1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Energy Model of devices
  4 *
  5 * Copyright (c) 2018-2021, Arm ltd.
  6 * Written by: Quentin Perret, Arm ltd.
  7 * Improvements provided by: Lukasz Luba, Arm ltd.
  8 */
  9
 10#define pr_fmt(fmt) "energy_model: " fmt
 11
 12#include <linux/cpu.h>
 13#include <linux/cpufreq.h>
 14#include <linux/cpumask.h>
 15#include <linux/debugfs.h>
 16#include <linux/energy_model.h>
 17#include <linux/sched/topology.h>
 18#include <linux/slab.h>
 19
 20/*
 21 * Mutex serializing the registrations of performance domains and letting
 22 * callbacks defined by drivers sleep.
 23 */
 24static DEFINE_MUTEX(em_pd_mutex);
 25
 26static bool _is_cpu_device(struct device *dev)
 27{
 28	return (dev->bus == &cpu_subsys);
 29}
 30
 31#ifdef CONFIG_DEBUG_FS
 32static struct dentry *rootdir;
 33
 34static void em_debug_create_ps(struct em_perf_state *ps, struct dentry *pd)
 35{
 36	struct dentry *d;
 37	char name[24];
 38
 39	snprintf(name, sizeof(name), "ps:%lu", ps->frequency);
 40
 41	/* Create per-ps directory */
 42	d = debugfs_create_dir(name, pd);
 43	debugfs_create_ulong("frequency", 0444, d, &ps->frequency);
 44	debugfs_create_ulong("power", 0444, d, &ps->power);
 45	debugfs_create_ulong("cost", 0444, d, &ps->cost);
 46	debugfs_create_ulong("inefficient", 0444, d, &ps->flags);
 47}
 48
 49static int em_debug_cpus_show(struct seq_file *s, void *unused)
 50{
 51	seq_printf(s, "%*pbl\n", cpumask_pr_args(to_cpumask(s->private)));
 52
 53	return 0;
 54}
 55DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);
 56
 57static int em_debug_flags_show(struct seq_file *s, void *unused)
 58{
 59	struct em_perf_domain *pd = s->private;
 60
 61	seq_printf(s, "%#lx\n", pd->flags);
 62
 63	return 0;
 64}
 65DEFINE_SHOW_ATTRIBUTE(em_debug_flags);
 66
 67static void em_debug_create_pd(struct device *dev)
 68{
 69	struct dentry *d;
 70	int i;
 71
 72	/* Create the directory of the performance domain */
 73	d = debugfs_create_dir(dev_name(dev), rootdir);
 74
 75	if (_is_cpu_device(dev))
 76		debugfs_create_file("cpus", 0444, d, dev->em_pd->cpus,
 77				    &em_debug_cpus_fops);
 78
 79	debugfs_create_file("flags", 0444, d, dev->em_pd,
 80			    &em_debug_flags_fops);
 81
 82	/* Create a sub-directory for each performance state */
 83	for (i = 0; i < dev->em_pd->nr_perf_states; i++)
 84		em_debug_create_ps(&dev->em_pd->table[i], d);
 85
 86}
 87
 88static void em_debug_remove_pd(struct device *dev)
 89{
 90	debugfs_lookup_and_remove(dev_name(dev), rootdir);
 91}
 92
 93static int __init em_debug_init(void)
 94{
 95	/* Create /sys/kernel/debug/energy_model directory */
 96	rootdir = debugfs_create_dir("energy_model", NULL);
 97
 98	return 0;
 99}
100fs_initcall(em_debug_init);
101#else /* CONFIG_DEBUG_FS */
102static void em_debug_create_pd(struct device *dev) {}
103static void em_debug_remove_pd(struct device *dev) {}
104#endif
105
106static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
107				int nr_states, struct em_data_callback *cb,
108				unsigned long flags)
109{
110	unsigned long power, freq, prev_freq = 0, prev_cost = ULONG_MAX;
111	struct em_perf_state *table;
112	int i, ret;
113	u64 fmax;
114
115	table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
116	if (!table)
117		return -ENOMEM;
118
119	/* Build the list of performance states for this performance domain */
120	for (i = 0, freq = 0; i < nr_states; i++, freq++) {
121		/*
122		 * active_power() is a driver callback which ceils 'freq' to
123		 * lowest performance state of 'dev' above 'freq' and updates
124		 * 'power' and 'freq' accordingly.
125		 */
126		ret = cb->active_power(dev, &power, &freq);
127		if (ret) {
128			dev_err(dev, "EM: invalid perf. state: %d\n",
129				ret);
130			goto free_ps_table;
131		}
132
133		/*
134		 * We expect the driver callback to increase the frequency for
135		 * higher performance states.
136		 */
137		if (freq <= prev_freq) {
138			dev_err(dev, "EM: non-increasing freq: %lu\n",
139				freq);
140			goto free_ps_table;
141		}
142
143		/*
144		 * The power returned by active_state() is expected to be
145		 * positive and be in range.
146		 */
147		if (!power || power > EM_MAX_POWER) {
148			dev_err(dev, "EM: invalid power: %lu\n",
149				power);
150			goto free_ps_table;
151		}
152
153		table[i].power = power;
154		table[i].frequency = prev_freq = freq;
155	}
156
157	/* Compute the cost of each performance state. */
158	fmax = (u64) table[nr_states - 1].frequency;
159	for (i = nr_states - 1; i >= 0; i--) {
160		unsigned long power_res, cost;
161
162		if (flags & EM_PERF_DOMAIN_ARTIFICIAL) {
163			ret = cb->get_cost(dev, table[i].frequency, &cost);
164			if (ret || !cost || cost > EM_MAX_POWER) {
165				dev_err(dev, "EM: invalid cost %lu %d\n",
166					cost, ret);
167				goto free_ps_table;
168			}
169		} else {
170			power_res = table[i].power;
171			cost = div64_u64(fmax * power_res, table[i].frequency);
172		}
173
174		table[i].cost = cost;
175
176		if (table[i].cost >= prev_cost) {
177			table[i].flags = EM_PERF_STATE_INEFFICIENT;
178			dev_dbg(dev, "EM: OPP:%lu is inefficient\n",
179				table[i].frequency);
180		} else {
181			prev_cost = table[i].cost;
182		}
183	}
184
185	pd->table = table;
186	pd->nr_perf_states = nr_states;
187
188	return 0;
189
190free_ps_table:
191	kfree(table);
192	return -EINVAL;
193}
194
195static int em_create_pd(struct device *dev, int nr_states,
196			struct em_data_callback *cb, cpumask_t *cpus,
197			unsigned long flags)
198{
199	struct em_perf_domain *pd;
200	struct device *cpu_dev;
201	int cpu, ret, num_cpus;
202
203	if (_is_cpu_device(dev)) {
204		num_cpus = cpumask_weight(cpus);
205
206		/* Prevent max possible energy calculation to not overflow */
207		if (num_cpus > EM_MAX_NUM_CPUS) {
208			dev_err(dev, "EM: too many CPUs, overflow possible\n");
209			return -EINVAL;
210		}
211
212		pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
213		if (!pd)
214			return -ENOMEM;
215
216		cpumask_copy(em_span_cpus(pd), cpus);
217	} else {
218		pd = kzalloc(sizeof(*pd), GFP_KERNEL);
219		if (!pd)
220			return -ENOMEM;
221	}
222
223	ret = em_create_perf_table(dev, pd, nr_states, cb, flags);
224	if (ret) {
225		kfree(pd);
226		return ret;
227	}
228
229	if (_is_cpu_device(dev))
230		for_each_cpu(cpu, cpus) {
231			cpu_dev = get_cpu_device(cpu);
232			cpu_dev->em_pd = pd;
233		}
234
235	dev->em_pd = pd;
236
237	return 0;
238}
239
240static void em_cpufreq_update_efficiencies(struct device *dev)
241{
242	struct em_perf_domain *pd = dev->em_pd;
243	struct em_perf_state *table;
244	struct cpufreq_policy *policy;
245	int found = 0;
246	int i;
247
248	if (!_is_cpu_device(dev) || !pd)
249		return;
250
251	policy = cpufreq_cpu_get(cpumask_first(em_span_cpus(pd)));
252	if (!policy) {
253		dev_warn(dev, "EM: Access to CPUFreq policy failed");
254		return;
255	}
256
257	table = pd->table;
258
259	for (i = 0; i < pd->nr_perf_states; i++) {
260		if (!(table[i].flags & EM_PERF_STATE_INEFFICIENT))
261			continue;
262
263		if (!cpufreq_table_set_inefficient(policy, table[i].frequency))
264			found++;
265	}
266
267	cpufreq_cpu_put(policy);
268
269	if (!found)
270		return;
271
272	/*
273	 * Efficiencies have been installed in CPUFreq, inefficient frequencies
274	 * will be skipped. The EM can do the same.
275	 */
276	pd->flags |= EM_PERF_DOMAIN_SKIP_INEFFICIENCIES;
277}
278
279/**
280 * em_pd_get() - Return the performance domain for a device
281 * @dev : Device to find the performance domain for
282 *
283 * Returns the performance domain to which @dev belongs, or NULL if it doesn't
284 * exist.
285 */
286struct em_perf_domain *em_pd_get(struct device *dev)
287{
288	if (IS_ERR_OR_NULL(dev))
289		return NULL;
290
291	return dev->em_pd;
292}
293EXPORT_SYMBOL_GPL(em_pd_get);
294
295/**
296 * em_cpu_get() - Return the performance domain for a CPU
297 * @cpu : CPU to find the performance domain for
298 *
299 * Returns the performance domain to which @cpu belongs, or NULL if it doesn't
300 * exist.
301 */
302struct em_perf_domain *em_cpu_get(int cpu)
303{
304	struct device *cpu_dev;
305
306	cpu_dev = get_cpu_device(cpu);
307	if (!cpu_dev)
308		return NULL;
309
310	return em_pd_get(cpu_dev);
311}
312EXPORT_SYMBOL_GPL(em_cpu_get);
313
314/**
315 * em_dev_register_perf_domain() - Register the Energy Model (EM) for a device
316 * @dev		: Device for which the EM is to register
317 * @nr_states	: Number of performance states to register
318 * @cb		: Callback functions providing the data of the Energy Model
319 * @cpus	: Pointer to cpumask_t, which in case of a CPU device is
320 *		obligatory. It can be taken from i.e. 'policy->cpus'. For other
321 *		type of devices this should be set to NULL.
322 * @microwatts	: Flag indicating that the power values are in micro-Watts or
323 *		in some other scale. It must be set properly.
324 *
325 * Create Energy Model tables for a performance domain using the callbacks
326 * defined in cb.
327 *
328 * The @microwatts is important to set with correct value. Some kernel
329 * sub-systems might rely on this flag and check if all devices in the EM are
330 * using the same scale.
331 *
332 * If multiple clients register the same performance domain, all but the first
333 * registration will be ignored.
334 *
335 * Return 0 on success
336 */
337int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
338				struct em_data_callback *cb, cpumask_t *cpus,
339				bool microwatts)
340{
341	unsigned long cap, prev_cap = 0;
342	unsigned long flags = 0;
343	int cpu, ret;
344
345	if (!dev || !nr_states || !cb)
346		return -EINVAL;
347
348	/*
349	 * Use a mutex to serialize the registration of performance domains and
350	 * let the driver-defined callback functions sleep.
351	 */
352	mutex_lock(&em_pd_mutex);
353
354	if (dev->em_pd) {
355		ret = -EEXIST;
356		goto unlock;
357	}
358
359	if (_is_cpu_device(dev)) {
360		if (!cpus) {
361			dev_err(dev, "EM: invalid CPU mask\n");
362			ret = -EINVAL;
363			goto unlock;
364		}
365
366		for_each_cpu(cpu, cpus) {
367			if (em_cpu_get(cpu)) {
368				dev_err(dev, "EM: exists for CPU%d\n", cpu);
369				ret = -EEXIST;
370				goto unlock;
371			}
372			/*
373			 * All CPUs of a domain must have the same
374			 * micro-architecture since they all share the same
375			 * table.
376			 */
377			cap = arch_scale_cpu_capacity(cpu);
378			if (prev_cap && prev_cap != cap) {
379				dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n",
380					cpumask_pr_args(cpus));
381
382				ret = -EINVAL;
383				goto unlock;
384			}
385			prev_cap = cap;
386		}
387	}
388
389	if (microwatts)
390		flags |= EM_PERF_DOMAIN_MICROWATTS;
391	else if (cb->get_cost)
392		flags |= EM_PERF_DOMAIN_ARTIFICIAL;
393
394	ret = em_create_pd(dev, nr_states, cb, cpus, flags);
395	if (ret)
396		goto unlock;
397
398	dev->em_pd->flags |= flags;
399
400	em_cpufreq_update_efficiencies(dev);
401
402	em_debug_create_pd(dev);
403	dev_info(dev, "EM: created perf domain\n");
404
405unlock:
406	mutex_unlock(&em_pd_mutex);
407	return ret;
408}
409EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
410
411/**
412 * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
413 * @dev		: Device for which the EM is registered
414 *
415 * Unregister the EM for the specified @dev (but not a CPU device).
416 */
417void em_dev_unregister_perf_domain(struct device *dev)
418{
419	if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
420		return;
421
422	if (_is_cpu_device(dev))
423		return;
424
425	/*
426	 * The mutex separates all register/unregister requests and protects
427	 * from potential clean-up/setup issues in the debugfs directories.
428	 * The debugfs directory name is the same as device's name.
429	 */
430	mutex_lock(&em_pd_mutex);
431	em_debug_remove_pd(dev);
432
433	kfree(dev->em_pd->table);
434	kfree(dev->em_pd);
435	dev->em_pd = NULL;
436	mutex_unlock(&em_pd_mutex);
437}
438EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);