Re: [PATCH v2 20/29] ASoC: tas2764: Add SDZ regulator

[James Calligeros]

Hi Mark,

On Wed, Feb 19, 2025 at 1:33 AM Mark Brown <broonie@xxxxxxxxxx> wrote:
>
> On Tue, Feb 18, 2025 at 06:35:54PM +1000, James Calligeros wrote:
>
> > Multiple amps can be connected to the same SDZ GPIO. Using raw GPIOs for
> > this breaks, as there is no concept of refcounting/sharing. In order to
> > model these platforms, introduce support for an SDZ "regulator". This
> > allows us to represent the SDZ GPIO as a simple regulator-fixed, and
> > then the regulator core takes care of refcounting so that all codecs are
> > only powered down once all the driver instances are in the suspend
> > state.
>
> I get that the reference counting that the regulator API does is useful
> here but this isn't a regulator so shouldn't be exposed as such,
> particularly since this winds up being visible in the DT ABI.  I
> could've sworn that someone did some helpers for this case but now I go
> looking I can't find them, we certainly don't use any in the regulator
> core.

>From what I recall, no attempt at shared GPIO infrastructure has actually
landed. The multiple {de}assertions of SDZ put each chip on the same line
into an unusable state that requires a full power cycle to clear, so
we can't live without
handling the shared GPIO somewhat sensibly.

One alternative off the top of my head is adding a dummy reset controller
to the DTs and integrating it into the ASoC machine driver (which we have
downstream). We could then put the GPIO behind a shared reset line, and hit
that instead of the GPIO. This does seem a little complex/odd, and IIRC we
considered this at some point and decided against it.

Is there any other option that may work here? I'm open to ideas.

Regards,
James