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Subject[PATCH 6/6] dma-mapping: support non-coherent devices in dma_common_get_sgtable
Date
We can use the arch_dma_coherent_to_pfn hook to provide a ->get_sgtable
implementation. Note that this isn't an endorsement of this interface
(which is a horrible bad idea), but it is required to move arm64 over
to the generic code without a loss of functionality.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/xen/swiotlb-xen.c | 2 +-
include/linux/dma-mapping.h | 7 ++++---
kernel/dma/mapping.c | 23 ++++++++++++++++-------
3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 470757ddddea..28819a0e61d0 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -689,7 +689,7 @@ xen_swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt,
handle, size, attrs);
}
#endif
- return dma_common_get_sgtable(dev, sgt, cpu_addr, handle, size);
+ return dma_common_get_sgtable(dev, sgt, cpu_addr, handle, size, attrs);
}

static int xen_swiotlb_mapping_error(struct device *dev, dma_addr_t dma_addr)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index c3378d4e0d57..bd81e74cca7b 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -483,8 +483,8 @@ dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma, void *cpu_addr,
#define dma_mmap_coherent(d, v, c, h, s) dma_mmap_attrs(d, v, c, h, s, 0)

int
-dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
- void *cpu_addr, dma_addr_t dma_addr, size_t size);
+dma_common_get_sgtable(struct device *dev, struct sg_table *sgt, void *cpu_addr,
+ dma_addr_t dma_addr, size_t size, unsigned long attrs);

static inline int
dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt, void *cpu_addr,
@@ -496,7 +496,8 @@ dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt, void *cpu_addr,
if (ops->get_sgtable)
return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
attrs);
- return dma_common_get_sgtable(dev, sgt, cpu_addr, dma_addr, size);
+ return dma_common_get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
+ attrs);
}

#define dma_get_sgtable(d, t, v, h, s) dma_get_sgtable_attrs(d, t, v, h, s, 0)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 42fd73aca305..58dec7a92b7b 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -202,17 +202,26 @@ EXPORT_SYMBOL(dmam_release_declared_memory);
* Create scatter-list for the already allocated DMA buffer.
*/
int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
- void *cpu_addr, dma_addr_t handle, size_t size)
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
{
- struct page *page = virt_to_page(cpu_addr);
+ struct page *page;
int ret;

- ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
- if (unlikely(ret))
- return ret;
+ if (!dev_is_dma_coherent(dev)) {
+ if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_COHERENT_TO_PFN))
+ return -ENXIO;

- sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
- return 0;
+ page = pfn_to_page(arch_dma_coherent_to_pfn(dev, cpu_addr,
+ dma_addr));
+ } else {
+ page = virt_to_page(cpu_addr);
+ }
+
+ ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+ if (!ret)
+ sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+ return ret;
}
EXPORT_SYMBOL(dma_common_get_sgtable);

--
2.18.0
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