linux-kernel - Re: [PATCH v1 3/4] dt-bindings: hwmon: Add binding for max6639

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Message-ID: <20220110012203.GA976519@roeck-us.net>
Date:   Sun, 9 Jan 2022 17:22:03 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marcello Sylvester Bauer <sylv@...v.io>
Cc:     linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        Jean Delvare <jdelvare@...e.com>,
        Rob Herring <robh+dt@...nel.org>,
        Roland Stigge <stigge@...com.de>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/4] dt-bindings: hwmon: Add binding for max6639

On Mon, Jan 03, 2022 at 05:33:48PM +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@...v.io>
> ---
>  .../bindings/hwmon/maxim,max6639.yaml         | 71 +++++++++++++++++++
>  1 file changed, 71 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..136ed37b6aac
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> @@ -0,0 +1,71 @@
> +# 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@...com.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
> +
> +  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.
> +      Fans PWM polarity is set to high (1) by default.

Should probably be pwm-polarity.

> +
> +  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.

Is there a fan in the world with pulses-per-revolution == 3 ?
Valid values should probably be 1, 2, 4.

> +
> +  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.

The above need to be per channel in devicetree data.

On higher level, max6639_platform_data should be removed entirely.
It isn't used by any in-kernel driver, and all its parameters are
per device and not per channel as they should be.

Guenter

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