Messages in this thread Patch in this message | | | From | Jacopo Mondi <> | Subject | [PATCH v2] base: dma-mapping: Postpone cpu addr translation on mmap() | Date | Fri, 13 Apr 2018 19:25:37 +0200 |
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Postpone calling virt_to_page() translation on memory locations not guaranteed to be backed by a struct page. Try first to map memory from device's coherent memory pool, then perform translation if that fails.
On some architectures, specifically SH when configured with 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 <laurent.pinchart@ideasonboard.com> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
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It has now been clarified this patch does not resolve the issue, but only mitigate it on platforms where dma_mmap_from_dev_coherent() succeeds and delay page_to_pfn() faulty conversion.
A suggested proper solution would be not relying on dma_common_mmap() but require all platforms to implement an mmap methods known to work, as noted by Christoph in v1 review.
v1 -> v2: - Save the 'pfn' temp variable performing the page_to_pfn() conversion in the remap_pfn_range() function call as suggested by Christoph.
--- drivers/base/dma-mapping.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c index 3b11835..d82566d 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; -- 2.7.4
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