This patch provides reliable mechanism for obtaining pages associated with a
given dma_mapping. This is a proof-of-concept patch.
Signed-off-by: Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
---
arch/arm/include/asm/dma-mapping.h | 8 ++++++
arch/arm/mm/dma-mapping.c | 44 ++++++++++++++++++++++++++++++++++++
include/linux/dma-mapping.h | 2 +
3 files changed, 54 insertions(+), 0 deletions(-)
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index ca7a378..79b6c3d 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -196,6 +196,14 @@ static inline int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
}
+static inline int dma_get_pages(struct device *dev, void *cpu_addr,
+ dma_addr_t dma_addr, struct page **pages, size_t n_pages)
+{
+ const struct dma_map_ops *ops = get_dma_ops(dev);
+ BUG_ON(!ops);
+ return ops->get_pages(dev, cpu_addr, dma_addr, pages, n_pages);
+}
+
static inline void *dma_alloc_writecombine(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t flag)
{
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 2287b01..93a3508 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -116,10 +116,14 @@ static void arm_dma_sync_single_for_device(struct device *dev,
static int arm_dma_set_mask(struct device *dev, u64 dma_mask);
+static int arm_dma_get_pages(struct device *dev, void *cpu_addr,
+ dma_addr_t dma_addr, struct page **pages, size_t n_pages);
+
struct dma_map_ops arm_dma_ops = {
.alloc = arm_dma_alloc,
.free = arm_dma_free,
.mmap = arm_dma_mmap,
+ .get_pages = arm_dma_get_pages,
.map_page = arm_dma_map_page,
.unmap_page = arm_dma_unmap_page,
.map_sg = arm_dma_map_sg,
@@ -531,6 +535,25 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
}
/*
+ * Get pages for the DMA-coherent memory.
+ */
+static int arm_dma_get_pages(struct device *dev, void *cpu_addr,
+ dma_addr_t dma_addr, struct page **pages, size_t n_pages)
+{
+#ifdef CONFIG_MMU
+ int i;
+ unsigned long pfn = dma_to_pfn(dev, dma_addr);
+
+ for (i = 0; i < n_pages; ++i)
+ pages[i] = pfn_to_page(pfn + i);
+
+ return n_pages;
+#else
+ return -ENXIO;
+#endif /* CONFIG_MMU */
+}
+
+/*
* free a page as defined by the above mapping.
* Must not be called with IRQs disabled.
*/
@@ -1033,6 +1056,26 @@ static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
return 0;
}
+static int arm_iommu_get_pages(struct device *dev, void *cpu_addr,
+ dma_addr_t dma_addr, struct page **pages, size_t n_pages)
+{
+ struct arm_vmregion *c;
+ int n_valid_pages;
+
+ c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
+
+ if (!c)
+ return -ENXIO;
+
+ n_valid_pages = (c->vm_end - c->vm_start) >> PAGE_SHIFT;
+ if (n_valid_pages < n_pages)
+ n_pages = n_valid_pages;
+
+ memcpy(pages, c->priv, n_pages * sizeof pages[0]);
+
+ return n_pages;
+}
+
/*
* free a page as defined by the above mapping.
* Must not be called with IRQs disabled.
@@ -1271,6 +1314,7 @@ struct dma_map_ops iommu_ops = {
.alloc = arm_iommu_alloc_attrs,
.free = arm_iommu_free_attrs,
.mmap = arm_iommu_mmap_attrs,
+ .get_pages = arm_iommu_get_pages,
.map_page = arm_iommu_map_page,
.unmap_page = arm_iommu_unmap_page,
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index b903a20..409d3a9 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -17,6 +17,8 @@ struct dma_map_ops {
struct dma_attrs *attrs);
int (*mmap)(struct device *, struct vm_area_struct *,
void *, dma_addr_t, size_t, struct dma_attrs *attrs);
+ int (*get_pages)(struct device *dev, void *vaddr, dma_addr_t dma_addr,
+ struct page **pages, size_t n_pages);
dma_addr_t (*map_page)(struct device *dev, struct page *page,
unsigned long offset, size_t size,
--
1.7.5.4
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