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/pm_qos.h>
  15
  16 #include "cpuidle.h"
  17
  18 LIST_HEAD(cpuidle_governors);
  19 struct cpuidle_governor *cpuidle_curr_governor;
  20
  21 /**
  22  * __cpuidle_find_governor - finds a governor of the specified name
  23  * @str: the name
  24  *
  25  * Must be called with cpuidle_lock acquired.
  26  */
  27 static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
  28 {
  29         struct cpuidle_governor *gov;
  30
  31         list_for_each_entry(gov, &cpuidle_governors, governor_list)
  32                 if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
  33                         return gov;
  34
  35         return NULL;
  36 }
  37
  38 /**
  39  * cpuidle_switch_governor - changes the governor
  40  * @gov: the new target governor
  41  * Must be called with cpuidle_lock acquired.
  42  */
  43 int cpuidle_switch_governor(struct cpuidle_governor *gov)
  44 {
  45         struct cpuidle_device *dev;
  46
  47         if (!gov)
  48                 return -EINVAL;
  49
  50         if (gov == cpuidle_curr_governor)
  51                 return 0;
  52
  53         cpuidle_uninstall_idle_handler();
  54
  55         if (cpuidle_curr_governor) {
  56                 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  57                         cpuidle_disable_device(dev);
  58         }
  59
  60         cpuidle_curr_governor = gov;
  61
  62         if (gov) {
  63                 list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
  64                         cpuidle_enable_device(dev);
  65                 cpuidle_install_idle_handler();
  66                 printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
  67         }
  68
  69         return 0;
  70 }
  71
  72 /**
  73  * cpuidle_register_governor - registers a governor
  74  * @gov: the governor
  75  */
  76 int cpuidle_register_governor(struct cpuidle_governor *gov)
  77 {
  78         int ret = -EEXIST;
  79
  80         if (!gov || !gov->select)
  81                 return -EINVAL;
  82
  83         if (cpuidle_disabled())
  84                 return -ENODEV;
  85
  86         mutex_lock(&cpuidle_lock);
  87         if (__cpuidle_find_governor(gov->name) == NULL) {
  88                 ret = 0;
  89                 list_add_tail(&gov->governor_list, &cpuidle_governors);
  90                 if (!cpuidle_curr_governor ||
  91                     cpuidle_curr_governor->rating < gov->rating)
  92                         cpuidle_switch_governor(gov);
  93         }
  94         mutex_unlock(&cpuidle_lock);
  95
  96         return ret;
  97 }
  98
  99 /**
 100  * cpuidle_governor_latency_req - Compute a latency constraint for CPU
 101  * @cpu: Target CPU
 102  */
 103 int cpuidle_governor_latency_req(unsigned int cpu)
 104 {
 105         int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
 106         struct device *device = get_cpu_device(cpu);
 107         int device_req = dev_pm_qos_raw_read_value(device);
 108
 109         return device_req < global_req ? device_req : global_req;
 110 }