RFC: changing DMA slave configuration API

[Linus Walleij]

On Mon, Jun 11, 2012 at 6:50 AM, Vinod Koul <vinod.koul at linux.intel.com> wrote:

> Do we have any users of peripheral to peripheral slave dma?
> IIRC  that is not the case, or does anyone know of existence or plans
> for such a h/w?

The U300 (COH901318) device can do this.

The usecase is basically that the modem CPU sets up a PCM
stream on the high-speed serial link (called MSL) and the DMA
controller reads 16 bit words from this link and routes it directly
to a PCM sink on an I2S hardware.

Actually it runs in both directions during a voicecall, you can
probably see the gain in power and CPU unload this will gain
on a phone.

However this is all out-of-tree code and not that big deal as
it's a legacy platform.

Yours,
Linus Walleij