1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  drivers/cpufreq/cpufreq_stats.c
4  *
5  *  Copyright (C) 2003-2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
6  *  (C) 2004 Zou Nan hai <nanhai.zou@intel.com>.
7  */
8 
9 #include <linux/cpu.h>
10 #include <linux/cpufreq.h>
11 #include <linux/module.h>
12 #include <linux/sched/clock.h>
13 #include <linux/slab.h>
14 
15 struct cpufreq_stats {
16 	unsigned int total_trans;
17 	unsigned long long last_time;
18 	unsigned int max_state;
19 	unsigned int state_num;
20 	unsigned int last_index;
21 	u64 *time_in_state;
22 	unsigned int *freq_table;
23 	unsigned int *trans_table;
24 
25 	/* Deferred reset */
26 	unsigned int reset_pending;
27 	unsigned long long reset_time;
28 };
29 
30 static void cpufreq_stats_update(struct cpufreq_stats *stats,
31 				 unsigned long long time)
32 {
33 	unsigned long long cur_time = local_clock();
34 
35 	stats->time_in_state[stats->last_index] += cur_time - time;
36 	stats->last_time = cur_time;
37 }
38 
39 static void cpufreq_stats_reset_table(struct cpufreq_stats *stats)
40 {
41 	unsigned int count = stats->max_state;
42 
43 	memset(stats->time_in_state, 0, count * sizeof(u64));
44 	memset(stats->trans_table, 0, count * count * sizeof(int));
45 	stats->last_time = local_clock();
46 	stats->total_trans = 0;
47 
48 	/* Adjust for the time elapsed since reset was requested */
49 	WRITE_ONCE(stats->reset_pending, 0);
50 	/*
51 	 * Prevent the reset_time read from being reordered before the
52 	 * reset_pending accesses in cpufreq_stats_record_transition().
53 	 */
54 	smp_rmb();
55 	cpufreq_stats_update(stats, READ_ONCE(stats->reset_time));
56 }
57 
58 static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
59 {
60 	struct cpufreq_stats *stats = policy->stats;
61 
62 	if (READ_ONCE(stats->reset_pending))
63 		return sprintf(buf, "%d\n", 0);
64 	else
65 		return sprintf(buf, "%u\n", stats->total_trans);
66 }
67 cpufreq_freq_attr_ro(total_trans);
68 
69 static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
70 {
71 	struct cpufreq_stats *stats = policy->stats;
72 	bool pending = READ_ONCE(stats->reset_pending);
73 	unsigned long long time;
74 	ssize_t len = 0;
75 	int i;
76 
77 	for (i = 0; i < stats->state_num; i++) {
78 		if (pending) {
79 			if (i == stats->last_index) {
80 				/*
81 				 * Prevent the reset_time read from occurring
82 				 * before the reset_pending read above.
83 				 */
84 				smp_rmb();
85 				time = local_clock() - READ_ONCE(stats->reset_time);
86 			} else {
87 				time = 0;
88 			}
89 		} else {
90 			time = stats->time_in_state[i];
91 			if (i == stats->last_index)
92 				time += local_clock() - stats->last_time;
93 		}
94 
95 		len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
96 			       nsec_to_clock_t(time));
97 	}
98 	return len;
99 }
100 cpufreq_freq_attr_ro(time_in_state);
101 
102 /* We don't care what is written to the attribute */
103 static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf,
104 			   size_t count)
105 {
106 	struct cpufreq_stats *stats = policy->stats;
107 
108 	/*
109 	 * Defer resetting of stats to cpufreq_stats_record_transition() to
110 	 * avoid races.
111 	 */
112 	WRITE_ONCE(stats->reset_time, local_clock());
113 	/*
114 	 * The memory barrier below is to prevent the readers of reset_time from
115 	 * seeing a stale or partially updated value.
116 	 */
117 	smp_wmb();
118 	WRITE_ONCE(stats->reset_pending, 1);
119 
120 	return count;
121 }
122 cpufreq_freq_attr_wo(reset);
123 
124 static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
125 {
126 	struct cpufreq_stats *stats = policy->stats;
127 	bool pending = READ_ONCE(stats->reset_pending);
128 	ssize_t len = 0;
129 	int i, j, count;
130 
131 	len += scnprintf(buf + len, PAGE_SIZE - len, "   From  :    To\n");
132 	len += scnprintf(buf + len, PAGE_SIZE - len, "         : ");
133 	for (i = 0; i < stats->state_num; i++) {
134 		if (len >= PAGE_SIZE)
135 			break;
136 		len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ",
137 				stats->freq_table[i]);
138 	}
139 	if (len >= PAGE_SIZE)
140 		return PAGE_SIZE;
141 
142 	len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
143 
144 	for (i = 0; i < stats->state_num; i++) {
145 		if (len >= PAGE_SIZE)
146 			break;
147 
148 		len += scnprintf(buf + len, PAGE_SIZE - len, "%9u: ",
149 				stats->freq_table[i]);
150 
151 		for (j = 0; j < stats->state_num; j++) {
152 			if (len >= PAGE_SIZE)
153 				break;
154 
155 			if (pending)
156 				count = 0;
157 			else
158 				count = stats->trans_table[i * stats->max_state + j];
159 
160 			len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ", count);
161 		}
162 		if (len >= PAGE_SIZE)
163 			break;
164 		len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
165 	}
166 
167 	if (len >= PAGE_SIZE) {
168 		pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n");
169 		return -EFBIG;
170 	}
171 	return len;
172 }
173 cpufreq_freq_attr_ro(trans_table);
174 
175 static struct attribute *default_attrs[] = {
176 	&total_trans.attr,
177 	&time_in_state.attr,
178 	&reset.attr,
179 	&trans_table.attr,
180 	NULL
181 };
182 static const struct attribute_group stats_attr_group = {
183 	.attrs = default_attrs,
184 	.name = "stats"
185 };
186 
187 static int freq_table_get_index(struct cpufreq_stats *stats, unsigned int freq)
188 {
189 	int index;
190 	for (index = 0; index < stats->max_state; index++)
191 		if (stats->freq_table[index] == freq)
192 			return index;
193 	return -1;
194 }
195 
196 void cpufreq_stats_free_table(struct cpufreq_policy *policy)
197 {
198 	struct cpufreq_stats *stats = policy->stats;
199 
200 	/* Already freed */
201 	if (!stats)
202 		return;
203 
204 	pr_debug("%s: Free stats table\n", __func__);
205 
206 	sysfs_remove_group(&policy->kobj, &stats_attr_group);
207 	kfree(stats->time_in_state);
208 	kfree(stats);
209 	policy->stats = NULL;
210 }
211 
212 void cpufreq_stats_create_table(struct cpufreq_policy *policy)
213 {
214 	unsigned int i = 0, count;
215 	struct cpufreq_stats *stats;
216 	unsigned int alloc_size;
217 	struct cpufreq_frequency_table *pos;
218 
219 	count = cpufreq_table_count_valid_entries(policy);
220 	if (!count)
221 		return;
222 
223 	/* stats already initialized */
224 	if (policy->stats)
225 		return;
226 
227 	stats = kzalloc(sizeof(*stats), GFP_KERNEL);
228 	if (!stats)
229 		return;
230 
231 	alloc_size = count * sizeof(int) + count * sizeof(u64);
232 
233 	alloc_size += count * count * sizeof(int);
234 
235 	/* Allocate memory for time_in_state/freq_table/trans_table in one go */
236 	stats->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
237 	if (!stats->time_in_state)
238 		goto free_stat;
239 
240 	stats->freq_table = (unsigned int *)(stats->time_in_state + count);
241 
242 	stats->trans_table = stats->freq_table + count;
243 
244 	stats->max_state = count;
245 
246 	/* Find valid-unique entries */
247 	cpufreq_for_each_valid_entry(pos, policy->freq_table)
248 		if (freq_table_get_index(stats, pos->frequency) == -1)
249 			stats->freq_table[i++] = pos->frequency;
250 
251 	stats->state_num = i;
252 	stats->last_time = local_clock();
253 	stats->last_index = freq_table_get_index(stats, policy->cur);
254 
255 	policy->stats = stats;
256 	if (!sysfs_create_group(&policy->kobj, &stats_attr_group))
257 		return;
258 
259 	/* We failed, release resources */
260 	policy->stats = NULL;
261 	kfree(stats->time_in_state);
262 free_stat:
263 	kfree(stats);
264 }
265 
266 void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
267 				     unsigned int new_freq)
268 {
269 	struct cpufreq_stats *stats = policy->stats;
270 	int old_index, new_index;
271 
272 	if (unlikely(!stats))
273 		return;
274 
275 	if (unlikely(READ_ONCE(stats->reset_pending)))
276 		cpufreq_stats_reset_table(stats);
277 
278 	old_index = stats->last_index;
279 	new_index = freq_table_get_index(stats, new_freq);
280 
281 	/* We can't do stats->time_in_state[-1]= .. */
282 	if (unlikely(old_index == -1 || new_index == -1 || old_index == new_index))
283 		return;
284 
285 	cpufreq_stats_update(stats, stats->last_time);
286 
287 	stats->last_index = new_index;
288 	stats->trans_table[old_index * stats->max_state + new_index]++;
289 	stats->total_trans++;
290 }
291