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| 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 | |
| 142 |
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