From 41d0bbc749471522714efd0649b7e033fefcbfb4 Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Mon, 9 Apr 2018 18:59:14 +0100 Subject: dma-coherent: clarify dma_mmap_from_dev_coherent documentation The use of "correctly mapped" here is misleading, since it can give the wrong expectation in the case that the memory *should* have been mapped from the per-device pool, but doing so failed for other reasons. Signed-off-by: Robin Murphy Signed-off-by: Christoph Hellwig --- drivers/base/dma-coherent.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'drivers') diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c index 1e6396bb807b..597d40893862 100644 --- a/drivers/base/dma-coherent.c +++ b/drivers/base/dma-coherent.c @@ -312,8 +312,9 @@ static int __dma_mmap_from_coherent(struct dma_coherent_mem *mem, * This checks whether the memory was allocated from the per-device * coherent memory pool and if so, maps that memory to the provided vma. * - * Returns 1 if we correctly mapped the memory, or 0 if the caller should - * proceed with mapping memory from generic pools. + * Returns 1 if @vaddr belongs to the device coherent pool and the caller + * should return @ret, or 0 if they should proceed with mapping memory from + * generic areas. */ int dma_mmap_from_dev_coherent(struct device *dev, struct vm_area_struct *vma, void *vaddr, size_t size, int *ret) -- cgit v1.2.3 From 60695be2bb6b0623f8e53bd9949d582a83c6d44a Mon Sep 17 00:00:00 2001 From: Jacopo Mondi Date: Fri, 13 Apr 2018 19:25:37 +0200 Subject: dma-mapping: postpone cpu addr translation on mmap Postpone calling virt_to_page() translation on memory locations not guaranteed to be backed by a struct page. Try first to map memory from the device coherent memory pool, then perform translation if that fails. On some architectures, specifically SH when configured with the SPARSEMEM memory model, assuming a struct page is always assigned to a memory address lead to unexpected hangs during the virtual to page address translation. This patch fixes that specific issue but applies in the general case too. Suggested-by: Laurent Pinchart Signed-off-by: Jacopo Mondi Reviewed-by: Robin Murphy Signed-off-by: Christoph Hellwig --- drivers/base/dma-mapping.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'drivers') diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c index 3b118353ea17..d82566d6e237 100644 --- a/drivers/base/dma-mapping.c +++ b/drivers/base/dma-mapping.c @@ -226,7 +226,6 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, #ifndef CONFIG_ARCH_NO_COHERENT_DMA_MMAP unsigned long user_count = vma_pages(vma); unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT; - unsigned long pfn = page_to_pfn(virt_to_page(cpu_addr)); unsigned long off = vma->vm_pgoff; vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); @@ -234,12 +233,11 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret)) return ret; - if (off < count && user_count <= (count - off)) { + if (off < count && user_count <= (count - off)) ret = remap_pfn_range(vma, vma->vm_start, - pfn + off, + page_to_pfn(virt_to_page(cpu_addr)) + off, user_count << PAGE_SHIFT, vma->vm_page_prot); - } #endif /* !CONFIG_ARCH_NO_COHERENT_DMA_MMAP */ return ret; -- cgit v1.2.3