/*
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* governor.c - governor support
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*
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* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
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* Shaohua Li <shaohua.li@intel.com>
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* Adam Belay <abelay@novell.com>
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*
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* This code is licenced under the GPL.
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*/
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#include <linux/cpu.h>
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#include <linux/cpuidle.h>
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#include <linux/mutex.h>
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#include <linux/pm_qos.h>
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#include "cpuidle.h"
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LIST_HEAD(cpuidle_governors);
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struct cpuidle_governor *cpuidle_curr_governor;
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/**
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* __cpuidle_find_governor - finds a governor of the specified name
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* @str: the name
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*
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* Must be called with cpuidle_lock acquired.
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*/
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static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
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{
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struct cpuidle_governor *gov;
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list_for_each_entry(gov, &cpuidle_governors, governor_list)
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if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
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return gov;
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return NULL;
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}
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/**
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* cpuidle_switch_governor - changes the governor
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* @gov: the new target governor
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* Must be called with cpuidle_lock acquired.
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*/
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int cpuidle_switch_governor(struct cpuidle_governor *gov)
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{
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struct cpuidle_device *dev;
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if (!gov)
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return -EINVAL;
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if (gov == cpuidle_curr_governor)
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return 0;
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cpuidle_uninstall_idle_handler();
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if (cpuidle_curr_governor) {
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list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
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cpuidle_disable_device(dev);
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}
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cpuidle_curr_governor = gov;
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if (gov) {
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list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
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cpuidle_enable_device(dev);
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cpuidle_install_idle_handler();
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printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
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}
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return 0;
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}
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/**
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* cpuidle_register_governor - registers a governor
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* @gov: the governor
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*/
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int cpuidle_register_governor(struct cpuidle_governor *gov)
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{
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int ret = -EEXIST;
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if (!gov || !gov->select)
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return -EINVAL;
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if (cpuidle_disabled())
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return -ENODEV;
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mutex_lock(&cpuidle_lock);
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if (__cpuidle_find_governor(gov->name) == NULL) {
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ret = 0;
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list_add_tail(&gov->governor_list, &cpuidle_governors);
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if (!cpuidle_curr_governor ||
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cpuidle_curr_governor->rating < gov->rating)
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cpuidle_switch_governor(gov);
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}
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mutex_unlock(&cpuidle_lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(cpuidle_register_governor);
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/**
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* cpuidle_governor_latency_req - Compute a latency constraint for CPU
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* @cpu: Target CPU
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*/
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int cpuidle_governor_latency_req(unsigned int cpu)
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{
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int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
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struct device *device = get_cpu_device(cpu);
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int device_req = dev_pm_qos_raw_read_value(device);
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return device_req < global_req ? device_req : global_req;
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}
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