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
  24 /**
  25  * __cpuidle_find_governor - finds a governor of the specified name
  26  * @str: the name
  27  *
  28  * Must be called with cpuidle_lock acquired.
  29  */
  30 static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
  31 {
  32         struct cpuidle_governor *gov;
  33
  34         list_for_each_entry(gov, &cpuidle_governors, governor_list)
  35                 if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
  36                         return gov;
  37
  38         return NULL;
  39 }
  40
  41 /**
  42  * cpuidle_switch_governor - changes the governor
  43  * @gov: the new target governor
  44  * Must be called with cpuidle_lock acquired.
  45  */
  46 int cpuidle_switch_governor(struct cpuidle_governor *gov)
  47 {
  48         struct cpuidle_device *dev;
  49
  50         if (!gov)
  51                 return -EINVAL;
  52
  53         if (gov == cpuidle_curr_governor)
  54                 return 0;
  55
  56         cpuidle_uninstall_idle_handler();
  57
  58         if (cpuidle_curr_governor) {
  59                 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  60                         cpuidle_disable_device(dev);
  61         }
  62
  63         cpuidle_curr_governor = gov;
  64
  65         if (gov) {
  66                 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  67                         cpuidle_enable_device(dev);
  68                 cpuidle_install_idle_handler();
  69                 printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
  70         }
  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 int cpuidle_governor_latency_req(unsigned int cpu)
 110 {
 111         int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
 112         struct device *device = get_cpu_device(cpu);
 113         int device_req = dev_pm_qos_raw_read_value(device);
 114
 115         return device_req < global_req ? device_req : global_req;
 116 }