Hi Robin, Laurent,
a long time passed, sorry about this.
On Wed, Nov 15, 2017 at 01:38:23PM +0000, Robin Murphy wrote:
> 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.I still need to carry this patch in my trees to have a working dma memory mapping on SH4 platforms. My understanding from your comment is that there may be a way forward for this patch, do you still think the same? Have you got any suggestion on how to improve this eventually for inclusion? Thanks j > > Robin. > > >Suggested-by: Laurent Pinchart <[email protected]> > >Signed-off-by: Jacopo Mondi <[email protected]> > >--- > > 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 > >[email protected] > >https://lists.linuxfoundation.org/mailman/listinfo/iommu > >
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