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 	if (gov) {
67 		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
68 			cpuidle_enable_device(dev);
69 		cpuidle_install_idle_handler();
70 		printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
71 	}
72 
73 	return 0;
74 }
75 
76 /**
77  * cpuidle_register_governor - registers a governor
78  * @gov: the governor
79  */
cpuidle_register_governor(struct cpuidle_governor * gov)80 int cpuidle_register_governor(struct cpuidle_governor *gov)
81 {
82 	int ret = -EEXIST;
83 
84 	if (!gov || !gov->select)
85 		return -EINVAL;
86 
87 	if (cpuidle_disabled())
88 		return -ENODEV;
89 
90 	mutex_lock(&cpuidle_lock);
91 	if (cpuidle_find_governor(gov->name) == NULL) {
92 		ret = 0;
93 		list_add_tail(&gov->governor_list, &cpuidle_governors);
94 		if (!cpuidle_curr_governor ||
95 		    !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
96 		    (cpuidle_curr_governor->rating < gov->rating &&
97 		     strncasecmp(param_governor, cpuidle_curr_governor->name,
98 				 CPUIDLE_NAME_LEN)))
99 			cpuidle_switch_governor(gov);
100 	}
101 	mutex_unlock(&cpuidle_lock);
102 
103 	return ret;
104 }
105 
106 /**
107  * cpuidle_governor_latency_req - Compute a latency constraint for CPU
108  * @cpu: Target CPU
109  */
cpuidle_governor_latency_req(unsigned int cpu)110 s64 cpuidle_governor_latency_req(unsigned int cpu)
111 {
112 	struct device *device = get_cpu_device(cpu);
113 	int device_req = dev_pm_qos_raw_resume_latency(device);
114 	int global_req = cpu_latency_qos_limit();
115 
116 	if (device_req > global_req)
117 		device_req = global_req;
118 
119 	return (s64)device_req * NSEC_PER_USEC;
120 }
121