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 <20230501091552.847240-3-patrick.rudolph@9elements.com> <fd20cad6-34f9-5f3c-abe7-cdf3a93d712c@axentia.se>
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From:   Patrick Rudolph <patrick.rudolph@9elements.com>
Date:   Tue, 2 May 2023 08:52:48 +0200
Message-ID: <CALNFmy1gxUD-C62SH5GxA=fq8eKYxiOHe8wqXGsVdzsyiJc6Xg@mail.gmail.com>
Subject: Re: [PATCH v14 2/4] dt-bindings: i2c: Add Maxim MAX735x/MAX736x variants
To:     Peter Rosin <peda@axentia.se>
Cc:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        linux-i2c@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Hi Peter,
it could indeed cause problems when VDD1 !=3D VDD2 and at both needs to
be enabled.
The pca9846 datasheet seems to refer to VDD1 as VDD. Thus I could add
an optional "vdd2" regulator to the binding and driver.

Please let me know if that's what you had in mind.
Regards,
Patrick

On Tue, May 2, 2023 at 8:03=E2=80=AFAM Peter Rosin <peda@axentia.se> wrote:
>
> Hi!
>
> 2023-05-01 at 11:15, Patrick Rudolph wrote:
> > Update the pca954x bindings to add support for the Maxim MAX735x/MAX736=
x
> > chips. The functionality will be provided by the existing pca954x drive=
r.
> >
> > For chips that are powered off by default add a regulator called vdd-su=
pply.
> >
> > Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
> > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> > ---
> >  .../bindings/i2c/i2c-mux-pca954x.yaml         | 22 +++++++++++++++++--
> >  1 file changed, 20 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml=
 b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
> > index e5c1070903ef..6fed6eae9c9b 100644
> > --- a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
> > +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
> > @@ -4,18 +4,29 @@
> >  $id: http://devicetree.org/schemas/i2c/i2c-mux-pca954x.yaml#
> >  $schema: http://devicetree.org/meta-schemas/core.yaml#
> >
> > -title: NXP PCA954x I2C bus switch
> > +title: NXP PCA954x I2C and compatible bus switches
> >
> >  maintainers:
> >    - Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> >  description:
> > -  The binding supports NXP PCA954x and PCA984x I2C mux/switch devices.
> > +  The NXP PCA954x and compatible devices are I2C bus
> > +  multiplexer/switches that share the same functionality
> > +  and register layout.
> > +  The devices usually have 4 or 8 child buses, which are
> > +  attached to the parent bus by using the SMBus "Send Byte"
> > +  command.
> >
> >  properties:
> >    compatible:
> >      oneOf:
> >        - enum:
> > +          - maxim,max7356
> > +          - maxim,max7357
> > +          - maxim,max7358
> > +          - maxim,max7367
> > +          - maxim,max7368
> > +          - maxim,max7369
> >            - nxp,pca9540
> >            - nxp,pca9542
> >            - nxp,pca9543
> > @@ -56,6 +67,9 @@ properties:
> >      description: if present, overrides i2c-mux-idle-disconnect
> >      $ref: /schemas/mux/mux-controller.yaml#/properties/idle-state
> >
> > +  vdd-supply:
> > +    description: A voltage regulator supplying power to the chip.
> > +
>
> The pca9846-9 chips do not have one VDD, they have separate supplies for
> "low level" (VDD1), and "core logic" (VDD2). I don't know how such a
> situation is normally reflected in bindings, but could it not cause
> headaches later if use of unqualified VDD is spreading for those chips?
> Possibly with different semantics depending on if vdd-supply is tied to
> VDD1, VDD2 or both?
>
> Cheers,
> Peter
>
> >  required:
> >    - compatible
> >    - reg
> > @@ -68,6 +82,8 @@ allOf:
> >            compatible:
> >              contains:
> >                enum:
> > +                - maxim,max7367
> > +                - maxim,max7369
> >                  - nxp,pca9542
> >                  - nxp,pca9543
> >                  - nxp,pca9544
> > @@ -94,6 +110,8 @@ examples:
> >              #size-cells =3D <0>;
> >              reg =3D <0x74>;
> >
> > +            vdd-supply =3D <&p3v3>;
> > +
> >              interrupt-parent =3D <&ipic>;
> >              interrupts =3D <17 IRQ_TYPE_LEVEL_LOW>;
> >              interrupt-controller;