[CPUFREQ] Keep userspace governor quiet when it is not being used
[linux-2.6.git] / 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 #include <asm/uaccess.h>
28
29
30 /**
31  * A few values needed by the userspace governor
32  */
33 static unsigned int     cpu_max_freq[NR_CPUS];
34 static unsigned int     cpu_min_freq[NR_CPUS];
35 static unsigned int     cpu_cur_freq[NR_CPUS]; /* current CPU freq */
36 static unsigned int     cpu_set_freq[NR_CPUS]; /* CPU freq desired by userspace */
37 static unsigned int     cpu_is_managed[NR_CPUS];
38
39 static DEFINE_MUTEX     (userspace_mutex);
40 static int cpus_using_userspace_governor;
41
42 #define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_GOVERNOR, "userspace", msg)
43
44 /* keep track of frequency transitions */
45 static int
46 userspace_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
47                        void *data)
48 {
49         struct cpufreq_freqs *freq = data;
50
51         if (!cpu_is_managed[freq->cpu])
52                 return 0;
53
54         dprintk("saving cpu_cur_freq of cpu %u to be %u kHz\n",
55                         freq->cpu, freq->new);
56         cpu_cur_freq[freq->cpu] = freq->new;
57
58         return 0;
59 }
60
61 static struct notifier_block userspace_cpufreq_notifier_block = {
62         .notifier_call  = userspace_cpufreq_notifier
63 };
64
65
66 /**
67  * cpufreq_set - set the CPU frequency
68  * @freq: target frequency in kHz
69  * @cpu: CPU for which the frequency is to be set
70  *
71  * Sets the CPU frequency to freq.
72  */
73 static int cpufreq_set(unsigned int freq, struct cpufreq_policy *policy)
74 {
75         int ret = -EINVAL;
76
77         dprintk("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
78
79         mutex_lock(&userspace_mutex);
80         if (!cpu_is_managed[policy->cpu])
81                 goto err;
82
83         cpu_set_freq[policy->cpu] = freq;
84
85         if (freq < cpu_min_freq[policy->cpu])
86                 freq = cpu_min_freq[policy->cpu];
87         if (freq > cpu_max_freq[policy->cpu])
88                 freq = cpu_max_freq[policy->cpu];
89
90         /*
91          * We're safe from concurrent calls to ->target() here
92          * as we hold the userspace_mutex lock. If we were calling
93          * cpufreq_driver_target, a deadlock situation might occur:
94          * A: cpufreq_set (lock userspace_mutex) -> cpufreq_driver_target(lock policy->lock)
95          * B: cpufreq_set_policy(lock policy->lock) -> __cpufreq_governor -> cpufreq_governor_userspace (lock userspace_mutex)
96          */
97         ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
98
99  err:
100         mutex_unlock(&userspace_mutex);
101         return ret;
102 }
103
104
105 /************************** sysfs interface ************************/
106 static ssize_t show_speed (struct cpufreq_policy *policy, char *buf)
107 {
108         return sprintf (buf, "%u\n", cpu_cur_freq[policy->cpu]);
109 }
110
111 static ssize_t
112 store_speed (struct cpufreq_policy *policy, const char *buf, size_t count)
113 {
114         unsigned int freq = 0;
115         unsigned int ret;
116
117         ret = sscanf (buf, "%u", &freq);
118         if (ret != 1)
119                 return -EINVAL;
120
121         cpufreq_set(freq, policy);
122
123         return count;
124 }
125
126 static struct freq_attr freq_attr_scaling_setspeed =
127 {
128         .attr = { .name = "scaling_setspeed", .mode = 0644, .owner = THIS_MODULE },
129         .show = show_speed,
130         .store = store_speed,
131 };
132
133 static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
134                                    unsigned int event)
135 {
136         unsigned int cpu = policy->cpu;
137         int rc = 0;
138
139         switch (event) {
140         case CPUFREQ_GOV_START:
141                 if (!cpu_online(cpu))
142                         return -EINVAL;
143                 BUG_ON(!policy->cur);
144                 mutex_lock(&userspace_mutex);
145                 rc = sysfs_create_file (&policy->kobj,
146                                         &freq_attr_scaling_setspeed.attr);
147                 if (rc)
148                         goto start_out;
149
150                 if (cpus_using_userspace_governor == 0) {
151                         cpufreq_register_notifier(
152                                         &userspace_cpufreq_notifier_block,
153                                         CPUFREQ_TRANSITION_NOTIFIER);
154                 }
155                 cpus_using_userspace_governor++;
156
157                 cpu_is_managed[cpu] = 1;
158                 cpu_min_freq[cpu] = policy->min;
159                 cpu_max_freq[cpu] = policy->max;
160                 cpu_cur_freq[cpu] = policy->cur;
161                 cpu_set_freq[cpu] = policy->cur;
162                 dprintk("managing cpu %u started (%u - %u kHz, currently %u kHz)\n", cpu, cpu_min_freq[cpu], cpu_max_freq[cpu], cpu_cur_freq[cpu]);
163 start_out:
164                 mutex_unlock(&userspace_mutex);
165                 break;
166         case CPUFREQ_GOV_STOP:
167                 mutex_lock(&userspace_mutex);
168                 cpus_using_userspace_governor--;
169                 if (cpus_using_userspace_governor == 0) {
170                         cpufreq_unregister_notifier(
171                                         &userspace_cpufreq_notifier_block,
172                                         CPUFREQ_TRANSITION_NOTIFIER);
173                 }
174
175                 cpu_is_managed[cpu] = 0;
176                 cpu_min_freq[cpu] = 0;
177                 cpu_max_freq[cpu] = 0;
178                 cpu_set_freq[cpu] = 0;
179                 sysfs_remove_file (&policy->kobj, &freq_attr_scaling_setspeed.attr);
180                 dprintk("managing cpu %u stopped\n", cpu);
181                 mutex_unlock(&userspace_mutex);
182                 break;
183         case CPUFREQ_GOV_LIMITS:
184                 mutex_lock(&userspace_mutex);
185                 dprintk("limit event for cpu %u: %u - %u kHz,"
186                         "currently %u kHz, last set to %u kHz\n",
187                         cpu, policy->min, policy->max,
188                         cpu_cur_freq[cpu], cpu_set_freq[cpu]);
189                 if (policy->max < cpu_set_freq[cpu]) {
190                         __cpufreq_driver_target(policy, policy->max,
191                                                 CPUFREQ_RELATION_H);
192                 }
193                 else if (policy->min > cpu_set_freq[cpu]) {
194                         __cpufreq_driver_target(policy, policy->min,
195                                                 CPUFREQ_RELATION_L);
196                 }
197                 else {
198                         __cpufreq_driver_target(policy, cpu_set_freq[cpu],
199                                                 CPUFREQ_RELATION_L);
200                 }
201                 cpu_min_freq[cpu] = policy->min;
202                 cpu_max_freq[cpu] = policy->max;
203                 cpu_cur_freq[cpu] = policy->cur;
204                 mutex_unlock(&userspace_mutex);
205                 break;
206         }
207         return rc;
208 }
209
210
211 struct cpufreq_governor cpufreq_gov_userspace = {
212         .name           = "userspace",
213         .governor       = cpufreq_governor_userspace,
214         .owner          = THIS_MODULE,
215 };
216 EXPORT_SYMBOL(cpufreq_gov_userspace);
217
218 static int __init cpufreq_gov_userspace_init(void)
219 {
220         return cpufreq_register_governor(&cpufreq_gov_userspace);
221 }
222
223
224 static void __exit cpufreq_gov_userspace_exit(void)
225 {
226         cpufreq_unregister_governor(&cpufreq_gov_userspace);
227 }
228
229
230 MODULE_AUTHOR ("Dominik Brodowski <linux@brodo.de>, Russell King <rmk@arm.linux.org.uk>");
231 MODULE_DESCRIPTION ("CPUfreq policy governor 'userspace'");
232 MODULE_LICENSE ("GPL");
233
234 fs_initcall(cpufreq_gov_userspace_init);
235 module_exit(cpufreq_gov_userspace_exit);