Messages in this thread |  | | Subject | Re: [RFC v2 2/2] base: dma-mapping: Postpone page_to_pfn() on mmap() | From | Robin Murphy <> | Date | Wed, 15 Nov 2017 13:38:23 +0000 |
| |
On 14/11/17 17:08, Jacopo Mondi wrote: > On SH4 architecture, with SPARSEMEM memory model, translating page to > pfn hangs the CPU. Post-pone translation to pfn after > dma_mmap_from_dev_coherent() function call as it succeeds and make page > translation not necessary. > > This patch was suggested by Laurent Pinchart and he's working to submit > a proper fix mainline. Not sending for inclusion at the moment.
Y'know, I think this patch does have some merit by itself - until we know that cpu_addr *doesn't* represent some device-private memory which is not guaranteed to be backed by a struct page, calling virt_to_page() on it is arguably semantically incorrect, even if it might happen to be benign in most cases.
Robin.
> Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org> > --- > drivers/base/dma-mapping.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c > index e584edd..73d64d3 100644 > --- a/drivers/base/dma-mapping.c > +++ b/drivers/base/dma-mapping.c > @@ -227,8 +227,8 @@ 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; > + unsigned long pfn; > > vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); > > @@ -236,6 +236,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, > return ret; > > if (off < count && user_count <= (count - off)) { > + pfn = page_to_pfn(virt_to_page(cpu_addr)); > ret = remap_pfn_range(vma, vma->vm_start, > pfn + off, > user_count << PAGE_SHIFT, > -- > 2.7.4 > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu >
|  |