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/slab.h>
13
14
15struct 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
30static void cpufreq_stats_update(struct cpufreq_stats *stats,
31				 unsigned long long time)
32{
33	unsigned long long cur_time = get_jiffies_64();
34
35	stats->time_in_state[stats->last_index] += cur_time - time;
36	stats->last_time = cur_time;
37}
38
39static 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 = get_jiffies_64();
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
58static 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}
67cpufreq_freq_attr_ro(total_trans);
68
69static 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 = get_jiffies_64() - 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 += get_jiffies_64() - stats->last_time;
93		}
94
95		len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
96			       jiffies_64_to_clock_t(time));
97	}
98	return len;
99}
100cpufreq_freq_attr_ro(time_in_state);
101
102/* We don't care what is written to the attribute */
103static 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, get_jiffies_64());
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}
122cpufreq_freq_attr_wo(reset);
123
124static 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 - 1)
135			break;
136		len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ",
137				stats->freq_table[i]);
138	}
139	if (len >= PAGE_SIZE - 1)
140		return PAGE_SIZE - 1;
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 - 1)
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 - 1)
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 - 1)
163			break;
164		len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
165	}
166
167	if (len >= PAGE_SIZE - 1) {
168		pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n");
169		return -EFBIG;
170	}
171	return len;
172}
173cpufreq_freq_attr_ro(trans_table);
174
175static struct attribute *default_attrs[] = {
176	&total_trans.attr,
177	&time_in_state.attr,
178	&reset.attr,
179	&trans_table.attr,
180	NULL
181};
182static const struct attribute_group stats_attr_group = {
183	.attrs = default_attrs,
184	.name = "stats"
185};
186
187static 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
196void 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
212void cpufreq_stats_create_table(struct cpufreq_policy *policy)
213{
214	unsigned int i = 0, count = 0, ret = -ENOMEM;
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 = get_jiffies_64();
253	stats->last_index = freq_table_get_index(stats, policy->cur);
254
255	policy->stats = stats;
256	ret = sysfs_create_group(&policy->kobj, &stats_attr_group);
257	if (!ret)
258		return;
259
260	/* We failed, release resources */
261	policy->stats = NULL;
262	kfree(stats->time_in_state);
263free_stat:
264	kfree(stats);
265}
266
267void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
268				     unsigned int new_freq)
269{
270	struct cpufreq_stats *stats = policy->stats;
271	int old_index, new_index;
272
273	if (unlikely(!stats))
274		return;
275
276	if (unlikely(READ_ONCE(stats->reset_pending)))
277		cpufreq_stats_reset_table(stats);
278
279	old_index = stats->last_index;
280	new_index = freq_table_get_index(stats, new_freq);
281
282	/* We can't do stats->time_in_state[-1]= .. */
283	if (unlikely(old_index == -1 || new_index == -1 || old_index == new_index))
284		return;
285
286	cpufreq_stats_update(stats, stats->last_time);
287
288	stats->last_index = new_index;
289	stats->trans_table[old_index * stats->max_state + new_index]++;
290	stats->total_trans++;
291}
292