Quelle  governor.c   Sprache: C

/*
 * governor.c - governor support
 *
 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *               Shaohua Li <shaohua.li@intel.com>
 *               Adam Belay <abelay@novell.com>
 *
 * This code is licenced under the GPL.
 */

#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/pm_qos.h>

#include "cpuidle.h"

char param_governor[CPUIDLE_NAME_LEN];

LIST_HEAD(cpuidle_governors);
struct cpuidle_governor *cpuidle_curr_governor;
struct cpuidle_governor *cpuidle_prev_governor;

/**
 * cpuidle_find_governor - finds a governor of the specified name
 * @str: the name
 *
 * Must be called with cpuidle_lock acquired.
 */
struct cpuidle_governor *cpuidle_find_governor(const char *str)
{
 struct cpuidle_governor *gov;

 list_for_each_entry(gov, &cpuidle_governors, governor_list)
  if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
   return gov;

 return NULL;
}

/**
 * cpuidle_switch_governor - changes the governor
 * @gov: the new target governor
 * Must be called with cpuidle_lock acquired.
 */
int cpuidle_switch_governor(struct cpuidle_governor *gov)
{
 struct cpuidle_device *dev;

 if (!gov)
  return -EINVAL;

 if (gov == cpuidle_curr_governor)
  return 0;

 cpuidle_uninstall_idle_handler();

 if (cpuidle_curr_governor) {
  list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
   cpuidle_disable_device(dev);
 }

 cpuidle_curr_governor = gov;

 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  cpuidle_enable_device(dev);

 cpuidle_install_idle_handler();
 pr_info("cpuidle: using governor %s\n", gov->name);

 return 0;
}

/**
 * cpuidle_register_governor - registers a governor
 * @gov: the governor
 */
int cpuidle_register_governor(struct cpuidle_governor *gov)
{
 int ret = -EEXIST;

 if (!gov || !gov->select)
  return -EINVAL;

 if (cpuidle_disabled())
  return -ENODEV;

 mutex_lock(&cpuidle_lock);
 if (cpuidle_find_governor(gov->name) == NULL) {
  ret = 0;
  list_add_tail(&gov->governor_list, &cpuidle_governors);
  if (!cpuidle_curr_governor ||
      !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
      (cpuidle_curr_governor->rating < gov->rating &&
       strncasecmp(param_governor, cpuidle_curr_governor->name,
     CPUIDLE_NAME_LEN)))
   cpuidle_switch_governor(gov);
 }
 mutex_unlock(&cpuidle_lock);

 return ret;
}

/**
 * cpuidle_governor_latency_req - Compute a latency constraint for CPU
 * @cpu: Target CPU
 */
s64 cpuidle_governor_latency_req(unsigned int cpu)
{
 struct device *device = get_cpu_device(cpu);
 int device_req = dev_pm_qos_raw_resume_latency(device);
 int global_req = cpu_latency_qos_limit();

 if (device_req > global_req)
  device_req = global_req;

 return (s64)device_req * NSEC_PER_USEC;
}