linux-kernel - Re: [PATCH 1/3] regulator: core: fix boot-on regulators use

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Date:   Mon, 7 Oct 2019 11:34:29 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Chunyan Zhang <zhang.chunyan@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        ckeepax@...nsource.cirrus.com, LKML <linux-kernel@...r.kernel.org>,
        Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH 1/3] regulator: core: fix boot-on regulators use_count
 usage

Hi Doug, Mark,

On 19-10-01 12:57, Doug Anderson wrote:
> Hi,
> 
> On Fri, Sep 27, 2019 at 1:47 AM Marco Felsch <m.felsch@...gutronix.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.

Sorry that won't fix my problem. If I drop the regulator-boot-on state
the fixed-regulator will disable this regulator but disable/enable this
regulator is only valid during suspend/resume. I don't say that my fix
is correct but we should fix this.

Regards,
  Marco

> -Doug
> 

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