linux-kernel - Re: [PATCH 1/2] cpufreq: Return error if ->get() failed in cpufreq_update

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Message-ID: <CAKohpokk5-6vGV93fZDob8Q=xZXsd7E4OkMUAC1M6Z71G=d1Ow@mail.gmail.com>
Date:	Tue, 25 Feb 2014 10:11:41 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"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>,
	Pierre Ossman <pierre-list@...man.eu>
Subject: Re: [PATCH 1/2] cpufreq: Return error if ->get() failed in cpufreq_update_policy()

On 18 February 2014 07:49, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 18 February 2014 03:30, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> On Monday, February 17, 2014 02:25:34 PM Srivatsa S. Bhat wrote:
>>> Why go to no_policy when we can actually set things right?
>>>
>>> Anyway, I am not arguing against this strongly. I just wanted to share my
>>> thoughts, since this is the approach that made more sense to me.
>>
>> And I agree with that.  In particular, since we're going to set the new
>> policy *anyway* at this point, we can adjust the current frequency just fine
>> in the process, can't we?
>
> Though I still feel that it wouldn't be the right thing to do as get()
> just can't
> return zero. Actually I was planning to place a WARN() over its return value
> of zero.
>
> Anyway, as two of the three are in favor of this we can get that in.. But how
> would that work?
>
> - What frequency should we call cpufreq_driver_target ?
> - Remember that it wouldn't do anything if policy->cur is same as new freq.
> - Also remember that drivers need special attention if new freq is > old
> freq or vice versa. As they will change voltage before or after change here.
> And because we actually don't know what frequency we are at currently, how
> will we decide that?

@Rafael/Srivatsa: Ping!!
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