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