text: // SPDX-License-Identifier: GPL-2.0-only
  
  /*
   *  linux/drivers/cpufreq/cpufreq_userspace.c
   *
   *  Copyright (C)  2001 Russell King
   *            (C)  2002 - 2004 Dominik Brodowski <linux@brodo.de>
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/cpufreq.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/slab.h>
  
  static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
  static DEFINE_MUTEX(userspace_mutex);
  
  /**
   * cpufreq_set - set the CPU frequency
   * @policy: pointer to policy struct where freq is being set
   * @freq: target frequency in kHz
   *
   * Sets the CPU frequency to freq.
   */
  static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
  {
  	int ret = -EINVAL;
  	unsigned int *setspeed = policy->governor_data;
  
  	pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
  
  	mutex_lock(&userspace_mutex);
  	if (!per_cpu(cpu_is_managed, policy->cpu))
  		goto err;
  
  	*setspeed = freq;
  
  	ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
   err:
  	mutex_unlock(&userspace_mutex);
  	return ret;
  }
  
  static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
  {
  	return sprintf(buf, "%u\n", policy->cur);
  }
  
  static int cpufreq_userspace_policy_init(struct cpufreq_policy *policy)
  {
  	unsigned int *setspeed;
  
  	setspeed = kzalloc(sizeof(*setspeed), GFP_KERNEL);
  	if (!setspeed)
  		return -ENOMEM;
  
  	policy->governor_data = setspeed;
  	return 0;
  }
  
  static void cpufreq_userspace_policy_exit(struct cpufreq_policy *policy)
  {
  	mutex_lock(&userspace_mutex);
  	kfree(policy->governor_data);
  	policy->governor_data = NULL;
  	mutex_unlock(&userspace_mutex);
  }
  
  static int cpufreq_userspace_policy_start(struct cpufreq_policy *policy)
  {
  	unsigned int *setspeed = policy->governor_data;
  
  	BUG_ON(!policy->cur);
  	pr_debug("started managing cpu %u\n", policy->cpu);
  
  	mutex_lock(&userspace_mutex);
  	per_cpu(cpu_is_managed, policy->cpu) = 1;
  	*setspeed = policy->cur;
  	mutex_unlock(&userspace_mutex);
  	return 0;
  }
  
  static void cpufreq_userspace_policy_stop(struct cpufreq_policy *policy)
  {
  	unsigned int *setspeed = policy->governor_data;
  
  	pr_debug("managing cpu %u stopped\n", policy->cpu);
  
  	mutex_lock(&userspace_mutex);
  	per_cpu(cpu_is_managed, policy->cpu) = 0;
  	*setspeed = 0;
  	mutex_unlock(&userspace_mutex);
  }
  
  static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
  {
  	unsigned int *setspeed = policy->governor_data;
  
  	mutex_lock(&userspace_mutex);
  
  	pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz, last set to %u kHz\n",
  		 policy->cpu, policy->min, policy->max, policy->cur, *setspeed);
  
  	if (policy->max < *setspeed)
  		__cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H);
  	else if (policy->min > *setspeed)
  		__cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L);
  	else
  		__cpufreq_driver_target(policy, *setspeed, CPUFREQ_RELATION_L);
  
  	mutex_unlock(&userspace_mutex);
  }
  
  static struct cpufreq_governor cpufreq_gov_userspace = {
  	.name		= "userspace",
  	.init		= cpufreq_userspace_policy_init,
  	.exit		= cpufreq_userspace_policy_exit,
  	.start		= cpufreq_userspace_policy_start,
  	.stop		= cpufreq_userspace_policy_stop,
  	.limits		= cpufreq_userspace_policy_limits,
  	.store_setspeed	= cpufreq_set,
  	.show_setspeed	= show_speed,
  	.owner		= THIS_MODULE,
  };
  
  static int __init cpufreq_gov_userspace_init(void)
  {
  	return cpufreq_register_governor(&cpufreq_gov_userspace);
  }
  
  static void __exit cpufreq_gov_userspace_exit(void)
  {
  	cpufreq_unregister_governor(&cpufreq_gov_userspace);
  }
  
  MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
  		"Russell King <rmk@arm.linux.org.uk>");
  MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
  MODULE_LICENSE("GPL");
  
  #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
  struct cpufreq_governor *cpufreq_default_governor(void)
  {
  	return &cpufreq_gov_userspace;
  }
  
  fs_initcall(cpufreq_gov_userspace_init);
  #else
  module_init(cpufreq_gov_userspace_init);
  #endif
  module_exit(cpufreq_gov_userspace_exit);
  