Re: [alsa-devel] [PATCH 1/2] powerpc: add platform registration for ALSA SoC drivers

[Mark Brown <broonie@opensource.wolfsonmicro.com>]

On Tue, Apr 27, 2010 at 04:03:27PM -0500, Timur Tabi wrote:

[Reflowing the text into 80 columns again]

> Mark Brown wrote:
> > It's entirely possible that if the board designer intended the verious
> > SSIs to be used in concert they've done something like cross wire the
> > clocks which creates a board-specific interrelationship that needs to be
> > dealt with.

> Fine, but I don't see how that can be handled with the current code.
> Each SSI is independent, and audio is streamed to it via DMA.  The
> current SSI driver would need to be completely rewritten in order to
> initiate both DMA operations simultaneously.  The clocking is the least
> of my problems.

I believe the usual technique is to start the DMA then clock the bus -
data doesn't flow over the bus until the clock appears and that appears
everywhere simultaneously.  Obviously some hardware really doesn't like
having the DMA blocked like that, but not all.