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/cpufreq.h>
  17 #include <linux/init.h>
  18 #include <linux/module.h>
  19 #include <linux/mutex.h>
  20
  21 static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
  22 static 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  */
  31 static 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
  58 static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
  59 {
  60         return sprintf(buf, "%u\n", policy->cur);
  61 }
  62
  63 static 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
 104 static
 105 #endif
 106 struct 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
 114 static int __init cpufreq_gov_userspace_init(void)
 115 {
 116         return cpufreq_register_governor(&cpufreq_gov_userspace);
 117 }
 118
 119 static void __exit cpufreq_gov_userspace_exit(void)
 120 {
 121         cpufreq_unregister_governor(&cpufreq_gov_userspace);
 122 }
 123
 124 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
 125                 "Russell King <rmk@arm.linux.org.uk>");
 126 MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
 127 MODULE_LICENSE("GPL");
 128
 129 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
 130 fs_initcall(cpufreq_gov_userspace_init);
 131 #else
 132 module_init(cpufreq_gov_userspace_init);
 133 #endif
 134 module_exit(cpufreq_gov_userspace_exit);