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 #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                 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
 190 static
 191 #endif
 192 struct 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
 200 static int __init cpufreq_gov_userspace_init(void)
 201 {
 202         return cpufreq_register_governor(&cpufreq_gov_userspace);
 203 }
 204
 205
 206 static void __exit cpufreq_gov_userspace_exit(void)
 207 {
 208         cpufreq_unregister_governor(&cpufreq_gov_userspace);
 209 }
 210
 211
 212 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
 213                 "Russell King <rmk@arm.linux.org.uk>");
 214 MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
 215 MODULE_LICENSE("GPL");
 216
 217 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
 218 fs_initcall(cpufreq_gov_userspace_init);
 219 #else
 220 module_init(cpufreq_gov_userspace_init);
 221 #endif
 222 module_exit(cpufreq_gov_userspace_exit);