linux-kernel - Re: [PATCH 1/2] dt-bindings: rtc: add properties to set battery-related functions

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Date:   Tue, 8 Aug 2023 08:25:33 -0400
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Conor Dooley <conor@...nel.org>
Cc:     a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, linux-rtc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        bruno.thomsen@...il.com, Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: Re: [PATCH 1/2] dt-bindings: rtc: add properties to set
 battery-related functions

On Tue, 8 Aug 2023 12:21:24 +0100
Conor Dooley <conor@...nel.org> wrote:

> Hey Hugo,
> 
> On Wed, Aug 02, 2023 at 03:11:52PM -0400, Hugo Villeneuve wrote:
> > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > 
> > These properties can be defined in the board's device tree to set the
> > default power-on values for battery-related functions.
> > 
> > Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > ---
> >  .../devicetree/bindings/rtc/rtc.yaml          | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/rtc/rtc.yaml b/Documentation/devicetree/bindings/rtc/rtc.yaml
> > index efb66df82782..0217d229e3fa 100644
> > --- a/Documentation/devicetree/bindings/rtc/rtc.yaml
> > +++ b/Documentation/devicetree/bindings/rtc/rtc.yaml
> > @@ -26,6 +26,25 @@ properties:
> >        0: not chargeable
> >        1: chargeable
> >  
> > +  battery-low-detect:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 1]
> > +    description: |
> > +      For RTC devices supporting a backup battery/supercap, this flag can be
> > +      used to configure the battery low detection reporting function:
> > +      0: disabled
> > +      1: enabled
> > +
> > +  battery-switch-over:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 1]
> > +    description: |
> > +      For RTC devices supporting a backup battery/supercap, this flag can be
> > +      used to configure the battery switch over when the main voltage source is
> > +      turned off:
> > +      0: disabled
> > +      1: enabled
> 
> Why are these implemented as enums? This seems to fall into the category
> of using DT to determine software policy - why's it not sufficient to
> have boolean properties that indicate hardware support and let the software
> decide what to do with them?

Hi Conor,
the reason is that I based the new properties on the existing property
"aux-voltage-chargeable":

-------------------
 aux-voltage-chargeable:
    $ref: /schemas/types.yaml#/definitions/uint32
    enum: [0, 1]
    description: |
      Tells whether the battery/supercap of the RTC (if any) is
      chargeable or not:
      0: not chargeable
      1: chargeable
-------------------

I agree with you that a boolean would be more appropriate. Should I
also submit a (separate) patch to fix the "aux-voltage-chargeable"
property to a boolean?

Hugo.


> Thanks,
> Conor.
> 
> > +
> >    quartz-load-femtofarads:
> >      description:
> >        The capacitive load of the quartz(x-tal), expressed in femto
> > -- 
> > 2.30.2
> >