summaryrefslogtreecommitdiffstats
path: root/drivers/cpufreq/cpufreq_userspace.c
blob: 03078090b5f76e15d263f3a035f575f9e7901342 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134

/*
 *  linux/drivers/cpufreq/cpufreq_userspace.c
 *
 *  Copyright (C)  2001 Russell King
 *            (C)  2002 - 2004 Dominik Brodowski <linux@brodo.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mutex.h>

static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
static DEFINE_MUTEX(userspace_mutex);

/**
 * cpufreq_set - set the CPU frequency
 * @policy: pointer to policy struct where freq is being set
 * @freq: target frequency in kHz
 *
 * Sets the CPU frequency to freq.
 */
static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
{
	int ret = -EINVAL;

	pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);

	mutex_lock(&userspace_mutex);
	if (!per_cpu(cpu_is_managed, policy->cpu))
		goto err;

	/*
	 * We're safe from concurrent calls to ->target() here
	 * as we hold the userspace_mutex lock. If we were calling
	 * cpufreq_driver_target, a deadlock situation might occur:
	 * A: cpufreq_set (lock userspace_mutex) ->
	 *      cpufreq_driver_target(lock policy->lock)
	 * B: cpufreq_set_policy(lock policy->lock) ->
	 *      __cpufreq_governor ->
	 *         cpufreq_governor_userspace (lock userspace_mutex)
	 */
	ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);

 err:
	mutex_unlock(&userspace_mutex);
	return ret;
}

static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
{
	return sprintf(buf, "%u\n", policy->cur);
}

static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
				   unsigned int event)
{
	unsigned int cpu = policy->cpu;
	int rc = 0;

	switch (event) {
	case CPUFREQ_GOV_START:
		BUG_ON(!policy->cur);
		pr_debug("started managing cpu %u\n", cpu);

		mutex_lock(&userspace_mutex);
		per_cpu(cpu_is_managed, cpu) = 1;
		mutex_unlock(&userspace_mutex);
		break;
	case CPUFREQ_GOV_STOP:
		pr_debug("managing cpu %u stopped\n", cpu);

		mutex_lock(&userspace_mutex);
		per_cpu(cpu_is_managed, cpu) = 0;
		mutex_unlock(&userspace_mutex);
		break;
	case CPUFREQ_GOV_LIMITS:
		mutex_lock(&userspace_mutex);
		pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz\n",
			cpu, policy->min, policy->max,
			policy->cur);

		if (policy->max < policy->cur)
			__cpufreq_driver_target(policy, policy->max,
						CPUFREQ_RELATION_H);
		else if (policy->min > policy->cur)
			__cpufreq_driver_target(policy, policy->min,
						CPUFREQ_RELATION_L);
		mutex_unlock(&userspace_mutex);
		break;
	}
	return rc;
}

#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
static
#endif
struct cpufreq_governor cpufreq_gov_userspace = {
	.name		= "userspace",
	.governor	= cpufreq_governor_userspace,
	.store_setspeed	= cpufreq_set,
	.show_setspeed	= show_speed,
	.owner		= THIS_MODULE,
};

static int __init cpufreq_gov_userspace_init(void)
{
	return cpufreq_register_governor(&cpufreq_gov_userspace);
}

static void __exit cpufreq_gov_userspace_exit(void)
{
	cpufreq_unregister_governor(&cpufreq_gov_userspace);
}

MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
		"Russell King <rmk@arm.linux.org.uk>");
MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
MODULE_LICENSE("GPL");

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
fs_initcall(cpufreq_gov_userspace_init);
#else
module_init(cpufreq_gov_userspace_init);
#endif
module_exit(cpufreq_gov_userspace_exit);