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

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Message-ID: <20140827191526.GS17528@sirena.org.uk>
Date:	Wed, 27 Aug 2014 20:15:26 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Tomasz Figa <tomasz.figa@...il.com>
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 Wed, Aug 27, 2014 at 08:52:49PM +0200, Tomasz Figa wrote:
> On 27.08.2014 20:47, Mark Brown wrote:

> > 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.

This is in the scenario where the previously running Linux changed the
mode to something other than normal and where the freshly booted Linux
can't figure out how to do that when it needs to.  I'm not sure how
plausible that scenario is, or that real systems would handle it
robustly.

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