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

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Date:	Thu, 21 Feb 2013 23:45:08 +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 20 February 2013 14:19, Mark Brown
<broonie@...nsource.wolfsonmicro.com> wrote:
> On Fri, Feb 15, 2013 at 12:56:32PM +0000, Lee Jones wrote:
>
>> +static int ab8500_gpadc_suspend(struct device *dev)
>> +{
>> +     struct ab8500_gpadc *gpadc = dev_get_drvdata(dev);
>> +
>> +     mutex_lock(&gpadc->ab8500_gpadc_lock);
>> +
>> +     pm_runtime_get_sync(dev);
>> +
>> +     regulator_disable(gpadc->regu);
>> +     return 0;
>> +}
>
> 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.

Regarding the mutex, I can't tell the reason behind it. It seems
strange but not sure.

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Kind regards
Ulf Hansson
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