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/cpu.h>
12#include <linux/cpuidle.h>
13#include <linux/mutex.h>
14#include <linux/module.h>
15#include <linux/pm_qos.h>
16
17#include "cpuidle.h"
18
19char param_governor[CPUIDLE_NAME_LEN];
20
21LIST_HEAD(cpuidle_governors);
22struct cpuidle_governor *cpuidle_curr_governor;
23struct cpuidle_governor *cpuidle_prev_governor;
24
25/**
26 * cpuidle_find_governor - finds a governor of the specified name
27 * @str: the name
28 *
29 * Must be called with cpuidle_lock acquired.
30 */
31struct cpuidle_governor *cpuidle_find_governor(const char *str)
32{
33 struct cpuidle_governor *gov;
34
35 list_for_each_entry(gov, &cpuidle_governors, governor_list)
36 if (!strncasecmp(s1: str, s2: gov->name, CPUIDLE_NAME_LEN))
37 return gov;
38
39 return NULL;
40}
41
42/**
43 * cpuidle_switch_governor - changes the governor
44 * @gov: the new target governor
45 * Must be called with cpuidle_lock acquired.
46 */
47int cpuidle_switch_governor(struct cpuidle_governor *gov)
48{
49 struct cpuidle_device *dev;
50
51 if (!gov)
52 return -EINVAL;
53
54 if (gov == cpuidle_curr_governor)
55 return 0;
56
57 cpuidle_uninstall_idle_handler();
58
59 if (cpuidle_curr_governor) {
60 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
61 cpuidle_disable_device(dev);
62 }
63
64 cpuidle_curr_governor = gov;
65
66 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
67 cpuidle_enable_device(dev);
68
69 cpuidle_install_idle_handler();
70 pr_info("cpuidle: using governor %s\n", gov->name);
71
72 return 0;
73}
74
75/**
76 * cpuidle_register_governor - registers a governor
77 * @gov: the governor
78 */
79int cpuidle_register_governor(struct cpuidle_governor *gov)
80{
81 int ret = -EEXIST;
82
83 if (!gov || !gov->select)
84 return -EINVAL;
85
86 if (cpuidle_disabled())
87 return -ENODEV;
88
89 mutex_lock(lock: &cpuidle_lock);
90 if (cpuidle_find_governor(str: gov->name) == NULL) {
91 ret = 0;
92 list_add_tail(new: &gov->governor_list, head: &cpuidle_governors);
93 if (!cpuidle_curr_governor ||
94 !strncasecmp(s1: param_governor, s2: gov->name, CPUIDLE_NAME_LEN) ||
95 (cpuidle_curr_governor->rating < gov->rating &&
96 strncasecmp(s1: param_governor, s2: cpuidle_curr_governor->name,
97 CPUIDLE_NAME_LEN)))
98 cpuidle_switch_governor(gov);
99 }
100 mutex_unlock(lock: &cpuidle_lock);
101
102 return ret;
103}
104
105/**
106 * cpuidle_governor_latency_req - Compute a latency constraint for CPU
107 * @cpu: Target CPU
108 */
109s64 cpuidle_governor_latency_req(unsigned int cpu)
110{
111 struct device *device = get_cpu_device(cpu);
112 int device_req = dev_pm_qos_raw_resume_latency(dev: device);
113 int global_req = cpu_latency_qos_limit();
114
115 if (device_req > global_req)
116 device_req = global_req;
117
118 return (s64)device_req * NSEC_PER_USEC;
119}
120