[PATCH v2 1/2] iommu/dma: Implement dma_{map,unmap}

Discussion:

[PATCH v2 1/2] iommu/dma: Implement dma_{map,unmap}_resource()

Robin Murphy

2016-10-26 17:43:56 UTC

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 <***@8bytes.org>
Signed-off-by: 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);
+}
+
+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);

--
1.9.1

Robin Murphy

2016-10-26 17:43:57 UTC

Permalink

With no coherency to worry about, just plug'em straight in.

CC: Catalin Marinas <***@arm.com>
CC: Will Deacon <***@arm.com>
Signed-off-by: Robin Murphy <***@arm.com>
---
arch/arm64/mm/dma-mapping.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 3f74d0d98de6..5cd0a383b14b 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -796,6 +796,8 @@ static void __iommu_unmap_sg_attrs(struct device *dev,
.sync_single_for_device = __iommu_sync_single_for_device,
.sync_sg_for_cpu = __iommu_sync_sg_for_cpu,
.sync_sg_for_device = __iommu_sync_sg_for_device,
+ .map_resource = iommu_dma_map_resource,
+ .unmap_resource = iommu_dma_unmap_resource,
.dma_supported = iommu_dma_supported,
.mapping_error = iommu_dma_mapping_error,
};

--
1.9.1

Joerg Roedel

2016-11-10 12:24:20 UTC

Permalink

Post by Robin Murphy
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.
---
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

Robin Murphy

2016-11-10 14:30:04 UTC

Permalink

Post by Joerg Roedel

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.

Catalin Marinas

2016-11-10 18:37:28 UTC

Permalink

Post by Robin Murphy

Post by Joerg Roedel

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.

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.

--
Catalin