linux-kernel - Re: [PATCH 5/6] cpufreq: Support for fast frequency switching

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Date:	Thu, 3 Mar 2016 12:16:55 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Juri Lelli <juri.lelli@....com>,
	Steve Muckle <steve.muckle@...aro.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH 5/6] cpufreq: Support for fast frequency switching

On Wed, Mar 02, 2016 at 03:12:33AM +0100, Rafael J. Wysocki wrote:
> The most important change from the previous version is that the
> ->fast_switch() callback takes an additional "relation" argument
> and now the governor can use it to choose a selection method.

> +unsigned int acpi_cpufreq_fast_switch(struct cpufreq_policy *policy,
> +				      unsigned int target_freq,
> +				      unsigned int relation)

Would it make sense to replace the {target_freq, relation} pair with
something like the CPPC {min_freq, max_freq} pair?

Then you could use the closest frequency to max provided it is larger
than min.

This communicates more actual information in the same number of
parameters and would thereby allow for a more flexible (better)
frequency selection.