linux-kernel - Re: [PATCH 3/4] ASoC: mediatek: mt8195: separate the common code from machine driver

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Date:   Fri, 5 Nov 2021 16:41:51 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Trevor Wu <trevor.wu@...iatek.com>, devicetree@...r.kernel.org,
        alsa-devel@...a-project.org, tiwai@...e.com,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        linux-mediatek@...ts.infradead.org, yc.hung@...iatek.com,
        matthias.bgg@...il.com, daniel.baluta@....com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/4] ASoC: mediatek: mt8195: separate the common code
 from machine driver

On Fri, Nov 05, 2021 at 11:16:05AM -0500, Pierre-Louis Bossart wrote:
> On 11/5/21 10:38 AM, Mark Brown wrote:

> > We shouldn't be requiring people to load completely different drivers
> > based on software configuration, what if a system wants to bypass the
> > DSP in some but not all configurations?  Can we not just have controls
> > allowing users to route round the DSP where appropriate?

> It was my understanding the card relies on separate components

> - a SOF-based component to provide support for DSP-managed interfaces
> - a 'non-SOF' component for 'regular' interfaces not handled by the DSP.

> this was the basis for the changes discussed in
> https://github.com/thesofproject/linux/pull/3217 and
> https://github.com/thesofproject/linux/pull/3236

So it's actually supposed to end up as two different cards which can't
possibly be interlinked?  That doesn't seem to add up entirely given
that there's stuff being moved out of the current card, and I thought
these systems had a fairly comprehensive audio muxing capability.
Trevor, could you be a bit more specific about what's actually going on
here physically please?

> But indeed if the same interface can be managed by the DSP or not,
> depending on software choices it's a different problem altogether.

> We've looked into this recently, if the choice to involve the DSP or not
> is at the interface level, it might be better to have both components
> expose different DAIs for the same interface, with some sort of run-time
> mutual exclusion, so that all possible/allowed permutations are allowed.

Yes, if the interface can optionally be completely hidden by the DSP
that's adding another layer of complication.

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