[alsa-devel] Managing resources of DSP from arm core side

[Peter Ujfalusi]

Hi Daniel,

On 28/01/2020 17.14, Daniel Baluta wrote:
> Hi Peter,
> 
> Liam mentioned that at some point (when working for OMAP)
> you might have had the same challenge I'm facing now.

Sorry for the delay...

> I'm trying to figure out how to properly manage resources needed by
> the IPs configured
> by DSP.
> 
> On i.MX8 we the following scenario:
> 
> - Application processor (arm64) exposes an ALSA sound card to applications
> - DSP (Hifi4) does the processing
> 
> DSP has direct access to  DAI registers but it doesn't have (easily)
> access to other resources
> like: pinctrl, power-domain, clocks, etc.
> 
> I was wondering how did you tackled this for OMAP?

It is (was, as the AESS/ABE support is not upstream) bit different.
>From the audio backend we do not touch the DAI registers, all setup is
done on the Linux side and the AESS 'only' managing the data flow.

So the back-ends are the DAIs and they are managed by Linux, the
front-end is AESS. DAIs are configured by fixing up the hw_params for
them in the AESS (front-end) stack, so they are configured correctly for
the use case.

It was pre DPCM, but the foundation was the same.

> I have already created a dummy CPU DAI on Linux that it will take care
> of this [1].
> 
> It is a part of a Back End link like this (simplified view):
> 
> links[i].cpus->name = "dummy_dai";
> links[i].platforms->name = "dsp";
> links[i].codecs->name = "cs42888";
> links[i].no_pcm = 1;
> 
> It works pretty well for basic playback / capture.
> 
> thanks,
> Daniel.
> 
> [1] https://marc.info/?l=alsa-devel&m=158022296519597&w=2
> 

- Péter

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