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  */
24 static DEFINE_MUTEX(em_pd_mutex);
25 
_is_cpu_device(struct device * dev)26 static bool _is_cpu_device(struct device *dev)
27 {
28 	return (dev->bus == &cpu_subsys);
29 }
30 
31 #ifdef CONFIG_DEBUG_FS
32 static struct dentry *rootdir;
33 
em_debug_create_ps(struct em_perf_state * ps,struct dentry * pd)34 static 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 
em_debug_cpus_show(struct seq_file * s,void * unused)49 static 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 }
55 DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);
56 
em_debug_flags_show(struct seq_file * s,void * unused)57 static 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 }
65 DEFINE_SHOW_ATTRIBUTE(em_debug_flags);
66 
em_debug_create_pd(struct device * dev)67 static 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 
em_debug_remove_pd(struct device * dev)88 static 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 
em_debug_init(void)96 static 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 }
103 fs_initcall(em_debug_init);
104 #else /* CONFIG_DEBUG_FS */
em_debug_create_pd(struct device * dev)105 static void em_debug_create_pd(struct device *dev) {}
em_debug_remove_pd(struct device * dev)106 static void em_debug_remove_pd(struct device *dev) {}
107 #endif
108 
em_create_perf_table(struct device * dev,struct em_perf_domain * pd,int nr_states,struct em_data_callback * cb,unsigned long flags)109 static 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 
193 free_ps_table:
194 	kfree(table);
195 	return -EINVAL;
196 }
197 
em_create_pd(struct device * dev,int nr_states,struct em_data_callback * cb,cpumask_t * cpus,unsigned long flags)198 static 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 
em_cpufreq_update_efficiencies(struct device * dev)243 static 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  */
em_pd_get(struct device * dev)289 struct 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 }
296 EXPORT_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  */
em_cpu_get(int cpu)305 struct 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 }
315 EXPORT_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  */
em_dev_register_perf_domain(struct device * dev,unsigned int nr_states,struct em_data_callback * cb,cpumask_t * cpus,bool microwatts)340 int 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 
408 unlock:
409 	mutex_unlock(&em_pd_mutex);
410 	return ret;
411 }
412 EXPORT_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  */
em_dev_unregister_perf_domain(struct device * dev)420 void 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 }
441 EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);
442