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 14:32:26 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Hugo Villeneuve <hugo@...ovil.com>
Cc:     Conor Dooley <conor@...nel.org>, a.zummo@...ertech.it,
        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 08/08/2023 08:25:33-0400, Hugo Villeneuve wrote:
> 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?
> 

No, this is an enum on purpose.
I will not take battery switch over related properties, this is not
hardware description but software configuration. There is an ioctl for
this.

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

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com