[PATCH 1/3] spi/qspi: Add memory mapped read support.

[Mark Brown]

On Wed, Oct 09, 2013 at 09:01:59PM +0200, Peter Korsgaard wrote:

> Indeed. I can see how such a feature could be useful in E.G. a lowlevel
> bootloader (because of simplicity), but am less convinced about it in
> Linux where we could conceivable do something else useful while waiting
> on the spi controller.

> But if there's number to prove otherwise..

I can see it being useful if there's a DMA controller that can do the
transfer as a memory to memory DMA - the hardware can probably issue
flash read commands a bit faster than the AP can so you should be able
to get closer to saturating the bus.  The patches didn't try to do that
or make it possible for something further up the stack to do it and the
differences should end up being fairly small with optimisations like
those in the pxa2xx or pl022 drivers (which I'm currently working on
pulling out into the framework).
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