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/mutex.h>
  12 #include <linux/cpuidle.h>
  13
  14 #include "cpuidle.h"
  15
  16 LIST_HEAD(cpuidle_governors);
  17 struct cpuidle_governor *cpuidle_curr_governor;
  18
  19 /**
  20  * __cpuidle_find_governor - finds a governor of the specified name
  21  * @str: the name
  22  *
  23  * Must be called with cpuidle_lock acquired.
  24  */
  25 static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
  26 {
  27         struct cpuidle_governor *gov;
  28
  29         list_for_each_entry(gov, &cpuidle_governors, governor_list)
  30                 if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
  31                         return gov;
  32
  33         return NULL;
  34 }
  35
  36 /**
  37  * cpuidle_switch_governor - changes the governor
  38  * @gov: the new target governor
  39  * Must be called with cpuidle_lock acquired.
  40  */
  41 int cpuidle_switch_governor(struct cpuidle_governor *gov)
  42 {
  43         struct cpuidle_device *dev;
  44
  45         if (!gov)
  46                 return -EINVAL;
  47
  48         if (gov == cpuidle_curr_governor)
  49                 return 0;
  50
  51         cpuidle_uninstall_idle_handler();
  52
  53         if (cpuidle_curr_governor) {
  54                 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  55                         cpuidle_disable_device(dev);
  56         }
  57
  58         cpuidle_curr_governor = gov;
  59
  60         if (gov) {
  61                 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  62                         cpuidle_enable_device(dev);
  63                 cpuidle_install_idle_handler();
  64                 printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
  65         }
  66
  67         return 0;
  68 }
  69
  70 /**
  71  * cpuidle_register_governor - registers a governor
  72  * @gov: the governor
  73  */
  74 int cpuidle_register_governor(struct cpuidle_governor *gov)
  75 {
  76         int ret = -EEXIST;
  77
  78         if (!gov || !gov->select)
  79                 return -EINVAL;
  80
  81         if (cpuidle_disabled())
  82                 return -ENODEV;
  83
  84         mutex_lock(&cpuidle_lock);
  85         if (__cpuidle_find_governor(gov->name) == NULL) {
  86                 ret = 0;
  87                 list_add_tail(&gov->governor_list, &cpuidle_governors);
  88                 if (!cpuidle_curr_governor ||
  89                     cpuidle_curr_governor->rating < gov->rating)
  90                         cpuidle_switch_governor(gov);
  91         }
  92         mutex_unlock(&cpuidle_lock);
  93
  94         return ret;
  95 }