2 files changed, 105 insertions, 0 deletions

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 0a2a88e5a383..1470c57933cf 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -322,6 +322,7 @@ 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)
 {
@@ -360,6 +361,11 @@ 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;