Root/drivers/cpufreq/cpufreq_userspace.c

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#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/smp.h>
17#include <linux/init.h>
18#include <linux/spinlock.h>
19#include <linux/interrupt.h>
20#include <linux/cpufreq.h>
21#include <linux/cpu.h>
22#include <linux/types.h>
23#include <linux/fs.h>
24#include <linux/sysfs.h>
25#include <linux/mutex.h>
26
27/**
28 * A few values needed by the userspace governor
29 */
30static DEFINE_PER_CPU(unsigned int, cpu_max_freq);
31static DEFINE_PER_CPU(unsigned int, cpu_min_freq);
32static DEFINE_PER_CPU(unsigned int, cpu_cur_freq); /* current CPU freq */
33static DEFINE_PER_CPU(unsigned int, cpu_set_freq); /* CPU freq desired by
34                            userspace */
35static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
36
37static DEFINE_MUTEX(userspace_mutex);
38static int cpus_using_userspace_governor;
39
40/* keep track of frequency transitions */
41static int
42userspace_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
43    void *data)
44{
45    struct cpufreq_freqs *freq = data;
46
47    if (!per_cpu(cpu_is_managed, freq->cpu))
48        return 0;
49
50    if (val == CPUFREQ_POSTCHANGE) {
51        pr_debug("saving cpu_cur_freq of cpu %u to be %u kHz\n",
52                freq->cpu, freq->new);
53        per_cpu(cpu_cur_freq, freq->cpu) = freq->new;
54    }
55
56    return 0;
57}
58
59static struct notifier_block userspace_cpufreq_notifier_block = {
60    .notifier_call = userspace_cpufreq_notifier
61};
62
63
64/**
65 * cpufreq_set - set the CPU frequency
66 * @policy: pointer to policy struct where freq is being set
67 * @freq: target frequency in kHz
68 *
69 * Sets the CPU frequency to freq.
70 */
71static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
72{
73    int ret = -EINVAL;
74
75    pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
76
77    mutex_lock(&userspace_mutex);
78    if (!per_cpu(cpu_is_managed, policy->cpu))
79        goto err;
80
81    per_cpu(cpu_set_freq, policy->cpu) = freq;
82
83    if (freq < per_cpu(cpu_min_freq, policy->cpu))
84        freq = per_cpu(cpu_min_freq, policy->cpu);
85    if (freq > per_cpu(cpu_max_freq, policy->cpu))
86        freq = per_cpu(cpu_max_freq, policy->cpu);
87
88    /*
89     * We're safe from concurrent calls to ->target() here
90     * as we hold the userspace_mutex lock. If we were calling
91     * cpufreq_driver_target, a deadlock situation might occur:
92     * A: cpufreq_set (lock userspace_mutex) ->
93     * cpufreq_driver_target(lock policy->lock)
94     * B: cpufreq_set_policy(lock policy->lock) ->
95     * __cpufreq_governor ->
96     * cpufreq_governor_userspace (lock userspace_mutex)
97     */
98    ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
99
100 err:
101    mutex_unlock(&userspace_mutex);
102    return ret;
103}
104
105
106static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
107{
108    return sprintf(buf, "%u\n", per_cpu(cpu_cur_freq, policy->cpu));
109}
110
111static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
112                   unsigned int event)
113{
114    unsigned int cpu = policy->cpu;
115    int rc = 0;
116
117    switch (event) {
118    case CPUFREQ_GOV_START:
119        if (!cpu_online(cpu))
120            return -EINVAL;
121        BUG_ON(!policy->cur);
122        mutex_lock(&userspace_mutex);
123
124        if (cpus_using_userspace_governor == 0) {
125            cpufreq_register_notifier(
126                    &userspace_cpufreq_notifier_block,
127                    CPUFREQ_TRANSITION_NOTIFIER);
128        }
129        cpus_using_userspace_governor++;
130
131        per_cpu(cpu_is_managed, cpu) = 1;
132        per_cpu(cpu_min_freq, cpu) = policy->min;
133        per_cpu(cpu_max_freq, cpu) = policy->max;
134        per_cpu(cpu_cur_freq, cpu) = policy->cur;
135        per_cpu(cpu_set_freq, cpu) = policy->cur;
136        pr_debug("managing cpu %u started "
137            "(%u - %u kHz, currently %u kHz)\n",
138                cpu,
139                per_cpu(cpu_min_freq, cpu),
140                per_cpu(cpu_max_freq, cpu),
141                per_cpu(cpu_cur_freq, cpu));
142
143        mutex_unlock(&userspace_mutex);
144        break;
145    case CPUFREQ_GOV_STOP:
146        mutex_lock(&userspace_mutex);
147        cpus_using_userspace_governor--;
148        if (cpus_using_userspace_governor == 0) {
149            cpufreq_unregister_notifier(
150                    &userspace_cpufreq_notifier_block,
151                    CPUFREQ_TRANSITION_NOTIFIER);
152        }
153
154        per_cpu(cpu_is_managed, cpu) = 0;
155        per_cpu(cpu_min_freq, cpu) = 0;
156        per_cpu(cpu_max_freq, cpu) = 0;
157        per_cpu(cpu_set_freq, cpu) = 0;
158        pr_debug("managing cpu %u stopped\n", cpu);
159        mutex_unlock(&userspace_mutex);
160        break;
161    case CPUFREQ_GOV_LIMITS:
162        mutex_lock(&userspace_mutex);
163        pr_debug("limit event for cpu %u: %u - %u kHz, "
164            "currently %u kHz, last set to %u kHz\n",
165            cpu, policy->min, policy->max,
166            per_cpu(cpu_cur_freq, cpu),
167            per_cpu(cpu_set_freq, cpu));
168        if (policy->max < per_cpu(cpu_set_freq, cpu)) {
169            __cpufreq_driver_target(policy, policy->max,
170                        CPUFREQ_RELATION_H);
171        } else if (policy->min > per_cpu(cpu_set_freq, cpu)) {
172            __cpufreq_driver_target(policy, policy->min,
173                        CPUFREQ_RELATION_L);
174        } else {
175            __cpufreq_driver_target(policy,
176                        per_cpu(cpu_set_freq, cpu),
177                        CPUFREQ_RELATION_L);
178        }
179        per_cpu(cpu_min_freq, cpu) = policy->min;
180        per_cpu(cpu_max_freq, cpu) = policy->max;
181        per_cpu(cpu_cur_freq, cpu) = policy->cur;
182        mutex_unlock(&userspace_mutex);
183        break;
184    }
185    return rc;
186}
187
188
189#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
190static
191#endif
192struct cpufreq_governor cpufreq_gov_userspace = {
193    .name = "userspace",
194    .governor = cpufreq_governor_userspace,
195    .store_setspeed = cpufreq_set,
196    .show_setspeed = show_speed,
197    .owner = THIS_MODULE,
198};
199
200static int __init cpufreq_gov_userspace_init(void)
201{
202    return cpufreq_register_governor(&cpufreq_gov_userspace);
203}
204
205
206static void __exit cpufreq_gov_userspace_exit(void)
207{
208    cpufreq_unregister_governor(&cpufreq_gov_userspace);
209}
210
211
212MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
213        "Russell King <rmk@arm.linux.org.uk>");
214MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
215MODULE_LICENSE("GPL");
216
217#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
218fs_initcall(cpufreq_gov_userspace_init);
219#else
220module_init(cpufreq_gov_userspace_init);
221#endif
222module_exit(cpufreq_gov_userspace_exit);
223

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