How to open IV reference stream for smart amp use case in linux (SOF-Driver)

[Venkata-Prasad-Potturu]

We are trying to open an IV reference stream when we start playback on Smart amp speaker.
Found a reference to open a IV reference stream from alsa ucm files in CRAS (chromium repo).
Taken sample ucm example from cras ucm as below and used the same in Linux machines (Pulse audio and Pipewire) , but IV reference stream is not opening.
Could you please help me to understand how to open IV reference stream of Smart amp for playback use case.
Thanks :)

HiFi.conf
SectionDevice."Speaker".0 {
Comment "Speaker"
Value {
PlaybackPriority 100
PlaybackPCM "hw:sofnau8821max,1"
EchoReferenceDev "Echo Reference"
}
EnableSequence [
cdev "hw:sofnau8821max"
exec "echo Speaker EnableSequence"
]
DisableSequence [
cdev "hw:sofnau8821max"
exec "echo Speaker DisableSequence"
]
}
SectionDevice."Echo Reference".0 {
Value {
CapturePCM "hw:sofnau8821max,1"
}
EnableSequence [
exec "echo Speaker reference capture path EnableSequence"
]
DisableSequence [
]
}

[Venkata-Prasad-Potturu]

@plbossart @ranj063
Please comment on this.

[lgirdwood]

@Venkata-Prasad-Potturu are you trying to tell CRAS which PCM is to be opened for IV ?

[Venkata-Prasad-Potturu]

@lgirdwood
Not CRAS, In our case we are using Pulseaudio and to open IV PCM stream we have mentioned in UCM file as above.
Is this correct way to open IV stream when playback starts on speaker.

[lgirdwood]

I think Pulseaudio is missing and unlikely to acquire SmartAmp support. I would reach out to pipewire developers for support in Pipewire.

[cujomalainey]

Indeed @Venkata-Prasad-Potturu EchoReferenceDev is a CRAS concept. I sent the patches definitions upstream, if they land pulse/pipewire should be more accepting of the definitions once implemented

[plbossart]

ironically it should be easier to upstream if this is not perceived as an Intel-only extension :-)

[plbossart]

Are we confusing echo reference and IV feedback by any chance? It's possible that for test purposes the IV feedback is provided to userspace, but the intended use for the IV feedback is to be used by a speaker protection module inside the DSP firmware.

[cujomalainey]

Patches sent again https://mailman.alsa-project.org/hyperkitty/list/alsa-devel@alsa-project.org/thread/JFOBKRMOJZRQAG4D6MNC2SYIMY7BHQO2/

[felakuti4life]

@cujomalainey Thanks for the clarification, this looks like exactly what would be needed. EchoReferenceDev is just in this case a generic coupled device.

[bhiregoudar]

It seems along with the changes provided by Curtis, pipewire/pulseaudio changes are also required to support the IV feedback path.
@felakuti4life @lgirdwood : Could you please take this forward for pipewire/pulseaudio?

[cujomalainey]

To close out this thread, it appears like it was a common misunderstanding of how echo refs are properly done in also. See Jaroslav's responses.