/*
   *  linux/drivers/cpufreq/cpufreq_userspace.c
   *
   *  Copyright (C)  2001 Russell King
   *            (C)  2002 - 2004 Dominik Brodowski <linux@brodo.de>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   */

  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/smp.h>
  #include <linux/init.h>
  #include <linux/spinlock.h>
  #include <linux/interrupt.h>
  #include <linux/cpufreq.h>

  #include <linux/cpu.h>

  #include <linux/types.h>
  #include <linux/fs.h>
  #include <linux/sysfs.h>

  #include <linux/mutex.h>

  /**
   * A few values needed by the userspace governor
   */

  static DEFINE_PER_CPU(unsigned int, cpu_max_freq);
  static DEFINE_PER_CPU(unsigned int, cpu_min_freq);
  static DEFINE_PER_CPU(unsigned int, cpu_cur_freq); /* current CPU freq */
  static DEFINE_PER_CPU(unsigned int, cpu_set_freq); /* CPU freq desired by
  							userspace */
  static DEFINE_PER_CPU(unsigned int, cpu_is_managed);

  static DEFINE_MUTEX(userspace_mutex);

  static int cpus_using_userspace_governor;

  /* keep track of frequency transitions */

  static int

  userspace_cpufreq_notifier(struct notifier_block *nb, unsigned long val,

  	void *data)

  {

  	struct cpufreq_freqs *freq = data;

  	if (!per_cpu(cpu_is_managed, freq->cpu))

  		return 0;

  	if (val == CPUFREQ_POSTCHANGE) {
  		pr_debug("saving cpu_cur_freq of cpu %u to be %u kHz
  ",
  				freq->cpu, freq->new);
  		per_cpu(cpu_cur_freq, freq->cpu) = freq->new;
  	}

  	return 0;

  }
  
  static struct notifier_block userspace_cpufreq_notifier_block = {

  	.notifier_call  = userspace_cpufreq_notifier

  };

  /**

   * 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;

  	pr_debug("cpufreq_set for cpu %u, freq %u kHz
  ", policy->cpu, freq);

  	mutex_lock(&userspace_mutex);

  	if (!per_cpu(cpu_is_managed, policy->cpu))

  		goto err;

  	per_cpu(cpu_set_freq, policy->cpu) = freq;

  	if (freq < per_cpu(cpu_min_freq, policy->cpu))
  		freq = per_cpu(cpu_min_freq, policy->cpu);
  	if (freq > per_cpu(cpu_max_freq, policy->cpu))
  		freq = per_cpu(cpu_max_freq, policy->cpu);

  
  	/*
  	 * We're safe from concurrent calls to ->target() here

  	 * as we hold the userspace_mutex lock. If we were calling

  	 * cpufreq_driver_target, a deadlock situation might occur:

  	 * A: cpufreq_set (lock userspace_mutex) ->
  	 *      cpufreq_driver_target(lock policy->lock)
  	 * B: cpufreq_set_policy(lock policy->lock) ->
  	 *      __cpufreq_governor ->
  	 *         cpufreq_governor_userspace (lock userspace_mutex)

  	 */

  	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
  ", per_cpu(cpu_cur_freq, policy->cpu));

  }

  static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
  				   unsigned int event)
  {
  	unsigned int cpu = policy->cpu;

  	int rc = 0;

  	switch (event) {
  	case CPUFREQ_GOV_START:
  		if (!cpu_online(cpu))
  			return -EINVAL;
  		BUG_ON(!policy->cur);

  		mutex_lock(&userspace_mutex);

  		if (cpus_using_userspace_governor == 0) {
  			cpufreq_register_notifier(
  					&userspace_cpufreq_notifier_block,
  					CPUFREQ_TRANSITION_NOTIFIER);
  		}
  		cpus_using_userspace_governor++;

  		per_cpu(cpu_is_managed, cpu) = 1;
  		per_cpu(cpu_min_freq, cpu) = policy->min;
  		per_cpu(cpu_max_freq, cpu) = policy->max;
  		per_cpu(cpu_cur_freq, cpu) = policy->cur;
  		per_cpu(cpu_set_freq, cpu) = policy->cur;

  		pr_debug("managing cpu %u started "

  			"(%u - %u kHz, currently %u kHz)
  ",
  				cpu,
  				per_cpu(cpu_min_freq, cpu),
  				per_cpu(cpu_max_freq, cpu),
  				per_cpu(cpu_cur_freq, cpu));

  		mutex_unlock(&userspace_mutex);

  		break;
  	case CPUFREQ_GOV_STOP:

  		mutex_lock(&userspace_mutex);

  		cpus_using_userspace_governor--;
  		if (cpus_using_userspace_governor == 0) {
  			cpufreq_unregister_notifier(
  					&userspace_cpufreq_notifier_block,
  					CPUFREQ_TRANSITION_NOTIFIER);
  		}

  		per_cpu(cpu_is_managed, cpu) = 0;
  		per_cpu(cpu_min_freq, cpu) = 0;
  		per_cpu(cpu_max_freq, cpu) = 0;
  		per_cpu(cpu_set_freq, cpu) = 0;

  		pr_debug("managing cpu %u stopped
  ", cpu);

  		mutex_unlock(&userspace_mutex);

  		break;
  	case CPUFREQ_GOV_LIMITS:

  		mutex_lock(&userspace_mutex);

  		pr_debug("limit event for cpu %u: %u - %u kHz, "

  			"currently %u kHz, last set to %u kHz
  ",
  			cpu, policy->min, policy->max,

  			per_cpu(cpu_cur_freq, cpu),
  			per_cpu(cpu_set_freq, cpu));
  		if (policy->max < per_cpu(cpu_set_freq, cpu)) {

  			__cpufreq_driver_target(policy, policy->max,
  						CPUFREQ_RELATION_H);

  		} else if (policy->min > per_cpu(cpu_set_freq, cpu)) {

  			__cpufreq_driver_target(policy, policy->min,
  						CPUFREQ_RELATION_L);

  		} else {
  			__cpufreq_driver_target(policy,
  						per_cpu(cpu_set_freq, cpu),

  						CPUFREQ_RELATION_L);
  		}

  		per_cpu(cpu_min_freq, cpu) = policy->min;
  		per_cpu(cpu_max_freq, cpu) = policy->max;
  		per_cpu(cpu_cur_freq, cpu) = policy->cur;

  		mutex_unlock(&userspace_mutex);

  		break;
  	}

  	return rc;

  }

  #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
  static
  #endif

  struct cpufreq_governor cpufreq_gov_userspace = {
  	.name		= "userspace",
  	.governor	= cpufreq_governor_userspace,

  	.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

  fs_initcall(cpufreq_gov_userspace_init);

  #else
  module_init(cpufreq_gov_userspace_init);
  #endif

  module_exit(cpufreq_gov_userspace_exit);