223 lines
7.1 KiB
C
223 lines
7.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_ENERGY_MODEL_H
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#define _LINUX_ENERGY_MODEL_H
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#include <linux/cpumask.h>
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#include <linux/device.h>
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#include <linux/jump_label.h>
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#include <linux/kobject.h>
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#include <linux/rcupdate.h>
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#include <linux/sched/cpufreq.h>
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#include <linux/sched/topology.h>
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#include <linux/types.h>
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/**
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* em_perf_state - Performance state of a performance domain
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* @frequency: The frequency in KHz, for consistency with CPUFreq
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* @power: The power consumed at this level (by 1 CPU or by a registered
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* device). It can be a total power: static and dynamic.
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* @cost: The cost coefficient associated with this level, used during
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* energy calculation. Equal to: power * max_frequency / frequency
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*/
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struct em_perf_state {
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unsigned long frequency;
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unsigned long power;
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unsigned long cost;
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};
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/**
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* em_perf_domain - Performance domain
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* @table: List of performance states, in ascending order
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* @nr_perf_states: Number of performance states
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* @milliwatts: Flag indicating the power values are in milli-Watts
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* or some other scale.
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* @cpus: Cpumask covering the CPUs of the domain. It's here
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* for performance reasons to avoid potential cache
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* misses during energy calculations in the scheduler
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* and simplifies allocating/freeing that memory region.
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*
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* In case of CPU device, a "performance domain" represents a group of CPUs
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* whose performance is scaled together. All CPUs of a performance domain
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* must have the same micro-architecture. Performance domains often have
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* a 1-to-1 mapping with CPUFreq policies. In case of other devices the @cpus
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* field is unused.
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*/
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struct em_perf_domain {
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struct em_perf_state *table;
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int nr_perf_states;
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int milliwatts;
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unsigned long cpus[];
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};
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#define em_span_cpus(em) (to_cpumask((em)->cpus))
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#ifdef CONFIG_ENERGY_MODEL
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#define EM_MAX_POWER 0xFFFF
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struct em_data_callback {
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/**
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* active_power() - Provide power at the next performance state of
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* a device
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* @power : Active power at the performance state
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* (modified)
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* @freq : Frequency at the performance state in kHz
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* (modified)
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* @dev : Device for which we do this operation (can be a CPU)
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*
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* active_power() must find the lowest performance state of 'dev' above
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* 'freq' and update 'power' and 'freq' to the matching active power
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* and frequency.
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*
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* In case of CPUs, the power is the one of a single CPU in the domain,
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* expressed in milli-Watts or an abstract scale. It is expected to
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* fit in the [0, EM_MAX_POWER] range.
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*
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* Return 0 on success.
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*/
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int (*active_power)(unsigned long *power, unsigned long *freq,
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struct device *dev);
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};
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#define EM_DATA_CB(_active_power_cb) { .active_power = &_active_power_cb }
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struct em_perf_domain *em_cpu_get(int cpu);
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struct em_perf_domain *em_pd_get(struct device *dev);
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int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
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struct em_data_callback *cb, cpumask_t *span,
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bool milliwatts);
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void em_dev_unregister_perf_domain(struct device *dev);
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/**
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* em_cpu_energy() - Estimates the energy consumed by the CPUs of a
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performance domain
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* @pd : performance domain for which energy has to be estimated
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* @max_util : highest utilization among CPUs of the domain
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* @sum_util : sum of the utilization of all CPUs in the domain
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*
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* This function must be used only for CPU devices. There is no validation,
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* i.e. if the EM is a CPU type and has cpumask allocated. It is called from
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* the scheduler code quite frequently and that is why there is not checks.
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*
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* Return: the sum of the energy consumed by the CPUs of the domain assuming
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* a capacity state satisfying the max utilization of the domain.
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*/
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static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
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unsigned long max_util, unsigned long sum_util)
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{
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unsigned long freq, scale_cpu;
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struct em_perf_state *ps;
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int i, cpu;
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if (!sum_util)
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return 0;
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/*
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* In order to predict the performance state, map the utilization of
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* the most utilized CPU of the performance domain to a requested
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* frequency, like schedutil.
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*/
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cpu = cpumask_first(to_cpumask(pd->cpus));
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scale_cpu = arch_scale_cpu_capacity(cpu);
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ps = &pd->table[pd->nr_perf_states - 1];
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freq = map_util_freq(max_util, ps->frequency, scale_cpu);
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/*
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* Find the lowest performance state of the Energy Model above the
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* requested frequency.
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*/
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for (i = 0; i < pd->nr_perf_states; i++) {
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ps = &pd->table[i];
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if (ps->frequency >= freq)
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break;
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}
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/*
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* The capacity of a CPU in the domain at the performance state (ps)
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* can be computed as:
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*
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* ps->freq * scale_cpu
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* ps->cap = -------------------- (1)
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* cpu_max_freq
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*
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* So, ignoring the costs of idle states (which are not available in
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* the EM), the energy consumed by this CPU at that performance state
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* is estimated as:
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*
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* ps->power * cpu_util
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* cpu_nrg = -------------------- (2)
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* ps->cap
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*
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* since 'cpu_util / ps->cap' represents its percentage of busy time.
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*
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* NOTE: Although the result of this computation actually is in
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* units of power, it can be manipulated as an energy value
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* over a scheduling period, since it is assumed to be
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* constant during that interval.
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*
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* By injecting (1) in (2), 'cpu_nrg' can be re-expressed as a product
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* of two terms:
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*
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* ps->power * cpu_max_freq cpu_util
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* cpu_nrg = ------------------------ * --------- (3)
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* ps->freq scale_cpu
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*
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* The first term is static, and is stored in the em_perf_state struct
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* as 'ps->cost'.
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*
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* Since all CPUs of the domain have the same micro-architecture, they
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* share the same 'ps->cost', and the same CPU capacity. Hence, the
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* total energy of the domain (which is the simple sum of the energy of
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* all of its CPUs) can be factorized as:
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*
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* ps->cost * \Sum cpu_util
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* pd_nrg = ------------------------ (4)
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* scale_cpu
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*/
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return ps->cost * sum_util / scale_cpu;
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}
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/**
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* em_pd_nr_perf_states() - Get the number of performance states of a perf.
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* domain
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* @pd : performance domain for which this must be done
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*
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* Return: the number of performance states in the performance domain table
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*/
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static inline int em_pd_nr_perf_states(struct em_perf_domain *pd)
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{
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return pd->nr_perf_states;
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}
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#else
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struct em_data_callback {};
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#define EM_DATA_CB(_active_power_cb) { }
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static inline
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int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
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struct em_data_callback *cb, cpumask_t *span,
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bool milliwatts)
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{
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return -EINVAL;
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}
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static inline void em_dev_unregister_perf_domain(struct device *dev)
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{
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}
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static inline struct em_perf_domain *em_cpu_get(int cpu)
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{
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return NULL;
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}
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static inline struct em_perf_domain *em_pd_get(struct device *dev)
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{
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return NULL;
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}
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static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
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unsigned long max_util, unsigned long sum_util)
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{
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return 0;
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}
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static inline int em_pd_nr_perf_states(struct em_perf_domain *pd)
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{
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return 0;
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}
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#endif
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#endif
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