linux-kernel - Re: [PATCH 4/6] regulator: lp872x: Add enable GPIO pin support

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Message-ID: <20151231214007.GC16023@sirena.org.uk>
Date:	Thu, 31 Dec 2015 21:40:07 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Paul Kocialkowski <contact@...lk.fr>
Cc:	Milo Kim <milo.kim@...com>, linux-kernel@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Benoît Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH 4/6] regulator: lp872x: Add enable GPIO pin support

On Wed, Dec 30, 2015 at 07:37:19PM +0100, Paul Kocialkowski wrote:
> Le mercredi 30 décembre 2015 à 16:33 +0000, Mark Brown a écrit :
> > On Wed, Dec 30, 2015 at 09:35:21AM +0100, Paul Kocialkowski wrote:

> > > In my opinion, it would be more elegant to adapt the core regulator
> > > framework to first enable the GPIO and then call the regulator enable
> > > ops callback instead of handling the GPIO in the driver.

> > Why would we want to actively manage both things at runtime?  It's more
> > work, what do we gain from it?

> Well, I figured that it would be best to disable the EN pin when we're
> not using any of the regulators, since that allows the chip to enter
> standby mode (and thus consume less power).

This doesn't sound like it's anything to do with the regulators, that's
a chip wide power management function which should be implemented via
runtime PM if there's any value in implementing it at all (if the device
is a primary PMIC normally this would be handled by the CPU core when it
enters low power state without any software).  It's not something we
should be considering on a per regulator basis since it's at the chip
level and on a per regulator basis it's not doing anything useful for
the reasons above.

> It also doesn't hurt regulators that only use a GPIO for enable.

It causes problems for any device with an optional GPIO,  it means that
we end up mantaining both GPIO and register which as I've said a couple
of times now defeats the point of having the GPIO.

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