Re: [PATCH 4/9] iommu/dma-iommu: Add iommu_dma_map_page_coherent

[Christoph Hellwig <hch@infradead.org>]

> @@ -693,7 +694,19 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
>  		unsigned long offset, size_t size, int prot)
>  {
>  	return __iommu_dma_map(dev, page_to_phys(page) + offset, size, prot,
> -			iommu_get_dma_domain(dev));
> +			iommu_get_dma_domain(dev), dma_get_mask(dev));
> +}
> +
> +dma_addr_t iommu_dma_map_page_coherent(struct device *dev, struct page *page,
> +		unsigned long offset, size_t size, int prot)
> +{

Note that my tree pointed to above removes the iommu_dma_map_page
wrapper.  I think for the coherent mappign we should also just
call __iommu_dma_map directly and not introduce another wrapper.

> +	dma_addr_t dma_mask = dev->coherent_dma_mask;
> +
> +	if (!dma_mask)
> +		dma_mask = dma_get_mask(dev);
> +
> +	return __iommu_dma_map(dev, page_to_phys(page) + offset, size, prot,
> +			iommu_get_dma_domain(dev), dma_mask);
>  }

In the DMA API there is no fallback when the coherent_dma_mask is not
set.  While various bits of legacy code do that we should not copy it
to new code.