Hi Jiri,
On Monday 28 February 2011 10:37:02 Jiri Slaby wrote:
> mem->dma_handle is a dma address obtained by dma_alloc_coherent which
> needn't be a physical address in presence of IOMMU. So ensure we are
> remapping (remap_pfn_range) the right page in __videobuf_mmap_mapper
> by using virt_to_phys(mem->vaddr) and not mem->dma_handle.
Quoting arch/arm/include/asm/memory.h,
/*
* These are *only* valid on the kernel direct mapped RAM memory.
* Note: Drivers should NOT use these. They are the wrong
* translation for translating DMA addresses. Use the driver
* DMA support - see dma-mapping.h.
*/
static inline unsigned long virt_to_phys(const volatile void *x)
{
return __virt_to_phys((unsigned long)(x));
}
Why would you use physically contiguous memory if you have an IOMMU anyway ?
> While at it, use PFN_DOWN instead of explicit shift.
>
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> drivers/media/video/videobuf-dma-contig.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/media/video/videobuf-dma-contig.c
> b/drivers/media/video/videobuf-dma-contig.c index c969111..19d3e4a 100644
> --- a/drivers/media/video/videobuf-dma-contig.c
> +++ b/drivers/media/video/videobuf-dma-contig.c
> @@ -300,7 +300,7 @@ static int __videobuf_mmap_mapper(struct videobuf_queue
> *q,
>
> vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> retval = remap_pfn_range(vma, vma->vm_start,
> - mem->dma_handle >> PAGE_SHIFT,
> + PFN_DOWN(virt_to_phys(mem->vaddr))
> size, vma->vm_page_prot);
> if (retval) {
> dev_err(q->dev, "mmap: remap failed with error %d. ", retval);
--
Regards,
Laurent Pinchart
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