cpuidle.c

/*
 *  (C) 2004-2009  Dominik Brodowski <linux@dominikbrodowski.de>
 *  (C) 2011       Thomas Renninger <trenn@novell.com> Novell Inc.
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 */

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include "cpuidle.h"
#include "cpupower_intern.h"

/*
 * helper function to check whether a file under "../cpuX/cpuidle/stateX/" dir
 * exists.
 * For example the functionality to disable c-states was introduced in later
 * kernel versions, this function can be used to explicitly check for this
 * feature.
 *
 * returns 1 if the file exists, 0 otherwise.
 */
static
unsigned int cpuidle_state_file_exists(unsigned int cpu,
				       unsigned int idlestate,
				       const char *fname)
{
	char path[SYSFS_PATH_MAX];
	struct stat statbuf;


	snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
		 cpu, idlestate, fname);
	if (stat(path, &statbuf) != 0)
		return 0;
	return 1;
}

/*
 * helper function to read file from /sys into given buffer
 * fname is a relative path under "cpuX/cpuidle/stateX/" dir
 * cstates starting with 0, C0 is not counted as cstate.
 * This means if you want C1 info, pass 0 as idlestate param
 */
static
unsigned int cpuidle_state_read_file(unsigned int cpu,
					    unsigned int idlestate,
					    const char *fname, char *buf,
					    size_t buflen)
{
	char path[SYSFS_PATH_MAX];
	int fd;
	ssize_t numread;

	snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
		 cpu, idlestate, fname);

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return 0;

	numread = read(fd, buf, buflen - 1);
	if (numread < 1) {
		close(fd);
		return 0;
	}

	buf[numread] = '\0';
	close(fd);

	return (unsigned int) numread;
}

/*
 * helper function to write a new value to a /sys file
 * fname is a relative path under "../cpuX/cpuidle/cstateY/" dir
 *
 * Returns the number of bytes written or 0 on error
 */
static
unsigned int cpuidle_state_write_file(unsigned int cpu,
				      unsigned int idlestate,
				      const char *fname,
				      const char *value, size_t len)
{
	char path[SYSFS_PATH_MAX];
	int fd;
	ssize_t numwrite;

	snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/cpuidle/state%u/%s",
		 cpu, idlestate, fname);

	fd = open(path, O_WRONLY);
	if (fd == -1)
		return 0;

	numwrite = write(fd, value, len);
	if (numwrite < 1) {
		close(fd);
		return 0;
	}

	close(fd);

	return (unsigned int) numwrite;
}

/* read access to files which contain one numeric value */

enum idlestate_value {
	IDLESTATE_USAGE,
	IDLESTATE_POWER,
	IDLESTATE_LATENCY,
	IDLESTATE_TIME,
	IDLESTATE_DISABLE,
	MAX_IDLESTATE_VALUE_FILES
};

static const char *idlestate_value_files[MAX_IDLESTATE_VALUE_FILES] = {
	[IDLESTATE_USAGE] = "usage",
	[IDLESTATE_POWER] = "power",
	[IDLESTATE_LATENCY] = "latency",
	[IDLESTATE_TIME]  = "time",
	[IDLESTATE_DISABLE]  = "disable",
};

static
unsigned long long cpuidle_state_get_one_value(unsigned int cpu,
					       unsigned int idlestate,
					       enum idlestate_value which)
{
	unsigned long long value;
	unsigned int len;
	char linebuf[MAX_LINE_LEN];
	char *endp;

	if (which >= MAX_IDLESTATE_VALUE_FILES)
		return 0;

	len = cpuidle_state_read_file(cpu, idlestate,
				      idlestate_value_files[which],
				      linebuf, sizeof(linebuf));
	if (len == 0)
		return 0;

	value = strtoull(linebuf, &endp, 0);

	if (endp == linebuf || errno == ERANGE)
		return 0;

	return value;
}

/* read access to files which contain one string */

enum idlestate_string {
	IDLESTATE_DESC,
	IDLESTATE_NAME,
	MAX_IDLESTATE_STRING_FILES
};

static const char *idlestate_string_files[MAX_IDLESTATE_STRING_FILES] = {
	[IDLESTATE_DESC] = "desc",
	[IDLESTATE_NAME] = "name",
};


static char *cpuidle_state_get_one_string(unsigned int cpu,
					unsigned int idlestate,
					enum idlestate_string which)
{
	char linebuf[MAX_LINE_LEN];
	char *result;
	unsigned int len;

	if (which >= MAX_IDLESTATE_STRING_FILES)
		return NULL;

	len = cpuidle_state_read_file(cpu, idlestate,
				      idlestate_string_files[which],
				      linebuf, sizeof(linebuf));
	if (len == 0)
		return NULL;

	result = strdup(linebuf);
	if (result == NULL)
		return NULL;

	if (result[strlen(result) - 1] == '\n')
		result[strlen(result) - 1] = '\0';

	return result;
}

/*
 * Returns:
 *    1  if disabled
 *    0  if enabled
 *    -1 if idlestate is not available
 *    -2 if disabling is not supported by the kernel
 */
int cpuidle_is_state_disabled(unsigned int cpu,
				unsigned int idlestate)
{
	if (cpuidle_state_count(cpu) <= idlestate)
		return -1;

	if (!cpuidle_state_file_exists(cpu, idlestate,
				 idlestate_value_files[IDLESTATE_DISABLE]))
		return -2;
	return cpuidle_state_get_one_value(cpu, idlestate, IDLESTATE_DISABLE);
}

/*
 * Pass 1 as last argument to disable or 0 to enable the state
 * Returns:
 *    0  on success
 *    negative values on error, for example:
 *      -1 if idlestate is not available
 *      -2 if disabling is not supported by the kernel
 *      -3 No write access to disable/enable C-states
 */
int cpuidle_state_disable(unsigned int cpu,
			    unsigned int idlestate,
			    unsigned int disable)
{
	char value[SYSFS_PATH_MAX];
	int bytes_written;

	if (cpuidle_state_count(cpu) <= idlestate)
		return -1;

	if (!cpuidle_state_file_exists(cpu, idlestate,
				 idlestate_value_files[IDLESTATE_DISABLE]))
		return -2;

	snprintf(value, SYSFS_PATH_MAX, "%u", disable);

	bytes_written = cpuidle_state_write_file(cpu, idlestate, "disable",
						   value, sizeof(disable));
	if (bytes_written)
		return 0;
	return -3;
}

unsigned long cpuidle_state_latency(unsigned int cpu,
					  unsigned int idlestate)
{
	return cpuidle_state_get_one_value(cpu, idlestate, IDLESTATE_LATENCY);
}

unsigned long cpuidle_state_usage(unsigned int cpu,
					unsigned int idlestate)
{
	return cpuidle_state_get_one_value(cpu, idlestate, IDLESTATE_USAGE);
}

unsigned long long cpuidle_state_time(unsigned int cpu,
					unsigned int idlestate)
{
	return cpuidle_state_get_one_value(cpu, idlestate, IDLESTATE_TIME);
}

char *cpuidle_state_name(unsigned int cpu, unsigned int idlestate)
{
	return cpuidle_state_get_one_string(cpu, idlestate, IDLESTATE_NAME);
}

char *cpuidle_state_desc(unsigned int cpu, unsigned int idlestate)
{
	return cpuidle_state_get_one_string(cpu, idlestate, IDLESTATE_DESC);
}

/*
 * Returns number of supported C-states of CPU core cpu
 * Negativ in error case
 * Zero if cpuidle does not export any C-states
 */
unsigned int cpuidle_state_count(unsigned int cpu)
{
	char file[SYSFS_PATH_MAX];
	struct stat statbuf;
	int idlestates = 1;


	snprintf(file, SYSFS_PATH_MAX, PATH_TO_CPU "cpuidle");
	if (stat(file, &statbuf) != 0 || !S_ISDIR(statbuf.st_mode))
		return 0;

	snprintf(file, SYSFS_PATH_MAX, PATH_TO_CPU "cpu%u/cpuidle/state0", cpu);
	if (stat(file, &statbuf) != 0 || !S_ISDIR(statbuf.st_mode))
		return 0;

	while (stat(file, &statbuf) == 0 && S_ISDIR(statbuf.st_mode)) {
		snprintf(file, SYSFS_PATH_MAX, PATH_TO_CPU
			 "cpu%u/cpuidle/state%d", cpu, idlestates);
		idlestates++;
	}
	idlestates--;
	return idlestates;
}

/* CPUidle general /sys/devices/system/cpu/cpuidle/ sysfs access ********/

/*
 * helper function to read file from /sys into given buffer
 * fname is a relative path under "cpu/cpuidle/" dir
 */
static unsigned int sysfs_cpuidle_read_file(const char *fname, char *buf,
					    size_t buflen)
{
	char path[SYSFS_PATH_MAX];

	snprintf(path, sizeof(path), PATH_TO_CPU "cpuidle/%s", fname);

	return sysfs_read_file(path, buf, buflen);
}



/* read access to files which contain one string */

enum cpuidle_string {
	CPUIDLE_GOVERNOR,
	CPUIDLE_GOVERNOR_RO,
	CPUIDLE_DRIVER,
	MAX_CPUIDLE_STRING_FILES
};

static const char *cpuidle_string_files[MAX_CPUIDLE_STRING_FILES] = {
	[CPUIDLE_GOVERNOR]	= "current_governor",
	[CPUIDLE_GOVERNOR_RO]	= "current_governor_ro",
	[CPUIDLE_DRIVER]	= "current_driver",
};


static char *sysfs_cpuidle_get_one_string(enum cpuidle_string which)
{
	char linebuf[MAX_LINE_LEN];
	char *result;
	unsigned int len;

	if (which >= MAX_CPUIDLE_STRING_FILES)
		return NULL;

	len = sysfs_cpuidle_read_file(cpuidle_string_files[which],
				linebuf, sizeof(linebuf));
	if (len == 0)
		return NULL;

	result = strdup(linebuf);
	if (result == NULL)
		return NULL;

	if (result[strlen(result) - 1] == '\n')
		result[strlen(result) - 1] = '\0';

	return result;
}

char *cpuidle_get_governor(void)
{
	char *tmp = sysfs_cpuidle_get_one_string(CPUIDLE_GOVERNOR_RO);
	if (!tmp)
		return sysfs_cpuidle_get_one_string(CPUIDLE_GOVERNOR);
	else
		return tmp;
}

char *cpuidle_get_driver(void)
{
	return sysfs_cpuidle_get_one_string(CPUIDLE_DRIVER);
}
/* CPUidle idlestate specific /sys/devices/system/cpu/cpuX/cpuidle/ access */