Re: [PATCH v4 1/3] dt-bindings: hwmon: fan: Add fan binding to schema

[Guenter Roeck]

On 3/4/24 16:22, Zev Weiss wrote:
> On Mon, Feb 26, 2024 at 04:56:04PM PST, baneric926@xxxxxxxxx wrote:
> > From: Naresh Solanki <naresh.solanki@xxxxxxxxxxxxx>
> >
> > Add common fan properties bindings to a schema.
> >
> > Bindings for fan controllers can reference the common schema for the
> > fan
> >
> > child nodes:
> >
> >  patternProperties:
> >    "^fan@[0-2]":
> >      type: object
> >      $ref: fan-common.yaml#
> >      unevaluatedProperties: false
> >
> > Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> > Signed-off-by: Naresh Solanki <naresh.solanki@xxxxxxxxxxxxx>
> > Signed-off-by: Billy Tsai <billy_tsai@xxxxxxxxxxxxxx>
> > Signed-off-by: Ban Feng <kcfeng0@xxxxxxxxxxx>
> > ---
> > .../devicetree/bindings/hwmon/fan-common.yaml | 78 +++++++++++++++++++
> > 1 file changed, 78 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/hwmon/fan-common.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/hwmon/fan-common.yaml b/Documentation/devicetree/bindings/hwmon/fan-common.yaml
> > new file mode 100644
> > index 000000000000..15c591c74545
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/hwmon/fan-common.yaml
> > @@ -0,0 +1,78 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/hwmon/fan-common.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Common Fan Properties
> > +
> > +maintainers:
> > +  - Naresh Solanki <naresh.solanki@xxxxxxxxxxxxx>
> > +  - Billy Tsai <billy_tsai@xxxxxxxxxxxxxx>
> > +
> > +properties:
> > +  max-rpm:
> > +    description:
> > +      Max RPM supported by fan.
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    maximum: 100000
> > +
> > +  min-rpm:
> > +    description:
> > +      Min RPM supported by fan.
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    maximum: 1000
>
> I can't say with certainty that it's not, but are we sure 1000 is low enough?  Looking at just what I've got on hand, an 80mm fan I have will run steadily at about 1500RPM, and I'd assume larger ones (e.g. 120mm) could potentially go significantly lower...

I have seen fans which run stable at < 400rpm.
One of my systems right now has:

fan1:              732 RPM  (min =    0 RPM)
fan2:                0 RPM  (min =    0 RPM)
fan3:              586 RPM  (min =    0 RPM)
fan4:              472 RPM  (min =    0 RPM)
fan5:              480 RPM  (min =    0 RPM)

Those are 80mm fans. A quick check shows that various Noctua fans have a
minimum speed of 300 rpm. So 1000 is indeed a bit high for the minimum speed.

Guenter