linux-kernel - Re: [PATCH v1 2/4] dt-bindings: mfd: Document Infineon/Cypress CG7153AM MCU

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Message-ID: <CAL_JsqLCW+zE2LfsVybuxn_xu1JwtLSXSbMNj-YYfVgtYhZcaQ@mail.gmail.com>
Date: Mon, 24 Mar 2025 21:59:58 -0500
From: Rob Herring <robh@...nel.org>
To: Svyatoslav Ryhel <clamor95@...il.com>
Cc: Lee Jones <lee@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Thierry Reding <thierry.reding@...il.com>, 
	Jonathan Hunter <jonathanh@...dia.com>, Sebastian Reichel <sre@...nel.org>, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org, 
	linux-pm@...r.kernel.org
Subject: Re: [PATCH v1 2/4] dt-bindings: mfd: Document Infineon/Cypress
 CG7153AM MCU

On Mon, Mar 24, 2025 at 12:06 PM Svyatoslav Ryhel <clamor95@...il.com> wrote:
>
> пн, 24 бер. 2025 р. о 18:52 Rob Herring <robh@...nel.org> пише:
> >
> > On Sun, Mar 23, 2025 at 09:14:22AM +0200, Svyatoslav Ryhel wrote:
> > > Add binding for Cypress CG7153AM embedded controller. Pegatron implemented
> > > a custom configuration of this MCU in their Chagall tablets, utilizing it
> > > for battery monitoring.
> > >
> > > Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> > > ---
> > >  .../bindings/mfd/cypress,cg7153am.yaml        | 55 +++++++++++++++++++
> > >  1 file changed, 55 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/mfd/cypress,cg7153am.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/mfd/cypress,cg7153am.yaml b/Documentation/devicetree/bindings/mfd/cypress,cg7153am.yaml
> > > new file mode 100644
> > > index 000000000000..f8469b5e3816
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/mfd/cypress,cg7153am.yaml
> > > @@ -0,0 +1,55 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/mfd/cypress,cg7153am.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Infineon/Cypress Semicon CG7153AM Microcontroller
> > > +
> > > +maintainers:
> > > +  - Svyatoslav Ryhel <clamor95@...il.com>
> > > +
> > > +description:
> > > +  The CG7153AM, an 8-bit programmable microcontroller from Infineon/Cypress
> > > +  Semiconductor, communicates over I2C and is implemented in devices like the
> > > +  Pegatron Chagall tablet for fuel gauge and battery control functions.
> > > +
> > > +$ref: /schemas/power/supply/power-supply.yaml
> > > +
> > > +properties:
> > > +  compatible:
> > > +    oneOf:
> > > +      - items:
> > > +          - enum:
> > > +              - pegatron,chagall-ec # Pegatron Chagall tablet device
> > > +          - const: cypress,cg7153am
> > > +      - items:
> > > +          const: cypress,cg7153am
> >
> > Is this just some general purpose uC which could be used for anything
> > and the interface exposed is Pegatron's invention. If so, then I'd drop
> > the cypress,cg7153am compatible. What use would it be to software?
> >
>
> Yeah, Cypress made an MPU, Pegatron used it as a base to make a fuel gauge.
>
> You propose smth like this?
>
>       - items:
>           - enum:
>               - pegatron,chagall-ec # Pegatron Chagall tablet device
>           - const: cypress,cg7153am
>
> Without oneOf and second item or remove cypress,cg7153am entirely and
> submit as pegatron,chagall-ec.yaml? Just to be clear.
>
> I am fine with removing oneOf and items: const: cypress,cg7153am, but
> I would like to preserve cypress,cg7153am as second compatible since
> this is an actual MCU model.

I would just drop the cypress compatible entirely. It needs to be
useful to a client (OS) in some way. If you said something like the
firmware downloading is defined by Cypress or some other feature, then
it would make sense. Otherwise, how this interface is implemented is
irrelevant. I can't think of any other embedded controller where we
have a compatible for the underlying MCU.

Rob