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	struct dentry *debug_dir;
 91
 92	debug_dir = debugfs_lookup(dev_name(dev), rootdir);
 93	debugfs_remove_recursive(debug_dir);
 94}
 95
 96static int __init em_debug_init(void)
 97{
 98	/* Create /sys/kernel/debug/energy_model directory */
 99	rootdir = debugfs_create_dir("energy_model", NULL);
100
101	return 0;
102}
103fs_initcall(em_debug_init);
104#else /* CONFIG_DEBUG_FS */
105static void em_debug_create_pd(struct device *dev) {}
106static void em_debug_remove_pd(struct device *dev) {}
107#endif
108
109static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
110				int nr_states, struct em_data_callback *cb,
111				unsigned long flags)
112{
113	unsigned long power, freq, prev_freq = 0, prev_cost = ULONG_MAX;
114	struct em_perf_state *table;
115	int i, ret;
116	u64 fmax;
117
118	table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
119	if (!table)
120		return -ENOMEM;
121
122	/* Build the list of performance states for this performance domain */
123	for (i = 0, freq = 0; i < nr_states; i++, freq++) {
124		/*
125		 * active_power() is a driver callback which ceils 'freq' to
126		 * lowest performance state of 'dev' above 'freq' and updates
127		 * 'power' and 'freq' accordingly.
128		 */
129		ret = cb->active_power(dev, &power, &freq);
130		if (ret) {
131			dev_err(dev, "EM: invalid perf. state: %d\n",
132				ret);
133			goto free_ps_table;
134		}
135
136		/*
137		 * We expect the driver callback to increase the frequency for
138		 * higher performance states.
139		 */
140		if (freq <= prev_freq) {
141			dev_err(dev, "EM: non-increasing freq: %lu\n",
142				freq);
143			goto free_ps_table;
144		}
145
146		/*
147		 * The power returned by active_state() is expected to be
148		 * positive and be in range.
149		 */
150		if (!power || power > EM_MAX_POWER) {
151			dev_err(dev, "EM: invalid power: %lu\n",
152				power);
153			goto free_ps_table;
154		}
155
156		table[i].power = power;
157		table[i].frequency = prev_freq = freq;
158	}
159
160	/* Compute the cost of each performance state. */
161	fmax = (u64) table[nr_states - 1].frequency;
162	for (i = nr_states - 1; i >= 0; i--) {
163		unsigned long power_res, cost;
164
165		if (flags & EM_PERF_DOMAIN_ARTIFICIAL) {
166			ret = cb->get_cost(dev, table[i].frequency, &cost);
167			if (ret || !cost || cost > EM_MAX_POWER) {
168				dev_err(dev, "EM: invalid cost %lu %d\n",
169					cost, ret);
170				goto free_ps_table;
171			}
172		} else {
173			power_res = table[i].power;
174			cost = div64_u64(fmax * power_res, table[i].frequency);
175		}
176
177		table[i].cost = cost;
178
179		if (table[i].cost >= prev_cost) {
180			table[i].flags = EM_PERF_STATE_INEFFICIENT;
181			dev_dbg(dev, "EM: OPP:%lu is inefficient\n",
182				table[i].frequency);
183		} else {
184			prev_cost = table[i].cost;
185		}
186	}
187
188	pd->table = table;
189	pd->nr_perf_states = nr_states;
190
191	return 0;
192
193free_ps_table:
194	kfree(table);
195	return -EINVAL;
196}
197
198static int em_create_pd(struct device *dev, int nr_states,
199			struct em_data_callback *cb, cpumask_t *cpus,
200			unsigned long flags)
201{
202	struct em_perf_domain *pd;
203	struct device *cpu_dev;
204	int cpu, ret, num_cpus;
205
206	if (_is_cpu_device(dev)) {
207		num_cpus = cpumask_weight(cpus);
208
209		/* Prevent max possible energy calculation to not overflow */
210		if (num_cpus > EM_MAX_NUM_CPUS) {
211			dev_err(dev, "EM: too many CPUs, overflow possible\n");
212			return -EINVAL;
213		}
214
215		pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
216		if (!pd)
217			return -ENOMEM;
218
219		cpumask_copy(em_span_cpus(pd), cpus);
220	} else {
221		pd = kzalloc(sizeof(*pd), GFP_KERNEL);
222		if (!pd)
223			return -ENOMEM;
224	}
225
226	ret = em_create_perf_table(dev, pd, nr_states, cb, flags);
227	if (ret) {
228		kfree(pd);
229		return ret;
230	}
231
232	if (_is_cpu_device(dev))
233		for_each_cpu(cpu, cpus) {
234			cpu_dev = get_cpu_device(cpu);
235			cpu_dev->em_pd = pd;
236		}
237
238	dev->em_pd = pd;
239
240	return 0;
241}
242
243static void em_cpufreq_update_efficiencies(struct device *dev)
244{
245	struct em_perf_domain *pd = dev->em_pd;
246	struct em_perf_state *table;
247	struct cpufreq_policy *policy;
248	int found = 0;
249	int i;
250
251	if (!_is_cpu_device(dev) || !pd)
252		return;
253
254	policy = cpufreq_cpu_get(cpumask_first(em_span_cpus(pd)));
255	if (!policy) {
256		dev_warn(dev, "EM: Access to CPUFreq policy failed");
257		return;
258	}
259
260	table = pd->table;
261
262	for (i = 0; i < pd->nr_perf_states; i++) {
263		if (!(table[i].flags & EM_PERF_STATE_INEFFICIENT))
264			continue;
265
266		if (!cpufreq_table_set_inefficient(policy, table[i].frequency))
267			found++;
268	}
269
270	cpufreq_cpu_put(policy);
271
272	if (!found)
273		return;
274
275	/*
276	 * Efficiencies have been installed in CPUFreq, inefficient frequencies
277	 * will be skipped. The EM can do the same.
278	 */
279	pd->flags |= EM_PERF_DOMAIN_SKIP_INEFFICIENCIES;
280}
281
282/**
283 * em_pd_get() - Return the performance domain for a device
284 * @dev : Device to find the performance domain for
285 *
286 * Returns the performance domain to which @dev belongs, or NULL if it doesn't
287 * exist.
288 */
289struct em_perf_domain *em_pd_get(struct device *dev)
290{
291	if (IS_ERR_OR_NULL(dev))
292		return NULL;
293
294	return dev->em_pd;
295}
296EXPORT_SYMBOL_GPL(em_pd_get);
297
298/**
299 * em_cpu_get() - Return the performance domain for a CPU
300 * @cpu : CPU to find the performance domain for
301 *
302 * Returns the performance domain to which @cpu belongs, or NULL if it doesn't
303 * exist.
304 */
305struct em_perf_domain *em_cpu_get(int cpu)
306{
307	struct device *cpu_dev;
308
309	cpu_dev = get_cpu_device(cpu);
310	if (!cpu_dev)
311		return NULL;
312
313	return em_pd_get(cpu_dev);
314}
315EXPORT_SYMBOL_GPL(em_cpu_get);
316
317/**
318 * em_dev_register_perf_domain() - Register the Energy Model (EM) for a device
319 * @dev		: Device for which the EM is to register
320 * @nr_states	: Number of performance states to register
321 * @cb		: Callback functions providing the data of the Energy Model
322 * @cpus	: Pointer to cpumask_t, which in case of a CPU device is
323 *		obligatory. It can be taken from i.e. 'policy->cpus'. For other
324 *		type of devices this should be set to NULL.
325 * @microwatts	: Flag indicating that the power values are in micro-Watts or
326 *		in some other scale. It must be set properly.
327 *
328 * Create Energy Model tables for a performance domain using the callbacks
329 * defined in cb.
330 *
331 * The @microwatts is important to set with correct value. Some kernel
332 * sub-systems might rely on this flag and check if all devices in the EM are
333 * using the same scale.
334 *
335 * If multiple clients register the same performance domain, all but the first
336 * registration will be ignored.
337 *
338 * Return 0 on success
339 */
340int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
341				struct em_data_callback *cb, cpumask_t *cpus,
342				bool microwatts)
343{
344	unsigned long cap, prev_cap = 0;
345	unsigned long flags = 0;
346	int cpu, ret;
347
348	if (!dev || !nr_states || !cb)
349		return -EINVAL;
350
351	/*
352	 * Use a mutex to serialize the registration of performance domains and
353	 * let the driver-defined callback functions sleep.
354	 */
355	mutex_lock(&em_pd_mutex);
356
357	if (dev->em_pd) {
358		ret = -EEXIST;
359		goto unlock;
360	}
361
362	if (_is_cpu_device(dev)) {
363		if (!cpus) {
364			dev_err(dev, "EM: invalid CPU mask\n");
365			ret = -EINVAL;
366			goto unlock;
367		}
368
369		for_each_cpu(cpu, cpus) {
370			if (em_cpu_get(cpu)) {
371				dev_err(dev, "EM: exists for CPU%d\n", cpu);
372				ret = -EEXIST;
373				goto unlock;
374			}
375			/*
376			 * All CPUs of a domain must have the same
377			 * micro-architecture since they all share the same
378			 * table.
379			 */
380			cap = arch_scale_cpu_capacity(cpu);
381			if (prev_cap && prev_cap != cap) {
382				dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n",
383					cpumask_pr_args(cpus));
384
385				ret = -EINVAL;
386				goto unlock;
387			}
388			prev_cap = cap;
389		}
390	}
391
392	if (microwatts)
393		flags |= EM_PERF_DOMAIN_MICROWATTS;
394	else if (cb->get_cost)
395		flags |= EM_PERF_DOMAIN_ARTIFICIAL;
396
397	ret = em_create_pd(dev, nr_states, cb, cpus, flags);
398	if (ret)
399		goto unlock;
400
401	dev->em_pd->flags |= flags;
402
403	em_cpufreq_update_efficiencies(dev);
404
405	em_debug_create_pd(dev);
406	dev_info(dev, "EM: created perf domain\n");
407
408unlock:
409	mutex_unlock(&em_pd_mutex);
410	return ret;
411}
412EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
413
414/**
415 * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
416 * @dev		: Device for which the EM is registered
417 *
418 * Unregister the EM for the specified @dev (but not a CPU device).
419 */
420void em_dev_unregister_perf_domain(struct device *dev)
421{
422	if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
423		return;
424
425	if (_is_cpu_device(dev))
426		return;
427
428	/*
429	 * The mutex separates all register/unregister requests and protects
430	 * from potential clean-up/setup issues in the debugfs directories.
431	 * The debugfs directory name is the same as device's name.
432	 */
433	mutex_lock(&em_pd_mutex);
434	em_debug_remove_pd(dev);
435
436	kfree(dev->em_pd->table);
437	kfree(dev->em_pd);
438	dev->em_pd = NULL;
439	mutex_unlock(&em_pd_mutex);
440}
441EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);