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

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Message-ID: <20191008154213.GL4382@sirena.co.uk>
Date:   Tue, 8 Oct 2019 16:42:13 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     Doug Anderson <dianders@...omium.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

On Tue, Oct 08, 2019 at 04:56:05PM +0200, Marco Felsch wrote:
> On 19-10-08 13:51, Mark Brown wrote:

> > No, we shouldn't do anything when the regulator probes - we'll only
> > disable unused regulators when we get to the end of boot (currently we
> > delay this by 30s to give userspace a chance to run, that's a hack but
> > we're fresh out of better ideas).  During boot the regulator state will
> > only be changed if some consumer appears and changes the state.

> Okay, so this won't disable the regualtor?

> 8<----------------------------------------------------------------
> static int reg_fixed_voltage_probe(struct platform_device *pdev)
> {
> 	...
> 
> 	if (config->enabled_at_boot)
> 		gflags = GPIOD_OUT_HIGH;
> 	else
> 		gflags = GPIOD_OUT_LOW;
> 
> 	...
> }
> 8<----------------------------------------------------------------

If this is a GPIO regulator then the Linux APIs mean you can't read the
status back so it's one of the regulators for which this property was
invented.  This is a real limitation of the Linux APIs, with most
hardware you can actually read the status back so we shouldn't need
this.

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