From mboxrd@z Thu Jan 1 00:00:00 1970 From: Quentin Perret Subject: Re: [PATCH v2 1/5] PM / OPP: Introduce a power estimation helper Date: Thu, 31 Jan 2019 09:51:04 +0000 Message-ID: <20190131095101.g64h32wxqa5rhbqh@queper01-lin> References: <20190130170506.20450-1-quentin.perret@arm.com> <20190130170506.20450-2-quentin.perret@arm.com> <20190131072633.bcqc75s6jmyt7fgx@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20190131072633.bcqc75s6jmyt7fgx@vireshk-i7> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Viresh Kumar Cc: nm@ti.com, linux-pm@vger.kernel.org, sboyd@kernel.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, mka@chromium.org, sudeep.holla@arm.com, dietmar.eggemann@arm.com, linux-arm-kernel@lists.infradead.org List-Id: linux-pm@vger.kernel.org On Thursday 31 Jan 2019 at 12:56:33 (+0530), Viresh Kumar wrote: > On 30-01-19, 17:05, Quentin Perret wrote: > > +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; > > The voltage is also stored as triplet now a days and we must consider > the higher value for these calculations. Also what about the case of > multiple regulators here or performance-states ? Well at least this is not worst than what we already do for IPA :-) https://elixir.bootlin.com/linux/latest/source/drivers/thermal/cpu_cooling.c#L245 In the case of multiple regulators, then maybe that should be dealt with at the dev_pm_op_get_voltage() ? Not sure. > > > + dev_pm_opp_put(opp); > > + if (!mV) > > + return -EINVAL; > > + > > + tmp = (u64)cap * mV * mV * (Hz / 1000000); > > + do_div(tmp, 1000000000); > > + > > + *mW = (unsigned long)tmp; > > I was thinking will it be better if we just save this information in > opp->power field during init, so we can just read a value here > instead. But I am still not sure :( Yeah, I had the exact same question. But, then I thought, we're only gonna use that once, so it's not clear we need to cache the value. And I don't think we want other subsystems to ask PM_OPP for power values directly. Those subsystems should ask the EM framework instead (which exists for that very reason). So we're probably not gonna expose a dev_pm_opp_get_power() accessor or so, I think. That's why I went that way. > > > + *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 > > + * 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) > > +{ > > + 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; > > What if no voltage is supplied in DT ? Then don't provide 'dynamic-power-coefficient' ? There is nothing you can do with that without voltages I think. With this implementation you'll get an error message at some point, which is probably sane. > > > + > > + 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; > > -- > > 2.20.1 > > -- > viresh Thanks, Quentin