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Wed, 30 Jan 2019 11:07:04 -0800 (PST) Date: Wed, 30 Jan 2019 11:07:03 -0800 From: Matthias Kaehlcke To: Quentin Perret Subject: Re: [PATCH v2 1/5] PM / OPP: Introduce a power estimation helper Message-ID: <20190130190703.GM81583@google.com> References: <20190130170506.20450-1-quentin.perret@arm.com> <20190130170506.20450-2-quentin.perret@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190130170506.20450-2-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-20190130_110706_522020_2A321A6A X-CRM114-Status: GOOD ( 32.54 ) 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: nm@ti.com, linux-pm@vger.kernel.org, sboyd@kernel.org, viresh.kumar@linaro.org, rjw@rjwysocki.net, linux-kernel@vger.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 Hi Quentin, On Wed, Jan 30, 2019 at 05:05:02PM +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 > > --- > > Matthias: Given this patch changed a bit I dropped your Reviewed-by and > Tested-by, but let me know if you think they still hold. > --- > drivers/opp/of.c | 88 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/pm_opp.h | 6 +++ > 2 files changed, 94 insertions(+) > > diff --git a/drivers/opp/of.c b/drivers/opp/of.c > index 06f0f632ec47..4c8bf172e9ed 100644 > --- a/drivers/opp/of.c > +++ b/drivers/opp/of.c > @@ -20,6 +20,7 @@ > #include > #include > #include > +#include nit: AFAIK typically alphabetical order is used for includes, though this file doesn't exactly adhere to it. > #include "opp.h" > > @@ -1047,3 +1048,90 @@ 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); > + > +/* > + * Callback function provided to the Energy Model framework upon registration. > + * This computes the power estimated by @CPU at the first OPP above @kHz (ceil), that's not entirely correct, it could be the OPP at @kHz. > + * and updates @kHz and @mW accordingly. The power is estimated as > + * P = C * V^2 * f with C being the CPU's capacitance and V and f respectively > + * the voltage and frequency of the OPP. > + * > + * Returns -ENODEV if the CPU device cannot be found, -EINVAL if the power > + * calculation failed because of missing parameters, 0 otherwise. > + */ > +static int __maybe_unused _get_cpu_power(unsigned long *mW, unsigned long *kHz, > + int cpu) why __maybe_unused? > +{ > + struct device *cpu_dev; > + struct dev_pm_opp *opp; > + struct device_node *np; > + unsigned long mV, Hz; > + 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; > + > + tmp = (u64)cap * mV * mV * (Hz / 1000000); > + do_div(tmp, 1000000000); > + > + *mW = (unsigned long)tmp; > + *kHz = Hz / 1000; > + > + return 0; > +} > + > +/** > + * dev_pm_opp_of_register_em() - Attempt to register an Energy Model > + * @cpus : CPUs for which an Energy Model has to be registered > + * @nr_opp : Number of OPPs to register in the Energy Model > + * > + * This checks whether the "dynamic-power-coefficient" devicetree binding has s/binding/property/ ? > + * been specified, and tries to register an Energy Model with it if it has. > + */ > +void dev_pm_opp_of_register_em(struct cpumask *cpus, int nr_opp) Is the nr_opp parameter really needed? The function looks up the CPU device and hence could determine the OPP count itself with dev_pm_opp_get_opp_count(). I see most cpufreq drivers call dev_pm_opp_get_opp_count() anyway, so passing the count as parameter can be considered a small optimization, not sure how relevant it is though, since dev_pm_opp_of_register_em() isn't called frequently. > +{ > + struct em_data_callback em_cb = EM_DATA_CB(_get_cpu_power); > + int ret, cpu = cpumask_first(cpus); > + struct device *cpu_dev; > + struct device_node *np; > + u32 cap; > + > + cpu_dev = get_cpu_device(cpu); > + if (!cpu_dev) > + return; > + > + np = of_node_get(cpu_dev->of_node); > + if (!np) > + return; > + > + /* Don't register an EM without the right DT binding */ > + ret = of_property_read_u32(np, "dynamic-power-coefficient", &cap); > + of_node_put(np); > + if (ret || !cap) > + return; > + > + em_register_perf_domain(cpus, nr_opp, &em_cb); > +} > +EXPORT_SYMBOL_GPL(dev_pm_opp_of_register_em); > diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h > index b895f4e79868..58ae08b024bd 100644 > --- a/include/linux/pm_opp.h > +++ b/include/linux/pm_opp.h > @@ -327,6 +327,7 @@ 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); > +void dev_pm_opp_of_register_em(struct cpumask *cpus, int nr_opp); > #else > static inline int dev_pm_opp_of_add_table(struct device *dev) > { > @@ -365,6 +366,11 @@ static inline struct device_node *dev_pm_opp_get_of_node(struct dev_pm_opp *opp) > { > return NULL; > } > + > +static inline void dev_pm_opp_of_register_em(struct cpumask *cpus, int nr_opp) > +{ > +} > + > static inline int of_get_required_opp_performance_state(struct device_node *np, int index) > { > return -ENOTSUPP; Tested-by: Matthias Kaehlcke _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel