Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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
21static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
22static 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 */
31static 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
58static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
59{
60 return sprintf(buf, "%u\n", policy->cur);
61}
62
63static 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
104static
105#endif
106struct 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
114static int __init cpufreq_gov_userspace_init(void)
115{
116 return cpufreq_register_governor(&cpufreq_gov_userspace);
117}
118
119static void __exit cpufreq_gov_userspace_exit(void)
120{
121 cpufreq_unregister_governor(&cpufreq_gov_userspace);
122}
123
124MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
125 "Russell King <rmk@arm.linux.org.uk>");
126MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
127MODULE_LICENSE("GPL");
128
129#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
130fs_initcall(cpufreq_gov_userspace_init);
131#else
132module_init(cpufreq_gov_userspace_init);
133#endif
134module_exit(cpufreq_gov_userspace_exit);