linux-kernel - Re: [PATCH 1/8] cpufreq: Revert commit a66b2e to fix cpufreq regression during suspend/resume

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Date:	Mon, 15 Jul 2013 11:48:04 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Paul Bolle <pebolle@...cali.nl>
CC:	Viresh Kumar <viresh.kumar@...aro.org>, rjw@...k.pl,
	toralf.foerster@....de, robert.jarzmik@...el.com,
	durgadoss.r@...el.com, tianyu.lan@...el.com,
	lantianyu1986@...il.com, dirk.brandewie@...il.com,
	stern@...land.harvard.edu, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] cpufreq: Revert commit a66b2e to fix cpufreq regression
 during suspend/resume

On 07/13/2013 06:16 PM, Paul Bolle wrote:
> On Fri, 2013-07-12 at 12:48 +0530, Viresh Kumar wrote:
>> On 12 July 2013 03:45, Srivatsa S. Bhat
>> <srivatsa.bhat@...ux.vnet.ibm.com> wrote:
>>> commit a66b2e (cpufreq: Preserve sysfs files across suspend/resume) has
>>> unfortunately caused several things in the cpufreq subsystem to break subtly
>>> after a suspend/resume cycle.
>>>
>>> The intention of that patch was to retain the file permissions of the
>>> cpufreq related sysfs files across suspend/resume. To achieve that, the commit
>>> completely removed the calls to cpufreq_add_dev() and __cpufreq_remove_dev()
>>> during suspend/resume transitions. But the problem is that those functions
>>> do 2 kinds of things:
>>>   1. Low-level initialization/tear-down that are critical to the correct
>>>      functioning of cpufreq-core.
>>>   2. Kobject and sysfs related initialization/teardown.
>>>
>>> Ideally we should have reorganized the code to cleanly separate these two
>>> responsibilities, and skipped only the sysfs related parts during
>>> suspend/resume. Since we skipped the entire callbacks instead (which also
>>> included some CPU and cpufreq-specific critical components), cpufreq
>>> subsystem started behaving erratically after suspend/resume.
>>>
>>> So revert the commit to fix the regression. We'll revisit and address the
>>> original goal of that commit separately, since it involves quite a bit of
>>> careful code reorganization and appears to be non-trivial.
>>>
>>> (While reverting the commit, note that another commit f51e1eb "cpufreq:
>>> Fix cpufreq regression after suspend/resume" already reverted part of the
>>> original set of changes. So revert only the remaining ones).
>>>
>>> Cc: stable@...r.kernel.org
>>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
>>> ---
>>>
>>>  drivers/cpufreq/cpufreq.c       |    4 +++-
>>>  drivers/cpufreq/cpufreq_stats.c |    6 ++----
>>>  2 files changed, 5 insertions(+), 5 deletions(-)
>>
>> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> 
> This seems to fix the "core stuck at some frequency after resume" issue
> I ran into since v3.10. So:
> 
> Tested-by: Paul Bolle <pebolle@...cali.nl>
> 

Thanks Paul!
 
Regards,
Srivatsa S. Bhat

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