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Subject[PATCH v8 15/15] 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:
--
2.19.1
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