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Date: Tue, 5 May 2026 20:25:56 -0500
From: Rob Herring <robh@kernel.org>
To: Changhuang Liang <changhuang.liang@starfivetech.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>, linux-kernel@vger.kernel.org,
	linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH v1 1/2] dt-bindings: hwmon: Add starfive,jhb100-fan-tach
Message-ID: <20260506012556.GB248179-robh@kernel.org>
References: <20260428082337.743546-1-changhuang.liang@starfivetech.com>
 <20260428082337.743546-2-changhuang.liang@starfivetech.com>
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In-Reply-To: <20260428082337.743546-2-changhuang.liang@starfivetech.com>

On Tue, Apr 28, 2026 at 01:23:36AM -0700, Changhuang Liang wrote:
> Add compatible "starfive,jhb100-fan-tach" for StarFive JHB100 Fan-Tach
> controller.
> 
> Signed-off-by: Changhuang Liang <changhuang.liang@starfivetech.com>
> ---
>  .../hwmon/starfive,jhb100-fan-tach.yaml       | 98 +++++++++++++++++++
>  1 file changed, 98 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/starfive,jhb100-fan-tach.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/starfive,jhb100-fan-tach.yaml b/Documentation/devicetree/bindings/hwmon/starfive,jhb100-fan-tach.yaml
> new file mode 100644
> index 000000000000..fdc8539ec804
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/starfive,jhb100-fan-tach.yaml
> @@ -0,0 +1,98 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/hwmon/starfive,jhb100-fan-tach.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: StarFive JHB100 Fan-Tach controller
> +
> +maintainers:
> +  - Changhuang Liang <changhuang.liang@starfivetech.com>
> +
> +description:
> +  The StarFive Fan-Tach controller can support up to 16 fan tach input.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - starfive,jhb100-fan-tach
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  resets:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +patternProperties:
> +  "^fan@[0-9]+$":

Unit-addresses are hex.

> +    $ref: fan-common.yaml#
> +    unevaluatedProperties: false
> +    required:
> +      - reg
> +      - tach-ch

You need constraints on the 'reg' values. Also, what does 'reg' 
represent in this case?

> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - resets
> +  - interrupts
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    fan-tach-controller@11be0000 {
> +        compatible = "starfive,jhb100-fan-tach";
> +        reg = <0x11be0000 0x400>;
> +        interrupts = <128>;
> +        clocks = <&per2crg 33>;
> +        resets = <&per2crg 5>;
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        fan@0 {
> +            reg = <0>;
> +            tach-ch = /bits/ 8 <0x0>, <0x8>;

How do you have 1 fan with 2 tach signals?

Rob