linux-kernel - Re: [RFC PATCH] cpufreq: cpufreq-cpu0: do not allow transitions with regulators suspended

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Message-ID: <528622AB.1050500@ti.com>
Date:	Fri, 15 Nov 2013 07:33:31 -0600
From:	Nishanth Menon <nm@...com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Shawn Guo <shawn.guo@...aro.org>
Subject: Re: [RFC PATCH] cpufreq: cpufreq-cpu0: do not allow transitions with
 regulators suspended

On 11/15/2013 04:27 AM, Viresh Kumar wrote:
> On 14 November 2013 22:34, Nishanth Menon <nm@...com> wrote:
>> I think it is still too early to do so :(
> 
> :)
:D

> 
>> equivalent patch: http://pastebin.mozilla.org/3603467 (with minor
>> changes for build)
>>
>> Basic tests: http://pastebin.mozilla.org/3603456 (governor is
>> functional, but governor kicks in early before i2c is resumed)
>>
>> With call stack: http://pastebin.mozilla.org/3603455 to highlight call
>> sequences
>>
>> Seems like we might want to pause governor as early in the suspend
>> sequence as possible to allow SoC and regulator stuff to suspend
>> themselves without cpufreq interfering.. just my 2 cents..
> 
> You made me spend a day on this :)
> It wasn't a day's job really but I got into a really hard to crack bug with my
> patch, I was calling __cpufreq_governor() from under write_lock_irqsave
> for cpufreq_driver_lock. And __cpufreq_governor() had:
> 
>  read_lock_irqsave(&cpufreq_driver_lock, flags);
> 
> I wasn't able to suspend my system: ARM, X86.. It simply stopped
> printing anything and I didn't had a clue of what's going on.. Hacked
> everything possible, even kernel/power/suspend.c to return early
> (yeah I used freezer > pm_test as well, but I wanted to return before
> freezing userspace)...
> 
> Then somehow I got to know that this is the wrong piece of code :)

Thanks a ton for your efforts in helping come with a generic solution.

> 
> But probably I have a solution now to which you can't say:

https://patchwork.kernel.org/patch/3187511/ as a link for the records :)

> 
> "I think it is still too early to do so :("
> 
> :)
> 
> Give it a try and give a Tested-by please :)
> 
Definitely - on it.. will feedback further on the patch in proposal.

-- 
Regards,
Nishanth Menon
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