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    Subject[PATCH v7 14/14] OPTIONAL: cpufreq: dt: Register an Energy Model
    Date
    *******************************************************************
    * 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 0a9ebf00be46..15ac9754afa2 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>
    @@ -149,8 +150,50 @@ 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;
    @@ -159,7 +202,7 @@ 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) {
    @@ -226,6 +269,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
    ret = -EPROBE_DEFER;
    goto out_free_opp;
    }
    + nr_opp = ret;

    if (fallback) {
    cpumask_setall(policy->cpus);
    @@ -278,6 +322,8 @@ 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);
    +
    return 0;

    out_free_cpufreq_table:
    --
    2.18.0
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