linux-kernel - Re: [PATCH v2 1/2] Add DT bindings YAML schema for PWM fan controller of LGM SoC

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Date:   Fri, 19 Jun 2020 08:14:13 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Rahul Tanwar <rahul.tanwar@...ux.intel.com>
Cc:     linux-pwm@...r.kernel.org, thierry.reding@...il.com,
        p.zabel@...gutronix.de, robh+dt@...nel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        andriy.shevchenko@...el.com, songjun.Wu@...el.com,
        cheol.yong.kim@...el.com, qi-ming.wu@...el.com,
        rahul.tanwar.linux@...il.com
Subject: Re: [PATCH v2 1/2] Add DT bindings YAML schema for PWM fan
 controller of LGM SoC

Hello,

On Thu, Jun 18, 2020 at 08:05:12PM +0800, Rahul Tanwar wrote:
> Intel's LGM(Lightning Mountain) SoC contains a PWM fan controller
> which is only used to control the fan attached to the system. This
> PWM controller does not have any other consumer other than fan.
> Add DT bindings documentation for this PWM fan controller.
> 
> Signed-off-by: Rahul Tanwar <rahul.tanwar@...ux.intel.com>
> ---
>  .../devicetree/bindings/pwm/intel,lgm-pwm.yaml     | 57 ++++++++++++++++++++++
>  1 file changed, 57 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml
> 
> diff --git a/Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml b/Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml
> new file mode 100644
> index 000000000000..e71cc25e4e6a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml
> @@ -0,0 +1,57 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pwm/intel,lgm-pwm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: LGM SoC PWM fan controller
> +
> +maintainers:
> +  - Rahul Tanwar <rahul.tanwar@...el.com>
> +
> +properties:
> +  compatible:
> +    const: intel,lgm-pwm
> +
> +  reg:
> +    maxItems: 1
> +
> +  "#pwm-cells":
> +    const: 2
> +
> +  clocks:
> +    maxItems: 1
> +
> +  resets:
> +    maxItems: 1
> +
> +  intel,fan-wire:
> +    $ref: '/schemas/types.yaml#/definitions/uint32'
> +    description: Specifies fan mode

The default when unspecified is 2.

> +
> +  intel,tach-plus:
> +    $ref: '/schemas/types.yaml#/definitions/uint32'
> +    description: Specifies fan tach pulse periods

Only used with fan-wire = 4, default = 2.

> +
> +  intel,max-rpm:
> +    $ref: '/schemas/types.yaml#/definitions/uint32'
> +    description: Specifies maximum RPM of fan attached to the system

Ditto.

Consistent with my concern that the fan code should not be part of the
PWM driver I wonder if this representation that mixes fan and PWM is
nice enough to be set in stone.

If we decide to keep it as is I wonder if we should drop #pwm-cells as
the hardware doesn't allow other uses for this PWM (IIUC) and so
referencing this node doesn't make sense.

> +required:
> +  - compatible
> +  - reg
> +  - "#pwm-cells"
> +  - clocks
> +  - resets
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    pwm: pwm@...00000 {
> +        compatible = "intel,lgm-pwm";
> +        reg = <0xe0d00000 0x30>;
> +        #pwm-cells = <2>;
> +        clocks = <&cgu0 126>;
> +        resets = <&rcu0 0x30 21>;
> +    };

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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