[PATCH v2 1/2] spi: spi-imx: enable dma support for escpi controller

[Mark Brown]

On Tue, Jan 14, 2014 at 11:02:31PM +0100, Marek Vasut wrote:
> On Tuesday, January 14, 2014 at 10:55:48 PM, Mark Brown wrote:

> > Or try to - the other trick here is getting 4MB of contiguous memory in
> > the first place (unless there's an IOMMU making everything pretty).

> Oh, but what if I want to make a really looong transfer ? Say, read entire SPI 
> NOR of 128MB in size ... Spansion has such big SPI NORs in their new portfolio.

Use scatter/gather - to the SPI controller and the outside world it
still looks like one big transfer (I'm missing a way to go from a
virtual address to a sg_list, that'd be handy).  It's an issue if the
DMA controller doesn't support it but but that's rare.
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