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

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Message-ID: <20170513000029.tgzt5p67tcl7uhbx@rob-hp-laptop>
Date:   Fri, 12 May 2017 19:00:29 -0500
From:   Rob Herring <robh@...nel.org>
To:     Moritz Fischer <mdf@...nel.org>
Cc:     linux-watchdog@...r.kernel.org, rtc-linux@...glegroups.com,
        linux-kernel@...r.kernel.org, lee.jones@...aro.org,
        devicetree@...r.kernel.org, linux@...ck-us.net, wim@...ana.be,
        alexandre.belloni@...e-electrons.com, a.zummo@...ertech.it,
        mark.rutland@....com, moritz.fischer@...us.com
Subject: Re: [RFC/PATCH 1/2] dt-binding: mfd: Add Maxim/Dallas DS1374 MFD
 device binding

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@...nel.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.

> +			<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.

> +
> +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@...a0000 {
> +	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@...a0000 {
> +	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
>