On Thu, 2010-03-25 at 09:17 +0200, Peter Ujfalusi wrote:

Hi,

On Thursday 25 March 2010 04:33:54 ext Candelaria Villarreal, Jorge wrote:

...

Hi,

I am trying to add support for a digital mixer. The digital mixer is connected like the following example:

Path 1 -------\ Path 2 --------\ MIXER ------> DAC----> ... Path 3 --------/ Path 4 -------/

However, I think ALSA does not support this configuration, as the DAC should be the first element in a route. I tried adding the DAC to the route first, and connected its output to the mixer inputs, like this:

 {"Mixer", "Multimedia Ext Switch", "HSDAC Left"},
    {"Mixer", "Multimedia Ext Switch", "HSDAC Right"},

    {"Mixer", "Voice Switch", "HSDAC Left"},
    {"Mixer", "Voice Switch", "HSDAC Right"},

    {"Mixer", "Multimedia Uplink Switch", "HSDAC Left"},
    {"Mixer", "Multimedia Uplink Switch", "HSDAC Right"},

    {"Mixer", "Multimedia Switch", "HSDAC Left"},
    {"Mixer", "Multimedia Switch", "HSDAC Right"},

But this does not seem to work. Can anyone give me some tips? Any comment would be appreciated.

The DAC is traditionally an endpoint (or source) widget within DAPM. This means it is does not have a source widget to supply it with audio.

Hmm, how these paths are connected, and where? What I mean is I suppose you have one path, which is connected to the main CPU, than I suspect you have a connection to a modem (voice?), than you have possibility to connect some other components via digital link?

What I did with the TWL4030 codec, is that I have moved the actual DAC power control from the DAPM_DAC to different widget (the DAPM_DAC is kind of a fake one). This was needed to support the digital loopback functionality.

So if you reorder the DAPM widgets (making sure that the switch order still OK), than I think you can treat one of the paths as normal playback path (fake DAPM_DAC -> mixer (have the DAC power bit handled here) -> ...). Than you might consider of adding the rest of the paths as DAPM_INPUT, and connect them to the mixer (which after the fake DAC). So you kind of have digital loopback from those to the analog domain.

This approach currently works well on the twl4030. However, you may want to consider using SND_SOC_DAPM_AIF_IN() for your input paths here. e.g.

AIF_IN -> MIXER -> DAC -> rest of codec

Liam

Liam Girdwood wrote:

On Thu, 2010-03-25 at 09:17 +0200, Peter Ujfalusi wrote:

...

What I did with the TWL4030 codec, is that I have moved the actual DAC power control from the DAPM_DAC to different widget (the DAPM_DAC is kind of a fake one). This was needed to support the digital loopback functionality.

So if you reorder the DAPM widgets (making sure that the switch order still OK), than I think you can treat one of the paths as normal playback path (fake DAPM_DAC -> mixer (have the DAC power bit handled here) -> ...). Than you might consider of adding the rest of the paths as DAPM_INPUT, and connect them to the mixer (which after the fake DAC). So you kind of have digital loopback from those to the analog domain.

This approach currently works well on the twl4030. However, you may want to consider using SND_SOC_DAPM_AIF_IN() for your input paths here. e.g.

AIF_IN -> MIXER -> DAC -> rest of codec

I see now, this is exactly what I was looking for. I will give it a try then. Thanks.