linux-kernel - Re: [PATCH v2 4/7] cpufreq: report whether cpufreq supports Frequency Invariance (FI)

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Message-ID: <20200805103531.GB4817@arm.com>
Date:   Wed, 5 Aug 2020 11:35:31 +0100
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     rjw@...ysocki.net, dietmar.eggemann@....com,
        catalin.marinas@....com, sudeep.holla@....com, will@...nel.org,
        linux@...linux.org.uk, mingo@...hat.com, peterz@...radead.org,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/7] cpufreq: report whether cpufreq supports
 Frequency Invariance (FI)

On Tuesday 04 Aug 2020 at 12:16:56 (+0530), Viresh Kumar wrote:
> On 03-08-20, 16:24, Ionela Voinescu wrote:
> > Right, cpufreq_register_driver() should check that at least one of them
> > is present
> 
> > (although currently cpufreq_register_driver() will return
> > -EINVAL if .fast_switch() alone is present - something to be fixed).
> 
> I think it is fine as there is no guarantee from cpufreq core if
> .fast_switch() will get called and so target/target_index must be
> present. We can't do fast-switch today without schedutil (as only that
> enables it) and if a notifier gets registered before the driver, then
> we are gone again.
> 
> > Will do, on both accounts.
> > 
> > 
> > > > +		static_branch_enable_cpuslocked(&cpufreq_set_freq_scale);
> > > > +		pr_debug("%s: Driver %s can provide frequency invariance.",
> > > > +			 __func__, driver->name);
> > > 
> > > I think a simpler print will work well too.
> > > 
> > >                 pr_debug("Freq invariance enabled");
> > > 
> > 
> > I think the right way of reporting this support is important here.
> 
> Yeah, we can't say it is enabled as you explained, though I meant
> something else here then, i.e. getting rid of driver name and
> unimportant stuff. What about this now:
> 
> pr_debug("supports frequency invariance");
> 
> This shall get printed as this finally:
> 
> cpufreq: supports frequency invariance
> 

Will do!

Thanks,
Ionela.

> -- 
> viresh