OPTIONAL: cpufreq: dt: Register an Energy Model

*******************************************************************
* 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>

diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index 0a9ebf00be468e2d78aad853d1dcb7fd0d97558e..399f54d0abf2a5b432093fefbc76fe1cf03b1e72 100644 (file)
--- 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 +150,47 @@ static int resources_available(void)
        return 0;
 }
 
+static int 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);
+
+       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 +199,7 @@ 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 +266,7 @@ 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 +319,8 @@ static int cpufreq_init(struct cpufreq_policy *policy)
        policy->cpuinfo.transition_latency = transition_latency;
        policy->dvfs_possible_from_any_cpu = true;
 
+       em_register_freq_domain(policy->cpus, nr_opp, &em_cb);
+
        return 0;
 
 out_free_cpufreq_table: