Re: [RFC PATCH v6 6/9] thermal: cpu_cooling: implement the power cooling device API

[Javi Merino]

On Tue, Dec 09, 2014 at 10:36:46AM +0000, Viresh Kumar wrote:
> On 9 December 2014 at 16:02, Javi Merino <javi.merino@xxxxxxx> wrote:
> > Sorry but I don't follow.  __cpufreq_cooling_register() is passed a
> > clip_cpus mask, not a single cpu.  How do I get "the cpu for which
> > __cpufreq_cooling_register() is called" if not by looping through all
> > the cpus in the mask?
> 
> Yeah, its np that is passed instead of cpu number. So, that wouldn't
> be usable. Also because of the limitations I explained earlier, it makes
> sense to iterate over all clip_cpus and finding which one owns OPPs.

Ok, how about this then?  I've pasted the whole commit so as to avoid
confusion.

diff --git a/Documentation/thermal/cpu-cooling-api.txt b/Documentation/thermal/cpu-cooling-api.txt
index fca24c931ec8..d438a900e374 100644
--- a/Documentation/thermal/cpu-cooling-api.txt
+++ b/Documentation/thermal/cpu-cooling-api.txt
@@ -25,8 +25,150 @@ the user. The registration APIs returns the cooling device pointer.
 
    clip_cpus: cpumask of cpus where the frequency constraints will happen.
 
-1.1.2 void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
+1.1.2 struct thermal_cooling_device *cpufreq_power_cooling_register(
+    const struct cpumask *clip_cpus, u32 capacitance,
+    get_static_t plat_static_func)
+
+Similar to cpufreq_cooling_register, this function registers a cpufreq
+cooling device.  Using this function, the cooling device will
+implement the power extensions by using a simple cpu power model.  The
+cpus must have registered their OPPs using the OPP library.
+
+The additional parameters are needed for the power model (See 2. Power
+models).  "capacitance" is the dynamic power coefficient (See 2.1
+Dynamic power).  "plat_static_func" is a function to calculate the
+static power consumed by these cpus (See 2.2 Static power).
+
+1.1.3 struct thermal_cooling_device *of_cpufreq_power_cooling_register(
+    struct device_node *np, const struct cpumask *clip_cpus, u32 capacitance,
+    get_static_t plat_static_func)
+
+Similar to cpufreq_power_cooling_register, this function register a
+cpufreq cooling device with power extensions using the device tree
+information supplied by the np parameter.
+
+1.1.4 void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
 
     This interface function unregisters the "thermal-cpufreq-%x" cooling device.
 
     cdev: Cooling device pointer which has to be unregistered.
+
+2. Power models
+
+The power API registration functions provide a simple power model for
+CPUs.  The current power is calculated as dynamic + (optionally)
+static power.  This power model requires that the operating-points of
+the CPUs are registered using the kernel's opp library and the
+`cpufreq_frequency_table` is assigned to the `struct device` of the
+cpu.  If you are using the `cpufreq-cpu0.c` driver then the
+`cpufreq_frequency_table` should already be assigned to the cpu
+device.
+
+The `plat_static_func` parameter of `cpufreq_power_cooling_register()`
+and `of_cpufreq_power_cooling_register()` is optional.  If you don't
+provide it, only dynamic power will be considered.
+
+2.1 Dynamic power
+
+The dynamic power consumption of a processor depends on many factors.
+For a given processor implementation the primary factors are:
+
+- The time the processor spends running, consuming dynamic power, as
+  compared to the time in idle states where dynamic consumption is
+  negligible.  Herein we refer to this as 'utilisation'.
+- The voltage and frequency levels as a result of DVFS.  The DVFS
+  level is a dominant factor governing power consumption.
+- In running time the 'execution' behaviour (instruction types, memory
+  access patterns and so forth) causes, in most cases, a second order
+  variation.  In pathological cases this variation can be significant,
+  but typically it is of a much lesser impact than the factors above.
+
+A high level dynamic power consumption model may then be represented as:
+
+Pdyn = f(run) * Voltage^2 * Frequency * Utilisation
+
+f(run) here represents the described execution behaviour and its
+result has a units of Watts/Hz/Volt^2 (this often expressed in
+mW/MHz/uVolt^2)
+
+The detailed behaviour for f(run) could be modelled on-line.  However,
+in practice, such an on-line model has dependencies on a number of
+implementation specific processor support and characterisation
+factors.  Therefore, in initial implementation that contribution is
+represented as a constant coefficient.  This is a simplification
+consistent with the relative contribution to overall power variation.
+
+In this simplified representation our model becomes:
+
+Pdyn = Kd * Voltage^2 * Frequency * Utilisation
+
+Where Kd (capacitance) represents an indicative running time dynamic
+power coefficient in fundamental units of mW/MHz/uVolt^2
+
+2.2 Static power
+
+Static leakage power consumption depends on a number of factors.  For a
+given circuit implementation the primary factors are:
+
+- Time the circuit spends in each 'power state'
+- Temperature
+- Operating voltage
+- Process grade
+
+The time the circuit spends in each 'power state' for a given
+evaluation period at first order means OFF or ON.  However,
+'retention' states can also be supported that reduce power during
+inactive periods without loss of context.
+
+Note: The visibility of state entries to the OS can vary, according to
+platform specifics, and this can then impact the accuracy of a model
+based on OS state information alone.  It might be possible in some
+cases to extract more accurate information from system resources.
+
+The temperature, operating voltage and process 'grade' (slow to fast)
+of the circuit are all significant factors in static leakage power
+consumption.  All of these have complex relationships to static power.
+
+Circuit implementation specific factors include the chosen silicon
+process as well as the type, number and size of transistors in both
+the logic gates and any RAM elements included.
+
+The static power consumption modelling must take into account the
+power managed regions that are implemented.  Taking the example of an
+ARM processor cluster, the modelling would take into account whether
+each CPU can be powered OFF separately or if only a single power
+region is implemented for the complete cluster.
+
+In one view, there are others, a static power consumption model can
+then start from a set of reference values for each power managed
+region (e.g. CPU, Cluster/L2) in each state (e.g. ON, OFF) at an
+arbitrary process grade, voltage and temperature point.  These values
+are then scaled for all of the following: the time in each state, the
+process grade, the current temperature and the operating voltage.
+However, since both implementation specific and complex relationships
+dominate the estimate, the appropriate interface to the model from the
+cpu cooling device is to provide a function callback that calculates
+the static power in this platform.  When registering the cpu cooling
+device pass a function pointer that follows the `get_static_t`
+prototype:
+
+    u32 plat_get_static(cpumask_t *cpumask, unsigned long voltage);
+
+with `cpumask` a cpumask of the cpus involved in the calculation and
+`voltage` the voltage at which they are operating.
+
+If `plat_static_func` is NULL, static power is considered to be
+negligible for this platform and only dynamic power is considered.
+
+The platform specific callback can then use any combination of tables
+and/or equations to permute the estimated value.  Process grade
+information is not passed to the model since access to such data, from
+on-chip measurement capability or manufacture time data, is platform
+specific.
+
+Note: the significance of static power for CPUs in comparison to
+dynamic power is highly dependent on implementation.  Given the
+potential complexity in implementation, the importance and accuracy of
+its inclusion when using cpu cooling devices should be assessed on a
+case by cases basis.
+
diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index ad09e51ffae4..959a103d18ba 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -24,11 +24,25 @@
 #include <linux/thermal.h>
 #include <linux/cpufreq.h>
 #include <linux/err.h>
+#include <linux/pm_opp.h>
 #include <linux/slab.h>
 #include <linux/cpu.h>
 #include <linux/cpu_cooling.h>
 
 /**
+ * struct power_table - frequency to power conversion
+ * @frequency:	frequency in KHz
+ * @power:	power in mW
+ *
+ * This structure is built when the cooling device registers and helps
+ * in translating frequency to power and viceversa.
+ */
+struct power_table {
+	u32 frequency;
+	u32 power;
+};
+
+/**
  * struct cpufreq_cooling_device - data for cooling device with cpufreq
  * @id: unique integer value corresponding to each cpufreq_cooling_device
  *	registered.
@@ -39,6 +53,15 @@
  * @cpufreq_val: integer value representing the absolute value of the clipped
  *	frequency.
  * @allowed_cpus: all the cpus involved for this cpufreq_cooling_device.
+ * @last_load: load measured by the latest call to cpufreq_get_actual_power()
+ * @time_in_idle: previous reading of the absolute time that this cpu was idle
+ * @time_in_idle_timestamp: wall time of the last invocation of
+ *	get_cpu_idle_time_us()
+ * @dyn_power_table: array of struct power_table for frequency to power
+ *	conversion
+ * @dyn_power_table_entries: number of entries in the @dyn_power_table array
+ * @cpu_dev: the first cpu_device from @allowed_cpus that has OPPs registered
+ * @plat_get_static_power: callback to calculate the static power
  *
  * This structure is required for keeping information of each
  * cpufreq_cooling_device registered. In order to prevent corruption of this a
@@ -51,6 +74,13 @@ struct cpufreq_cooling_device {
 	unsigned int cpufreq_val;
 	struct cpumask allowed_cpus;
 	struct list_head node;
+	u32 last_load;
+	u64 time_in_idle[NR_CPUS];
+	u64 time_in_idle_timestamp[NR_CPUS];
+	struct power_table *dyn_power_table;
+	int dyn_power_table_entries;
+	struct device *cpu_dev;
+	get_static_t plat_get_static_power;
 };
 static DEFINE_IDR(cpufreq_idr);
 static DEFINE_MUTEX(cooling_cpufreq_lock);
@@ -338,6 +368,204 @@ static int cpufreq_thermal_notifier(struct notifier_block *nb,
 	return 0;
 }
 
+/**
+ * build_dyn_power_table() - create a dynamic power to frequency table
+ * @cpufreq_device:	the cpufreq cooling device in which to store the table
+ * @capacitance: dynamic power coefficient for these cpus
+ *
+ * Build a dynamic power to frequency table for this cpu and store it
+ * in @cpufreq_device.  This table will be used in cpu_power_to_freq() and
+ * cpu_freq_to_power() to convert between power and frequency
+ * efficiently.  Power is stored in mW, frequency in KHz.  The
+ * resulting table is in ascending order.
+ *
+ * Return: 0 on success, -E* on error.
+ */
+static int build_dyn_power_table(struct cpufreq_cooling_device *cpufreq_device,
+				u32 capacitance)
+{
+	struct power_table *power_table;
+	struct dev_pm_opp *opp;
+	struct device *dev = NULL;
+	int num_opps = 0, cpu, i, ret = 0;
+	unsigned long freq;
+
+	rcu_read_lock();
+
+	for_each_cpu(cpu, &cpufreq_device->allowed_cpus) {
+		dev = get_cpu_device(cpu);
+		if (!dev) {
+			dev_warn(&cpufreq_device->cool_dev->device,
+				"No cpu device for cpu %d\n", cpu);
+			continue;
+		}
+
+		num_opps = dev_pm_opp_get_opp_count(dev);
+		if (num_opps > 0) {
+			break;
+		} else if (num_opps < 0) {
+			ret = num_opps;
+			goto unlock;
+		}
+	}
+
+	if (num_opps == 0) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	power_table = devm_kcalloc(&cpufreq_device->cool_dev->device, num_opps,
+				sizeof(*power_table), GFP_KERNEL);
+
+	for (freq = 0, i = 0;
+	     opp = dev_pm_opp_find_freq_ceil(dev, &freq), !IS_ERR(opp);
+	     freq++, i++) {
+		u32 freq_mhz, voltage_mv;
+		u64 power;
+
+		freq_mhz = freq / 1000000;
+		voltage_mv = dev_pm_opp_get_voltage(opp) / 1000;
+
+		/*
+		 * Do the multiplication with MHz and millivolt so as
+		 * to not overflow.
+		 */
+		power = (u64)capacitance * freq_mhz * voltage_mv * voltage_mv;
+		do_div(power, 1000000000);
+
+		/* frequency is stored in power_table in KHz */
+		power_table[i].frequency = freq / 1000;
+		power_table[i].power = power;
+	}
+
+	if (i == 0) {
+		ret = PTR_ERR(opp);
+		goto unlock;
+	}
+
+	cpufreq_device->cpu_dev = dev;
+	cpufreq_device->dyn_power_table = power_table;
+	cpufreq_device->dyn_power_table_entries = i;
+
+unlock:
+	rcu_read_unlock();
+	return ret;
+}
+
+static u32 cpu_freq_to_power(struct cpufreq_cooling_device *cpufreq_device,
+			     u32 freq)
+{
+	int i;
+	struct power_table *pt = cpufreq_device->dyn_power_table;
+
+	for (i = 1; i < cpufreq_device->dyn_power_table_entries; i++)
+		if (freq < pt[i].frequency)
+			break;
+
+	return pt[i - 1].power;
+}
+
+static u32 cpu_power_to_freq(struct cpufreq_cooling_device *cpufreq_device,
+			u32 power)
+{
+	int i;
+	struct power_table *pt = cpufreq_device->dyn_power_table;
+
+	for (i = 1; i < cpufreq_device->dyn_power_table_entries; i++)
+		if (power < pt[i].power)
+			break;
+
+	return pt[i - 1].frequency;
+}
+
+/**
+ * get_load() - get load for a cpu since last updated
+ * @cpufreq_device:	&struct cpufreq_cooling_device for this cpu
+ * @cpu:	cpu number
+ *
+ * Return: The average load of cpu @cpu in percentage since this
+ * function was last called.
+ */
+static u32 get_load(struct cpufreq_cooling_device *cpufreq_device, int cpu)
+{
+	u32 load;
+	u64 now, now_idle, delta_time, delta_idle;
+
+	now_idle = get_cpu_idle_time(cpu, &now, 0);
+	delta_idle = now_idle - cpufreq_device->time_in_idle[cpu];
+	delta_time = now - cpufreq_device->time_in_idle_timestamp[cpu];
+
+	if (delta_time <= delta_idle)
+		load = 0;
+	else
+		load = div64_u64(100 * (delta_time - delta_idle), delta_time);
+
+	cpufreq_device->time_in_idle[cpu] = now_idle;
+	cpufreq_device->time_in_idle_timestamp[cpu] = now;
+
+	return load;
+}
+
+/**
+ * get_static_power() - calculate the static power consumed by the cpus
+ * @cpufreq_device:	struct &cpufreq_cooling_device for this cpu cdev
+ * @freq:	frequency in KHz
+ *
+ * Calculate the static power consumed by the cpus described by
+ * @cpu_actor running at frequency @freq.  This function relies on a
+ * platform specific function that should have been provided when the
+ * actor was registered.  If it wasn't, the static power is assumed to
+ * be negligible.
+ *
+ * Return: The static power consumed by the cpus.  It returns 0 on
+ * error or if there is no plat_get_static_power().
+ */
+static u32 get_static_power(struct cpufreq_cooling_device *cpufreq_device,
+			unsigned long freq)
+{
+	struct dev_pm_opp *opp;
+	unsigned long voltage;
+	struct cpumask *cpumask = &cpufreq_device->allowed_cpus;
+	unsigned long freq_hz = freq * 1000;
+
+	if (!cpufreq_device->plat_get_static_power)
+		return 0;
+
+	rcu_read_lock();
+
+	opp = dev_pm_opp_find_freq_exact(cpufreq_device->cpu_dev, freq_hz,
+					true);
+	voltage = dev_pm_opp_get_voltage(opp);
+
+	rcu_read_unlock();
+
+	if (voltage == 0) {
+		dev_warn_ratelimited(cpufreq_device->cpu_dev,
+				"Failed to get voltage for frequency %lu: %ld\n",
+				freq_hz, IS_ERR(opp) ? PTR_ERR(opp) : 0);
+		return 0;
+	}
+
+	return cpufreq_device->plat_get_static_power(cpumask, voltage);
+}
+
+/**
+ * get_dynamic_power() - calculate the dynamic power
+ * @cpufreq_device:	&cpufreq_cooling_device for this cdev
+ * @freq:	current frequency
+ *
+ * Return: the dynamic power consumed by the cpus described by
+ * @cpufreq_device.
+ */
+static u32 get_dynamic_power(struct cpufreq_cooling_device *cpufreq_device,
+			unsigned long freq)
+{
+	u32 raw_cpu_power;
+
+	raw_cpu_power = cpu_freq_to_power(cpufreq_device, freq);
+	return (raw_cpu_power * cpufreq_device->last_load) / 100;
+}
+
 /* cpufreq cooling device callback functions are defined below */
 
 /**
@@ -407,8 +635,106 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
 	return cpufreq_apply_cooling(cpufreq_device, state);
 }
 
+/**
+ * cpufreq_get_actual_power() - get the current power
+ * @cdev:	&thermal_cooling_device pointer
+ *
+ * Return the current power consumption of the cpus in milliwatts.
+ */
+static u32 cpufreq_get_actual_power(struct thermal_cooling_device *cdev)
+{
+	unsigned long freq;
+	int cpu;
+	u32 static_power, dynamic_power, total_load = 0;
+	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
+
+	freq = cpufreq_quick_get(cpumask_any(&cpufreq_device->allowed_cpus));
+
+	for_each_cpu(cpu, &cpufreq_device->allowed_cpus) {
+		u32 load;
+
+		if (cpu_online(cpu))
+			load = get_load(cpufreq_device, cpu);
+		else
+			load = 0;
+
+		total_load += load;
+	}
+
+	cpufreq_device->last_load = total_load;
+
+	static_power = get_static_power(cpufreq_device, freq);
+	dynamic_power = get_dynamic_power(cpufreq_device, freq);
+
+	return static_power + dynamic_power;
+}
+
+/**
+ * cpufreq_state2power() - convert a cpu cdev state to power consumed
+ * @cdev:	&thermal_cooling_device pointer
+ * @state:	cooling device state to be converted
+ *
+ * Convert cooling device state @state into power consumption in milliwatts.
+ */
+static u32 cpufreq_state2power(struct thermal_cooling_device *cdev,
+			unsigned long state)
+{
+	unsigned int freq, num_cpus;
+	cpumask_t cpumask;
+	u32 static_power, dynamic_power;
+	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
+
+	cpumask_and(&cpumask, &cpufreq_device->allowed_cpus, cpu_online_mask);
+	num_cpus = cpumask_weight(&cpumask);
+
+	freq = get_cpu_frequency(cpumask_any(&cpumask), state);
+	if (!freq)
+		return 0;
+
+	static_power = get_static_power(cpufreq_device, freq);
+	dynamic_power = cpu_freq_to_power(cpufreq_device, freq) * num_cpus;
+
+	return static_power + dynamic_power;
+}
+
+/**
+ * cpufreq_power2state() - convert power to a cooling device state
+ * @cdev:	&thermal_cooling_device pointer
+ * @power:	power in milliwatts to be converted
+ *
+ * Calculate a cooling device state for the cpus described by @cdev
+ * that would allow them to consume at most @power mW.
+ */
+static unsigned long cpufreq_power2state(struct thermal_cooling_device *cdev,
+					u32 power)
+{
+	unsigned int cpu, cur_freq, target_freq;
+	s32 dyn_power;
+	u32 last_load, normalised_power;
+	unsigned long cdev_state;
+	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
+
+	cpu = cpumask_any_and(&cpufreq_device->allowed_cpus, cpu_online_mask);
+
+	cur_freq = cpufreq_quick_get(cpu);
+	dyn_power = power - get_static_power(cpufreq_device, cur_freq);
+	dyn_power = dyn_power > 0 ? dyn_power : 0;
+	last_load = cpufreq_device->last_load ?: 1;
+	normalised_power = (dyn_power * 100) / last_load;
+	target_freq = cpu_power_to_freq(cpufreq_device, normalised_power);
+
+	cdev_state = cpufreq_cooling_get_level(cpu, target_freq);
+	if (cdev_state == THERMAL_CSTATE_INVALID) {
+		pr_err_ratelimited("Failed to convert %dKHz for cpu %d into a cdev state\n",
+				target_freq, cpu);
+		return 0;
+	}
+
+	return cdev_state;
+}
+
 /* Bind cpufreq callbacks to thermal cooling device ops */
-static struct thermal_cooling_device_ops const cpufreq_cooling_ops = {
+static struct thermal_cooling_device_ops cpufreq_cooling_ops = {
 	.get_max_state = cpufreq_get_max_state,
 	.get_cur_state = cpufreq_get_cur_state,
 	.set_cur_state = cpufreq_set_cur_state,
@@ -434,7 +760,8 @@ static struct notifier_block thermal_cpufreq_notifier_block = {
  */
 static struct thermal_cooling_device *
 __cpufreq_cooling_register(struct device_node *np,
-			   const struct cpumask *clip_cpus)
+			const struct cpumask *clip_cpus, u32 capacitance,
+			get_static_t plat_static_func)
 {
 	struct thermal_cooling_device *cool_dev;
 	struct cpufreq_cooling_device *cpufreq_dev = NULL;
@@ -464,10 +791,23 @@ __cpufreq_cooling_register(struct device_node *np,
 
 	cpumask_copy(&cpufreq_dev->allowed_cpus, clip_cpus);
 
+	if (capacitance) {
+		cpufreq_cooling_ops.get_actual_power = cpufreq_get_actual_power;
+		cpufreq_cooling_ops.state2power = cpufreq_state2power;
+		cpufreq_cooling_ops.power2state = cpufreq_power2state;
+		cpufreq_dev->plat_get_static_power = plat_static_func;
+
+		ret = build_dyn_power_table(cpufreq_dev, capacitance);
+		if (ret) {
+			cool_dev = ERR_PTR(ret);
+			goto free;
+		}
+	}
+
 	ret = get_idr(&cpufreq_idr, &cpufreq_dev->id);
 	if (ret) {
-		kfree(cpufreq_dev);
-		return ERR_PTR(-EINVAL);
+		cool_dev = ERR_PTR(-EINVAL);
+		goto free;
 	}
 
 	snprintf(dev_name, sizeof(dev_name), "thermal-cpufreq-%d",
@@ -475,11 +815,8 @@ __cpufreq_cooling_register(struct device_node *np,
 
 	cool_dev = thermal_of_cooling_device_register(np, dev_name, cpufreq_dev,
 						      &cpufreq_cooling_ops);
-	if (IS_ERR(cool_dev)) {
-		release_idr(&cpufreq_idr, cpufreq_dev->id);
-		kfree(cpufreq_dev);
-		return cool_dev;
-	}
+	if (IS_ERR(cool_dev))
+		goto release_idr;
 	cpufreq_dev->cool_dev = cool_dev;
 	cpufreq_dev->cpufreq_state = 0;
 	mutex_lock(&cooling_cpufreq_lock);
@@ -494,6 +831,12 @@ __cpufreq_cooling_register(struct device_node *np,
 	mutex_unlock(&cooling_cpufreq_lock);
 
 	return cool_dev;
+
+release_idr:
+	release_idr(&cpufreq_idr, cpufreq_dev->id);
+free:
+	kfree(cpufreq_dev);
+	return cool_dev;
 }
 
 /**
@@ -510,7 +853,7 @@ __cpufreq_cooling_register(struct device_node *np,
 struct thermal_cooling_device *
 cpufreq_cooling_register(const struct cpumask *clip_cpus)
 {
-	return __cpufreq_cooling_register(NULL, clip_cpus);
+	return __cpufreq_cooling_register(NULL, clip_cpus, 0, NULL);
 }
 EXPORT_SYMBOL_GPL(cpufreq_cooling_register);
 
@@ -534,11 +877,77 @@ of_cpufreq_cooling_register(struct device_node *np,
 	if (!np)
 		return ERR_PTR(-EINVAL);
 
-	return __cpufreq_cooling_register(np, clip_cpus);
+	return __cpufreq_cooling_register(np, clip_cpus, 0, NULL);
 }
 EXPORT_SYMBOL_GPL(of_cpufreq_cooling_register);
 
 /**
+ * cpufreq_power_cooling_register() - create cpufreq cooling device with power extensions
+ * @clip_cpus:	cpumask of cpus where the frequency constraints will happen
+ * @capacitance:	dynamic power coefficient for these cpus
+ * @plat_static_func:	function to calculate the static power consumed by these
+ *			cpus (optional)
+ *
+ * This interface function registers the cpufreq cooling device with
+ * the name "thermal-cpufreq-%x".  This api can support multiple
+ * instances of cpufreq cooling devices.  Using this function, the
+ * cooling device will implement the power extensions by using a
+ * simple cpu power model.  The cpus must have registered their OPPs
+ * using the OPP library.
+ *
+ * An optional @plat_static_func may be provided to calculate the
+ * static power consumed by these cpus.  If the platform's static
+ * power consumption is unknown or negligible, make it NULL.
+ *
+ * Return: a valid struct thermal_cooling_device pointer on success,
+ * on failure, it returns a corresponding ERR_PTR().
+ */
+struct thermal_cooling_device *
+cpufreq_power_cooling_register(const struct cpumask *clip_cpus, u32 capacitance,
+			get_static_t plat_static_func)
+{
+	return __cpufreq_cooling_register(NULL, clip_cpus, capacitance,
+				plat_static_func);
+}
+EXPORT_SYMBOL(cpufreq_power_cooling_register);
+
+/**
+ * of_cpufreq_power_cooling_register() - create cpufreq cooling device with power extensions
+ * @np:	a valid struct device_node to the cooling device device tree node
+ * @clip_cpus:	cpumask of cpus where the frequency constraints will happen
+ * @capacitance:	dynamic power coefficient for these cpus
+ * @plat_static_func:	function to calculate the static power consumed by these
+ *			cpus (optional)
+ *
+ * This interface function registers the cpufreq cooling device with
+ * the name "thermal-cpufreq-%x".  This api can support multiple
+ * instances of cpufreq cooling devices.  Using this API, the cpufreq
+ * cooling device will be linked to the device tree node provided.
+ * Using this function, the cooling device will implement the power
+ * extensions by using a simple cpu power model.  The cpus must have
+ * registered their OPPs using the OPP library.
+ *
+ * An optional @plat_static_func may be provided to calculate the
+ * static power consumed by these cpus.  If the platform's static
+ * power consumption is unknown or negligible, make it NULL.
+ *
+ * Return: a valid struct thermal_cooling_device pointer on success,
+ * on failure, it returns a corresponding ERR_PTR().
+ */
+struct thermal_cooling_device *
+of_cpufreq_power_cooling_register(struct device_node *np,
+			const struct cpumask *clip_cpus, u32 capacitance,
+			get_static_t plat_static_func)
+{
+	if (!np)
+		return ERR_PTR(-EINVAL);
+
+	return __cpufreq_cooling_register(np, clip_cpus, capacitance,
+				plat_static_func);
+}
+EXPORT_SYMBOL(of_cpufreq_power_cooling_register);
+
+/**
  * cpufreq_cooling_unregister - function to remove cpufreq cooling device.
  * @cdev: thermal cooling device pointer.
  *
diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
index c303d383def1..5c4f4567acf0 100644
--- a/include/linux/cpu_cooling.h
+++ b/include/linux/cpu_cooling.h
@@ -28,6 +28,8 @@
 #include <linux/thermal.h>
 #include <linux/cpumask.h>
 
+typedef u32 (*get_static_t)(cpumask_t *cpumask, unsigned long voltage);
+
 #ifdef CONFIG_CPU_THERMAL
 /**
  * cpufreq_cooling_register - function to create cpufreq cooling device.
@@ -37,14 +39,38 @@ struct thermal_cooling_device *
 cpufreq_cooling_register(const struct cpumask *clip_cpus);
 
 /**
+ * cpufreq_power_cooling_register() - create cpufreq cooling device with power extensions
+ * @clip_cpus: cpumask of cpus where the frequency constraints will happen
+ * @capacitance:	dynamic power coefficient for these cpus
+ * @plat_static_func:	function to calculate the static power consumed by these
+ *			cpus (optional)
+ */
+struct thermal_cooling_device *
+cpufreq_power_cooling_register(const struct cpumask *clip_cpus,
+			u32 capacitance, get_static_t plat_static_func);
+
+#ifdef CONFIG_THERMAL_OF
+/**
  * of_cpufreq_cooling_register - create cpufreq cooling device based on DT.
  * @np: a valid struct device_node to the cooling device device tree node.
  * @clip_cpus: cpumask of cpus where the frequency constraints will happen
  */
-#ifdef CONFIG_THERMAL_OF
 struct thermal_cooling_device *
 of_cpufreq_cooling_register(struct device_node *np,
 			    const struct cpumask *clip_cpus);
+
+/**
+ * of_cpufreq_power_cooling_register() - create cpufreq cooling device with power extensions
+ * @np:	a valid struct device_node to the cooling device device tree node
+ * @clip_cpus:	cpumask of cpus where the frequency constraints will happen
+ * @capacitance:	dynamic power coefficient for these cpus
+ * @plat_static_func:	function to calculate the static power consumed by these
+ *			cpus (optional)
+ */
+struct thermal_cooling_device *
+of_cpufreq_power_cooling_register(struct device_node *np,
+				const struct cpumask *clip_cpus,
+				u32 capacitance, get_static_t plat_static_func);
 #else
 static inline struct thermal_cooling_device *
 of_cpufreq_cooling_register(struct device_node *np,
@@ -52,6 +78,14 @@ of_cpufreq_cooling_register(struct device_node *np,
 {
 	return NULL;
 }
+
+struct thermal_cooling_device *
+of_cpufreq_power_cooling_register(struct device_node *np,
+				const struct cpumask *clip_cpus,
+				u32 capacitance, get_static_t plat_static_func)
+{
+	return NULL;
+}
 #endif
 
 /**
@@ -68,11 +102,24 @@ cpufreq_cooling_register(const struct cpumask *clip_cpus)
 	return NULL;
 }
 static inline struct thermal_cooling_device *
+cpufreq_power_cooling_register(const struct cpumask *clip_cpus,
+			u32 capacitance, get_static_t plat_static_func)
+{
+	return NULL;
+}
+static inline struct thermal_cooling_device *
 of_cpufreq_cooling_register(struct device_node *np,
 			    const struct cpumask *clip_cpus)
 {
 	return NULL;
 }
+static inline struct thermal_cooling_device *
+of_cpufreq_power_cooling_register(struct device_node *np,
+				const struct cpumask *clip_cpus,
+				u32 capacitance, get_static_t plat_static_func)
+{
+	return NULL;
+}
 static inline
 void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
 {

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