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
19 char param_governor[CPUIDLE_NAME_LEN];
20
21 LIST_HEAD(cpuidle_governors);
22 struct cpuidle_governor *cpuidle_curr_governor;
23 struct 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 */
cpuidle_find_governor(const char * str)31 struct 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(str, 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 */
cpuidle_switch_governor(struct cpuidle_governor * gov)47 int 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 */
cpuidle_register_governor(struct cpuidle_governor * gov)79 int 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(&cpuidle_lock);
90 if (cpuidle_find_governor(gov->name) == NULL) {
91 ret = 0;
92 list_add_tail(&gov->governor_list, &cpuidle_governors);
93 if (!cpuidle_curr_governor ||
94 !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
95 (cpuidle_curr_governor->rating < gov->rating &&
96 strncasecmp(param_governor, cpuidle_curr_governor->name,
97 CPUIDLE_NAME_LEN)))
98 cpuidle_switch_governor(gov);
99 }
100 mutex_unlock(&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 */
cpuidle_governor_latency_req(unsigned int cpu)109 s64 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(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