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

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Message-ID: <20150304114355.GA16032@frolo.macqel>
Date:	Wed, 4 Mar 2015 12:43:55 +0100
From:	Philippe De Muyter <phdm@...qel.be>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
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

Hi Alexandre,

On Wed, Mar 04, 2015 at 11:38:14AM +0100, Alexandre Belloni wrote:
> 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.

As far as I know, it's purely hardware related.

> 
> 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().

My current entry is :

&i2c2 {
	...
        ab1805@69 {
                compatible = "abracon,abx805-rtc";
                reg = <0x69>;
                position = <3>;
        };
};

It would then become :

&i2c2 {
	...
        ab1805@69 {
                compatible = "abracon,abx805-rtc";
                reg = <0x69>;
                position = <3>;
		abracon,tc-diode = "schottky";
		abracon,tc-resistor = <3>;
        };
};

or if you change the driver's name to "abx80x-rtc"

                compatible = "abracon,abx80x-rtc";

That's fine for me.  Thanks !

Philippe

-- 
Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles
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