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From: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
To: Mark Brown <broonie@kernel.org>
Cc: Doug Anderson <dianders@chromium.org>,
	milo.kim@ti.com, axel.lin@ingics.com,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	olof@lixom.net, Paul Stewart <pstew@chromium.org>,
	stable@vger.kernel.org, lgirdwood@gmail.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] regulator: core: Fix enable GPIO reference counting
Date: Mon, 02 Mar 2015 21:21:45 +0100	[thread overview]
Message-ID: <54F4C659.2080404@collabora.co.uk> (raw)
In-Reply-To: <20150302185713.GF21293@sirena.org.uk>

Hello Mark,

On 03/02/2015 07:57 PM, Mark Brown wrote:
> On Fri, Feb 27, 2015 at 10:01:23PM +0100, Javier Martinez Canillas wrote:
> 
>> I noticed the same problem in regulator_suspend_finish() when I was working
>> on S2R for Exynos a couple of months ago and had patch [0] on my local tree
>> but never found the time to do extensive testing so I never posted it.
> 
> Please don't bury patches in the middle of mails where they're hard to
> apply if they're useful.
>

Sorry, if my intention was you to apply the patch then I would had posted
it properly. But what I wanted was to share that I had the same issue and
my approach to see if that also fixed Doug's issue.

Otherwise is hard to maintain a conversation across different threads.
 
>> I see that the check is already in _regulator_enable() so another option
>> is to call _regulator_enable() instead of _regulator_do_enable() in
>> regulator_suspend_finish().
> 
> I'm not entirely sure what "the check" is?
>

The check I was referring to is _regulator_is_enabled() but now looking again
I see that _regulator_enable() can't be used in regulator_suspend_finish()
because that will increment the reference counting which is wrong.

>> Trying to enable an already enabled regulator may cause issues so is
>> better to skip enabling regulators that were not disabled before suspend.
> 
>>  		mutex_lock(&rdev->mutex);
>>  		if (rdev->use_count > 0  || rdev->constraints->always_on) {
>> -			error = _regulator_do_enable(rdev);
>> -			if (error)
>> -				ret = error;
>> +			if (!_regulator_is_enabled(rdev)) {
>> +			    error = _regulator_do_enable(rdev);
>> +			    if (error)
>> +				    ret = error;
>> +			}
> 
> This seems like a better fix or at least a better approach - essentially
> the assumption in most of the code is that regulator enables are just
> register writes so repeated updates don't have any effect.  We may need

Which doesn't seem to be the case for all regulators since at least I got
failures when a FET in the tps65090 pmu was tried to be enabled twice.

> a specific per client count here...  I've not looked at the code and I

Sorry, I'm not sure I understood what you meant. The suspend path:

suspend_prepare() -> suspend_set_state() -> .set_suspend_*

doesn't decrement use_count so is correct to call _regulator_do_enable()
directly. The problem is the assumption that all regulators were either
disabled on suspend or that enabling an enabled regulator is a no-op.

I'll post as a proper patch so you can review it.

Best regards,
Javier

  reply	other threads:[~2015-03-02 20:21 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-27 19:41 Doug Anderson
2015-02-27 20:08 ` Greg KH
2015-02-27 21:01 ` Javier Martinez Canillas
2015-03-02 18:57   ` Mark Brown
2015-03-02 20:21     ` Javier Martinez Canillas [this message]
2015-03-03 14:24       ` Mark Brown
2015-03-02 18:47 ` Mark Brown
2015-03-02 21:13   ` Doug Anderson
2015-03-03 14:23     ` Mark Brown
2015-03-03 23:21       ` Doug Anderson
2015-03-04 11:27         ` Mark Brown
2015-03-04 17:13           ` Doug Anderson

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