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authorAlexey Brodkin <abrodkin@synopsys.com>2016-11-03 18:06:13 +0300
committerVineet Gupta <vgupta@synopsys.com>2016-11-03 20:01:07 +0300
commita79a812131b07254c09cf325ec68c0d05aaed0b5 (patch)
tree0b4d5bd96a3999319b2f4f6c31c558bcda35c1b0 /arch/arc
parent8f6d9eb2a3f38f1acd04efa0aeb8b81f5373c923 (diff)
downloadlinux-a79a812131b07254c09cf325ec68c0d05aaed0b5.tar.xz
arc: Implement arch-specific dma_map_ops.mmap
We used to use generic implementation of dma_map_ops.mmap which is dma_common_mmap() but that only worked for simpler cached mappings when vaddr = paddr. If a driver requests uncached DMA buffer kernel maps it to virtual address so that MMU gets involved and page uncached status takes into account. In that case usage of dma_common_mmap() lead to mapping of vaddr to vaddr for user-space which is obviously wrong. For more detals please refer to verbose explanation here [1]. So here we implement our own version of mmap() which always deals with dma_addr and maps underlying memory to user-space properly (note that DMA buffer mapped to user-space is always uncached because there's no way to properly manage cache from user-space). [1] https://lkml.org/lkml/2016/10/26/973 Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: <stable@vger.kernel.org> #4.5+ Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
-rw-r--r--arch/arc/mm/dma.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 60aab5a7522b..cd8aad8226dd 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -105,6 +105,31 @@ static void arc_dma_free(struct device *dev, size_t size, void *vaddr,
__free_pages(page, get_order(size));
}
+static int arc_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
+{
+ unsigned long user_count = vma_pages(vma);
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ unsigned long pfn = __phys_to_pfn(plat_dma_to_phys(dev, dma_addr));
+ unsigned long off = vma->vm_pgoff;
+ int ret = -ENXIO;
+
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+ if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
+ return ret;
+
+ if (off < count && user_count <= (count - off)) {
+ ret = remap_pfn_range(vma, vma->vm_start,
+ pfn + off,
+ user_count << PAGE_SHIFT,
+ vma->vm_page_prot);
+ }
+
+ return ret;
+}
+
/*
* streaming DMA Mapping API...
* CPU accesses page via normal paddr, thus needs to explicitly made
@@ -193,6 +218,7 @@ static int arc_dma_supported(struct device *dev, u64 dma_mask)
struct dma_map_ops arc_dma_ops = {
.alloc = arc_dma_alloc,
.free = arc_dma_free,
+ .mmap = arc_dma_mmap,
.map_page = arc_dma_map_page,
.map_sg = arc_dma_map_sg,
.sync_single_for_device = arc_dma_sync_single_for_device,