linux-kernel - Re: [PATCH] cpufreq: exynos5440: Fix to skip when new frequency same as current

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Date:	Thu, 08 Aug 2013 01:25:08 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>,
	Amit Daniel Kachhap <amit.daniel@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH] cpufreq: exynos5440: Fix to skip when new frequency same as current

On Wednesday, August 07, 2013 05:03:59 PM Viresh Kumar wrote:
> On 7 August 2013 17:00, Sudeep KarkadaNagesha
> <Sudeep.KarkadaNagesha@....com> wrote:
> > Any particular reason we need this check in all drivers after your
> > commit: 5a1c0228 "cpufreq: Avoid calling cpufreq driver's target()
> > routine if target_freq == policy->cur"
> >
> > I think it can removed from all drivers, am I missing something ?
> 
> Yeah.. Just a bit though :)
> 
> So, cpufreq core checks this when we call target for any frequency.
> Now, cpufreq driver actually does a cpufreq_frequency_table_target()
> and so the frequency may vary than what is requested, in case
> requested frequency isn't picked from the table.
> 
> In such cases we check it again to be sure that we aren't at this
> frequency already..
> 
> Earlier I thought of calling cpufreq_frequency_table_target() in the
> core before calling target but dropped the idea as I wasn't sure of
> the side effects.
> 
> @Rafael: Do you see why we shouldn't/can't call
> cpufreq_frequency_table_target() from the core itself and so drivers
> never need to do it?

It looks like it would require us to redefine .target() to take next_state
instead of target_freq (at least in the acpi-cpufreq case), wouldn't it?

Rafael

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