Documentation/power/energy-model.rst

1 .. SPDX-License-Identifier: GPL-2.0
8 -----------
12 subsystems willing to use that information to make energy-aware decisions.
18 each and every client subsystem to re-implement support for each and every
23 The figure below depicts an example of drivers (Arm-specific here, but the
27        +---------------+  +-----------------+  +---------------+
29        +---------------+  +-----------------+  +---------------+
32                +---------+         |         +---------+
35                         +---------------------+
38                         +---------------------+
41                 +----------+       |       +---------+
43         +---------------+  +---------------+  +--------------+
44         |  cpufreq-dt   |  |   arm_scmi    |  |    Other     |
45         +---------------+  +---------------+  +--------------+
48         +--------------+   +---------------+  +--------------+
50         +--------------+   +---------------+  +--------------+
53 'performance domain' in the system. A performance domain is a group of CPUs
55 1-to-1 mapping with CPUFreq policies. All CPUs in a performance domain are
56 required to have the same micro-architecture. CPUs in different performance
57 domains can have different micro-architectures.
61 ------------
96 performance domain.
102 The energy consumed by a performance domain can be estimated using the
111 -----------------
114 performance domain in the Energy Model framework using the (fake) 'foo'
118   -> drivers/cpufreq/foo_cpufreq.c
123   04		long freq, power;
126   07		freq = foo_get_freq_ceil(dev, *KHz);
127   08		if (freq < 0);
128   09			return freq;
130   11		/* Estimate the power cost for the dev at the relevant freq. */
131   12		power = foo_estimate_power(dev, freq);
137   18		*KHz = freq;
148   29		cpu_dev = get_cpu_device(cpumask_first(policy->cpus));
158   39     	/* And register the new performance domain */
159   40     	em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, policy->cpus);