linux-kernel - Re: [PATCH v2] rtc: add Abracon ABx80x driver

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Message-ID: <20150304103814.GE3989@piout.net>
Date:	Wed, 4 Mar 2015 11:38:14 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Philippe De Muyter <phdm@...qel.be>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com
Subject: Re: [PATCH v2] rtc: add Abracon ABx80x driver

On 04/03/2015 at 10:55:56 +0100, Philippe De Muyter wrote :
> > The "AB08XX Real-Time Clock Family" document states that they are all
> > software and pin compatible (including the AB18xx).
> 
> Which part(s) do you really have ?  Mine is a 1805.  Do all the parts have
> the trickle charger ?  As I don't know, I prefer not to pretend that the
> driver supports those chips.
> 

I have the AB0805. The trickle charger is not available on ABx8x1 and
ABx8x3.

> > > My hardware colleagues told me that the only way to enable the 'ultra low-power'
> > > functionality is enabling the trickle charger.  And the 'ultra low-power'
> > > functionality is the reason we choose that chip, so I would at least
> > > keep that as the default behaviour.
> > > 
> > 
> > My concern is that you have a static configuration. I would expose a
> > sysfs interface to configure the diode, resistor and enable/disable the
> > trickle charger. Would that work for you?
> 
> I think a 'of_xxx' dts/dtb description is the way to go, but I did not want to
> introduce unnecessaty complexity without knowing other usages.  My hardware
> colleagues followed the recommended design from Abracon.
> 

Yeah, I'm not sure about the DT description, some may argue this is
configuration. But I guess it actually depends on the battery you are
using so that could count as hardware description.

I'll use:
 abracon,tc-diode = "(standard|schottky)"
 abracon,tc-resistor = <(0|3|6|11)>

If both are defined and valid, I'll enable the trickle charger with the
provided configuration in probe().

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