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 if (gov) { 67 list_for_each_entry(dev, &cpuidle_detected_devices, device_list) 68 cpuidle_enable_device(dev); 69 cpuidle_install_idle_handler(); 70 printk(KERN_INFO "cpuidle: using governor %s\n", gov->name); 71 } 72 73 return 0; 74 } 75 76 /** 77 * cpuidle_register_governor - registers a governor 78 * @gov: the governor 79 */ 80 int cpuidle_register_governor(struct cpuidle_governor *gov) 81 { 82 int ret = -EEXIST; 83 84 if (!gov || !gov->select) 85 return -EINVAL; 86 87 if (cpuidle_disabled()) 88 return -ENODEV; 89 90 mutex_lock(&cpuidle_lock); 91 if (cpuidle_find_governor(gov->name) == NULL) { 92 ret = 0; 93 list_add_tail(&gov->governor_list, &cpuidle_governors); 94 if (!cpuidle_curr_governor || 95 !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) || 96 (cpuidle_curr_governor->rating < gov->rating && 97 strncasecmp(param_governor, cpuidle_curr_governor->name, 98 CPUIDLE_NAME_LEN))) 99 cpuidle_switch_governor(gov); 100 } 101 mutex_unlock(&cpuidle_lock); 102 103 return ret; 104 } 105 106 /** 107 * cpuidle_governor_latency_req - Compute a latency constraint for CPU 108 * @cpu: Target CPU 109 */ 110 s64 cpuidle_governor_latency_req(unsigned int cpu) 111 { 112 int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY); 113 struct device *device = get_cpu_device(cpu); 114 int device_req = dev_pm_qos_raw_resume_latency(device); 115 116 if (device_req > global_req) 117 device_req = global_req; 118 119 return (s64)device_req * NSEC_PER_USEC; 120 } 121