linux-kernel - Re: [PATCH] cpufreq: dt: Set default policy->transition_delay

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Date:   Tue, 27 Jun 2017 02:15:12 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Leo Yan <leo.yan@...aro.org>,
        Brendan Jackman <brendan.jackman@....com>,
        linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [PATCH] cpufreq: dt: Set default policy->transition_delay_ns

On Monday, May 22, 2017 04:57:27 PM Viresh Kumar wrote:
> On 22-05-17, 19:17, Leo Yan wrote:
> > This afternoon Amit pointed me for this patch, should fix as below?
> > Otherwise it seems directly assign the same value from unit 'ns' to
> > 'us' but without any value conversion.
> > 
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index 76877a6..dcc90fc 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -538,7 +538,7 @@ static int sugov_init(struct cpufreq_policy *policy)
> >                 unsigned int lat;
> >  
> >                 tunables->rate_limit_us = LATENCY_MULTIPLIER;
> > -               lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
> > +               lat = policy->cpuinfo.transition_latency / NSEC_PER_MSEC;
> >                 if (lat)
> >                         tunables->rate_limit_us *= lat;
> >         }
> 
> I will let Rafael comment in as well. NSEC_PER_USEC is used in the
> earlier governors as well (ondemand/conservative) in exactly the same
> way as schedutil is using.

The reason why it is used by schedutil is because the other governors used it
that way.  IOW, doesn't matter. :-)

Thanks,
Rafael