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path: root/drivers/opp/of.c
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-rw-r--r--drivers/opp/of.c99
1 files changed, 99 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);