Re: Nokia N900 headset detection & MIC Bias + TVOUT

["Pali Rohár" <pali.rohar@gmail.com>]

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On Monday 09 January 2017 20:22:01 Mark Brown wrote:
> On Mon, Jan 09, 2017 at 02:13:17PM +0100, Pali Rohár wrote:
> > So... can I call snd_soc_dapm_mutex_lock(dapm) at function startup,
> > start doing cable detection and when needed call this?
> > 
> > snd_soc_dapm_enable_pin_unlocked(dapm, "HS Mic");
> > snd_soc_dapm_sync_unlocked(dapm);
> > 
> > And at the end of function revert back "HS Mic" pin status and call
> > snd_soc_dapm_mutex_unlock(dapm)?
> 
> You shouldn't need to lock I'd expect, and you'll want to sync at any
> point where you need an actual change.  Note that if something holds
> the microphone bias on (like something using the microphone)
> separately then that'll take effect so if you really need things to
> get turned off then that won't work but you probably have trouble
> anyway in that situation.

This is needed for cable/jack detection at time when jack is inserted. 
So before it there cannot be any user of (disconnected) microphone.

What I need is to enable mic bias, measure ADC of some time period, 
check status of some GPIOs. Then disable mic bias, measure ADC again and 
check GPIOs. I in this detection procedure I need to ensure that nobody 
changes mic bias. So I though that locking the whole procedure could 
ensure that.

-- 
Pali Rohár
pali.rohar@gmail.com

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