[alsa-devel] FW: [PATCH v3] ASoC: Add support for TI LM49453 Audio codec

Liam Girdwood lrg at ti.com
Wed Feb 8 11:57:30 CET 2012

On Wed, 2012-02-08 at 16:06 +0530, Vinod Koul wrote:
> On Wed, 2012-02-08 at 09:54 +0000, Liam Girdwood wrote:
> > Atm, the machine driver would have to enable any system clocks before
> > the codec driver could use them. 
> But how would machine driver know _when_?

The machine driver gets all the PCM ops that the codec driver does and
is responsible for configuring CODEC PLLs and clocks (usually in it's

> We want to dynamical turn off this clock when not is use and turn on
> only when codec is using. So I was thinking of turning this ON in
> codecs .set_bias_level callback, but how to propagate this into machine
> driver?

It's usually done in the machine driver hw_params() since at this point
we know the rate, format etc that can have a bearing on the clock
configuration. You could switch it OFF in machine hw_free().


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