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Mon, 28 Jan 2019 11:02:52 -0800 (PST) Date: Mon, 28 Jan 2019 11:02:51 -0800 From: Matthias Kaehlcke To: Quentin Perret Subject: Re: [PATCH 1/7] PM / OPP: Introduce a power estimation helper Message-ID: <20190128190251.GH81583@google.com> References: <20190128165522.31749-1-quentin.perret@arm.com> <20190128165522.31749-2-quentin.perret@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190128165522.31749-2-quentin.perret@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190128_110254_645978_A96A6441 X-CRM114-Status: GOOD ( 29.93 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, rjw@rjwysocki.net, nm@ti.com, lorenzo.pieralisi@arm.com, devicetree@vger.kernel.org, sboyd@kernel.org, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, liviu.dudau@arm.com, linux-kernel@vger.kernel.org, robh+dt@kernel.org, sudeep.holla@arm.com, dietmar.eggemann@arm.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org rHi Quentin, On Mon, Jan 28, 2019 at 04:55:16PM +0000, Quentin Perret wrote: > The Energy Model (EM) framework provides an API to let drivers register > the active power of CPUs. The drivers are expected to provide a callback > method which estimates the power consumed by a CPU at each available > performance levels. How exactly this should be implemented, however, > depends on the platform. > > On some systems, PM_OPP knows the voltage and frequency at which CPUs > can run. When coupled with the CPU 'capacitance' (as provided by the > 'dynamic-power-coefficient' devicetree binding), it is possible to > estimate the dynamic power consumption of a CPU as P = C * V^2 * f, with > C its capacitance and V and f respectively the voltage and frequency of > the OPP. The Intelligent Power Allocator (IPA) thermal governor already > implements that estimation method, in the thermal framework. > > However, this power estimation method can be applied to any platform > where all the parameters are known (C, V and f), and not only those > suffering thermal issues. As such, the code implementing this feature > can be re-used to also populate the EM framework now used by EAS. > > As a first step, introduce in PM_OPP a helper function which CPUFreq > drivers can use to register into the EM framework. This duplicates the > power estimation done in IPA until it can be migrated to using the EM > framework. This will be done later, once the EM framework has support > for at least all platforms currently supported by IPA. > > Signed-off-by: Quentin Perret > --- > drivers/opp/of.c | 60 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/pm_opp.h | 5 ++++ > 2 files changed, 65 insertions(+) > > diff --git a/drivers/opp/of.c b/drivers/opp/of.c > index 06f0f632ec47..7572a2eb2fd4 100644 > --- a/drivers/opp/of.c > +++ b/drivers/opp/of.c > @@ -1047,3 +1047,63 @@ struct device_node *dev_pm_opp_get_of_node(struct dev_pm_opp *opp) > return of_node_get(opp->np); > } > EXPORT_SYMBOL_GPL(dev_pm_opp_get_of_node); > + > +/** > + * 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 > + * @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. > +{ > + unsigned long mV, Hz, MHz; > + struct device *cpu_dev; > + struct dev_pm_opp *opp; > + struct device_node *np; > + u32 cap; > + u64 tmp; > + int ret; > + > + cpu_dev = get_cpu_device(cpu); > + if (!cpu_dev) > + return -ENODEV; > + > + np = of_node_get(cpu_dev->of_node); > + if (!np) > + return -EINVAL; > + > + ret = of_property_read_u32(np, "dynamic-power-coefficient", &cap); > + of_node_put(np); > + if (ret) > + 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); > + if (!mV) > + return -EINVAL; > + > + MHz = Hz / 1000000; > + tmp = (u64)cap * mV * mV * MHz; > + do_div(tmp, 1000000000); > + > + *mW = (unsigned long)tmp; > + *KHz = Hz / 1000; > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(of_dev_pm_opp_get_cpu_power); > diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h > index 0a2a88e5a383..fedde14f5187 100644 > --- a/include/linux/pm_opp.h > +++ b/include/linux/pm_opp.h > @@ -322,6 +322,7 @@ int dev_pm_opp_of_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpuma > struct device_node *dev_pm_opp_of_get_opp_desc_node(struct device *dev); > struct device_node *dev_pm_opp_get_of_node(struct dev_pm_opp *opp); > int of_get_required_opp_performance_state(struct device_node *np, int index); > +int of_dev_pm_opp_get_cpu_power(unsigned long *mW, unsigned long *KHz, int cpu); > #else > static inline int dev_pm_opp_of_add_table(struct device *dev) > { > @@ -364,6 +365,10 @@ static inline int of_get_required_opp_performance_state(struct device_node *np, > { > return -ENOTSUPP; > } > +static inline int of_dev_pm_opp_get_cpu_power(unsigned long *mW, unsigned long *KHz, int cpu) > +{ > + return -ENOTSUPP; > +} > #endif > > #endif /* __LINUX_OPP_H__ */ Besides the nits above: Reviewed-by: Matthias Kaehlcke Tested-by: Matthias Kaehlcke _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel