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

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Message-ID: <CAKohpon=rVBHZHCz_C7pFoQARXspDJyyPoocTvh8hHjAHPu-og@mail.gmail.com>
Date:	Tue, 16 Jul 2013 15:05:26 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
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 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.
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