Re: [PATCH v2 25/26] omap3isp: Move to videobuf2

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tim,

On Wednesday 18 March 2015 10:19:15 Tim Nordell wrote:
> Laurent -
> 
> On 03/18/15 09:59, Laurent Pinchart wrote:
> > Hi Tim,
> > The names might be a bit misleading, vb2-dma-contig requires contiguous
> > memory in the device memory space, not in physical memory. The IOMMU,
> > managed through dma_map_sg_attrs, should have mapped the userptr buffer
> > contiguously in the ISP DMA address space. If it hasn't, that's what need
> > to be investigated.
>
> I see now that it's the sg_dma_address(...) call that it's using and I
> was assuming that was the physical memory address for the memory backing
> up the buffer.
> 
> So the vb2_dc_get_contiguous_size(...) should be against the view of
> memory that the IOMMU presents to the OMAP3 ISP?  That is, the DMA
> addresses that the OMAP3 ISP can see?

Correct. sg_dma_address() should contain the DMA virtual address when an IOMMU 
is used.

> I was assuming it was checking the physical memory layout to it without
> looking too closely to the code.  Armed with that knowledge, I'll dig a
> little deeper to see if I can figure out what happened here.

Thank you.

-- 
Regards,

Laurent Pinchart