1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * (C) 2004-2009 Dominik Brodowski <linux@dominikbrodowski.de>
4 * (C) 2011 Thomas Renninger <trenn@novell.com> Novell Inc.
5 */
6
7#include <stdio.h>
8#include <errno.h>
9#include <stdlib.h>
10#include <string.h>
11#include <sys/types.h>
12#include <sys/stat.h>
13#include <fcntl.h>
14#include <unistd.h>
15
16#include "cpuidle.h"
17#include "cpupower_intern.h"
18
19/*
20 * helper function to check whether a file under "../cpuX/cpuidle/stateX/" dir
21 * exists.
22 * For example the functionality to disable c-states was introduced in later
23 * kernel versions, this function can be used to explicitly check for this
24 * feature.
25 *
26 * returns 1 if the file exists, 0 otherwise.
27 */
28static
29unsigned int cpuidle_state_file_exists(unsigned int cpu,
30 unsigned int idlestate,
31 const char *fname)
32{
33 char path[SYSFS_PATH_MAX];
34 struct stat statbuf;
35
36
37 snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
38 cpu, idlestate, fname);
39 if (stat(path, &statbuf) != 0)
40 return 0;
41 return 1;
42}
43
44/*
45 * helper function to read file from /sys into given buffer
46 * fname is a relative path under "cpuX/cpuidle/stateX/" dir
47 * cstates starting with 0, C0 is not counted as cstate.
48 * This means if you want C1 info, pass 0 as idlestate param
49 */
50static
51unsigned int cpuidle_state_read_file(unsigned int cpu,
52 unsigned int idlestate,
53 const char *fname, char *buf,
54 size_t buflen)
55{
56 char path[SYSFS_PATH_MAX];
57 int fd;
58 ssize_t numread;
59
60 snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
61 cpu, idlestate, fname);
62
63 fd = open(path, O_RDONLY);
64 if (fd == -1)
65 return 0;
66
67 numread = read(fd, buf, buflen - 1);
68 if (numread < 1) {
69 close(fd);
70 return 0;
71 }
72
73 buf[numread] = '\0';
74 close(fd);
75
76 return (unsigned int) numread;
77}
78
79/*
80 * helper function to write a new value to a /sys file
81 * fname is a relative path under "../cpuX/cpuidle/cstateY/" dir
82 *
83 * Returns the number of bytes written or 0 on error
84 */
85static
86unsigned int cpuidle_state_write_file(unsigned int cpu,
87 unsigned int idlestate,
88 const char *fname,
89 const char *value, size_t len)
90{
91 char path[SYSFS_PATH_MAX];
92 int fd;
93 ssize_t numwrite;
94
95 snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
96 cpu, idlestate, fname);
97
98 fd = open(path, O_WRONLY);
99 if (fd == -1)
100 return 0;
101
102 numwrite = write(fd, value, len);
103 if (numwrite < 1) {
104 close(fd);
105 return 0;
106 }
107
108 close(fd);
109
110 return (unsigned int) numwrite;
111}
112
113/* read access to files which contain one numeric value */
114
115enum idlestate_value {
116 IDLESTATE_USAGE,
117 IDLESTATE_POWER,
118 IDLESTATE_LATENCY,
119 IDLESTATE_RESIDENCY,
120 IDLESTATE_TIME,
121 IDLESTATE_DISABLE,
122 MAX_IDLESTATE_VALUE_FILES
123};
124
125static const char *idlestate_value_files[MAX_IDLESTATE_VALUE_FILES] = {
126 [IDLESTATE_USAGE] = "usage",
127 [IDLESTATE_POWER] = "power",
128 [IDLESTATE_LATENCY] = "latency",
129 [IDLESTATE_RESIDENCY] = "residency",
130 [IDLESTATE_TIME] = "time",
131 [IDLESTATE_DISABLE] = "disable",
132};
133
134static
135unsigned long long cpuidle_state_get_one_value(unsigned int cpu,
136 unsigned int idlestate,
137 enum idlestate_value which)
138{
139 unsigned long long value;
140 unsigned int len;
141 char linebuf[MAX_LINE_LEN];
142 char *endp;
143
144 if (which >= MAX_IDLESTATE_VALUE_FILES)
145 return 0;
146
147 len = cpuidle_state_read_file(cpu, idlestate,
148 idlestate_value_files[which],
149 linebuf, sizeof(linebuf));
150 if (len == 0)
151 return 0;
152
153 value = strtoull(linebuf, &endp, 0);
154
155 if (endp == linebuf || errno == ERANGE)
156 return 0;
157
158 return value;
159}
160
161/* read access to files which contain one string */
162
163enum idlestate_string {
164 IDLESTATE_DESC,
165 IDLESTATE_NAME,
166 MAX_IDLESTATE_STRING_FILES
167};
168
169static const char *idlestate_string_files[MAX_IDLESTATE_STRING_FILES] = {
170 [IDLESTATE_DESC] = "desc",
171 [IDLESTATE_NAME] = "name",
172};
173
174
175static char *cpuidle_state_get_one_string(unsigned int cpu,
176 unsigned int idlestate,
177 enum idlestate_string which)
178{
179 char linebuf[MAX_LINE_LEN];
180 char *result;
181 unsigned int len;
182
183 if (which >= MAX_IDLESTATE_STRING_FILES)
184 return NULL;
185
186 len = cpuidle_state_read_file(cpu, idlestate,
187 idlestate_string_files[which],
188 linebuf, sizeof(linebuf));
189 if (len == 0)
190 return NULL;
191
192 result = strdup(linebuf);
193 if (result == NULL)
194 return NULL;
195
196 if (result[strlen(result) - 1] == '\n')
197 result[strlen(result) - 1] = '\0';
198
199 return result;
200}
201
202/*
203 * Returns:
204 * 1 if disabled
205 * 0 if enabled
206 * -1 if idlestate is not available
207 * -2 if disabling is not supported by the kernel
208 */
209int cpuidle_is_state_disabled(unsigned int cpu,
210 unsigned int idlestate)
211{
212 if (cpuidle_state_count(cpu) <= idlestate)
213 return -1;
214
215 if (!cpuidle_state_file_exists(cpu, idlestate,
216 fname: idlestate_value_files[IDLESTATE_DISABLE]))
217 return -2;
218 return cpuidle_state_get_one_value(cpu, idlestate, which: IDLESTATE_DISABLE);
219}
220
221/*
222 * Pass 1 as last argument to disable or 0 to enable the state
223 * Returns:
224 * 0 on success
225 * negative values on error, for example:
226 * -1 if idlestate is not available
227 * -2 if disabling is not supported by the kernel
228 * -3 No write access to disable/enable C-states
229 */
230int cpuidle_state_disable(unsigned int cpu,
231 unsigned int idlestate,
232 unsigned int disable)
233{
234 char value[SYSFS_PATH_MAX];
235 int bytes_written;
236 int len;
237
238 if (cpuidle_state_count(cpu) <= idlestate)
239 return -1;
240
241 if (!cpuidle_state_file_exists(cpu, idlestate,
242 fname: idlestate_value_files[IDLESTATE_DISABLE]))
243 return -2;
244
245 len = snprintf(value, SYSFS_PATH_MAX, "%u", disable);
246
247 bytes_written = cpuidle_state_write_file(cpu, idlestate, "disable",
248 value, len);
249 if (bytes_written)
250 return 0;
251 return -3;
252}
253
254unsigned long cpuidle_state_latency(unsigned int cpu,
255 unsigned int idlestate)
256{
257 return cpuidle_state_get_one_value(cpu, idlestate, which: IDLESTATE_LATENCY);
258}
259
260unsigned long cpuidle_state_residency(unsigned int cpu,
261 unsigned int idlestate)
262{
263 return cpuidle_state_get_one_value(cpu, idlestate, which: IDLESTATE_RESIDENCY);
264}
265
266unsigned long cpuidle_state_usage(unsigned int cpu,
267 unsigned int idlestate)
268{
269 return cpuidle_state_get_one_value(cpu, idlestate, which: IDLESTATE_USAGE);
270}
271
272unsigned long long cpuidle_state_time(unsigned int cpu,
273 unsigned int idlestate)
274{
275 return cpuidle_state_get_one_value(cpu, idlestate, which: IDLESTATE_TIME);
276}
277
278char *cpuidle_state_name(unsigned int cpu, unsigned int idlestate)
279{
280 return cpuidle_state_get_one_string(cpu, idlestate, which: IDLESTATE_NAME);
281}
282
283char *cpuidle_state_desc(unsigned int cpu, unsigned int idlestate)
284{
285 return cpuidle_state_get_one_string(cpu, idlestate, which: IDLESTATE_DESC);
286}
287
288/*
289 * Returns number of supported C-states of CPU core cpu
290 * Negativ in error case
291 * Zero if cpuidle does not export any C-states
292 */
293unsigned int cpuidle_state_count(unsigned int cpu)
294{
295 char file[SYSFS_PATH_MAX];
296 struct stat statbuf;
297 int idlestates = 1;
298
299
300 snprintf(file, SYSFS_PATH_MAX, PATH_TO_CPU "cpuidle");
301 if (stat(file, &statbuf) != 0 || !S_ISDIR(statbuf.st_mode))
302 return 0;
303
304 snprintf(file, SYSFS_PATH_MAX, PATH_TO_CPU "cpu%u/cpuidle/state0", cpu);
305 if (stat(file, &statbuf) != 0 || !S_ISDIR(statbuf.st_mode))
306 return 0;
307
308 while (stat(file, &statbuf) == 0 && S_ISDIR(statbuf.st_mode)) {
309 snprintf(file, SYSFS_PATH_MAX, PATH_TO_CPU
310 "cpu%u/cpuidle/state%d", cpu, idlestates);
311 idlestates++;
312 }
313 idlestates--;
314 return idlestates;
315}
316
317/* CPUidle general /sys/devices/system/cpu/cpuidle/ sysfs access ********/
318
319/*
320 * helper function to read file from /sys into given buffer
321 * fname is a relative path under "cpu/cpuidle/" dir
322 */
323static unsigned int sysfs_cpuidle_read_file(const char *fname, char *buf,
324 size_t buflen)
325{
326 char path[SYSFS_PATH_MAX];
327
328 snprintf(path, sizeof(path), PATH_TO_CPU "cpuidle/%s", fname);
329
330 return cpupower_read_sysfs(path, buf, buflen);
331}
332
333
334
335/* read access to files which contain one string */
336
337enum cpuidle_string {
338 CPUIDLE_GOVERNOR,
339 CPUIDLE_GOVERNOR_RO,
340 CPUIDLE_DRIVER,
341 MAX_CPUIDLE_STRING_FILES
342};
343
344static const char *cpuidle_string_files[MAX_CPUIDLE_STRING_FILES] = {
345 [CPUIDLE_GOVERNOR] = "current_governor",
346 [CPUIDLE_GOVERNOR_RO] = "current_governor_ro",
347 [CPUIDLE_DRIVER] = "current_driver",
348};
349
350
351static char *sysfs_cpuidle_get_one_string(enum cpuidle_string which)
352{
353 char linebuf[MAX_LINE_LEN];
354 char *result;
355 unsigned int len;
356
357 if (which >= MAX_CPUIDLE_STRING_FILES)
358 return NULL;
359
360 len = sysfs_cpuidle_read_file(cpuidle_string_files[which],
361 linebuf, sizeof(linebuf));
362 if (len == 0)
363 return NULL;
364
365 result = strdup(linebuf);
366 if (result == NULL)
367 return NULL;
368
369 if (result[strlen(result) - 1] == '\n')
370 result[strlen(result) - 1] = '\0';
371
372 return result;
373}
374
375char *cpuidle_get_governor(void)
376{
377 char *tmp = sysfs_cpuidle_get_one_string(which: CPUIDLE_GOVERNOR_RO);
378 if (!tmp)
379 return sysfs_cpuidle_get_one_string(which: CPUIDLE_GOVERNOR);
380 else
381 return tmp;
382}
383
384char *cpuidle_get_driver(void)
385{
386 return sysfs_cpuidle_get_one_string(which: CPUIDLE_DRIVER);
387}
388/* CPUidle idlestate specific /sys/devices/system/cpu/cpuX/cpuidle/ access */
389

source code of linux/tools/power/cpupower/lib/cpuidle.c