linux-kernel - Re: [PATCH v2 3/5] dt-binding: pcf85063: add xtal load capacitance

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Message-ID: <20190115210827.GA25046@bogus>
Date:   Tue, 15 Jan 2019 15:08:27 -0600
From:   Rob Herring <robh@...nel.org>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Andrew Jeffery <andrew@...id.au>,
        Fabio Estevam <fabio.estevam@....com>,
        Joel Stanley <joel@....id.au>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Urs Fässler <urs.fassler@....ch>,
        Shawn Guo <shawnguo@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org,
        Søren Andersen <san@...v.dk>
Subject: Re: [PATCH v2 3/5] dt-binding: pcf85063: add xtal load capacitance

On Tue, Jan 08, 2019 at 07:54:12PM +0100, Sam Ravnborg wrote:
> The NXP pcf85063 supports two different xtal load capacitance
> - 7000fF  (7pF)    HW default, Linux driver default
> - 12500fF (12.5pF) Minimum power consumption
> 
> To obtain a precise RTC the pcf85063 must be configured
> with the correct capacitance load of the xtal.
> 
> Add a property to specify the xtal capacitance load.
> The default value matches that of the current Linux driver.
> 
> With a dedicated binding remove the entry in rtc.txt
> 
> Signed-off-by: Søren Andersen <san@...v.dk>
> Signed-off-by: Sam Ravnborg <sam@...nborg.org>
> Cc: Alessandro Zummo <a.zummo@...ertech.it>
> Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Urs Fässler <urs.fassler@....ch>
> ---
>  Documentation/devicetree/bindings/rtc/nxp,pcf85063.txt | 18 ++++++++++++++++++
>  Documentation/devicetree/bindings/rtc/rtc.txt          |  1 -
>  2 files changed, 18 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/devicetree/bindings/rtc/nxp,pcf85063.txt
> 
> diff --git a/Documentation/devicetree/bindings/rtc/nxp,pcf85063.txt b/Documentation/devicetree/bindings/rtc/nxp,pcf85063.txt
> new file mode 100644
> index 000000000000..ad5e8eaa370e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rtc/nxp,pcf85063.txt
> @@ -0,0 +1,18 @@
> +* NXP PCF85063 Real Time Clock
> +
> +Required properties:
> +- compatible: Should contain "nxp,pcf85063".
> +- reg: I2C address for chip.
> +
> +Optional property:
> +- quartz-load-femtofarads: The capacitive load of the quartz(x-tal),

Probably should put this in rtc.txt so it can be shared.

> +  expressed in femto Farad (fF). Valid values are 7000 and 12500.
> +  Default value (if no value is specified) is 7000fF.
> +
> +Example:
> +
> +pcf85063: pcf85063@51 {

rtc@51

> +	compatible = "nxp,pcf85063";
> +	reg = <0x51>;
> +	quartz-load-femtofarads = <12500>;
> +};
> diff --git a/Documentation/devicetree/bindings/rtc/rtc.txt b/Documentation/devicetree/bindings/rtc/rtc.txt
> index e07b15d151ac..efac6dc5b914 100644
> --- a/Documentation/devicetree/bindings/rtc/rtc.txt
> +++ b/Documentation/devicetree/bindings/rtc/rtc.txt
> @@ -52,7 +52,6 @@ microcrystal,rv3029	Real Time Clock Module with I2C-Bus
>  nxp,pcf2127		Real-time clock
>  nxp,pcf2129		Real-time clock
>  nxp,pcf8563		Real-time clock/calendar
> -nxp,pcf85063		Tiny Real-Time Clock
>  pericom,pt7c4338	Real-time Clock Module
>  ricoh,r2025sd		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
>  ricoh,r2221tl		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
> -- 
> 2.12.0
>