linux-kernel - Re: [PATCH 3/4] rtc: ds1307: add calibration of

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Date:   Tue, 8 May 2018 12:40:25 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Giulio Benetti <giulio.benetti@...ronovasrl.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Mark Rutland <mark.rutland@....com>,
        "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" 
        <linux-rtc@...r.kernel.org>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] rtc: ds1307: add calibration of_ for mt41txx chips.

On Tue, May 8, 2018 at 9:56 AM, Giulio Benetti
<giulio.benetti@...ronovasrl.com> wrote:
> m41txx chips can hold a calibration value to get really near to real
> tick value.

Typo in the subject.

> Add calibration property(ranging between (-31) and 31), so on every probe
> calibration value will be written to rtc.
> This is because ic could loose supply due to low battery.
>
> Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
> ---
>  .../devicetree/bindings/rtc/rtc-ds1307.txt    |  2 ++

Put all the binding changes in separate patch (or maybe 2: new
compatible and new properties).

>  drivers/rtc/rtc-ds1307.c                      | 33 +++++++++++++++++++
>  2 files changed, 35 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/rtc/rtc-ds1307.txt b/Documentation/devicetree/bindings/rtc/rtc-ds1307.txt
> index ce6469c1a516..d3d70a5495c5 100644
> --- a/Documentation/devicetree/bindings/rtc/rtc-ds1307.txt
> +++ b/Documentation/devicetree/bindings/rtc/rtc-ds1307.txt
> @@ -34,6 +34,8 @@ Optional properties:
>  - trickle-diode-disable : ds1339, ds1340 and ds 1388 only
>         Do not use internal trickle charger diode
>         Should be given if internal trickle charger diode should be disabled
> +- calibration: m41t0, m41t00, m41t11 only

Needs a vendor prefix.

Calibration of what and what are the units?

> +       Set calibration value to correct external bias, ranging between (-31) and 31.
>
>  Example:
>         rtc1: ds1339@68 {