summaryrefslogtreecommitdiff
path: root/drivers/cpuidle/governor.c
blob: 70b59642a7087a7593fffdfd9158ddfe4ba619b5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
/*
 * governor.c - governor support
 *
 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *               Shaohua Li <shaohua.li@intel.com>
 *               Adam Belay <abelay@novell.com>
 *
 * This code is licenced under the GPL.
 */

#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/cpuidle.h>

#include "cpuidle.h"

LIST_HEAD(cpuidle_governors);
struct cpuidle_governor *cpuidle_curr_governor;

/**
 * __cpuidle_find_governor - finds a governor of the specified name
 * @str: the name
 *
 * Must be called with cpuidle_lock aquired.
 */
static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
{
	struct cpuidle_governor *gov;

	list_for_each_entry(gov, &cpuidle_governors, governor_list)
		if (!strnicmp(str, gov->name, CPUIDLE_NAME_LEN))
			return gov;

	return NULL;
}

/**
 * cpuidle_switch_governor - changes the governor
 * @gov: the new target governor
 *
 * NOTE: "gov" can be NULL to specify disabled
 * Must be called with cpuidle_lock aquired.
 */
int cpuidle_switch_governor(struct cpuidle_governor *gov)
{
	struct cpuidle_device *dev;

	if (gov == cpuidle_curr_governor)
		return 0;

	cpuidle_uninstall_idle_handler();

	if (cpuidle_curr_governor) {
		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
			cpuidle_disable_device(dev);
		module_put(cpuidle_curr_governor->owner);
	}

	cpuidle_curr_governor = gov;

	if (gov) {
		if (!try_module_get(cpuidle_curr_governor->owner))
			return -EINVAL;
		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
			cpuidle_enable_device(dev);
		cpuidle_install_idle_handler();
		printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
	}

	return 0;
}

/**
 * cpuidle_register_governor - registers a governor
 * @gov: the governor
 */
int cpuidle_register_governor(struct cpuidle_governor *gov)
{
	int ret = -EEXIST;

	if (!gov || !gov->select)
		return -EINVAL;

	mutex_lock(&cpuidle_lock);
	if (__cpuidle_find_governor(gov->name) == NULL) {
		ret = 0;
		list_add_tail(&gov->governor_list, &cpuidle_governors);
		if (!cpuidle_curr_governor ||
		    cpuidle_curr_governor->rating < gov->rating)
			cpuidle_switch_governor(gov);
	}
	mutex_unlock(&cpuidle_lock);

	return ret;
}

/**
 * cpuidle_replace_governor - find a replacement governor
 * @exclude_rating: the rating that will be skipped while looking for
 * new governor.
 */
static struct cpuidle_governor *cpuidle_replace_governor(int exclude_rating)
{
	struct cpuidle_governor *gov;
	struct cpuidle_governor *ret_gov = NULL;
	unsigned int max_rating = 0;

	list_for_each_entry(gov, &cpuidle_governors, governor_list) {
		if (gov->rating == exclude_rating)
			continue;
		if (gov->rating > max_rating) {
			max_rating = gov->rating;
			ret_gov = gov;
		}
	}

	return ret_gov;
}

/**
 * cpuidle_unregister_governor - unregisters a governor
 * @gov: the governor
 */
void cpuidle_unregister_governor(struct cpuidle_governor *gov)
{
	if (!gov)
		return;

	mutex_lock(&cpuidle_lock);
	if (gov == cpuidle_curr_governor) {
		struct cpuidle_governor *new_gov;
		new_gov = cpuidle_replace_governor(gov->rating);
		cpuidle_switch_governor(new_gov);
	}
	list_del(&gov->governor_list);
	mutex_unlock(&cpuidle_lock);
}