On Mon, Feb 04, 2019 at 11:09:48AM +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 <[email protected]> > Tested-by: Matthias Kaehlcke <[email protected]> > --- > drivers/opp/of.c | 99 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/pm_opp.h | 6 +++ > 2 files changed, 105 insertions(+) > > diff --git a/drivers/opp/of.c b/drivers/opp/of.c > index 06f0f632ec47..cd58959e5158 100644 > --- a/drivers/opp/of.c > +++ b/drivers/opp/of.c > @@ -20,6 +20,7 @@ > #include <linux/pm_domain.h> > #include <linux/slab.h> > #include <linux/export.h> > +#include <linux/energy_model.h> > > #include "opp.h" > > @@ -1047,3 +1048,101 @@ 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 @kHz if it is the frequency > + * of an existing OPP, or at the frequency of the first OPP above @kHz > otherwise > + * (see dev_pm_opp_find_freq_ceil()). This function updates @kHz to the > ceiled > + * frequency and @mW to the associated power. 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) > +{ > + 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 > + * > + * This checks whether the "dynamic-power-coefficient" devicetree property > has > + * been specified, and tries to register an Energy Model with it if it has. > + */ > +void dev_pm_opp_of_register_em(struct cpumask *cpus) > +{ > + struct em_data_callback em_cb = EM_DATA_CB(_get_cpu_power); > + int ret, nr_opp, cpu = cpumask_first(cpus); > + struct device *cpu_dev; > + struct device_node *np; > + u32 cap; > + > + cpu_dev = get_cpu_device(cpu); > + if (!cpu_dev) > + return; > + > + nr_opp = dev_pm_opp_get_opp_count(cpu_dev); > + if (nr_opp <= 0) > + return; > + > + np = of_node_get(cpu_dev->of_node); > + if (!np) > + return; > + > + /* > + * Register an EM only if the 'dynamic-power-coefficient' property is > + * set in devicetree. It is assumed the voltage values are known if that > + * property is set since it is useless otherwise. If voltages are not > + * known, just let the EM registration fail with an error to alert the > + * user about the inconsistent configuration. > + */ > + 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..c9c76310865a 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); > #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) > +{ > +} > + > static inline int of_get_required_opp_performance_state(struct device_node > *np, int index) > { > return -ENOTSUPP;
There is the option to remove the OPP check from the cpufreq drivers and instead return an error from dev_pm_opp_of_register_em(), but with the more complex error handling it might be more hassle than it's worth. Reviewed-by: Matthias Kaehlcke <[email protected]>
