linux-kernel - Re: [PATCH v15 1/8] dt-bindings: mfd: Initial commit of silergy,sy7636a.yaml

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Date:   Tue, 23 Nov 2021 23:29:26 +1000
From:   Alistair Francis <alistair23@...il.com>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     Alistair Francis <alistair@...stair23.me>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>, lgirdwood@...il.com,
        Rob Herring <robh+dt@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        rui.zhang@...el.com, devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        linux-hwmon@...r.kernel.org, amitk@...nel.org,
        linux-pm@...r.kernel.org, dl-linux-imx <linux-imx@....com>,
        Shawn Guo <shawnguo@...nel.org>, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v15 1/8] dt-bindings: mfd: Initial commit of silergy,sy7636a.yaml

On Thu, Nov 18, 2021 at 7:40 AM Andreas Kemnade <andreas@...nade.info> wrote:
>
> On Wed, 10 Nov 2021 22:29:41 +1000
> Alistair Francis <alistair@...stair23.me> wrote:
>
> > Initial support for the Silergy SY7636A Power Management chip
> > and regulator.
> >
> > Signed-off-by: Alistair Francis <alistair@...stair23.me>
> > Reviewed-by: Rob Herring <robh@...nel.org>
> > Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>
> > ---
> >  .../bindings/mfd/silergy,sy7636a.yaml         | 79 +++++++++++++++++++
> >  1 file changed, 79 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/mfd/silergy,sy7636a.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/mfd/silergy,sy7636a.yaml b/Documentation/devicetree/bindings/mfd/silergy,sy7636a.yaml
> > new file mode 100644
> > index 000000000000..0566f9498e2f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mfd/silergy,sy7636a.yaml
> [...]
> > +  regulators:
> > +    type: object
> > +
> > +    properties:
> > +      compatible:
> > +        const: silergy,sy7636a-regulator
> > +
> > +      vcom:
> > +        type: object
> > +        $ref: /schemas/regulator/regulator.yaml#
> > +        properties:
> > +          regulator-name:
> > +            const: vcom
> > +
> hmm, this is what? If I understand it correctly, vcom means some
> voltage for compensation. On other comparable pmics (e.g. TPS65185
> which has also a sane public datasheet, MAX17135) I have seen some
> methods to measure a voltage while the display is doing something
> defined and then program this voltage non-volatile for compensation
> during manufacturing.
>
> If I understand the code correctly all the bunch of voltages are
> powered up if this one is enabled.
> So at least a description should be suitable.
>
> The other comparable PMICs have at least regulators named VCOM, DISPLAY
> (controls several regulators, started with delays configured via
> registers) and V3P3. MAX17135 source can be found in NXP kernels,
> TPS65185 in Kobo vendor kernels.
>
> So I would expect to see something similar here and a description or at
> least not such a misleading name as vcom if it is for some reason not
> feasible to separate the regulators.

This is a vcom in the sense of voltage for compensation. We just
currently don't support setting the vcom.

I had a look at the Kobo code and this is similar to
https://github.com/akemnade/linux/blob/kobo/epdc-pmic-5.15/drivers/regulator/sy7636-regulator.c#L614

So I think that vcom is still the appropriate name for this.

Alistair

>
> Regards,
> Andreas