xref: /linux/drivers/cpufreq/cpufreq_userspace.c (revision b889fcf63cb62e7fdb7816565e28f44dbe4a76a5)
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/kernel.h>
17 #include <linux/module.h>
18 #include <linux/smp.h>
19 #include <linux/init.h>
20 #include <linux/spinlock.h>
21 #include <linux/interrupt.h>
22 #include <linux/cpufreq.h>
23 #include <linux/cpu.h>
24 #include <linux/types.h>
25 #include <linux/fs.h>
26 #include <linux/sysfs.h>
27 #include <linux/mutex.h>
28 
29 /**
30  * A few values needed by the userspace governor
31  */
32 static DEFINE_PER_CPU(unsigned int, cpu_max_freq);
33 static DEFINE_PER_CPU(unsigned int, cpu_min_freq);
34 static DEFINE_PER_CPU(unsigned int, cpu_cur_freq); /* current CPU freq */
35 static DEFINE_PER_CPU(unsigned int, cpu_set_freq); /* CPU freq desired by
36 							userspace */
37 static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
38 
39 static DEFINE_MUTEX(userspace_mutex);
40 static int cpus_using_userspace_governor;
41 
42 /* keep track of frequency transitions */
43 static int
44 userspace_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
45 	void *data)
46 {
47 	struct cpufreq_freqs *freq = data;
48 
49 	if (!per_cpu(cpu_is_managed, freq->cpu))
50 		return 0;
51 
52 	if (val == CPUFREQ_POSTCHANGE) {
53 		pr_debug("saving cpu_cur_freq of cpu %u to be %u kHz\n",
54 				freq->cpu, freq->new);
55 		per_cpu(cpu_cur_freq, freq->cpu) = freq->new;
56 	}
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  * @policy: pointer to policy struct where freq is being set
69  * @freq: target frequency in kHz
70  *
71  * Sets the CPU frequency to freq.
72  */
73 static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
74 {
75 	int ret = -EINVAL;
76 
77 	pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
78 
79 	mutex_lock(&userspace_mutex);
80 	if (!per_cpu(cpu_is_managed, policy->cpu))
81 		goto err;
82 
83 	per_cpu(cpu_set_freq, policy->cpu) = freq;
84 
85 	if (freq < per_cpu(cpu_min_freq, policy->cpu))
86 		freq = per_cpu(cpu_min_freq, policy->cpu);
87 	if (freq > per_cpu(cpu_max_freq, policy->cpu))
88 		freq = per_cpu(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) ->
95 	 *      cpufreq_driver_target(lock policy->lock)
96 	 * B: cpufreq_set_policy(lock policy->lock) ->
97 	 *      __cpufreq_governor ->
98 	 *         cpufreq_governor_userspace (lock userspace_mutex)
99 	 */
100 	ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
101 
102  err:
103 	mutex_unlock(&userspace_mutex);
104 	return ret;
105 }
106 
107 
108 static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
109 {
110 	return sprintf(buf, "%u\n", per_cpu(cpu_cur_freq, policy->cpu));
111 }
112 
113 static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
114 				   unsigned int event)
115 {
116 	unsigned int cpu = policy->cpu;
117 	int rc = 0;
118 
119 	switch (event) {
120 	case CPUFREQ_GOV_START:
121 		if (!cpu_online(cpu))
122 			return -EINVAL;
123 		BUG_ON(!policy->cur);
124 		mutex_lock(&userspace_mutex);
125 
126 		if (cpus_using_userspace_governor == 0) {
127 			cpufreq_register_notifier(
128 					&userspace_cpufreq_notifier_block,
129 					CPUFREQ_TRANSITION_NOTIFIER);
130 		}
131 		cpus_using_userspace_governor++;
132 
133 		per_cpu(cpu_is_managed, cpu) = 1;
134 		per_cpu(cpu_min_freq, cpu) = policy->min;
135 		per_cpu(cpu_max_freq, cpu) = policy->max;
136 		per_cpu(cpu_cur_freq, cpu) = policy->cur;
137 		per_cpu(cpu_set_freq, cpu) = policy->cur;
138 		pr_debug("managing cpu %u started "
139 			"(%u - %u kHz, currently %u kHz)\n",
140 				cpu,
141 				per_cpu(cpu_min_freq, cpu),
142 				per_cpu(cpu_max_freq, cpu),
143 				per_cpu(cpu_cur_freq, cpu));
144 
145 		mutex_unlock(&userspace_mutex);
146 		break;
147 	case CPUFREQ_GOV_STOP:
148 		mutex_lock(&userspace_mutex);
149 		cpus_using_userspace_governor--;
150 		if (cpus_using_userspace_governor == 0) {
151 			cpufreq_unregister_notifier(
152 					&userspace_cpufreq_notifier_block,
153 					CPUFREQ_TRANSITION_NOTIFIER);
154 		}
155 
156 		per_cpu(cpu_is_managed, cpu) = 0;
157 		per_cpu(cpu_min_freq, cpu) = 0;
158 		per_cpu(cpu_max_freq, cpu) = 0;
159 		per_cpu(cpu_set_freq, cpu) = 0;
160 		pr_debug("managing cpu %u stopped\n", cpu);
161 		mutex_unlock(&userspace_mutex);
162 		break;
163 	case CPUFREQ_GOV_LIMITS:
164 		mutex_lock(&userspace_mutex);
165 		pr_debug("limit event for cpu %u: %u - %u kHz, "
166 			"currently %u kHz, last set to %u kHz\n",
167 			cpu, policy->min, policy->max,
168 			per_cpu(cpu_cur_freq, cpu),
169 			per_cpu(cpu_set_freq, cpu));
170 		if (policy->max < per_cpu(cpu_set_freq, cpu)) {
171 			__cpufreq_driver_target(policy, policy->max,
172 						CPUFREQ_RELATION_H);
173 		} else if (policy->min > per_cpu(cpu_set_freq, cpu)) {
174 			__cpufreq_driver_target(policy, policy->min,
175 						CPUFREQ_RELATION_L);
176 		} else {
177 			__cpufreq_driver_target(policy,
178 						per_cpu(cpu_set_freq, cpu),
179 						CPUFREQ_RELATION_L);
180 		}
181 		per_cpu(cpu_min_freq, cpu) = policy->min;
182 		per_cpu(cpu_max_freq, cpu) = policy->max;
183 		per_cpu(cpu_cur_freq, cpu) = policy->cur;
184 		mutex_unlock(&userspace_mutex);
185 		break;
186 	}
187 	return rc;
188 }
189 
190 
191 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
192 static
193 #endif
194 struct cpufreq_governor cpufreq_gov_userspace = {
195 	.name		= "userspace",
196 	.governor	= cpufreq_governor_userspace,
197 	.store_setspeed	= cpufreq_set,
198 	.show_setspeed	= show_speed,
199 	.owner		= THIS_MODULE,
200 };
201 
202 static int __init cpufreq_gov_userspace_init(void)
203 {
204 	return cpufreq_register_governor(&cpufreq_gov_userspace);
205 }
206 
207 
208 static void __exit cpufreq_gov_userspace_exit(void)
209 {
210 	cpufreq_unregister_governor(&cpufreq_gov_userspace);
211 }
212 
213 
214 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
215 		"Russell King <rmk@arm.linux.org.uk>");
216 MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
217 MODULE_LICENSE("GPL");
218 
219 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
220 fs_initcall(cpufreq_gov_userspace_init);
221 #else
222 module_init(cpufreq_gov_userspace_init);
223 #endif
224 module_exit(cpufreq_gov_userspace_exit);
225