linux-kernel - Re: [PATCH] rtc: ds1307: add trickle charger device tree binding

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Message-ID: <20140908135242.GA21412@amd>
Date:	Mon, 8 Sep 2014 15:52:42 +0200
From:	Pavel Machek <pavel@...x.de>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Matti Vaittinen <matti.vaittinen@....com>,
	ext Guenter Roeck <linux@...ck-us.net>,
	Jason Cooper <jason@...edaemon.net>,
	"a.zummo@...ertech.it" <a.zummo@...ertech.it>,
	"jic23@...nel.org" <jic23@...nel.org>,
	"arno@...isbad.org" <arno@...isbad.org>,
	"jgunthorpe@...idianresearch.com" <jgunthorpe@...idianresearch.com>,
	"san@...etechnology.dk" <san@...etechnology.dk>,
	"hs@...x.de" <hs@...x.de>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
	Sverdlin Alexander <alexander.sverdlin@....com>
Subject: Re: [PATCH] rtc: ds1307: add trickle charger device tree binding

Hi!

> I would suggest we have two properties that describe the resistor's
> rating and whether or not there is a diode:
> 
> trickle-resistor-ohms = <250>
> diode-connected;
> 
> That's easy for a human to write and/or validate, we can easily extend
> it in future, requires no proliferation of macros, and describes the
> hardware rather than telling software what to do.
> 
> The driver becomes a little more complicated, but gains sanity checking,
> which is a good thing.

Certainly looks better than register bit defines.

As rtc-bq32k has similar options, I'm interested, too. I believe we
should add

trickle-charge-enable;

(we may not want to charge at all), and I believe the diode should be

disconnect-diode;

... With diode connected, charge is slower, and that probably should
be the default value. We don't want to give too much current in
default case.  (bq32k has hard-coded resistor value for
diode/not-diode case).

Thanks and best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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