linux-kernel - Re: [PATCH 03/13] RTC: ds1307: Add DS1341 specific power-saving options

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Date:	Tue, 21 Jun 2016 23:07:39 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Rob Herring <robh@...nel.org>
Cc:	Andrey Smirnov <andrew.smirnov@...il.com>,
	rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/13] RTC: ds1307: Add DS1341 specific power-saving
 options

On 21/06/2016 at 15:49:04 -0500, Rob Herring wrote :
> So wouldn't you want to set one mode while running and the lower power 
> mode while suspended? I'm trying to understand the frequency of changing 
> this. If it is always one setting for a board, then yes it belongs in 
> DT. If it is a user decision, then it probably shouldn't be in DT.
> 
> Seeing as these are reused, I've probably already had this discussion...
> 

I would agree with Rob here. It may be better to provide a sysfs
interface to configure that particular behavior. This is usually ok
because the use case is:
 - the RTC is not configured, time has never been set
 - time is set for the first time
 - the user can set the oscillator mode/detection/...
 - on subsequent reboots, the mode is kept alongside the time and date

I would advise against trying to set a mode automatically in the driver
because you may have unexpected power cuts and it may then let the RTC
consume more power than what you really want.

> > > They should have vendor prefix and be explicit that they are boolean.
> > 
> > I was trying to be consistent with ds1339 and ds1390 bindings which do
> > not have vendor prefixes. Will fix in v2.
> 
> Okay, then they are fine if you are using existing properties. Perhaps 
> these should all be in a common binding doc though.
> 

I'll try to collect the existing common properties and write that doc
this week.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com