linux-kernel - Re: [PATCH v2 1/3] dt-bindings: rtc: pcf8523: add DSM pm option for battery switch-over

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Message-ID: <20200723174905.GA596242@bogus>
Date:   Thu, 23 Jul 2020 11:49:05 -0600
From:   Rob Herring <robh@...nel.org>
To:     miguelborgesdefreitas@...il.com
Cc:     a.zummo@...ertech.it, baruch@...s.co.il, linux@...linux.org.uk,
        alexandre.belloni@...tlin.com, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] dt-bindings: rtc: pcf8523: add DSM pm option for
 battery switch-over

On Mon, Jul 20, 2020 at 12:23:59PM +0100, miguelborgesdefreitas@...il.com wrote:
> From: Miguel Borges de Freitas <miguelborgesdefreitas@...il.com>
> 
> This adds direct-switching mode as a configurable DT flag for
> RTC modules supporting it (e.g. nxp pcf8523).
> DSM switches the power source to the battery supply whenever the
> VDD drops below VBAT. The option is recommended for hw designs
> where VDD is always expected to be higher than VBAT.
> 
> Signed-off-by: Miguel Borges de Freitas <miguelborgesdefreitas@...il.com>
> ---
> Changes in v2:
> - Added extended commit message for git history
> - Separate dt bindings documentation into a single patch
> 
>  Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt | 7 ++++++-
>  Documentation/devicetree/bindings/rtc/rtc.yaml        | 7 +++++++
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt b/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
> index 0b1080c..f715a8f 100644
> --- a/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
> +++ b/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
> @@ -4,10 +4,14 @@ Required properties:
>  - compatible: Should contain "nxp,pcf8523".
>  - reg: I2C address for chip.
>  
> -Optional property:
> +Optional properties:
>  - quartz-load-femtofarads: The capacitive load of the quartz(x-tal),
>    expressed in femto Farad (fF). Valid values are 7000 and 12500.
>    Default value (if no value is specified) is 12500fF.
> +- pm-enable-dsm: battery switch-over function is enabled in direct
> +  switching mode. The power failure condition happens when VDD < VBAT,
> +  without requiring VDD to drop below Vth(sw)bat.
> +  Default value (if not provided) is the standard mode.
>  
>  Example:
>  
> @@ -15,4 +19,5 @@ pcf8523: rtc@68 {
>  	compatible = "nxp,pcf8523";
>  	reg = <0x68>;
>  	quartz-load-femtofarads = <7000>;
> +	pm-enable-dsm;
>  };
> diff --git a/Documentation/devicetree/bindings/rtc/rtc.yaml b/Documentation/devicetree/bindings/rtc/rtc.yaml
> index ee237b2..a0048f4 100644
> --- a/Documentation/devicetree/bindings/rtc/rtc.yaml
> +++ b/Documentation/devicetree/bindings/rtc/rtc.yaml
> @@ -47,4 +47,11 @@ properties:
>      description:
>        Enables wake up of host system on alarm.
>  
> +  pm-enable-dsm:
> +    $ref: /schemas/types.yaml#/definitions/flag
> +    description:
> +      Enables the battery switch-over function in direct switching
> +      mode. Should be set in systems where VDD is higher than VBAT
> +      at all times.

I'm all for common properties, but is this common across vendors?

> +
>  ...
> -- 
> 1.8.3.1
>