will.deacon@....com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>
Subject: Re: [PATCH v8 01/17] arm: make SWIOTLB available

On Wed, Oct 09, 2013 at 09:48:14PM +0100, Stefano Stabellini wrote:
> IOMMU_HELPER is needed because SWIOTLB calls iommu_is_span_boundary,
> provided by lib/iommu_helper.c.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> CC: will.deacon@....com
> CC: linux@....linux.org.uk

[...]

> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> index 5b579b9..9aa5384 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -10,6 +10,7 @@
>  
>  #include <asm-generic/dma-coherent.h>
>  #include <asm/memory.h>
> +#include <asm/cacheflush.h>
>  
>  #define DMA_ERROR_CODE	(~0)
>  extern struct dma_map_ops arm_dma_ops;
> @@ -86,6 +87,42 @@ static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
>  }
>  #endif
>  
> +static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
> +{
> +	unsigned int offset = paddr & ~PAGE_MASK;
> +	return pfn_to_dma(dev, paddr >> PAGE_SHIFT) + offset;

__phys_to_pfn instead of the explicit shift?

> +}
> +
> +static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> +{
> +	unsigned int offset = dev_addr & ~PAGE_MASK;
> +	return (dma_to_pfn(dev, dev_addr) << PAGE_SHIFT) + offset;i

then __pfn_to_phys here.

> +}
> +
> +static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
> +{
> +	u64 limit, mask;
> +	
> +	if (dev->dma_mask)
> +		mask = *dev->dma_mask;
> +	else 
> +		mask = dev->coherent_dma_mask;
> +
> +	if (mask == 0)
> +		return 0;
> +
> +	limit = (mask + 1) & ~mask;

This looks like homebrew alignment to me. Can you use __ALIGN_KERNEL_MASK or
one of thoese guys from kernel.h?

Will
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