linux-kernel - Re: [RFC 1/3] dt-bindings: rtc: Add Realtek RTD1295

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Message-ID: <20170827134729.GE13622@lunn.ch>
Date:   Sun, 27 Aug 2017 15:47:29 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Andreas Färber <afaerber@...e.de>
Cc:     Rob Herring <robh@...nel.org>, linux-rtc@...r.kernel.org,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Roc He <hepeng@...oo.tv>, devicetree@...r.kernel.org,
        ????????? <jiang.liqin@...iatech.com>,
        linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 1/3] dt-bindings: rtc: Add Realtek RTD1295

> Thanks. Did you read the RFC question in the cover letter as well and
> have any comments? Downstream has an rtc-base-year = <2014>; property
> that I had left out in this RFC and due to your ack not included in v2.
> 
> Should we default to 2014 in the driver and add an optional base-year
> property once we encounter a diverging device, or should we make it
> required from the beginning? I did not spot any other rtc binding with
> such a property and would appreciate a clarification.

Hi Andreas

>From the perspective of the hardware, does it care what the base is?

A device using a different base will initially return the wrong
time. But once the correct time has been written back, it will be O.K.

This only becomes an issue if a device is used with different OSs,
which have different bases. Swapping back and forth between OSs then
becomes an issue.

KISS suggests not having a base in DT until it is actually
required. Since it is an additional property, it does not break
backwards compatibility when added.

	  Andrew