LXR linux/drivers/cpuidle/governor.c

   1/*
   2 * governor.c - governor support
   3 *
   4 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
   5 *               Shaohua Li <shaohua.li@intel.com>
   6 *               Adam Belay <abelay@novell.com>
   7 *
   8 * This code is licenced under the GPL.
   9 */
  10
  11#include <linux/cpu.h>
  12#include <linux/cpuidle.h>
  13#include <linux/mutex.h>
  14#include <linux/module.h>
  15#include <linux/pm_qos.h>
  16
  17#include "cpuidle.h"
  18
  19char param_governor[CPUIDLE_NAME_LEN];
  20
  21LIST_HEAD(cpuidle_governors);
  22struct cpuidle_governor *cpuidle_curr_governor;
  23struct cpuidle_governor *cpuidle_prev_governor;
  24
  25/**
  26 * cpuidle_find_governor - finds a governor of the specified name
  27 * @str: the name
  28 *
  29 * Must be called with cpuidle_lock acquired.
  30 */
  31struct cpuidle_governor *cpuidle_find_governor(const char *str)
  32{
  33        struct cpuidle_governor *gov;
  34
  35        list_for_each_entry(gov, &cpuidle_governors, governor_list)
  36                if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
  37                        return gov;
  38
  39        return NULL;
  40}
  41
  42/**
  43 * cpuidle_switch_governor - changes the governor
  44 * @gov: the new target governor
  45 * Must be called with cpuidle_lock acquired.
  46 */
  47int cpuidle_switch_governor(struct cpuidle_governor *gov)
  48{
  49        struct cpuidle_device *dev;
  50
  51        if (!gov)
  52                return -EINVAL;
  53
  54        if (gov == cpuidle_curr_governor)
  55                return 0;
  56
  57        cpuidle_uninstall_idle_handler();
  58
  59        if (cpuidle_curr_governor) {
  60                list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  61                        cpuidle_disable_device(dev);
  62        }
  63
  64        cpuidle_curr_governor = gov;
  65
  66        if (gov) {
  67                list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  68                        cpuidle_enable_device(dev);
  69                cpuidle_install_idle_handler();
  70                printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
  71        }
  72
  73        return 0;
  74}
  75
  76/**
  77 * cpuidle_register_governor - registers a governor
  78 * @gov: the governor
  79 */
  80int cpuidle_register_governor(struct cpuidle_governor *gov)
  81{
  82        int ret = -EEXIST;
  83
  84        if (!gov || !gov->select)
  85                return -EINVAL;
  86
  87        if (cpuidle_disabled())
  88                return -ENODEV;
  89
  90        mutex_lock(&cpuidle_lock);
  91        if (cpuidle_find_governor(gov->name) == NULL) {
  92                ret = 0;
  93                list_add_tail(&gov->governor_list, &cpuidle_governors);
  94                if (!cpuidle_curr_governor ||
  95                    !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
  96                    (cpuidle_curr_governor->rating < gov->rating &&
  97                     strncasecmp(param_governor, cpuidle_curr_governor->name,
  98                                 CPUIDLE_NAME_LEN)))
  99                        cpuidle_switch_governor(gov);
 100        }
 101        mutex_unlock(&cpuidle_lock);
 102
 103        return ret;
 104}
 105
 106/**
 107 * cpuidle_governor_latency_req - Compute a latency constraint for CPU
 108 * @cpu: Target CPU
 109 */
 110s64 cpuidle_governor_latency_req(unsigned int cpu)
 111{
 112        struct device *device = get_cpu_device(cpu);
 113        int device_req = dev_pm_qos_raw_resume_latency(device);
 114        int global_req = cpu_latency_qos_limit();
 115
 116        if (device_req > global_req)
 117                device_req = global_req;
 118
 119        return (s64)device_req * NSEC_PER_USEC;
 120}
 121