linux-kernel - Re: [PATCH 01/35] mfd: ab8500-gpadc: Implemented suspend/resume

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Date:	Mon, 25 Feb 2013 10:27:36 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Lee Jones <lee.jones@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	sameo@...ux.intel.com, arnd@...db.de, linus.walleij@...ricsson.com,
	Daniel WILLERUD <daniel.willerud@...ricsson.com>
Subject: Re: [PATCH 01/35] mfd: ab8500-gpadc: Implemented suspend/resume

On 22 February 2013 11:38, Mark Brown
<broonie@...nsource.wolfsonmicro.com> wrote:
> On Thu, Feb 21, 2013 at 11:45:08PM +0100, Ulf Hansson wrote:
>> On 20 February 2013 14:19, Mark Brown
>
>> > This doesn't look especially sane...  You're doing a runtime get, taking
>> > the lock without releasing it and disabling the regulator.  This is
>> > *very* odd, both the changelog and the code need to explain what's going
>> > on and why it's safe in a lot more detail here.
>
>> You need to do pm_runtime_get_sync to be able to make sure resources
>> (which seems to be only the regulator) are safe to switch off. To my
>> understanding this is a generic way to use for being able to switch
>> off resources at a device suspend when runtime pm is used in
>> conjunction.
>
> Are you sure this actually does what you think it does, especially when
> run on modern kernels?

Not sure, what you are thinking of more precisely here. Runtime pm has
been in the kernel for quite some time now.

Anyway, to make it a bit clearer, we switch the regulator on/off at
the runtime suspend/resume callbacks. We want to take similar actions
in device suspend/resume.
To accomplish this a pm_runtime_get_sync is done in suspend and vice
verse in resume, otherwise you can not safely handle the regulator.

Kind regards
Ulf Hansson
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