[PATCH 07/11] fsmc/nand: Provide contiguous buffers to dma

[viresh kumar]

On Wed, Oct 10, 2012 at 10:37 PM, Linus Walleij
<linus.walleij at linaro.org> wrote:
> The real problem is likely the DMA driver. The stuf that get
> fed into dma.device_prep_dma_memcpy() needs to be
> converted to a scatterlist and then set up in the LLI list
> for the controller.
>
> IIRC SPEAr is using drivers/dma/dw_dmac.c so

Both dw_dmac and pl080 for different SPEAr SoC's.

> check this driver's dwc_prep_dma_memcpy().
> It does seem like it is checking whether src or
> dest is scattered in this for() loop:
>
> for (offset = 0; offset < len; offset += xfer_count << src_width) {}
>
> dma_sync_single_for_device() is translating the virtual
> address to physical for every chunk BTW.
>
> So instead of doing this copying, debug the problem, and
> see if there is a bug in that for()-loop or similar, if it needs
> to be rewritten or so.

But what's the problem you saw vipin, for which you generated this patch?