linux-kernel - Re: [Update PATCH 1/1] Cpufreq: Make governor data on nonboot cpus across system suspend/resume

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Message-ID: <5286F57F.6000908@intel.com>
Date:	Sat, 16 Nov 2013 12:33:03 +0800
From:	Lan Tianyu <tianyu.lan@...el.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>,
	Nishanth Menon <nm@...com>
Subject: Re: [Update PATCH 1/1] Cpufreq: Make governor data on nonboot cpus
 across system suspend/resume

On 11/15/2013 06:22 PM, Viresh Kumar wrote:
> On 15 November 2013 13:45, Lan Tianyu <tianyu.lan@...el.com> wrote:
>> Currently, governor of nonboot cpus will be put to EXIT when system suspend.
>> Since all these cpus will be unplugged and the governor usage_count decreases
>> to zero. The governor data and its sysfs interfaces will be freed or released.
>> This makes user config of these governors loss during suspend and resume.
>>
>> This doesn't happen on the governor covering boot cpu because it isn't
>> unplugged during system suspend.
>>
>> To fix this issue, skipping governor exit during system suspend and check
>> policy governor data to determine whether the governor is really needed
>> to be initialized when do init. If not, return EALREADY to indicate the
>> governor has been initialized and should do nothing. __cpufreq_governor()
>> convert EALREADY to 0 as return value for INIT event since governor is
>> still under INIT state and can do START operation.
>>
>> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>
>> ---
>
> Hi Lan..
>

Hi Viresh:

> Apologies!!
>
> I already had a solution for this as this was reported by few Broadcom people
> as well. But I haven't send it to mainline yet as it was untested. It
> looked similar
> to what you had..
>
> And so I would have taken your patch (as you have sent it first to the list and
> there is no real advantage of my patch over yours, they were almost same) :)
>
> But then I went chasing another bug posted by Nishant:
>
> https://lkml.org/lkml/2013/10/24/369
>
> And the final solution I have to write solved all the problems you and he
> reported.
>
> Please have a look at that patch (you are cc'd) and give it a try to see
> if it fixes your problem..

Never mind. I think it should work and will try it.

>
> Btw, One question about your setup:
> - you must have a multi cluster/socket SoC as you have atleast one more
> policy structure than used for group containing boot cpu..

Actually, I test on a laptop and find this issue when reading code to 
fix other bug. :)

All cpus have their own policys.

> - Are you using separate governor for both groups?

Just to produce the bug, I set one non-boot cpu to conservative gov. All 
other remain default "ondemand".

> - Or are you using CPUFREQ_HAVE_GOVERNOR_PER_POLICY stuff
> to use same governor with separate tunables for both groups?
>

No, I am not using this.

> Just wanted to know if somebody else is also using
> CPUFREQ_HAVE_GOVERNOR_PER_POLICY :)
>


-- 
Best Regards
Tianyu Lan
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