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

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Message-ID: <CAKohpokjtaCJj3QCDyoQ+1UviLX8ZSnpWk05Jh4U02pmrq897g@mail.gmail.com>
Date:	Fri, 15 Nov 2013 15:52:24 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lan Tianyu <tianyu.lan@...el.com>
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 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..

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..

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

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