linux-kernel - Re: [PATCH 1/2] dt-bindings: hwmon: Add binding for max6639

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Date:   Thu, 29 Sep 2022 14:32:51 -0500
From:   Rob Herring <robh@...nel.org>
To:     Naresh Solanki <naresh.solanki@...ements.com>
Cc:     devicetree@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Roland Stigge <stigge@...com.de>, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        Marcello Sylvester Bauer <sylv@...v.io>
Subject: Re: [PATCH 1/2] dt-bindings: hwmon: Add binding for max6639

On Thu, Sep 22, 2022 at 07:07:17AM +0200, Naresh Solanki wrote:
> From: Marcello Sylvester Bauer <sylv@...v.io>
> 
> Add Devicetree binding documentation for Maxim MAX6639 temperature
> monitor with PWM fan-speed controller.
> 
> Signed-off-by: Marcello Sylvester Bauer <sylv@...v.io>
> Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
> ---
>  .../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..c845fb989af2
> --- /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@...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
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +required:
> +  - compatible
> +  - reg
> +  - "fan@0"
> +  - "fan@1"
> +
> +additionalProperties: false
> +
> +patternProperties:
> +  "^fan@[0-1]$":
> +    type: object
> +    description: |
> +      Represents the two fans and their specific configuration.
> +
> +    properties:
> +      reg:
> +        description: |
> +          The fan number.

Addresses are a property of the parent (the fan controller), not the 
fan. 

> +        items:
> +          minimum: 0
> +          maximum: 1
> +
> +      pwm-polarity:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        enum: [0, 1]
> +        default: 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.

IIRC, the PWM binding provides for this. The parent should probably be a 
PWM provider.

> +
> +      pulses-per-revolution:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        enum: [1, 2, 3, 4]
> +        default: 2
> +        description:
> +          Value specifying the number of pulses per revolution of the controlled
> +          FAN.
> +
> +      maxim,rpm-range:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        enum: [2000, 4000, 8000, 16000]
> +        default: 4000
> +        description:
> +          Scales the tachometer counter by setting the maximum (full-scale) value
> +          of the RPM range for max6639.

Is this a property of the fan? How is this maxim specific?


The bigger issue here is we need a common fan binding. I'm not inclined 
to accept any more fan controller bindings with fan properties until we 
do.

Rob