[PATCH 3/7] ARM: dma-mapping: Always pass proper prot flags to iommu_map()

[Will Deacon]

On Tue, Sep 24, 2013 at 04:06:57PM +0100, Andreas Herrmann wrote:
> ... otherwise it is impossible for the low level iommu driver to
> figure out which pte flags should be used.
> 
> In __map_sg_chunk we can derive the flags from dma_data_direction.
> 
> In __iommu_create_mapping we should treat the memory like
> DMA_BIDIRECTIONAL and pass both IOMMU_READ and IOMMU_WRITE to
> iommu_map.
> __iommu_create_mapping is used during dma_alloc_coherent (via
> arm_iommu_alloc_attrs).  AFAIK dma_alloc_coherent is responsible for
> allocation _and_ mapping.  I think this implies that access to the
> mapped pages should be allowed.
> 
> Cc: Marek Szyprowski <m.szyprowski at samsung.com>
> Signed-off-by: Andreas Herrmann <andreas.herrmann at calxeda.com>
> ---
>  arch/arm/mm/dma-mapping.c |   20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f5e1a84..95abed8 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1232,7 +1232,8 @@ __iommu_create_mapping(struct device *dev, struct page **pages, size_t size)
>  				break;
>  
>  		len = (j - i) << PAGE_SHIFT;
> -		ret = iommu_map(mapping->domain, iova, phys, len, 0);
> +		ret = iommu_map(mapping->domain, iova, phys, len,
> +				IOMMU_READ|IOMMU_WRITE);
>  		if (ret < 0)
>  			goto fail;
>  		iova += len;
> @@ -1444,6 +1445,7 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
>  	int ret = 0;
>  	unsigned int count;
>  	struct scatterlist *s;
> +	int prot;
>  
>  	size = PAGE_ALIGN(size);
>  	*handle = DMA_ERROR_CODE;
> @@ -1460,7 +1462,21 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
>  			!dma_get_attr(DMA_ATTR_SKIP_CPU_SYNC, attrs))
>  			__dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir);
>  
> -		ret = iommu_map(mapping->domain, iova, phys, len, 0);
> +		switch (dir) {
> +		case DMA_BIDIRECTIONAL:
> +			prot = IOMMU_READ | IOMMU_WRITE;
> +			break;
> +		case DMA_TO_DEVICE:
> +			prot = IOMMU_READ;
> +			break;
> +		case DMA_FROM_DEVICE:
> +			prot = IOMMU_WRITE;
> +			break;
> +		default:
> +			prot = 0;
> +		}
> +
> +		ret = iommu_map(mapping->domain, iova, phys, len, prot);

I already added this code to arm_coherent_iommu_map_page but forgot to
update the rest of the time. Could you shift the switch into a helper and
call that instead of inlining it explicitly?

Cheers,

Will