drivers/cpuidle/governor.c

0001 /*
0002  * governor.c - governor support
0003  *
0004  * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
0005  *               Shaohua Li <shaohua.li@intel.com>
0006  *               Adam Belay <abelay@novell.com>
0007  *
0008  * This code is licenced under the GPL.
0009  */
0010
0011 #include <linux/cpu.h>
0012 #include <linux/cpuidle.h>
0013 #include <linux/mutex.h>
0014 #include <linux/module.h>
0015 #include <linux/pm_qos.h>
0016
0017 #include "cpuidle.h"
0018
0019 char param_governor[CPUIDLE_NAME_LEN];
0020
0021 LIST_HEAD(cpuidle_governors);
0022 struct cpuidle_governor *cpuidle_curr_governor;
0023 struct cpuidle_governor *cpuidle_prev_governor;
0024
0025 /**
0026  * cpuidle_find_governor - finds a governor of the specified name
0027  * @str: the name
0028  *
0029  * Must be called with cpuidle_lock acquired.
0030  */
0031 struct cpuidle_governor *cpuidle_find_governor(const char *str)
0032 {
0033     struct cpuidle_governor *gov;
0034
0035     list_for_each_entry(gov, &cpuidle_governors, governor_list)
0036         if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
0037             return gov;
0038
0039     return NULL;
0040 }
0041
0042 /**
0043  * cpuidle_switch_governor - changes the governor
0044  * @gov: the new target governor
0045  * Must be called with cpuidle_lock acquired.
0046  */
0047 int cpuidle_switch_governor(struct cpuidle_governor *gov)
0048 {
0049     struct cpuidle_device *dev;
0050
0051     if (!gov)
0052         return -EINVAL;
0053
0054     if (gov == cpuidle_curr_governor)
0055         return 0;
0056
0057     cpuidle_uninstall_idle_handler();
0058
0059     if (cpuidle_curr_governor) {
0060         list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
0061             cpuidle_disable_device(dev);
0062     }
0063
0064     cpuidle_curr_governor = gov;
0065
0066     if (gov) {
0067         list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
0068             cpuidle_enable_device(dev);
0069         cpuidle_install_idle_handler();
0070         printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
0071     }
0072
0073     return 0;
0074 }
0075
0076 /**
0077  * cpuidle_register_governor - registers a governor
0078  * @gov: the governor
0079  */
0080 int cpuidle_register_governor(struct cpuidle_governor *gov)
0081 {
0082     int ret = -EEXIST;
0083
0084     if (!gov || !gov->select)
0085         return -EINVAL;
0086
0087     if (cpuidle_disabled())
0088         return -ENODEV;
0089
0090     mutex_lock(&cpuidle_lock);
0091     if (cpuidle_find_governor(gov->name) == NULL) {
0092         ret = 0;
0093         list_add_tail(&gov->governor_list, &cpuidle_governors);
0094         if (!cpuidle_curr_governor ||
0095             !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
0096             (cpuidle_curr_governor->rating < gov->rating &&
0097              strncasecmp(param_governor, cpuidle_curr_governor->name,
0098                  CPUIDLE_NAME_LEN)))
0099             cpuidle_switch_governor(gov);
0100     }
0101     mutex_unlock(&cpuidle_lock);
0102
0103     return ret;
0104 }
0105
0106 /**
0107  * cpuidle_governor_latency_req - Compute a latency constraint for CPU
0108  * @cpu: Target CPU
0109  */
0110 s64 cpuidle_governor_latency_req(unsigned int cpu)
0111 {
0112     struct device *device = get_cpu_device(cpu);
0113     int device_req = dev_pm_qos_raw_resume_latency(device);
0114     int global_req = cpu_latency_qos_limit();
0115
0116     if (device_req > global_req)
0117         device_req = global_req;
0118
0119     return (s64)device_req * NSEC_PER_USEC;
0120 }