Re: [PATCH 1/3] regulator: core: fix boot-on regulators use_count usage

From: Doug Anderson <dianders@chromium.org>
To: Marco Felsch <m.felsch@pengutronix.de>
Cc: Mark Brown <broonie@kernel.org>,
	Chunyan Zhang <zhang.chunyan@linaro.org>,
	Liam Girdwood <lgirdwood@gmail.com>,
	ckeepax@opensource.cirrus.com,
	LKML <linux-kernel@vger.kernel.org>,
	Sascha Hauer <kernel@pengutronix.de>
Subject: Re: [PATCH 1/3] regulator: core: fix boot-on regulators use_count usage
Date: Tue, 1 Oct 2019 12:57:31 -0700	[thread overview]
Message-ID: <CAD=FV=XM0i=GsvttJjug6VPOJJGHRqFmsmCp-1XXNvmsYp9sJA@mail.gmail.com> (raw)
In-Reply-To: <20190927084710.mt42454vsrjm3yh3@pengutronix.de>

Hi,

On Fri, Sep 27, 2019 at 1:47 AM Marco Felsch <m.felsch@pengutronix.de> wrote:
> > > > > It should be possible to do a regulator_disable() though I'm not
> > > > > sure anyone actually uses that.  The pattern for a regular
> > > > > consumer should be the normal enable/disable pair to handle
> > > > > shared usage, only an exclusive consumer should be able to use
> > > > > just a straight disable.
>
> In my case it is a regulator-fixed which uses the enable/disable pair.
> But as my descriptions says this will not work currently because boot-on
> marked regulators can't be disabled right now (using the same logic as
> always-on regulators).
>
> > > > Ah, I see, I wasn't aware of the "exclusive" special case!  Marco: is
> > > > this working for you?  I wonder if we need to match
> > > > "regulator->enable_count" to "rdev->use_count" at the end of
> > > > _regulator_get() in the exclusive case...
>
> So my fix isn't correct to fix this in general?

I don't think your fix is correct.  It sounds as if the intention of
"regulator-boot-on" is to have the OS turn the regulator on at bootup
and it keep an implicit reference until someone explicitly tells the
OS to drop the reference.

> > > Yes, I think that case has been missed when adding the enable
> > > counts - I've never actually had a system myself that made any
> > > use of this stuff.  It probably needs an audit of the users to
> > > make sure nobody's relying on the current behaviour though I
> > > can't think how they would.
> >
> > Marco: I'm going to assume you'll tackle this since I don't actually
> > have any use cases that need this.
>
> My use case is a simple regulator-fixed which is turned on by the
> bootloader or to be more precise by the pmic-rom. To map that correctly
> I marked this regulator as boot-on. Unfortunately as I pointed out above
> this is handeld the same way as always-on.

It's a fixed regulator controlled by a GPIO?  Presumably the GPIO can
be read.  That would mean it ideally shouldn't be using
"regulator-boot-on" since this is _not_ a regulator whose software
state can't be read.  Just remove the property.

-Doug