[alsa-devel] mic bias for tlv320aic3x?
pmeerw at pmeerw.net
Wed Nov 28 10:28:53 CET 2012
> > I'd like to enable 2V mic bias on the tlv320aic3x (which offers 2V, 2.5V,
> > AVDD, off) -- I'd have expected some control in alsamixer to so, but there
> > is none
> > what is the proper way to implement mic bias selection?
> As platform data or possibly via an API offered to the machine driver,
> we've yet to see any use case where it's something that should be varied
> directly from the application layer.
I can see the platform data way
I'd be happy with an API to control from the machine driver -- is
snd_soc_dapm_enable_pin() to be used for this + some SND_SOC_DAPM_MIC?
I am missing the overall strategy how this is supposed to work
is there a good reference driver?
per default, Mic Bias is off
there already are some mic bias definitions in tlv320aic3x:
/* Mic Bias */
SND_SOC_DAPM_REG(snd_soc_dapm_micbias, "Mic Bias 2V",
MICBIAS_CTRL, 6, 3, 1, 0),
SND_SOC_DAPM_REG(snd_soc_dapm_micbias, "Mic Bias 2.5V",
MICBIAS_CTRL, 6, 3, 2, 0),
SND_SOC_DAPM_REG(snd_soc_dapm_micbias, "Mic Bias AVDD",
MICBIAS_CTRL, 6, 3, 3, 0),
however, those are not referenced anywhere and it is not clear how to
access those from the machine driver
as for the use case: user wants to connect either a microphone or line-in
to a connector, hence mic bias selection is necessary -- this doesn't
sound so unusual
thanks, regards, p.
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