linux-kernel - Re: [PATCH 1/1] regulator: max77802: set opmode to normal if off is read from hw

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Date:	Wed, 27 Aug 2014 20:52:49 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Mark Brown <broonie@...nel.org>
CC:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Yuvaraj Kumar C D <yuvaraj.cd@...il.com>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] regulator: max77802: set opmode to normal if off
 is read from hw

On 27.08.2014 20:47, Mark Brown wrote:
> On Wed, Aug 27, 2014 at 08:39:39PM +0200, Tomasz Figa wrote:
>> On 27.08.2014 20:37, Mark Brown wrote:
> 
>>> That's essentially the situation the patch is trying to fix - if we boot
>>> and the regulator is off there's no way to figure out what the operating
>>> mode would have been so we have to pick something.  If you've got an
>>> idea for something better to do...
> 
>> Probably the only way to correctly handle this is to specify the right
>> operating mode in DT (after defining a binding for it).
> 
> I'm not convinced that's worth it - chances are that if anything changed
> the mode it was a previously running Linux which will most likely be
> doing the same things when it starts running anyway.
> 

The previously running Linux would have changed the opmode accidentally,
due to hardware design of PMIC chip, which doesn't allow powering off a
regulator in other way than setting opmode to OFF.

If you provide the "active" opmode to that Linux, after a warm reboot it
will be able to power on such regulator to correct opmode, without
defaulting it incorrectly to NORMAL.
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