linux-kernel - Re: [PATCH V2] cpufreq: Make sure CPU is running on a freq from freq-table

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Message-ID: <CAKohpokyY0ueNXBQn+Vt5A9V65_ko7D5R=iruUzi6cD9YuXOig@mail.gmail.com>
Date:	Thu, 28 Nov 2013 19:11:17 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Dirk Brandewie <dirk.brandewie@...il.com>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Patch Tracking <patches@...aro.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>,
	Nishanth Menon <nm@...com>, Carlos Hernandez <ceh@...com>
Subject: Re: [PATCH V2] cpufreq: Make sure CPU is running on a freq from freq-table

On 28 November 2013 18:39, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> acpi-cpufreq is one at least.
>
> Anyway, this isn't about ACPI or anything like that, but hardware.  Generally
> speaking, on modern Intel hardware the processor itself chooses the frequency
> to run at and it may do that behind your back.  Moreover, it can choose a
> frequency different from the one you asked for.  And it won't choose one that
> it can't run at for that matter. :-)
>
> Overall, I don't believe that the problem you're trying to address is relevant
> for any non-exotic x86 hardware.

Okay.. So wouldn't it be better that we add this special flag only when we
face a real problem? Otherwise this flag might stay unused for long time
and then we might end up removing it..

>> > So there should be a flag for
>> > drivers indicating whether or not frequencies (or operation points in
>> > general) are directly testable and the check should only be done for
>> > the drivers with the flag set.
>>
>> Probably a flag with properties exactly opposite to what you mentioned,
>> so that we don't need to modify most of the drivers..
>
> That would work too if you prefer it.

In case we need this flag, what should we name it?
ALLOW_UNKNOWN_FREQ ??
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