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/drivers/cpuidle/governor.c

https://bitbucket.org/ndreys/linux-sunxi
C | 138 lines | 80 code | 23 blank | 35 comment | 17 complexity | 0fbc7b9e2b80c3777b8f8b1867995bf4 MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
  1/*
  2 * governor.c - governor support
  3 *
  4 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
  5 *               Shaohua Li <shaohua.li@intel.com>
  6 *               Adam Belay <abelay@novell.com>
  7 *
  8 * This code is licenced under the GPL.
  9 */
 10
 11#include <linux/mutex.h>
 12#include <linux/module.h>
 13#include <linux/cpuidle.h>
 14
 15#include "cpuidle.h"
 16
 17LIST_HEAD(cpuidle_governors);
 18struct cpuidle_governor *cpuidle_curr_governor;
 19
 20/**
 21 * __cpuidle_find_governor - finds a governor of the specified name
 22 * @str: the name
 23 *
 24 * Must be called with cpuidle_lock acquired.
 25 */
 26static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
 27{
 28	struct cpuidle_governor *gov;
 29
 30	list_for_each_entry(gov, &cpuidle_governors, governor_list)
 31		if (!strnicmp(str, gov->name, CPUIDLE_NAME_LEN))
 32			return gov;
 33
 34	return NULL;
 35}
 36
 37/**
 38 * cpuidle_switch_governor - changes the governor
 39 * @gov: the new target governor
 40 *
 41 * NOTE: "gov" can be NULL to specify disabled
 42 * Must be called with cpuidle_lock acquired.
 43 */
 44int cpuidle_switch_governor(struct cpuidle_governor *gov)
 45{
 46	struct cpuidle_device *dev;
 47
 48	if (gov == cpuidle_curr_governor)
 49		return 0;
 50
 51	cpuidle_uninstall_idle_handler();
 52
 53	if (cpuidle_curr_governor) {
 54		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
 55			cpuidle_disable_device(dev);
 56		module_put(cpuidle_curr_governor->owner);
 57	}
 58
 59	cpuidle_curr_governor = gov;
 60
 61	if (gov) {
 62		if (!try_module_get(cpuidle_curr_governor->owner))
 63			return -EINVAL;
 64		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
 65			cpuidle_enable_device(dev);
 66		cpuidle_install_idle_handler();
 67		printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
 68	}
 69
 70	return 0;
 71}
 72
 73/**
 74 * cpuidle_register_governor - registers a governor
 75 * @gov: the governor
 76 */
 77int cpuidle_register_governor(struct cpuidle_governor *gov)
 78{
 79	int ret = -EEXIST;
 80
 81	if (!gov || !gov->select)
 82		return -EINVAL;
 83
 84	mutex_lock(&cpuidle_lock);
 85	if (__cpuidle_find_governor(gov->name) == NULL) {
 86		ret = 0;
 87		list_add_tail(&gov->governor_list, &cpuidle_governors);
 88		if (!cpuidle_curr_governor ||
 89		    cpuidle_curr_governor->rating < gov->rating)
 90			cpuidle_switch_governor(gov);
 91	}
 92	mutex_unlock(&cpuidle_lock);
 93
 94	return ret;
 95}
 96
 97/**
 98 * cpuidle_replace_governor - find a replacement governor
 99 * @exclude_rating: the rating that will be skipped while looking for
100 * new governor.
101 */
102static struct cpuidle_governor *cpuidle_replace_governor(int exclude_rating)
103{
104	struct cpuidle_governor *gov;
105	struct cpuidle_governor *ret_gov = NULL;
106	unsigned int max_rating = 0;
107
108	list_for_each_entry(gov, &cpuidle_governors, governor_list) {
109		if (gov->rating == exclude_rating)
110			continue;
111		if (gov->rating > max_rating) {
112			max_rating = gov->rating;
113			ret_gov = gov;
114		}
115	}
116
117	return ret_gov;
118}
119
120/**
121 * cpuidle_unregister_governor - unregisters a governor
122 * @gov: the governor
123 */
124void cpuidle_unregister_governor(struct cpuidle_governor *gov)
125{
126	if (!gov)
127		return;
128
129	mutex_lock(&cpuidle_lock);
130	if (gov == cpuidle_curr_governor) {
131		struct cpuidle_governor *new_gov;
132		new_gov = cpuidle_replace_governor(gov->rating);
133		cpuidle_switch_governor(new_gov);
134	}
135	list_del(&gov->governor_list);
136	mutex_unlock(&cpuidle_lock);
137}
138