1 
2 /*
3  *  linux/drivers/cpufreq/cpufreq_userspace.c
4  *
5  *  Copyright (C)  2001 Russell King
6  *            (C)  2002 - 2004 Dominik Brodowski <linux@brodo.de>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  *
12  */
13 
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 
16 #include <linux/cpufreq.h>
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/mutex.h>
20 
21 static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
22 static DEFINE_MUTEX(userspace_mutex);
23 
24 /**
25  * cpufreq_set - set the CPU frequency
26  * @policy: pointer to policy struct where freq is being set
27  * @freq: target frequency in kHz
28  *
29  * Sets the CPU frequency to freq.
30  */
31 static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
32 {
33 	int ret = -EINVAL;
34 
35 	pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
36 
37 	mutex_lock(&userspace_mutex);
38 	if (!per_cpu(cpu_is_managed, policy->cpu))
39 		goto err;
40 
41 	/*
42 	 * We're safe from concurrent calls to ->target() here
43 	 * as we hold the userspace_mutex lock. If we were calling
44 	 * cpufreq_driver_target, a deadlock situation might occur:
45 	 * A: cpufreq_set (lock userspace_mutex) ->
46 	 *      cpufreq_driver_target(lock policy->lock)
47 	 * B: cpufreq_set_policy(lock policy->lock) ->
48 	 *      __cpufreq_governor ->
49 	 *         cpufreq_governor_userspace (lock userspace_mutex)
50 	 */
51 	ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
52 
53  err:
54 	mutex_unlock(&userspace_mutex);
55 	return ret;
56 }
57 
58 static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
59 {
60 	return sprintf(buf, "%u\n", policy->cur);
61 }
62 
63 static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
64 				   unsigned int event)
65 {
66 	unsigned int cpu = policy->cpu;
67 	int rc = 0;
68 
69 	switch (event) {
70 	case CPUFREQ_GOV_START:
71 		BUG_ON(!policy->cur);
72 		pr_debug("started managing cpu %u\n", cpu);
73 
74 		mutex_lock(&userspace_mutex);
75 		per_cpu(cpu_is_managed, cpu) = 1;
76 		mutex_unlock(&userspace_mutex);
77 		break;
78 	case CPUFREQ_GOV_STOP:
79 		pr_debug("managing cpu %u stopped\n", cpu);
80 
81 		mutex_lock(&userspace_mutex);
82 		per_cpu(cpu_is_managed, cpu) = 0;
83 		mutex_unlock(&userspace_mutex);
84 		break;
85 	case CPUFREQ_GOV_LIMITS:
86 		mutex_lock(&userspace_mutex);
87 		pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz\n",
88 			cpu, policy->min, policy->max,
89 			policy->cur);
90 
91 		if (policy->max < policy->cur)
92 			__cpufreq_driver_target(policy, policy->max,
93 						CPUFREQ_RELATION_H);
94 		else if (policy->min > policy->cur)
95 			__cpufreq_driver_target(policy, policy->min,
96 						CPUFREQ_RELATION_L);
97 		mutex_unlock(&userspace_mutex);
98 		break;
99 	}
100 	return rc;
101 }
102 
103 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
104 static
105 #endif
106 struct cpufreq_governor cpufreq_gov_userspace = {
107 	.name		= "userspace",
108 	.governor	= cpufreq_governor_userspace,
109 	.store_setspeed	= cpufreq_set,
110 	.show_setspeed	= show_speed,
111 	.owner		= THIS_MODULE,
112 };
113 
114 static int __init cpufreq_gov_userspace_init(void)
115 {
116 	return cpufreq_register_governor(&cpufreq_gov_userspace);
117 }
118 
119 static void __exit cpufreq_gov_userspace_exit(void)
120 {
121 	cpufreq_unregister_governor(&cpufreq_gov_userspace);
122 }
123 
124 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
125 		"Russell King <rmk@arm.linux.org.uk>");
126 MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
127 MODULE_LICENSE("GPL");
128 
129 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
130 fs_initcall(cpufreq_gov_userspace_init);
131 #else
132 module_init(cpufreq_gov_userspace_init);
133 #endif
134 module_exit(cpufreq_gov_userspace_exit);
135