1 // SPDX-License-Identifier: GPL-2.0
3 * Energy Model of devices
5 * Copyright (c) 2018-2020, Arm ltd.
6 * Written by: Quentin Perret, Arm ltd.
7 * Improvements provided by: Lukasz Luba, Arm ltd.
10 #define pr_fmt(fmt) "energy_model: " fmt
12 #include <linux/cpu.h>
13 #include <linux/cpumask.h>
14 #include <linux/debugfs.h>
15 #include <linux/energy_model.h>
16 #include <linux/sched/topology.h>
17 #include <linux/slab.h>
20 * Mutex serializing the registrations of performance domains and letting
21 * callbacks defined by drivers sleep.
23 static DEFINE_MUTEX(em_pd_mutex);
25 static bool _is_cpu_device(struct device *dev)
27 return (dev->bus == &cpu_subsys);
30 #ifdef CONFIG_DEBUG_FS
31 static struct dentry *rootdir;
33 static void em_debug_create_ps(struct em_perf_state *ps, struct dentry *pd)
38 snprintf(name, sizeof(name), "ps:%lu", ps->frequency);
40 /* Create per-ps directory */
41 d = debugfs_create_dir(name, pd);
42 debugfs_create_ulong("frequency", 0444, d, &ps->frequency);
43 debugfs_create_ulong("power", 0444, d, &ps->power);
44 debugfs_create_ulong("cost", 0444, d, &ps->cost);
47 static int em_debug_cpus_show(struct seq_file *s, void *unused)
49 seq_printf(s, "%*pbl\n", cpumask_pr_args(to_cpumask(s->private)));
53 DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);
55 static void em_debug_create_pd(struct device *dev)
60 /* Create the directory of the performance domain */
61 d = debugfs_create_dir(dev_name(dev), rootdir);
63 if (_is_cpu_device(dev))
64 debugfs_create_file("cpus", 0444, d, dev->em_pd->cpus,
67 /* Create a sub-directory for each performance state */
68 for (i = 0; i < dev->em_pd->nr_perf_states; i++)
69 em_debug_create_ps(&dev->em_pd->table[i], d);
73 static void em_debug_remove_pd(struct device *dev)
75 struct dentry *debug_dir;
77 debug_dir = debugfs_lookup(dev_name(dev), rootdir);
78 debugfs_remove_recursive(debug_dir);
81 static int __init em_debug_init(void)
83 /* Create /sys/kernel/debug/energy_model directory */
84 rootdir = debugfs_create_dir("energy_model", NULL);
88 core_initcall(em_debug_init);
89 #else /* CONFIG_DEBUG_FS */
90 static void em_debug_create_pd(struct device *dev) {}
91 static void em_debug_remove_pd(struct device *dev) {}
94 static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
95 int nr_states, struct em_data_callback *cb)
97 unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
98 unsigned long power, freq, prev_freq = 0;
99 struct em_perf_state *table;
103 table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
107 /* Build the list of performance states for this performance domain */
108 for (i = 0, freq = 0; i < nr_states; i++, freq++) {
110 * active_power() is a driver callback which ceils 'freq' to
111 * lowest performance state of 'dev' above 'freq' and updates
112 * 'power' and 'freq' accordingly.
114 ret = cb->active_power(&power, &freq, dev);
116 dev_err(dev, "EM: invalid perf. state: %d\n",
122 * We expect the driver callback to increase the frequency for
123 * higher performance states.
125 if (freq <= prev_freq) {
126 dev_err(dev, "EM: non-increasing freq: %lu\n",
132 * The power returned by active_state() is expected to be
133 * positive, in milli-watts and to fit into 16 bits.
135 if (!power || power > EM_MAX_POWER) {
136 dev_err(dev, "EM: invalid power: %lu\n",
141 table[i].power = power;
142 table[i].frequency = prev_freq = freq;
145 * The hertz/watts efficiency ratio should decrease as the
146 * frequency grows on sane platforms. But this isn't always
147 * true in practice so warn the user if a higher OPP is more
148 * power efficient than a lower one.
150 opp_eff = freq / power;
151 if (opp_eff >= prev_opp_eff)
152 dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
154 prev_opp_eff = opp_eff;
157 /* Compute the cost of each performance state. */
158 fmax = (u64) table[nr_states - 1].frequency;
159 for (i = 0; i < nr_states; i++) {
160 table[i].cost = div64_u64(fmax * table[i].power,
165 pd->nr_perf_states = nr_states;
174 static int em_create_pd(struct device *dev, int nr_states,
175 struct em_data_callback *cb, cpumask_t *cpus)
177 struct em_perf_domain *pd;
178 struct device *cpu_dev;
181 if (_is_cpu_device(dev)) {
182 pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
186 cpumask_copy(em_span_cpus(pd), cpus);
188 pd = kzalloc(sizeof(*pd), GFP_KERNEL);
193 ret = em_create_perf_table(dev, pd, nr_states, cb);
199 if (_is_cpu_device(dev))
200 for_each_cpu(cpu, cpus) {
201 cpu_dev = get_cpu_device(cpu);
211 * em_pd_get() - Return the performance domain for a device
212 * @dev : Device to find the performance domain for
214 * Returns the performance domain to which @dev belongs, or NULL if it doesn't
217 struct em_perf_domain *em_pd_get(struct device *dev)
219 if (IS_ERR_OR_NULL(dev))
224 EXPORT_SYMBOL_GPL(em_pd_get);
227 * em_cpu_get() - Return the performance domain for a CPU
228 * @cpu : CPU to find the performance domain for
230 * Returns the performance domain to which @cpu belongs, or NULL if it doesn't
233 struct em_perf_domain *em_cpu_get(int cpu)
235 struct device *cpu_dev;
237 cpu_dev = get_cpu_device(cpu);
241 return em_pd_get(cpu_dev);
243 EXPORT_SYMBOL_GPL(em_cpu_get);
246 * em_dev_register_perf_domain() - Register the Energy Model (EM) for a device
247 * @dev : Device for which the EM is to register
248 * @nr_states : Number of performance states to register
249 * @cb : Callback functions providing the data of the Energy Model
250 * @cpus : Pointer to cpumask_t, which in case of a CPU device is
251 * obligatory. It can be taken from i.e. 'policy->cpus'. For other
252 * type of devices this should be set to NULL.
254 * Create Energy Model tables for a performance domain using the callbacks
257 * If multiple clients register the same performance domain, all but the first
258 * registration will be ignored.
260 * Return 0 on success
262 int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
263 struct em_data_callback *cb, cpumask_t *cpus)
265 unsigned long cap, prev_cap = 0;
268 if (!dev || !nr_states || !cb)
272 * Use a mutex to serialize the registration of performance domains and
273 * let the driver-defined callback functions sleep.
275 mutex_lock(&em_pd_mutex);
282 if (_is_cpu_device(dev)) {
284 dev_err(dev, "EM: invalid CPU mask\n");
289 for_each_cpu(cpu, cpus) {
290 if (em_cpu_get(cpu)) {
291 dev_err(dev, "EM: exists for CPU%d\n", cpu);
296 * All CPUs of a domain must have the same
297 * micro-architecture since they all share the same
300 cap = arch_scale_cpu_capacity(cpu);
301 if (prev_cap && prev_cap != cap) {
302 dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n",
303 cpumask_pr_args(cpus));
312 ret = em_create_pd(dev, nr_states, cb, cpus);
316 em_debug_create_pd(dev);
317 dev_info(dev, "EM: created perf domain\n");
320 mutex_unlock(&em_pd_mutex);
323 EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
326 * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
327 * @dev : Device for which the EM is registered
329 * Unregister the EM for the specified @dev (but not a CPU device).
331 void em_dev_unregister_perf_domain(struct device *dev)
333 if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
336 if (_is_cpu_device(dev))
340 * The mutex separates all register/unregister requests and protects
341 * from potential clean-up/setup issues in the debugfs directories.
342 * The debugfs directory name is the same as device's name.
344 mutex_lock(&em_pd_mutex);
345 em_debug_remove_pd(dev);
347 kfree(dev->em_pd->table);
350 mutex_unlock(&em_pd_mutex);
352 EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);