Re: [PATCH 1/2] dt-bindings: rtc: add battery-low-hw-alarm property

From: Alexandre Belloni
Date: Sat Apr 06 2019 - 08:56:06 EST


On 06/04/2019 01:07:13-0500, Rob Herring wrote:
> On Wed, Apr 03, 2019 at 04:52:44PM +0200, Flavio Suligoi wrote:
> > Some RTC devices have a battery-low automatic detection circuit.
> > The battery-low event is usually reported with:
> >
> > - a bit change in a RTC status register
> > - a hw signaling (generally using an interrupt generation), changing
> > the hw level of a specific pin;
> >
> > The new property "battery-low-hw-alarm" enable the RTC to generate the
> > hw signaling in case of battery-low event.
> >
> > Signed-off-by: Flavio Suligoi <f.suligoi@xxxxxxx>
> > ---
> > Documentation/devicetree/bindings/rtc/rtc.txt | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/rtc/rtc.txt b/Documentation/devicetree/bindings/rtc/rtc.txt
> > index a97fc6a..f93a44d 100644
> > --- a/Documentation/devicetree/bindings/rtc/rtc.txt
> > +++ b/Documentation/devicetree/bindings/rtc/rtc.txt
> > @@ -31,6 +31,9 @@ below.
> > expressed in femto Farad (fF).
> > The default value shall be listed (if optional),
> > and likewise all valid values.
> > +- battery-low-hw-alarm : Enable the "battery-low" output pin. This function
> > + is available on the following devices:
> > + - pcf2127 - pin used for alarm: INTn
>
> Boolean? If there's cases where which pin is selectable, then we'd need
> this to take a value. Not sure how likely that is?
>

Indeed, there is at least the pcf85363 that has two possible pins for
that interrupt. How would you select the pin then? a zero based index? a
string?

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