| Message ID | 65a75c2ea16d0fff8e8ec18a8f42e204c33249ed.1437148528.git.robin.murphy@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Jul 17, 2015 at 04:58:21PM +0100, Robin Murphy wrote: > The default dma_common_get_sgtable() implementation relies on the CPU > address of the buffer being a regular lowmem address. This is not always > the case on arm64, since allocations from the various DMA pools may have > remapped vmalloc addresses, rendering the use of virt_to_page() invalid. > > Fix this by providing our own implementation based on the fact that we > can safely derive a physical address from the DMA address in both cases. > > CC: Jon Medhurst <tixy@linaro.org> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > arch/arm64/mm/dma-mapping.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c > index d16a1ce..4b9b600 100644 > --- a/arch/arm64/mm/dma-mapping.c > +++ b/arch/arm64/mm/dma-mapping.c > @@ -337,10 +337,24 @@ static int __swiotlb_mmap(struct device *dev, > return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size); > } > > +int __swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt, > + void *cpu_addr, dma_addr_t handle, size_t size, > + struct dma_attrs *attrs) > +{ > + int ret = sg_alloc_table(sgt, 1, GFP_KERNEL); > + > + if (!ret) > + sg_set_page(sgt->sgl, phys_to_page(dma_to_phys(dev, handle)), > + PAGE_ALIGN(size), 0); > + > + return ret; > +} Any reason not to do this in dma_common_get_sgtable? Will
Hi Will, On 20/07/15 17:36, Will Deacon wrote: > On Fri, Jul 17, 2015 at 04:58:21PM +0100, Robin Murphy wrote: >> The default dma_common_get_sgtable() implementation relies on the CPU >> address of the buffer being a regular lowmem address. This is not always >> the case on arm64, since allocations from the various DMA pools may have >> remapped vmalloc addresses, rendering the use of virt_to_page() invalid. >> >> Fix this by providing our own implementation based on the fact that we >> can safely derive a physical address from the DMA address in both cases. >> >> CC: Jon Medhurst <tixy@linaro.org> >> Signed-off-by: Robin Murphy <robin.murphy@arm.com> >> --- >> arch/arm64/mm/dma-mapping.c | 14 ++++++++++++++ >> 1 file changed, 14 insertions(+) >> >> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c >> index d16a1ce..4b9b600 100644 >> --- a/arch/arm64/mm/dma-mapping.c >> +++ b/arch/arm64/mm/dma-mapping.c >> @@ -337,10 +337,24 @@ static int __swiotlb_mmap(struct device *dev, >> return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size); >> } >> >> +int __swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt, >> + void *cpu_addr, dma_addr_t handle, size_t size, >> + struct dma_attrs *attrs) >> +{ >> + int ret = sg_alloc_table(sgt, 1, GFP_KERNEL); >> + >> + if (!ret) >> + sg_set_page(sgt->sgl, phys_to_page(dma_to_phys(dev, handle)), >> + PAGE_ALIGN(size), 0); >> + >> + return ret; >> +} > > Any reason not to do this in dma_common_get_sgtable? Summarising the discussion over at [1], most architectures seem to depend on dma_common_get_sgtable, but only a handful implement dma_to_phys (plus this approach seems to match the original intent). There doesn't seem to be a nice solution for doing this in common code without a big cross-architecture patch, and it's somewhat questionable how widely this is actually needed. Robin. [1]:http://thread.gmane.org/gmane.linux.kernel/1998795 > > Will >
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c index d16a1ce..4b9b600 100644 --- a/arch/arm64/mm/dma-mapping.c +++ b/arch/arm64/mm/dma-mapping.c @@ -337,10 +337,24 @@ static int __swiotlb_mmap(struct device *dev, return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size); } +int __swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt, + void *cpu_addr, dma_addr_t handle, size_t size, + struct dma_attrs *attrs) +{ + int ret = sg_alloc_table(sgt, 1, GFP_KERNEL); + + if (!ret) + sg_set_page(sgt->sgl, phys_to_page(dma_to_phys(dev, handle)), + PAGE_ALIGN(size), 0); + + return ret; +} + static struct dma_map_ops swiotlb_dma_ops = { .alloc = __dma_alloc, .free = __dma_free, .mmap = __swiotlb_mmap, + .get_sgtable = __swiotlb_get_sgtable, .map_page = __swiotlb_map_page, .unmap_page = __swiotlb_unmap_page, .map_sg = __swiotlb_map_sg_attrs,
The default dma_common_get_sgtable() implementation relies on the CPU address of the buffer being a regular lowmem address. This is not always the case on arm64, since allocations from the various DMA pools may have remapped vmalloc addresses, rendering the use of virt_to_page() invalid. Fix this by providing our own implementation based on the fact that we can safely derive a physical address from the DMA address in both cases. CC: Jon Medhurst <tixy@linaro.org> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- arch/arm64/mm/dma-mapping.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)