From: Matthias Kaehlcke <mka@chromium.org>
To: Quentin Perret <quentin.perret@arm.com>
Cc: rjw@rjwysocki.net, viresh.kumar@linaro.org, sudeep.holla@arm.com,
liviu.dudau@arm.com, lorenzo.pieralisi@arm.com,
robh+dt@kernel.org, mark.rutland@arm.com, nm@ti.com,
sboyd@kernel.org, linux-arm-kernel@lists.infradead.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pm@vger.kernel.org, dietmar.eggemann@arm.com
Subject: Re: [PATCH 1/7] PM / OPP: Introduce a power estimation helper
Date: Tue, 29 Jan 2019 09:52:15 -0800 [thread overview]
Message-ID: <20190129175215.GK81583@google.com> (raw)
In-Reply-To: <20190129090331.fgygq3dsaoqvegsl@queper01-lin>
Hi Quentin,
On Tue, Jan 29, 2019 at 09:03:34AM +0000, Quentin Perret wrote:
> Hi Matthias,
>
> On Monday 28 Jan 2019 at 11:02:51 (-0800), Matthias Kaehlcke wrote:
> > > +/**
> > > + * of_dev_pm_opp_get_cpu_power() - Estimates the power of a CPU
> > > + * @mW: pointer to the power estimate in milli-watts
> > > + * @KHz: pointer to the OPP's frequency, in kilo-hertz
> >
> > nit: should be kHz
>
> Right, I can change that :-)
>
> >
> > > + * @cpu: CPU for which power needs to be estimated
> > > + *
> > > + * Computes the power estimated by @CPU at the first OPP above @KHz (ceil),
> > > + * and updates @KHz and @mW accordingly.
> > > + *
> > > + * The power is estimated as P = C * V^2 * f, with C the CPU's capacitance
> > > + * (read from the 'dynamic-power-coefficient' devicetree binding) and V and f
> > > + * respectively the voltage and frequency of the OPP.
> > > + *
> > > + * Return: -ENODEV if the CPU device cannot be found, -EINVAL if the power
> > > + * calculation failed because of missing parameters, 0 otherwise.
> > > + */
> > > +int of_dev_pm_opp_get_cpu_power(unsigned long *mW, unsigned long *KHz, int cpu)
> >
> > I think it is more common to put the input parameters first, then the
> > output ones, i.e. cpu, kHz, mW.
>
> Hmm, the issue is this must match the expectations of the EM framework:
>
> https://elixir.bootlin.com/linux/v5.0-rc4/source/include/linux/energy_model.h#L62
>
> So, I don't really have a choice. Or we can change the core code if this
> _really_ is a problem -- we don't have users yet so now is the best time
> to do so I guess ...
I see.
I think it would be preferable to follow the common scheme, but it's
also not a major issue, up to you whether you want to change the
definition of the callback. It's certainly true that now would be the
best time for a change.
Cheers
Matthias
next prev parent reply other threads:[~2019-01-29 17:52 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-28 16:55 [PATCH 0/7] Register an Energy Model for Arm reference platforms Quentin Perret
2019-01-28 16:55 ` [PATCH 1/7] PM / OPP: Introduce a power estimation helper Quentin Perret
2019-01-28 19:02 ` Matthias Kaehlcke
2019-01-29 9:03 ` Quentin Perret
2019-01-29 17:52 ` Matthias Kaehlcke [this message]
2019-01-29 5:10 ` Viresh Kumar
2019-01-29 9:09 ` Quentin Perret
2019-01-28 16:55 ` [PATCH 2/7] cpufreq: dt: Register an Energy Model Quentin Perret
2019-01-28 19:36 ` Matthias Kaehlcke
2019-01-29 5:21 ` Viresh Kumar
2019-01-29 9:15 ` Quentin Perret
2019-01-30 5:18 ` Viresh Kumar
2019-01-30 9:12 ` Quentin Perret
2019-01-30 10:17 ` Viresh Kumar
2019-01-30 10:20 ` Quentin Perret
2019-01-29 5:30 ` Viresh Kumar
2019-01-29 9:10 ` Quentin Perret
2019-01-28 16:55 ` [PATCH 3/7] cpufreq: scpi: " Quentin Perret
2019-01-29 5:31 ` Viresh Kumar
2019-01-28 16:55 ` [PATCH 4/7] cpufreq: arm_big_little: " Quentin Perret
2019-01-28 16:55 ` [PATCH 5/7] cpufreq: scmi: " Quentin Perret
2019-01-28 16:55 ` [PATCH 6/7] arm64: dts: juno: Add cpu dynamic-power-coefficient information Quentin Perret
2019-01-29 15:27 ` Sudeep Holla
2019-01-30 10:23 ` Quentin Perret
2019-01-28 16:55 ` [PATCH 7/7] arm: dts: vexpress-v2p-ca15_a7: " Quentin Perret
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