xref: /openbmc/linux/drivers/cpuidle/governor.c (revision 8e774e02)
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 
24 /**
25  * __cpuidle_find_governor - finds a governor of the specified name
26  * @str: the name
27  *
28  * Must be called with cpuidle_lock acquired.
29  */
30 static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
31 {
32 	struct cpuidle_governor *gov;
33 
34 	list_for_each_entry(gov, &cpuidle_governors, governor_list)
35 		if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
36 			return gov;
37 
38 	return NULL;
39 }
40 
41 /**
42  * cpuidle_switch_governor - changes the governor
43  * @gov: the new target governor
44  * Must be called with cpuidle_lock acquired.
45  */
46 int cpuidle_switch_governor(struct cpuidle_governor *gov)
47 {
48 	struct cpuidle_device *dev;
49 
50 	if (!gov)
51 		return -EINVAL;
52 
53 	if (gov == cpuidle_curr_governor)
54 		return 0;
55 
56 	cpuidle_uninstall_idle_handler();
57 
58 	if (cpuidle_curr_governor) {
59 		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
60 			cpuidle_disable_device(dev);
61 	}
62 
63 	cpuidle_curr_governor = gov;
64 
65 	if (gov) {
66 		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
67 			cpuidle_enable_device(dev);
68 		cpuidle_install_idle_handler();
69 		printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
70 	}
71 
72 	return 0;
73 }
74 
75 /**
76  * cpuidle_register_governor - registers a governor
77  * @gov: the governor
78  */
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  */
109 int cpuidle_governor_latency_req(unsigned int cpu)
110 {
111 	int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
112 	struct device *device = get_cpu_device(cpu);
113 	int device_req = dev_pm_qos_raw_resume_latency(device);
114 
115 	return device_req < global_req ? device_req : global_req;
116 }
117