linux-kernel - Re: [PATCH] regulator: twl: Enable regulators over the powerbus as well

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Message-ID: <20160325150259.GA9372@earth>
Date:	Fri, 25 Mar 2016 16:02:59 +0100
From:	Sebastian Reichel <sre@...nel.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>, tony@...mide.com,
	lgirdwood@...il.com, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regulator: twl: Enable regulators over the powerbus as
 well

Hi Mark,

On Fri, Mar 25, 2016 at 11:17:57AM +0000, Mark Brown wrote:
> On Wed, Mar 23, 2016 at 09:22:36PM +0200, Ivaylo Dimitrov wrote:
> 
> > Assigning a device group to a regulator does not change its state. To
> > change the state of a regulator a message over the powerbus is required.
> > Also, the check for the current state of a regulator should not count on
> > a device group being assigned, but on the current resource state.
> 
> How did this driver ever work then?  It sounds like there must be
> something else going on here.

From my understanding of the twl4030 TRM assigning a device group
means "<device group> wants this regulator enabled". It does not
change the regulator mode (sleep vs normal or in regulator-framework
terms: REGULATOR_STATUS_NORMAL vs REGULATOR_STATUS_STANDBY).

It usually works, since the default state is normal. If the system
is rebooted from a non-mainline kernel, which left the regulator in
sleep/standby, nothing in the kernel switches it to normal.

-- Sebastian

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