[alsa-devel] Problems with ALC882

[Takashi Iwai]

At Fri, 18 Jan 2008 17:50:38 +0100,
Christophe Osuna wrote:
> 
> 2008/1/18, Takashi Iwai <tiwai at suse.de>:
> > At Fri, 18 Jan 2008 17:10:06 +0100,
> > Christophe Osuna wrote:
> > >
> > > I have tried alsa-driver-hg20080117; it shows two additional mixer
> > > options (Mic Boost and Front Mic Boost) but in the end it's the same:
> > > I am unable to access the 3rd ADC.
> >
> > Looks like your board disables the third ADC.  The driver probes it
> > and the codec returns it's no audio-input widget.  Check codec#* proc
> > output.
> >
> 
> I have copied the contents of /proc/asound/card0/codec#2 at the end of
> this message. Notice that there are three nodes (0x07, 0x08 and 0x09)
> which claim to support PCM input.

Ah, then it's in patch_realtek.c where alc880_pcm_analog_capture
claims substreams = 2.  Feel free to fix it.

> > > The ALC882 datasheet states that "3 stereo ADCs support 16/20-bit PCM
> > > format, two for microphone array, one for legacy mixer recording".
> > > This is the only place that suggests there could be a difference, but
> > > I do not understand this sentence as "only 2 ADC can be used at a
> > > time" (English is not my native language). The block diagram in the
> > > following page does not suggest such a limit either.
> >
> > The reality bites sometimes :)
> 
> I really want to believe this codec can do three things at a time.

Not always.  There must be a reason for one codec being disabled on
many devices.

> > > Besides that I have read in the same datasheet that "rates in
> > > sub-multiples (1/n) of 48kHz are interleaving n frames containing no
> > > sample blocks" and so we can have 8 kHz by setting one sample block
> > > every six frames. Still, I can't set the device to 8 kHz.
> >
> > How did you test it?  The driver itself supports 8kHz, as long as the
> > codec chip really returns the capability.
> 
> The same nodes I mentionned above (0x07, 0x08 and 0x09 in
> /proc/asound/card0/codec#2) show no support for 8 kHz sample rate.
> This is confirmed by the failing calls to
> snd_pcm_hw_params_set_rate().

Then actually the codec doesn't support 8kHz.  Or, at least, the
hardware vendor doesn't want it to work on 8kHz by any reason.

Of course, you can try to override in the driver, but it's definitely
at your own risk...


Takashi