From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] rtc: ds1307: add trickle charger device tree binding
Date: Mon, 8 Sep 2014 15:58:25 +0100
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To: Pavel Machek <pavel@denx.de>
Cc: Matti Vaittinen <matti.vaittinen@nsn.com>, ext Guenter Roeck <linux@roeck-us.net>, Jason Cooper <jason@lakedaemon.net>, "a.zummo@towertech.it" <a.zummo@towertech.it>, "jic23@kernel.org" <jic23@kernel.org>, "arno@natisbad.org" <arno@natisbad.org>, "jgunthorpe@obsidianresearch.com" <jgunthorpe@obsidianresearch.com>, "san@rosetechnology.dk" <san@rosetechnology.dk>, "hs@denx.de" <hs@denx.de>, "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "rtc-linux@googlegroups.com" <rtc-linux@googlegroups.com>, Sverdlin Alexander <alexander.sverdlin@nsn.com>
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On Mon, Sep 08, 2014 at 02:52:42PM +0100, Pavel Machek wrote:
> 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).

I agree that if one case is less likely to be problematic / damaging
that should be the default.

Mark.