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
 19char param_governor[CPUIDLE_NAME_LEN];
 20
 21LIST_HEAD(cpuidle_governors);
 22struct cpuidle_governor *cpuidle_curr_governor;
 23struct 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 */
 31struct 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 */
 47int 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 */
 79int 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 */
109s64 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	int global_wake_req = cpu_wakeup_latency_qos_limit();
115
116	if (global_req > global_wake_req)
117		global_req = global_wake_req;
118
119	if (device_req > global_req)
120		device_req = global_req;
121
122	return (s64)device_req * NSEC_PER_USEC;
123}