Re: [PATCH v3 3/4] dt-bindings: hwmon: Add binding for max6639

[sylv <sylv@xxxxxxx>]

On Mon, 2022-01-24 at 21:08 -0800, Guenter Roeck wrote:
> On Wed, Jan 19, 2022 at 10:53:54AM +0100, Marcello Sylvester Bauer
> wrote:
> > Add Devicetree binding documentation for Maxim MAX6639 temperature
> > monitor with PWM fan-speed controller.
> > 
> > The devicetree documentation for the SD3078 device tree.
> > 
> > Signed-off-by: Marcello Sylvester Bauer <sylv@xxxxxxx>
> > ---
> >  .../bindings/hwmon/maxim,max6639.yaml         | 112
> > ++++++++++++++++++
> >  1 file changed, 112 insertions(+)
> >  create mode 100644
> > Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> > b/Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> > new file mode 100644
> > index 000000000000..7093cbeba44b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> > @@ -0,0 +1,112 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +
> > +$id: http://devicetree.org/schemas/hwmon/maxim,max6639.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Maxim max6639
> > +
> > +maintainers:
> > +  - Roland Stigge <stigge@xxxxxxxxx>
> > +
> > +description: |
> > +  The MAX6639 is a 2-channel temperature monitor with dual,
> > automatic, PWM
> > +  fan-speed controller.  It monitors its own temperature and one
> > external
> > +  diode-connected transistor or the temperatures of two external
> > diode-connected
> > +  transistors, typically available in CPUs, FPGAs, or GPUs.
> > +
> > +  Datasheets:
> > +   
> > https://datasheets.maximintegrated.com/en/ds/MAX6639-MAX6639F.pdf
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - maxim,max6639
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  '#address-cells':
> > +    const: 1
> > +
> > +  '#size-cells':
> > +    const: 0
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - "channel@0"
> > +  - "channel@1"
> > +
> > +additionalProperties: false
> > +
> > +patternProperties:
> > +  "^channel@[0-1]$":
> > +    type: object
> > +    description: |
> > +      Represents the two fans and their specific configuration.
> > +
> > +    properties:
> > +      reg:
> > +        description: |
> > +          The fan number.
> > +        items:
> > +          minimum: 0
> > +          maximum: 1
> > +
> > +      pwm-polarity:
> > +        $ref: /schemas/types.yaml#/definitions/uint32
> > +        enum: [0, 1]
> > +        description:
> > +          PWM output is low at 100% duty cycle when this bit is
> > set to zero. PWM
> > +          output is high at 100% duty cycle when this bit is set
> > to 1.
> > +
> > +      pulses-per-revolution:
> > +        $ref: /schemas/types.yaml#/definitions/uint32
> > +        enum: [1, 2, 3, 4]
> > +        description:
> > +          Value specifying the number of pulses per revolution of
> > the controlled
> > +          FAN.
> > +
> 
> I think the above two properties should be optional.
> pulses-per-revolution is 2 for almost all fans out there,
> and pwm polarity is positive almost all the time.

makes sense. I guess I'll keep the default values like before and
also set rpm-range (resp. rpm-max) to 4000.

> 
> > +      rpm-range:
> > +        $ref: /schemas/types.yaml#/definitions/uint32
> > +        enum: [2000, 4000, 8000, 16000]
> > +        description:
> > +          Scales the tachometer counter by setting the maximum
> > (full-scale) value
> > +          of the RPM range.
> > +
> Isn't this the maximum rpm ? Using the term "range" seems to be
> a bit misleading.

Yeah, the data sheet explicitly calls this register "rpm fan range".
But since this is not a vendor specific property and the purpose is
to set a maximum rpm value, it should rather be called "rpm-max".

Thanks!

Marcello

> 
> > +    required:
> > +      - reg
> > +      - pwm-polarity
> > +      - pulses-per-revolution
> > +      - rpm-range
> > +
> > +examples:
> > +  - |
> > +    i2c {
> > +      #address-cells = <1>;
> > +      #size-cells = <0>;
> > +
> > +      max6639@10 {
> > +        compatible = "maxim,max6639";
> > +        reg = <0x10>;
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        channel@0 {
> > +          reg = <0x0>;
> > +          pwm-polarity = <1>;
> > +          pulses-per-revolution = <2>;
> > +          rpm-range = <4000>;
> > +        };
> > +
> > +        channel@1 {
> > +          reg = <0x1>;
> > +          pwm-polarity = <1>;
> > +          pulses-per-revolution = <2>;
> > +          rpm-range = <4000>;
> > +        };
> > +      };
> > +    };
> > +...