linux-kernel - Re: [PATCH v2 2/2] intel_pstate: Set core to min P state during core offline

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Date:	Wed, 19 Mar 2014 00:22:15 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
CC:	Viresh Kumar <viresh.kumar@...aro.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Patrick Marlier <patrick.marlier@...il.com>,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: Re: [PATCH v2 2/2] intel_pstate: Set core to min P state during core
 offline

On 03/18/2014 08:31 PM, Dirk Brandewie wrote:
> On 03/17/2014 10:44 PM, Viresh Kumar wrote:
>> On Sat, Mar 15, 2014 at 2:33 AM,  <dirk.brandewie@...il.com> wrote:
>>> +
>>>   static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
>>>   {
>>>          struct cpudata *cpu;
>>> @@ -818,7 +824,7 @@ static struct cpufreq_driver intel_pstate_driver = {
>>>          .setpolicy      = intel_pstate_set_policy,
>>>          .get            = intel_pstate_get,
>>>          .init           = intel_pstate_cpu_init,
>>> -       .exit           = intel_pstate_cpu_exit,
>>> +       .stop           = intel_pstate_cpu_stop,
>>
>> Probably, keep exit as is and only change P-state in stop(). So that
>> allocation of resources happen in init() and they are freed in exit()?
>>
> I looked at doing just that but it junked up the code.  if stop() is called
> during PREPARE then init() will be called via __cpufreq_add_dev() in the
> ONLINE
> and DOWN_FAILED case. So once stop() is called the driver will be ready for
> init() to be called exactly like when exit() is called.
>

I'm sorry, but that didn't make much sense to me. Can you be a little
more specific as to what problems you hit while trying to have a
->stop() which sets min P state and a separate ->exit() which frees
the resources? I think we can achieve this with almost no trouble.

If you ignore the failure case (such as DOWN_FAILED) for now, do you
still see any serious roadblocks?

Regards,
Srivatsa S. Bhat

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