linux-kernel - Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve

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Message-ID: <20160721234134.GW27987@graphite.smuckle.net>
Date:	Thu, 21 Jul 2016 16:41:34 -0700
From:	Steve Muckle <steve.muckle@...aro.org>
To:	Steve Muckle <steve.muckle@...aro.org>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq()

On Thu, Jul 21, 2016 at 04:36:48PM -0700, Steve Muckle wrote:
> On Thu, Jul 21, 2016 at 04:30:03PM -0700, Viresh Kumar wrote:
> > On 21-07-16, 16:21, Steve Muckle wrote:
> > > On Thu, Jul 21, 2016 at 01:30:41PM -0700, Viresh Kumar wrote:
> > > > Okay, but in that case shouldn't we do something like this:
> > > > 
> > > > unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy,
> > > >                                         unsigned int target_freq)
> > > > {
> > > >        target_freq = clamp_val(target_freq, policy->min, policy->max);
> > > >        policy->cached_target_freq = target_freq;
> > > > 
> > > >        if (cpufreq_driver->target_index) {
> > > >        		policy->cached_resolved_idx =
> > > >        		        cpufreq_frequency_table_target(policy, target_freq,
> > > >        		                                       CPUFREQ_RELATION_L);
> > > >        		return policy->freq_table[policy->cached_resolved_idx].frequency;
> > > >        }
> > > > 
> > > >        if (cpufreq_driver->resolve_freq)
> > > >                return cpufreq_driver->resolve_freq(policy, target_freq);
> > > > }
> > > 
> > > Thanks for the review.
> > > 
> > > My thinking (noted in the commit text) was that the caller of
> > > cpufreq_driver_resolve_freq() would verify that the driver supported the
> > > proper calls before using this API.
> > 
> > Okay, but the caller isn't doing that today. Right?
> 
> There is no caller yet.

Sorry, of course this is not true.

I'm still of the opinion that modifying the governor (I could fix up
schedutil now) or adding a check in driver init would be better than any
unnecessary logic in the fast path.