| Message ID | 4e84146ae49a4edd5f1226d76617be9aa92a58ee.1477503578.git.robin.murphy@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Oct 26, 2016 at 06:43:56PM +0100, Robin Murphy wrote: > With the new dma_{map,unmap}_resource() functions added to the DMA API > for the benefit of cases like slave DMA, add suitable implementations to > the arsenal of our generic layer. Since cache maintenance should not be > a concern, these can both be standalone callback implementations without > the need for arch code wrappers. > > CC: Joerg Roedel <joro@8bytes.org> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > > v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky. > > drivers/iommu/dma-iommu.c | 13 +++++++++++++ > include/linux/dma-iommu.h | 4 ++++ > 2 files changed, 17 insertions(+) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index c5ab8667e6f2..a2fd90a6a782 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, > __iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg)); > } > > +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys, > + size_t size, enum dma_data_direction dir, unsigned long attrs) > +{ > + return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys), > + size, dma_direction_to_prot(dir, false) | IOMMU_MMIO); > +} Isn't the whole point of map_resource that we can map regions which have no 'struct page' associated? The use phys_to_page() will certainly not do the right thing here. Joerg
On 10/11/16 12:24, Joerg Roedel wrote: > On Wed, Oct 26, 2016 at 06:43:56PM +0100, Robin Murphy wrote: >> With the new dma_{map,unmap}_resource() functions added to the DMA API >> for the benefit of cases like slave DMA, add suitable implementations to >> the arsenal of our generic layer. Since cache maintenance should not be >> a concern, these can both be standalone callback implementations without >> the need for arch code wrappers. >> >> CC: Joerg Roedel <joro@8bytes.org> >> Signed-off-by: Robin Murphy <robin.murphy@arm.com> >> --- >> >> v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky. >> >> drivers/iommu/dma-iommu.c | 13 +++++++++++++ >> include/linux/dma-iommu.h | 4 ++++ >> 2 files changed, 17 insertions(+) >> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index c5ab8667e6f2..a2fd90a6a782 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, >> __iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg)); >> } >> >> +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys, >> + size_t size, enum dma_data_direction dir, unsigned long attrs) >> +{ >> + return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys), >> + size, dma_direction_to_prot(dir, false) | IOMMU_MMIO); >> +} > > Isn't the whole point of map_resource that we can map regions which have > no 'struct page' associated? The use phys_to_page() will certainly not > do the right thing here. Perhaps it's a bit cheeky, but the struct page pointer is never dereferenced - the only thing iommu_dma_map_page() does with it is immediately convert it back again. Is there ever a case where page_to_phys(phys_to_page(phys)) != phys ? Robin.
On Thu, Nov 10, 2016 at 02:30:04PM +0000, Robin Murphy wrote: > On 10/11/16 12:24, Joerg Roedel wrote: > > On Wed, Oct 26, 2016 at 06:43:56PM +0100, Robin Murphy wrote: > >> With the new dma_{map,unmap}_resource() functions added to the DMA API > >> for the benefit of cases like slave DMA, add suitable implementations to > >> the arsenal of our generic layer. Since cache maintenance should not be > >> a concern, these can both be standalone callback implementations without > >> the need for arch code wrappers. > >> > >> CC: Joerg Roedel <joro@8bytes.org> > >> Signed-off-by: Robin Murphy <robin.murphy@arm.com> > >> --- > >> > >> v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky. > >> > >> drivers/iommu/dma-iommu.c | 13 +++++++++++++ > >> include/linux/dma-iommu.h | 4 ++++ > >> 2 files changed, 17 insertions(+) > >> > >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > >> index c5ab8667e6f2..a2fd90a6a782 100644 > >> --- a/drivers/iommu/dma-iommu.c > >> +++ b/drivers/iommu/dma-iommu.c > >> @@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, > >> __iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg)); > >> } > >> > >> +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys, > >> + size_t size, enum dma_data_direction dir, unsigned long attrs) > >> +{ > >> + return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys), > >> + size, dma_direction_to_prot(dir, false) | IOMMU_MMIO); > >> +} > > > > Isn't the whole point of map_resource that we can map regions which have > > no 'struct page' associated? The use phys_to_page() will certainly not > > do the right thing here. > > Perhaps it's a bit cheeky, but the struct page pointer is never > dereferenced - the only thing iommu_dma_map_page() does with it is > immediately convert it back again. Is there ever a case where > page_to_phys(phys_to_page(phys)) != phys ? Without SPARSEMEM_VMEMMAP or FLATMEM, it wouldn't work. For example, __page_to_pfn() in the SPARSEMEM case, used by page_to_phys(), even accesses the page structure (through page_to_section()). If the page struct is not relevant to the iommu code in question, you could factor it out into an __iommu_dma_map_pfn(). Or maybe move the whole logic to iommu_dma_map_resource() and call it from iommu_dma_map_page() with the page_to_phys(page) argument.
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index c5ab8667e6f2..a2fd90a6a782 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, __iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg)); } +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys, + size_t size, enum dma_data_direction dir, unsigned long attrs) +{ + return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys), + size, dma_direction_to_prot(dir, false) | IOMMU_MMIO); +} + +void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle, + size_t size, enum dma_data_direction dir, unsigned long attrs) +{ + iommu_dma_unmap_page(dev, handle, size, dir, attrs); +} + int iommu_dma_supported(struct device *dev, u64 mask) { /* diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h index 32c589062bd9..7f7e9a7e3839 100644 --- a/include/linux/dma-iommu.h +++ b/include/linux/dma-iommu.h @@ -61,6 +61,10 @@ void iommu_dma_unmap_page(struct device *dev, dma_addr_t handle, size_t size, enum dma_data_direction dir, unsigned long attrs); void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir, unsigned long attrs); +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys, + size_t size, enum dma_data_direction dir, unsigned long attrs); +void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle, + size_t size, enum dma_data_direction dir, unsigned long attrs); int iommu_dma_supported(struct device *dev, u64 mask); int iommu_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
With the new dma_{map,unmap}_resource() functions added to the DMA API for the benefit of cases like slave DMA, add suitable implementations to the arsenal of our generic layer. Since cache maintenance should not be a concern, these can both be standalone callback implementations without the need for arch code wrappers. CC: Joerg Roedel <joro@8bytes.org> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky. drivers/iommu/dma-iommu.c | 13 +++++++++++++ include/linux/dma-iommu.h | 4 ++++ 2 files changed, 17 insertions(+)