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

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Message-ID: <CAKohpokGtcJbdzt0FPZnKjSFi54Np+Ss7--Z83UEZp8FMY94pQ@mail.gmail.com>
Date:	Tue, 18 Feb 2014 07:49:58 +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 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?
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