Re: [RFC PATCH v2 1/2] dt-bindings: hwmon: emc2305: Add fan-shutdown-percent property

[Conor Dooley <conor@kernel.org>]

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On Fri, Mar 13, 2026 at 07:14:33PM +0200, Florin Leotescu wrote:
> On Thu, Mar 12, 2026 at 05:37:51PM +0000, Conor Dooley wrote:
> > On Thu, Mar 12, 2026 at 02:22:47PM +0200, florin.leotescu@oss.nxp.com wrote:
> > > From: Florin Leotescu <florin.leotescu@nxp.com>
> > > 
> > > The EMC2305 fan controller supports multiple independent PWM fan
> > > outputs. Some systems require fans to enter a defined safe state
> > > during system shutdown or reboot handoff, until firmware or the next
> > > boot stage reconfigures the controller.
> > > 
> > > Add an optional "fan-shutdown-percent" property to fan child nodes
> > > allowing the shutdown fan speed to be configured per fan output.
> > > 
> > > Signed-off-by: Florin Leotescu <florin.leotescu@nxp.com>
> > > ---
> > >  .../devicetree/bindings/hwmon/microchip,emc2305.yaml      | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml b/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml
> > > index d3f06ebc19fa..7bcadfab9fc4 100644
> > > --- a/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml
> > > +++ b/Documentation/devicetree/bindings/hwmon/microchip,emc2305.yaml
> > > @@ -54,6 +54,12 @@ patternProperties:
> > >            The fan number used to determine the associated PWM channel.
> > >          maxItems: 1
> > >  
> > > +      fan-shutdown-percent:
> > > +        description:
> > > +          Fan RPM in percent set during shutdown.
> > 
> > This sounds like something generic, that other devices might need and
> > should be in fan-common.yaml?
> >
> Thanks for the feedback.
> 
> The property name was reused from pwm-fan.yaml where it already exists
> with the same meaning. I kept it local to minimize the scope of the change.
> 
> However, if you prefer it to be modelled as a common property, I can adjust it in the next revision.

I see. Makes me wonder why half the properties in pwm-fan aren't also in
fan-common.

I suppose there's a reason for it, carry on I guess.. Can be lifted if
there are more users other than you and pwm-fan.

> > > +        minimum: 0
> > > +        maximum: 100
> > > +
> > >      required:
> > >        - reg
> > >  
> > > @@ -80,12 +86,14 @@ examples:
> > >              fan@0 {
> > >                  reg = <0x0>;
> > >                  pwms = <&fan_controller 26000 PWM_POLARITY_INVERTED 1>;
> > > +                fan-shutdown-percent = <100>;

Also leads to the question of why these devices aren't pwm-fans. Too
late now to change anything, I just wanna understand why.

> > >                  #cooling-cells = <2>;
> > >              };
> > >  
> > >              fan@1 {
> > >                  reg = <0x1>;
> > >                  pwms = <&fan_controller 26000 0 1>;
> > > +                fan-shutdown-percent = <50>;
> > >                  #cooling-cells = <2>;
> > >              };
> > >  
> > > -- 
> > > 2.34.1
> > > 
> 
> 

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