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/module.h>
  13 #include <linux/cpuidle.h>
  14
  15 #include "cpuidle.h"
  16
  17 LIST_HEAD(cpuidle_governors);
  18 struct cpuidle_governor *cpuidle_curr_governor;
  19
  20 /**
  21  * __cpuidle_find_governor - finds a governor of the specified name
  22  * @str: the name
  23  *
  24  * Must be called with cpuidle_lock acquired.
  25  */
  26 static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
  27 {
  28         struct cpuidle_governor *gov;
  29
  30         list_for_each_entry(gov, &cpuidle_governors, governor_list)
  31                 if (!strnicmp(str, gov->name, CPUIDLE_NAME_LEN))
  32                         return gov;
  33
  34         return NULL;
  35 }
  36
  37 /**
  38  * cpuidle_switch_governor - changes the governor
  39  * @gov: the new target governor
  40  *
  41  * NOTE: "gov" can be NULL to specify disabled
  42  * Must be called with cpuidle_lock acquired.
  43  */
  44 int cpuidle_switch_governor(struct cpuidle_governor *gov)
  45 {
  46         struct cpuidle_device *dev;
  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                 module_put(cpuidle_curr_governor->owner);
  57         }
  58
  59         cpuidle_curr_governor = gov;
  60
  61         if (gov) {
  62                 if (!try_module_get(cpuidle_curr_governor->owner))
  63                         return -EINVAL;
  64                 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  65                         cpuidle_enable_device(dev);
  66                 cpuidle_install_idle_handler();
  67                 printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
  68         }
  69
  70         return 0;
  71 }
  72
  73 /**
  74  * cpuidle_register_governor - registers a governor
  75  * @gov: the governor
  76  */
  77 int cpuidle_register_governor(struct cpuidle_governor *gov)
  78 {
  79         int ret = -EEXIST;
  80
  81         if (!gov || !gov->select)
  82                 return -EINVAL;
  83
  84         if (cpuidle_disabled())
  85                 return -ENODEV;
  86
  87         mutex_lock(&cpuidle_lock);
  88         if (__cpuidle_find_governor(gov->name) == NULL) {
  89                 ret = 0;
  90                 list_add_tail(&gov->governor_list, &cpuidle_governors);
  91                 if (!cpuidle_curr_governor ||
  92                     cpuidle_curr_governor->rating < gov->rating)
  93                         cpuidle_switch_governor(gov);
  94         }
  95         mutex_unlock(&cpuidle_lock);
  96
  97         return ret;
  98 }
  99
 100 /**
 101  * cpuidle_replace_governor - find a replacement governor
 102  * @exclude_rating: the rating that will be skipped while looking for
 103  * new governor.
 104  */
 105 static struct cpuidle_governor *cpuidle_replace_governor(int exclude_rating)
 106 {
 107         struct cpuidle_governor *gov;
 108         struct cpuidle_governor *ret_gov = NULL;
 109         unsigned int max_rating = 0;
 110
 111         list_for_each_entry(gov, &cpuidle_governors, governor_list) {
 112                 if (gov->rating == exclude_rating)
 113                         continue;
 114                 if (gov->rating > max_rating) {
 115                         max_rating = gov->rating;
 116                         ret_gov = gov;
 117                 }
 118         }
 119
 120         return ret_gov;
 121 }
 122
 123 /**
 124  * cpuidle_unregister_governor - unregisters a governor
 125  * @gov: the governor
 126  */
 127 void cpuidle_unregister_governor(struct cpuidle_governor *gov)
 128 {
 129         if (!gov)
 130                 return;
 131
 132         mutex_lock(&cpuidle_lock);
 133         if (gov == cpuidle_curr_governor) {
 134                 struct cpuidle_governor *new_gov;
 135                 new_gov = cpuidle_replace_governor(gov->rating);
 136                 cpuidle_switch_governor(new_gov);
 137         }
 138         list_del(&gov->governor_list);
 139         mutex_unlock(&cpuidle_lock);
 140 }
 141