linux-kernel - Re: [PATCH 3/6] regulator: lp872x: Remove warning about invalid DVS GPIO

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Date:	Wed, 23 Dec 2015 12:50:20 +0100
From:	Paul Kocialkowski <contact@...lk.fr>
To:	Mark Brown <broonie@...nel.org>
Cc:	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>,
	Milo Kim <milo.kim@...com>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH 3/6] regulator: lp872x: Remove warning about invalid DVS
 GPIO

Le mercredi 23 décembre 2015 à 11:41 +0000, Mark Brown a écrit :
> On Wed, Dec 23, 2015 at 11:58:36AM +0100, Paul Kocialkowski wrote:
> > Some devices don't hook the DVS pin to a GPIO but to ground or VCC.
> > In those cases, it is not a problem to have no DVS GPIO.
> 
> I would expect the driver at least needs to know how the pins or
> strapped, or otherwise have configuration for ignoring the input on the
> pins.  This just deletes the warnings, it doesn't have any handling for
> this case that I can see.

When the DVS GPIO is invalid, lp872x_init_dvs jumps to the
set_default_dvs_mode label, which instructs the chip not to use the DVS
pin at all and do it all in software instead (by clearing the
LP8720_EXT_DVS_M bit in the LP872X_GENERAL_CFG register).

That is reflected later in the code, when setting the bucks (the DVS pin
only applies to the bucks) by checking for the LP8720_EXT_DVS_M bit on
the LP872X_GENERAL_CFG register (in lp872x_select_buck_vout_addr) to
decide whether to use software or hardware DVS selection.

As far as I understood, everything goes well when the GPIO is invalid.

-- 
Paul Kocialkowski, Replicant developer

Replicant is a fully free Android distribution running on several
devices, a free software mobile operating system putting the emphasis on
freedom and privacy/security.

Website: https://www.replicant.us/
Blog: https://blog.replicant.us/
Wiki/tracker/forums: https://redmine.replicant.us/

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