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

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Message-ID: <3894986.dK3STNSG71@vostro.rjw.lan>
Date:	Tue, 25 Feb 2014 14:10:23 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
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 Tuesday, February 25, 2014 11:38:14 AM Viresh Kumar wrote:
> On 25 February 2014 11:23, Srivatsa S. Bhat
> <srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> > Hmm, that's a good point. However, lets first think about the simple scenario
> > that the driver _is_ able to detect the current frequency from the hardware
> > (a non-zero, sane value) say X KHz, and that frequency is different from what
> > the cpufreq subsystem thinks it is (Y KHz).
> >
> > In the current code, when we observe this, we send out a notification and try
> > to adjust to X KHz. Instead, what I'm suggesting is to invoke the driver to
> > set the frequency to Y KHz, since that's what the cpufreq subsystems wants the
> > frequency to be at.
> 
> Actually we don't know at this point what cpufreq wants :)
> Governor will decide what frequency to run CPU at and lets leave it to
> that point.
> As the transition that we might end up doing here would be simply overridden
> very soon. And to be honest this decision must be taken by governor and not
> core. We just want to make sure core is in sync with hardware.

Well, why exactly does the core need to operate "current frequency" at all?

Rafael

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