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

[Guenter Roeck <linux@roeck-us.net>]

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@sylv.io>
> ---
>  .../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@antcom.de>
> +
> +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.

> +      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.

> +    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>;
> +        };
> +      };
> +    };
> +...