1 ============================= 2 Subsystem Trace Points: power 3 ============================= 4 5 The power tracing system captures events related to power transitions 6 within the kernel. Broadly speaking there are three major subheadings: 7 8 - Power state switch which reports events related to suspend (S-states), 9 cpuidle (C-states) and cpufreq (P-states) 10 - System clock related changes 11 - Power domains related changes and transitions 12 13 This document describes what each of the tracepoints is and why they 14 might be useful. 15 16 Cf. include/trace/events/power.h for the events definitions. 17 18 1. Power state switch events 19 ============================ 20 21 1.1 Trace API 22 ----------------- 23 24 A 'cpu' event class gathers the CPU-related events: cpuidle and 25 cpufreq. 26 :: 27 28 cpu_idle "state=%lu cpu_id=%lu" 29 cpu_frequency "state=%lu cpu_id=%lu" 30 cpu_frequency_limits "min=%lu max=%lu cpu_id=%lu" 31 32 A suspend event is used to indicate the system going in and out of the 33 suspend mode: 34 :: 35 36 machine_suspend "state=%lu" 37 38 39 Note: the value of '-1' or '4294967295' for state means an exit from the current state, 40 i.e. trace_cpu_idle(4, smp_processor_id()) means that the system 41 enters the idle state 4, while trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()) 42 means that the system exits the previous idle state. 43 44 The event which has 'state=4294967295' in the trace is very important to the user 45 space tools which are using it to detect the end of the current state, and so to 46 correctly draw the states diagrams and to calculate accurate statistics etc. 47 48 2. Clocks events 49 ================ 50 The clock events are used for clock enable/disable and for 51 clock rate change. 52 :: 53 54 clock_enable "%s state=%lu cpu_id=%lu" 55 clock_disable "%s state=%lu cpu_id=%lu" 56 clock_set_rate "%s state=%lu cpu_id=%lu" 57 58 The first parameter gives the clock name (e.g. "gpio1_iclk"). 59 The second parameter is '1' for enable, '0' for disable, the target 60 clock rate for set_rate. 61 62 3. Power domains events 63 ======================= 64 The power domain events are used for power domains transitions 65 :: 66 67 power_domain_target "%s state=%lu cpu_id=%lu" 68 69 The first parameter gives the power domain name (e.g. "mpu_pwrdm"). 70 The second parameter is the power domain target state. 71 72 4. PM QoS events 73 ================ 74 The PM QoS events are used for QoS add/update/remove request and for 75 target/flags update. 76 :: 77 78 pm_qos_update_target "action=%s prev_value=%d curr_value=%d" 79 pm_qos_update_flags "action=%s prev_value=0x%x curr_value=0x%x" 80 81 The first parameter gives the QoS action name (e.g. "ADD_REQ"). 82 The second parameter is the previous QoS value. 83 The third parameter is the current QoS value to update. 84 85 There are also events used for device PM QoS add/update/remove request. 86 :: 87 88 dev_pm_qos_add_request "device=%s type=%s new_value=%d" 89 dev_pm_qos_update_request "device=%s type=%s new_value=%d" 90 dev_pm_qos_remove_request "device=%s type=%s new_value=%d" 91 92 The first parameter gives the device name which tries to add/update/remove 93 QoS requests. 94 The second parameter gives the request type (e.g. "DEV_PM_QOS_RESUME_LATENCY"). 95 The third parameter is value to be added/updated/removed. 96 97 And, there are events used for CPU latency QoS add/update/remove request. 98 :: 99 100 pm_qos_add_request "value=%d" 101 pm_qos_update_request "value=%d" 102 pm_qos_remove_request "value=%d" 103 104 The parameter is the value to be added/updated/removed.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.