On Tue, Jun 09, 2015 at 12:27:10PM -0400, Dan Williams wrote: > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index 7e7583ddd607..9f6ff6671f01 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -1502,7 +1502,7 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg, > return -ENOMEM; > > for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s)) { > - phys_addr_t phys = page_to_phys(sg_page(s)); > + phys_addr_t phys = sg_phys(s) - s->offset; So sg_phys() turns out to be 'page_to_phys(sg_page(s)) + s->offset', which makes the above statement to: page_to_phys(sg_page(s)) + s->offset - s->offset; The compiler will probably optimize that away, but it still doesn't look like an improvement. > unsigned int len = PAGE_ALIGN(s->offset + s->length); > > if (!is_coherent && > diff --git a/arch/microblaze/kernel/dma.c b/arch/microblaze/kernel/dma.c > index ed7ba8a11822..dcb3c594d626 100644 > --- a/arch/microblaze/kernel/dma.c > +++ b/arch/microblaze/kernel/dma.c > @@ -61,7 +61,7 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, > /* FIXME this part of code is untested */ > for_each_sg(sgl, sg, nents, i) { > sg->dma_address = sg_phys(sg); > - __dma_sync(page_to_phys(sg_page(sg)) + sg->offset, > + __dma_sync(sg_phys(sg), > sg->length, direction); Here the replacement makes sense, but weird indendation. Could all be moved to one line, I guess. > } > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 68d43beccb7e..9b9ada71e0d3 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -1998,7 +1998,7 @@ static int __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn, > sg_res = aligned_nrpages(sg->offset, sg->length); > sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + sg->offset; > sg->dma_length = sg->length; > - pteval = page_to_phys(sg_page(sg)) | prot; > + pteval = (sg_phys(sg) - sg->offset) | prot; Here it doesn't make sense too. In general, please remove the cases where you have to subtract sg->offset after the conversion. Joerg -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html