Re: [RFC/PATCH 1/2] dt-binding: mfd: Add Maxim/Dallas DS1374 MFD device binding

[Moritz Fischer <mdf@kernel.org>]

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On Fri, May 12, 2017 at 07:00:29PM -0500, Rob Herring wrote:
> On Tue, May 09, 2017 at 11:20:20AM -0700, Moritz Fischer wrote:
> > This adds a binding for the Maxim/Dallas DS1374 MFD.
> > 
> > Signed-off-by: Moritz Fischer <mdf@kernel.org>
> > ---
> > 
> > Hi all,
> > 
> > I'm not entirely sure aobut the binding, does anyone
> > have a better suggestion for the remap-wdt-reset property?
> > 
> > Thanks,
> > 
> > Moritz
> > 
> > ---
> >  Documentation/devicetree/bindings/mfd/ds1374.txt   | 63 ++++++++++++++++++++++
> >  .../devicetree/bindings/trivial-devices.txt        |  1 -
> >  drivers/rtc/Kconfig                                |  2 +
> >  3 files changed, 65 insertions(+), 1 deletion(-)
> >  create mode 100644 Documentation/devicetree/bindings/mfd/ds1374.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/mfd/ds1374.txt b/Documentation/devicetree/bindings/mfd/ds1374.txt
> > new file mode 100644
> > index 0000000..b22396f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mfd/ds1374.txt
> > @@ -0,0 +1,63 @@
> > +* Device tree bindings for Maxim/Dallas DS1374 Multi Function Device (MFD)
> > +
> > +The Maxim/Dallas DS1374 is a multi function device that combines rtc,
> > +watchdog or alarm, as well as trickle charger.
> > +
> > +The DS1374 is connected via I2C.
> > +
> > +Required properties:
> > +- compatible: "dallas,ds1374"
> > +- reg: I2C slave address
> > +- dallas,ds1374-mode: Should be one of the following values:
> 
> Just "dallas,mode" is sufficient.

Will fix.
> 
> > +			<0> for RTC
> > +			<1> for RTC + Alarm (Interrupt)
> > +			<2> for RTC + Watchdog
> > +
> > +Required child:
> > +A single available child device of type matching the "dallas,ds1374-mode"
> > +property.
> > +
> > +Optional properties (watchdog):
> > +- dallas,ds1374-remap-wdt-reset: Boolean describing whether the INT pin
> > +				 on the device is used as interrupt for
> > +				 the alarm
> 
> Isn't presence of the interrupt property or not enough? It would be 
> kind of useless to have no interrupt and also not do anything on 
> timeout.

So you're saying:

If interrupt not present AND mode = <0> ignore interrupt

If interrupt present AND mode = <1> (maybe define here would be nicer),
make it an interrupt.

If interrupt not present AND mode = <2> then this implies that reset
output is mapped to RST pin.

If Interrupt present AND mode = <2> then this implies that the reset
output is (re)mapped to INT pin?

> 
> > +
> > +See ../watchdog/* for generic watchdog bindings.
> > +
> > +Optional properties (real time clock):
> > +- interrupt: phandle to interrupt cell for the rtc's alarm feature
> > +
> > +See ../rtc/* for generic rtc bindings.
> > +
> > +Optional properties (trickle-charger):
> > +- dallas,trickle-resistor-ohms : Selected resistor for trickle charger
> > +	Values usable for ds1374 are 250, 2000, 4000
> > +	Should be given if trickle charger should be enabled
> > +- dallas,trickle-diode-disable : Do not use internal trickle charger diode
> > +	Should be given if internal trickle charger diode should be disabled
> > +
> > +Example for rtc with alarm mode and interrupt:
> > +
> > +i2c@12ca0000 {
> > +	rtc@68 {
> > +		compatible = "ds1374";
> > +		reg = <0x68>;
> > +		interrupts = <&gpio0 62>;
> > +		dallas,ds1374-mode = <2>
> > +
> > +		dallas,trickle-resistor-ohms = <250>;
> > +		dallas,trickle-diode-disable;
> > +	};
> > +};
> > +
> > +Example for rtc with watchdog and reset on timeout, with reset remapped
> > +to the INT pin:
> > +
> > +i2c@12ca0000 {
> > +	rtc@68 {
> > +		compatible = "ds1374";
> > +		reg = <0x68>;
> > +		dallas,ds1374-mode = <2>
> > +		dallas,ds1374-remap-wdt-reset;
> > +	};
> > +};
> > diff --git a/Documentation/devicetree/bindings/trivial-devices.txt b/Documentation/devicetree/bindings/trivial-devices.txt
> > index 3e0a34c..f7a50e5 100644
> > --- a/Documentation/devicetree/bindings/trivial-devices.txt
> > +++ b/Documentation/devicetree/bindings/trivial-devices.txt
> > @@ -29,7 +29,6 @@ cirrus,cs42l51		Cirrus Logic CS42L51 audio codec
> >  dallas,ds1307		64 x 8, Serial, I2C Real-Time Clock
> >  dallas,ds1338		I2C RTC with 56-Byte NV RAM
> >  dallas,ds1340		I2C RTC with Trickle Charger
> > -dallas,ds1374		I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output
> >  dallas,ds1631		High-Precision Digital Thermometer
> >  dallas,ds1682		Total-Elapsed-Time Recorder with Alarm
> >  dallas,ds1775		Tiny Digital Thermometer and Thermostat
> > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > index 8d3b957..e6763fe 100644
> > --- a/drivers/rtc/Kconfig
> > +++ b/drivers/rtc/Kconfig
> > @@ -250,6 +250,8 @@ config RTC_DRV_DS1307_CENTURY
> >  
> >  config RTC_DRV_DS1374
> >  	tristate "Dallas/Maxim DS1374"
> > +	depends on MFD_DS1374
> > +	depends on REGMAP_I2C
> >  	help
> >  	  If you say yes here you get support for Dallas Semiconductor
> >  	  DS1374 real-time clock chips. If an interrupt is associated
> > -- 
> > 2.7.4
> > 

Thanks for the review,

Moritz

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