drivers/cpuquiet/governor.c

   1 /*
   2  * Copyright (c) 2012 NVIDIA CORPORATION.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; version 2 of the License.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  16  *
  17  */
  18
  19 #include <linux/mutex.h>
  20 #include <linux/module.h>
  21 #include <linux/cpuquiet.h>
  22
  23 #include "cpuquiet.h"
  24
  25 LIST_HEAD(cpuquiet_governors);
  26 struct cpuquiet_governor *cpuquiet_curr_governor;
  27
  28 struct cpuquiet_governor *cpuquiet_get_first_governor(void)
  29 {
  30         if (!list_empty(&cpuquiet_governors))
  31                 return list_entry(&cpuquiet_governors, struct cpuquiet_governor,
  32                                         governor_list);
  33         else
  34                 return NULL;
  35 }
  36
  37 struct cpuquiet_governor *cpuquiet_find_governor(const char *str)
  38 {
  39         struct cpuquiet_governor *gov;
  40
  41         list_for_each_entry(gov, &cpuquiet_governors, governor_list)
  42                 if (!strnicmp(str, gov->name, CPUQUIET_NAME_LEN))
  43                         return gov;
  44
  45         return NULL;
  46 }
  47
  48 int cpuquiet_switch_governor(struct cpuquiet_governor *gov)
  49 {
  50         int err = 0;
  51
  52         if (cpuquiet_curr_governor) {
  53                 if (cpuquiet_curr_governor->stop)
  54                         cpuquiet_curr_governor->stop();
  55                 module_put(cpuquiet_curr_governor->owner);
  56         }
  57
  58         cpuquiet_curr_governor = gov;
  59
  60         if (gov) {
  61                 if (!try_module_get(cpuquiet_curr_governor->owner))
  62                         return -EINVAL;
  63                 if (gov->start)
  64                         err = gov->start();
  65                 if (!err)
  66                         cpuquiet_curr_governor = gov;
  67         }
  68
  69         return err;
  70 }
  71
  72 int cpuquiet_register_governor(struct cpuquiet_governor *gov)
  73 {
  74         int ret = -EEXIST;
  75
  76         if (!gov)
  77                 return -EINVAL;
  78
  79         mutex_lock(&cpuquiet_lock);
  80         if (cpuquiet_find_governor(gov->name) == NULL) {
  81                 ret = 0;
  82                 list_add_tail(&gov->governor_list, &cpuquiet_governors);
  83                 if (!cpuquiet_curr_governor && cpuquiet_get_driver())
  84                         cpuquiet_switch_governor(gov);
  85         }
  86         mutex_unlock(&cpuquiet_lock);
  87
  88         return ret;
  89 }
  90
  91 void cpuquiet_unregister_governor(struct cpuquiet_governor *gov)
  92 {
  93         if (!gov)
  94                 return;
  95
  96         mutex_lock(&cpuquiet_lock);
  97         if (cpuquiet_curr_governor == gov)
  98                 cpuquiet_switch_governor(NULL);
  99         list_del(&gov->governor_list);
 100         mutex_unlock(&cpuquiet_lock);
 101 }