1 ============================= 1 =============================
2 Subsystem Trace Points: power 2 Subsystem Trace Points: power
3 ============================= 3 =============================
4 4
5 The power tracing system captures events relat 5 The power tracing system captures events related to power transitions
6 within the kernel. Broadly speaking there are 6 within the kernel. Broadly speaking there are three major subheadings:
7 7
8 - Power state switch which reports events re 8 - Power state switch which reports events related to suspend (S-states),
9 cpuidle (C-states) and cpufreq (P-states) 9 cpuidle (C-states) and cpufreq (P-states)
10 - System clock related changes 10 - System clock related changes
11 - Power domains related changes and transiti 11 - Power domains related changes and transitions
12 12
13 This document describes what each of the trace 13 This document describes what each of the tracepoints is and why they
14 might be useful. 14 might be useful.
15 15
16 Cf. include/trace/events/power.h for the event 16 Cf. include/trace/events/power.h for the events definitions.
17 17
18 1. Power state switch events 18 1. Power state switch events
19 ============================ 19 ============================
20 20
21 1.1 Trace API 21 1.1 Trace API
22 ----------------- 22 -----------------
23 23
24 A 'cpu' event class gathers the CPU-related ev 24 A 'cpu' event class gathers the CPU-related events: cpuidle and
25 cpufreq. 25 cpufreq.
26 :: 26 ::
27 27
28 cpu_idle "state=%lu cpu_id=%lu" 28 cpu_idle "state=%lu cpu_id=%lu"
29 cpu_frequency "state=%lu cpu_id=%lu" 29 cpu_frequency "state=%lu cpu_id=%lu"
30 cpu_frequency_limits "min=%lu max=%lu cpu_i 30 cpu_frequency_limits "min=%lu max=%lu cpu_id=%lu"
31 31
32 A suspend event is used to indicate the system 32 A suspend event is used to indicate the system going in and out of the
33 suspend mode: 33 suspend mode:
34 :: 34 ::
35 35
36 machine_suspend "state=%lu" 36 machine_suspend "state=%lu"
37 37
38 38
39 Note: the value of '-1' or '4294967295' for st 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()) mea 40 i.e. trace_cpu_idle(4, smp_processor_id()) means that the system
41 enters the idle state 4, while trace_cpu_idle( 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 42 means that the system exits the previous idle state.
43 43
44 The event which has 'state=4294967295' in the 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 e 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 calc 46 correctly draw the states diagrams and to calculate accurate statistics etc.
47 47
48 2. Clocks events 48 2. Clocks events
49 ================ 49 ================
50 The clock events are used for clock enable/dis 50 The clock events are used for clock enable/disable and for
51 clock rate change. 51 clock rate change.
52 :: 52 ::
53 53
54 clock_enable "%s state=%lu cpu_id=% 54 clock_enable "%s state=%lu cpu_id=%lu"
55 clock_disable "%s state=%lu cpu_id=% 55 clock_disable "%s state=%lu cpu_id=%lu"
56 clock_set_rate "%s state=%lu 56 clock_set_rate "%s state=%lu cpu_id=%lu"
57 57
58 The first parameter gives the clock name (e.g. 58 The first parameter gives the clock name (e.g. "gpio1_iclk").
59 The second parameter is '1' for enable, '0' fo 59 The second parameter is '1' for enable, '0' for disable, the target
60 clock rate for set_rate. 60 clock rate for set_rate.
61 61
62 3. Power domains events 62 3. Power domains events
63 ======================= 63 =======================
64 The power domain events are used for power dom 64 The power domain events are used for power domains transitions
65 :: 65 ::
66 66
67 power_domain_target "%s state=%lu cpu_id=% 67 power_domain_target "%s state=%lu cpu_id=%lu"
68 68
69 The first parameter gives the power domain nam 69 The first parameter gives the power domain name (e.g. "mpu_pwrdm").
70 The second parameter is the power domain targe 70 The second parameter is the power domain target state.
71 71
72 4. PM QoS events 72 4. PM QoS events
73 ================ 73 ================
74 The PM QoS events are used for QoS add/update/ 74 The PM QoS events are used for QoS add/update/remove request and for
75 target/flags update. 75 target/flags update.
76 :: 76 ::
77 77
78 pm_qos_update_target "action=% 78 pm_qos_update_target "action=%s prev_value=%d curr_value=%d"
79 pm_qos_update_flags "action=% 79 pm_qos_update_flags "action=%s prev_value=0x%x curr_value=0x%x"
80 80
81 The first parameter gives the QoS action name 81 The first parameter gives the QoS action name (e.g. "ADD_REQ").
82 The second parameter is the previous QoS value 82 The second parameter is the previous QoS value.
83 The third parameter is the current QoS value t 83 The third parameter is the current QoS value to update.
84 84
85 There are also events used for device PM QoS a 85 There are also events used for device PM QoS add/update/remove request.
86 :: 86 ::
87 87
88 dev_pm_qos_add_request "device=% 88 dev_pm_qos_add_request "device=%s type=%s new_value=%d"
89 dev_pm_qos_update_request "device=% 89 dev_pm_qos_update_request "device=%s type=%s new_value=%d"
90 dev_pm_qos_remove_request "device=% 90 dev_pm_qos_remove_request "device=%s type=%s new_value=%d"
91 91
92 The first parameter gives the device name whic 92 The first parameter gives the device name which tries to add/update/remove
93 QoS requests. 93 QoS requests.
94 The second parameter gives the request type (e 94 The second parameter gives the request type (e.g. "DEV_PM_QOS_RESUME_LATENCY").
95 The third parameter is value to be added/updat 95 The third parameter is value to be added/updated/removed.
96 96
97 And, there are events used for CPU latency QoS 97 And, there are events used for CPU latency QoS add/update/remove request.
98 :: 98 ::
99 99
100 pm_qos_add_request "value=%d" 100 pm_qos_add_request "value=%d"
101 pm_qos_update_request "value=%d" 101 pm_qos_update_request "value=%d"
102 pm_qos_remove_request "value=%d" 102 pm_qos_remove_request "value=%d"
103 103
104 The parameter is the value to be added/updated 104 The parameter is the value to be added/updated/removed.
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