Re: [PATCH v2 3/5] ASoC: dt-bindings: wm8904: Add DMIC, GPIO, MIC and EQ support

[Mark Brown]

On Wed, Mar 05, 2025 at 09:52:09AM +0000, Charles Keepax wrote:
> On Wed, Mar 05, 2025 at 07:45:50AM +0100, Krzysztof Kozlowski wrote:
> > On 27/02/2025 16:34, Ernest Van Hoecke wrote:

> > > I expect most users to use the first five Retune Mobile registers and
> > > not care about the rest, which require a proprietary tool and are not
> > > well documented. The example in the binding shows how some simple
> > > static EQ can be configured. Anyone interested in the extended config
> > > can also use it (statically).

> > No, if this is suitable for dynamic configuration then it's a proof it
> > is not suitable for DT.

> Whilst I can see the argument that this could be exposed as an
> ALSA control. I would also suggest that this is not adding some new
> feature, these values have been filled in from pdata for 16 years
> now. Changing the way such a vintage part works at this point feels
> more problematic to me than a slightly iffy DT property.

> On the flip side of the argument, the parameters that are filled
> into this are almost certainly specific tuning for the hardware,
> so in many ways this is hardware description and there is a
> certain appeal to shipping the tuning with the hardware (ie. in
> DT).

Right, the intended use case for the dynamic configuration is lab tuning
rather than with end users - most things that are configured like this
*can* be tuned interactively (or interactively from the point of view of
the driver) but that doesn't translate to end users doing it.  It's more
like coefficient data that could also be loaded from a firmware blob
(but again, there's a proprietary tool here and it's not expecting to
produce anything except a list of register values), we do have some EFI
examples of pulling tuning data from the firmware for things like
speaker correction (which is one of the use cases here) IIRC.

Like Charles says this scheme has been deployed for a decade or
something, it seems unhelpful to upend everything right now.  We could
also implement an alternative scheme but providing something that makes
DT transition easy seems productive.

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