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Commit 6e8d7968 authored by Laura Abbott's avatar Laura Abbott Committed by Catalin Marinas
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arm64: Implement custom mmap functions for dma mapping 



The current dma_ops do not specify an mmap function so maping
falls back to the default implementation. There are at least
two issues with using the default implementation:

1) The pgprot is always pgprot_noncached (strongly ordered)
memory even with coherent operations
2) dma_common_mmap calls virt_to_page on the remapped non-coherent
address which leads to invalid memory being mapped.

Fix both these issue by implementing a custom mmap function which
correctly accounts for remapped addresses and sets vm_pg_prot
appropriately.

Signed-off-by: default avatarLaura Abbott <lauraa@codeaurora.org>
[catalin.marinas@arm.com: replaced "arm64_" with "__" prefix for consistency]
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 31b1e940

arch/arm64/mm/dma-mapping.c

+44 −0
Original line number Diff line number Diff line
@@ -221,9 +221,52 @@ static void __swiotlb_sync_sg_for_device(struct device *dev, 
			       sg->length, dir);

}



/* vma->vm_page_prot must be set appropriately before calling this function */

static int __dma_common_mmap(struct device *dev, struct vm_area_struct *vma,

			     void *cpu_addr, dma_addr_t dma_addr, size_t size)

{

	int ret = -ENXIO;

	unsigned long nr_vma_pages = (vma->vm_end - vma->vm_start) >>

					PAGE_SHIFT;

	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;

	unsigned long pfn = dma_to_phys(dev, dma_addr) >> PAGE_SHIFT;

	unsigned long off = vma->vm_pgoff;



	if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))

		return ret;



	if (off < nr_pages && nr_vma_pages <= (nr_pages - off)) {

		ret = remap_pfn_range(vma, vma->vm_start,

				      pfn + off,

				      vma->vm_end - vma->vm_start,

				      vma->vm_page_prot);

	}



	return ret;

}



static int __swiotlb_mmap_noncoherent(struct device *dev,

		struct vm_area_struct *vma,

		void *cpu_addr, dma_addr_t dma_addr, size_t size,

		struct dma_attrs *attrs)

{

	vma->vm_page_prot = pgprot_dmacoherent(vma->vm_page_prot);

	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);

}



static int __swiotlb_mmap_coherent(struct device *dev,

		struct vm_area_struct *vma,

		void *cpu_addr, dma_addr_t dma_addr, size_t size,

		struct dma_attrs *attrs)

{

	/* Just use whatever page_prot attributes were specified */

	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);

}



struct dma_map_ops noncoherent_swiotlb_dma_ops = {

	.alloc = __dma_alloc_noncoherent,

	.free = __dma_free_noncoherent,

	.mmap = __swiotlb_mmap_noncoherent,

	.map_page = __swiotlb_map_page,

	.unmap_page = __swiotlb_unmap_page,

	.map_sg = __swiotlb_map_sg_attrs,
@@ -240,6 +283,7 @@ EXPORT_SYMBOL(noncoherent_swiotlb_dma_ops); 
struct dma_map_ops coherent_swiotlb_dma_ops = {

	.alloc = __dma_alloc_coherent,

	.free = __dma_free_coherent,

	.mmap = __swiotlb_mmap_coherent,

	.map_page = swiotlb_map_page,

	.unmap_page = swiotlb_unmap_page,

	.map_sg = swiotlb_map_sg_attrs,