linux-kernel - Re: [PATCH] mmc: move regulator handling to core

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Message-ID: <20091203134031.GA1311@rakim.wolfsonmicro.main>
Date:	Thu, 3 Dec 2009 13:40:32 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Daniel Mack <daniel@...aq.de>
Cc:	linux-kernel@...r.kernel.org, Liam Girdwood <lrg@...mlogic.co.uk>,
	Pierre Ossman <pierre@...man.eu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matt Fleming <matt@...sole-pimps.org>,
	Adrian Hunter <adrian.hunter@...ia.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Eric Miao <eric.y.miao@...il.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Cliff Brake <cbrake@...-systems.com>,
	Jarkko Lavinen <jarkko.lavinen@...ia.com>,
	linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] mmc: move regulator handling to core

On Thu, Dec 03, 2009 at 02:32:00PM +0100, Daniel Mack wrote:
> On Thu, Dec 03, 2009 at 01:22:41PM +0000, Mark Brown wrote:
> > On Thu, Dec 03, 2009 at 02:14:23PM +0100, Daniel Mack wrote:

> > > I would expect the power to be killed when the last user stops using it.
> > > Which should result in the same effect if you only have one host, one
> > > regulator, and one user.

> > Yes, it's always fine in that case (modulo always_on and/or regulators
> > without power control). 

> Well, it didn't for me and always_on, though, due to the return values I
> described.

I mean your new code is fine.

> > This goes back to the thing about using
> > regulator_get_exclusive(), the message given was that the MMC drivers
> > really needed to be able to guarantee that the power would be removed
> > when that was requested.

> > Like I say, if there isn't a *strict* requirement but it's only
> > desirable (possibly strongly desirable) then your approach is obviously
> > preferable.

> The mmci people would need to answer that. To me, the code just looked
> like a power saving feature.

> If this driver needs it, the only tweak to my patch to let that
> particular call site use regulator_get_exclusive, and the core will
> still do the right thing. For this case, the behaviour should be exactly
> the same than it currently is, correct?

No, you'll also need to update the way the driver bootstraps the
reference count since with regulator_get_exclusive() the reference count
is initialised to 1 if the regulator is enabled when it is claimed.
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