linux-kernel - Re: [patch 2.6.28-rc3] regulator: add REGULATOR_MODE

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Date:	Thu, 15 Jan 2009 12:29:38 +0000
From:	Mark Brown <broonie@...ena.org.uk>
To:	David Brownell <david-b@...bell.net>
Cc:	Liam Girdwood <lrg@...mlogic.co.uk>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [patch 2.6.28-rc3] regulator: add REGULATOR_MODE_OFF

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Fcc: +sent-mail

On Wed, Jan 14, 2009 at 11:03:09PM -0800, David Brownell wrote:

> introspection.  Example:  troubleshooting, as we previously
> discussed; or, I can see some regulators that are wrongly
> enabled, primarily because of bootloader goofage.

> That raises an issue:  how can Linux get such regulators to
> turn off?  Clock frameworks have the same issue, and they
> tend to resolve this with a SoC-specific Kconfig option to
> disable unused clocks (in a late_initcall, after everthing
> has had a chance to start up).  That conserves power.

That's something that should be done by constraints - add a new flag
that can be set.

> I'm thinking it'd be worth having a similar Kconfig option
> for regulators too.  It could kick in regulator core code to
> call regulator_ops.disable() whenever regulator_dev.use_count
> is zero, possibly warning if !regulator_ops.is_disabled().
> (Handling constraints.always_on too.)

> Comments?

Given the model the API has of not doing anything unless explicitly
told to I'd not expect to see this as a Kconfig option but rather as
something enabled per regulator or at least per board.

The warning would be a bit interesting; ideally there should be one
since it's probably an indication that something is wrong but there
are probably going to be use cases for it that can't be covered by
always_on, not that I can think of any right now.
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