linux-kernel - Re: [PATCH 7/8] cpufreq: Preserve policy structure across suspend/resume

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Date:	Tue, 16 Jul 2013 15:24:40 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
CC:	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 7/8] cpufreq: Preserve policy structure across suspend/resume

On 07/16/2013 03:05 PM, Viresh Kumar wrote:
> On 16 July 2013 14:59, Srivatsa S. Bhat
> <srivatsa.bhat@...ux.vnet.ibm.com> wrote:
>> On 07/16/2013 02:40 PM, Viresh Kumar wrote:
> 
>>> So, even if you don't keep the fallback storage, things should work
>>> without any issue (probably worth trying as this will get rid of a per
>>> cpu variable :))
>>>
>>
>> No, I already tried that and it didn't work ;-( The thing is, we need the
>> __cpufreq_add_dev() code to call the ->init() routines of drivers etc. But if
>> it finds the policy structure, it will skip all of that initialization and happily
>> proceed. Which is precisely the cause of all the erratic behaviour we are seeing
>> (ie., lack of proper initialization post-resume).
> 
> I missed that point. :)
> 
>> So this approach keeps the memory preserved in a fallback storage and lets the
>> init code run to full completion without any issues.
>>
>> Perhaps we could do some _more_ code reorganization in the future to take this
>> issue into account etc., but IMHO that might be non-trivial. I'm trying to keep
>> this as simple and straight-forward as possible as a first step, to atleast get
>> it properly working. (Changing the order in which init is done is kinda scary
>> since its hard to comprehend what assumptions we might be breaking!).
>>
>> We can perhaps revisit your idea later and optimize out the extra per-cpu data.
> 
> No, we don't need to optimize it that way. Current design looks good
> for now.

Cool! Thanks :)

Regards,
Srivatsa S. Bhat

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