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    SubjectRe: [PATCH v10 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model
    Hi Quentin,

    On Mon, Dec 03, 2018 at 09:56:28AM +0000, Quentin Perret wrote:
    > *******************************************************************
    > * This patch illustrates the usage of the newly introduced Energy *
    > * Model framework and isn't supposed to be merged as-is. *
    > *******************************************************************
    >
    > The Energy Model framework provides an API to register the active power
    > of CPUs. Call this API from the cpufreq-dt driver with an estimation
    > of the power as P = C * V^2 * f with C, V, and f respectively the
    > capacitance of the CPU and the voltage and frequency of the OPP.
    >
    > The CPU capacitance is read from the "dynamic-power-coefficient" DT
    > binding (originally introduced for thermal/IPA), and the voltage and
    > frequency values from PM_OPP.
    >
    > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
    > Cc: Viresh Kumar <viresh.kumar@linaro.org>
    > Signed-off-by: Quentin Perret <quentin.perret@arm.com>
    > ---
    > drivers/cpufreq/cpufreq-dt.c | 48 +++++++++++++++++++++++++++++++++++-
    > 1 file changed, 47 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
    > index e58bfcb1169e..4cfef5554d86 100644
    > --- a/drivers/cpufreq/cpufreq-dt.c
    > +++ b/drivers/cpufreq/cpufreq-dt.c
    > @@ -16,6 +16,7 @@
    > #include <linux/cpu_cooling.h>
    > #include <linux/cpufreq.h>
    > #include <linux/cpumask.h>
    > +#include <linux/energy_model.h>
    > #include <linux/err.h>
    > #include <linux/module.h>
    > #include <linux/of.h>
    > @@ -150,8 +151,50 @@ static int resources_available(void)
    > return 0;
    > }
    >
    > +static int __maybe_unused of_est_power(unsigned long *mW, unsigned long *KHz,
    > + int cpu)
    > +{
    > + unsigned long mV, Hz, MHz;
    > + struct device *cpu_dev;
    > + struct dev_pm_opp *opp;
    > + struct device_node *np;
    > + u32 cap;
    > + u64 tmp;
    > +
    > + cpu_dev = get_cpu_device(cpu);
    > + if (!cpu_dev)
    > + return -ENODEV;
    > +
    > + np = of_node_get(cpu_dev->of_node);
    > + if (!np)
    > + return -EINVAL;
    > +
    > + if (of_property_read_u32(np, "dynamic-power-coefficient", &cap))
    > + 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;
    > +}
    > +
    > static int cpufreq_init(struct cpufreq_policy *policy)
    > {
    > + struct em_data_callback em_cb = EM_DATA_CB(of_est_power);
    > struct cpufreq_frequency_table *freq_table;
    > struct opp_table *opp_table = NULL;
    > struct private_data *priv;
    > @@ -160,7 +203,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
    > unsigned int transition_latency;
    > bool fallback = false;
    > const char *name;
    > - int ret;
    > + int ret, nr_opp;
    >
    > cpu_dev = get_cpu_device(policy->cpu);
    > if (!cpu_dev) {
    > @@ -237,6 +280,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
    > ret = -EPROBE_DEFER;
    > goto out_free_opp;
    > }
    > + nr_opp = ret;
    >
    > if (fallback) {
    > cpumask_setall(policy->cpus);
    > @@ -280,6 +324,8 @@ static int cpufreq_init(struct cpufreq_policy *policy)
    > policy->cpuinfo.transition_latency = transition_latency;
    > policy->dvfs_possible_from_any_cpu = true;
    >
    > + em_register_perf_domain(policy->cpus, nr_opp, &em_cb);

    Shouldn't there also be a function to unregister a perf domain to be
    called from cpufreq_exit()?

    ->exit() is called on suspend when the CPUs are taken offline, and
    ->init() on resume, hence em_register_perf_domain() is called multiple
    times, but without doing any cleanup.

    Cheers

    Matthias
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