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
  19 char param_governor[CPUIDLE_NAME_LEN];
  20
  21 LIST_HEAD(cpuidle_governors);
  22 struct cpuidle_governor *cpuidle_curr_governor;
  23 struct 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  */
  31 struct 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  */
  47 int 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         list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  67                 cpuidle_enable_device(dev);
  68
  69         cpuidle_install_idle_handler();
  70         pr_info("cpuidle: using governor %s\n", gov->name);
  71
  72         return 0;
  73 }
  74
  75 /**
  76  * cpuidle_register_governor - registers a governor
  77  * @gov: the governor
  78  */
  79 int cpuidle_register_governor(struct cpuidle_governor *gov)
  80 {
  81         int ret = -EEXIST;
  82
  83         if (!gov || !gov->select)
  84                 return -EINVAL;
  85
  86         if (cpuidle_disabled())
  87                 return -ENODEV;
  88
  89         mutex_lock(&cpuidle_lock);
  90         if (cpuidle_find_governor(gov->name) == NULL) {
  91                 ret = 0;
  92                 list_add_tail(&gov->governor_list, &cpuidle_governors);
  93                 if (!cpuidle_curr_governor ||
  94                     !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
  95                     (cpuidle_curr_governor->rating < gov->rating &&
  96                      strncasecmp(param_governor, cpuidle_curr_governor->name,
  97                                  CPUIDLE_NAME_LEN)))
  98                         cpuidle_switch_governor(gov);
  99         }
 100         mutex_unlock(&cpuidle_lock);
 101
 102         return ret;
 103 }
 104
 105 /**
 106  * cpuidle_governor_latency_req - Compute a latency constraint for CPU
 107  * @cpu: Target CPU
 108  */
 109 s64 cpuidle_governor_latency_req(unsigned int cpu)
 110 {
 111         struct device *device = get_cpu_device(cpu);
 112         int device_req = dev_pm_qos_raw_resume_latency(device);
 113         int global_req = cpu_latency_qos_limit();
 114
 115         if (device_req > global_req)
 116                 device_req = global_req;
 117
 118         return (s64)device_req * NSEC_PER_USEC;
 119 }