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From: Quentin Perret <quentin.perret@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"open list:THERMAL" <linux-pm@vger.kernel.org>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	Ingo Molnar <mingo@redhat.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Chris Redpath <chris.redpath@arm.com>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Thara Gopinath <thara.gopinath@linaro.org>,
	viresh kumar <viresh.kumar@linaro.org>,
	Todd Kjos <tkjos@google.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	"Cc: Steve Muckle" <smuckle@google.com>,
	adharmap@quicinc.com, "Kannan, Saravana" <skannan@quicinc.com>,
	pkondeti@codeaurora.org, Juri Lelli <juri.lelli@redhat.com>,
	Eduardo Valentin <edubezval@gmail.com>,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	currojerez@riseup.net, Javi Merino <javi.merino@kernel.org>
Subject: Re: [RFC PATCH v4 12/12] OPTIONAL: cpufreq: dt: Register an Energy Model
Date: Fri, 6 Jul 2018 11:18:58 +0100	[thread overview]
Message-ID: <20180706101858.GC11862@e108498-lin.cambridge.arm.com> (raw)
In-Reply-To: <CAKfTPtAANKzw7QTzKiU_ntiGYMxZD3etd8wMzXtngwUWHXj+Hg@mail.gmail.com>

On Friday 06 Jul 2018 at 12:10:02 (+0200), Vincent Guittot wrote:
> On Thu, 28 Jun 2018 at 13:41, Quentin Perret <quentin.perret@arm.com> wrote:
> > +static int of_est_power(unsigned long *mW, unsigned long *KHz, int cpu)
> > +{
> > +       unsigned long mV, Hz, MHz;
> > +       struct device *cpu_dev;
> > +       struct dev_pm_opp *opp;
> > +       struct device_node *np;
> > +       u32 cap;
> > +       u64 tmp;
> > +
> > +       cpu_dev = get_cpu_device(cpu);
> > +       if (!cpu_dev)
> > +               return -ENODEV;
> > +
> > +       np = of_node_get(cpu_dev->of_node);
> > +       if (!np)
> > +               return -EINVAL;
> > +
> > +       if (of_property_read_u32(np, "dynamic-power-coefficient", &cap))
> > +               return -EINVAL;
> > +
> > +       Hz = *KHz * 1000;
> > +       opp = dev_pm_opp_find_freq_ceil(cpu_dev, &Hz);
> > +       if (IS_ERR(opp))
> > +               return -EINVAL;
> > +
> > +       mV = dev_pm_opp_get_voltage(opp) / 1000;
> > +       dev_pm_opp_put(opp);
> > +
> > +       MHz = Hz / 1000000;
> > +       tmp = (u64)cap * mV * mV * MHz;
> > +       do_div(tmp, 1000000000);
> 
> Could you explain the formula above ? and especially the 1000000000 it
> seems related to the use of mV and mW instead of uV and uW ...

That's correct, this is just a matter of units. I simply tried to
reproduce here what is currently done for IPA:

https://elixir.bootlin.com/linux/latest/source/drivers/thermal/cpu_cooling.c#L252

> 
> Can't you just optimize that into
> tmp = (u64)cap * mV * mV * Hz;
> do_div(tmp, 1000);

I don't think that'll work. If you use Hz instead of MHz you'll need to
divide tmp by 1000000000000000 to get milli-watts, as specified by the
EM framework.

FYI, I don't consider this patch to be ready to be merged. I kept it
self-contained and simple for the example but I actually think that this
of_est_power function should probably be factored-out somewhere else.
scpi-cpufreq could use it as well. Anyway, I guess we can discuss that
later once the APIs of the EM framework are agreed :-)

Thanks,
Quentin

  reply	other threads:[~2018-07-06 10:19 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-28 11:40 [RFC PATCH v4 00/12] Energy Aware Scheduling Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 01/12] sched: Relocate arch_scale_cpu_capacity Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 02/12] sched/cpufreq: Factor out utilization to frequency mapping Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 03/12] PM: Introduce an Energy Model management framework Quentin Perret
2018-07-05 14:31   ` Peter Zijlstra
2018-07-05 15:24     ` Quentin Perret
2018-07-05 14:39   ` Peter Zijlstra
2018-07-05 15:09     ` Quentin Perret
2018-07-05 15:06   ` Peter Zijlstra
2018-07-05 15:32     ` Quentin Perret
2018-07-06  9:57   ` Vincent Guittot
2018-07-06 10:03     ` Peter Zijlstra
2018-07-06 10:06       ` Quentin Perret
2018-07-06 10:05     ` Quentin Perret
2018-07-09 18:07   ` Dietmar Eggemann
2018-07-10  8:32     ` Quentin Perret
2018-07-16 10:29       ` Quentin Perret
2018-07-17  8:57         ` Dietmar Eggemann
2018-07-17 14:19           ` Quentin Perret
2018-07-17 16:00             ` Dietmar Eggemann
2018-06-28 11:40 ` [RFC PATCH v4 04/12] PM / EM: Expose the Energy Model in sysfs Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 05/12] sched/topology: Reference the Energy Model of CPUs when available Quentin Perret
2018-07-05 17:29   ` Peter Zijlstra
2018-07-05 17:48     ` Quentin Perret
2018-07-05 17:33   ` Peter Zijlstra
2018-07-05 17:50     ` Quentin Perret
2018-07-05 18:14       ` Peter Zijlstra
2018-06-28 11:40 ` [RFC PATCH v4 06/12] sched/topology: Lowest energy aware balancing sched_domain level pointer Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 07/12] sched/topology: Introduce sched_energy_present static key Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 08/12] sched: Add over-utilization/tipping point indicator Quentin Perret
2018-07-06 11:32   ` Peter Zijlstra
2018-07-06 13:20     ` Quentin Perret
2018-07-06 13:24       ` Peter Zijlstra
2018-07-06 13:40         ` Quentin Perret
2018-07-06 11:39   ` Peter Zijlstra
2018-07-06 11:41   ` Peter Zijlstra
2018-07-06 11:49     ` Valentin Schneider
2018-06-28 11:40 ` [RFC PATCH v4 09/12] sched/fair: Introduce an energy estimation helper function Quentin Perret
2018-07-06 13:12   ` Peter Zijlstra
2018-07-06 15:12     ` Quentin Perret
2018-07-06 15:49       ` Peter Zijlstra
2018-07-06 17:04         ` Quentin Perret
2018-07-09 12:01           ` Peter Zijlstra
2018-07-09 15:28             ` Quentin Perret
2018-07-09 15:42               ` Peter Zijlstra
2018-07-09 16:07                 ` Quentin Perret
2018-07-06 15:50       ` Peter Zijlstra
2018-06-28 11:40 ` [RFC PATCH v4 10/12] sched/fair: Select an energy-efficient CPU on task wake-up Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 11/12] OPTIONAL: arch_topology: Start Energy Aware Scheduling Quentin Perret
2018-06-28 11:40 ` [RFC PATCH v4 12/12] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret
2018-07-06 10:10   ` Vincent Guittot
2018-07-06 10:18     ` Quentin Perret [this message]
2018-07-30 15:53       ` Vincent Guittot
2018-07-30 16:20         ` Quentin Perret

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