Re: [PATCH v1 1/2] dt-bindings: hwmon: Add starfive,jhb100-fan-tach

[Changhuang Liang]

Hi, Rob

Thanks for the review.

> 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@xxxxxxxxxxxxxxxx>
> > ---
> >  .../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.yam
> > l
> >
> b/Documentation/devicetree/bindings/hwmon/starfive,jhb100-fan-tach.yam
> > l
> > 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@xxxxxxxxxxxxxxxx>
> > +
> > +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?

"reg" is only used to distinguish between different fan instances.

> 
> > +
> > +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?

On our platform, two fans share one PWM channel. It seems there was a misunderstanding earlier.
I will change it to the form of one tach per fan.

Best Regards,
Changhuang