1 =============================
2 Subsystem Trace Points: power
3 =============================
4
5 The power tracing system captures events relat
6 within the kernel. Broadly speaking there are
7
8 - Power state switch which reports events re
9 cpuidle (C-states) and cpufreq (P-states)
10 - System clock related changes
11 - Power domains related changes and transiti
12
13 This document describes what each of the trace
14 might be useful.
15
16 Cf. include/trace/events/power.h for the event
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 ev
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_i
31
32 A suspend event is used to indicate the system
33 suspend mode:
34 ::
35
36 machine_suspend "state=%lu"
37
38
39 Note: the value of '-1' or '4294967295' for st
40 i.e. trace_cpu_idle(4, smp_processor_id()) mea
41 enters the idle state 4, while trace_cpu_idle(
42 means that the system exits the previous idle
43
44 The event which has 'state=4294967295' in the
45 space tools which are using it to detect the e
46 correctly draw the states diagrams and to calc
47
48 2. Clocks events
49 ================
50 The clock events are used for clock enable/dis
51 clock rate change.
52 ::
53
54 clock_enable "%s state=%lu cpu_id=%
55 clock_disable "%s state=%lu cpu_id=%
56 clock_set_rate "%s state=%lu
57
58 The first parameter gives the clock name (e.g.
59 The second parameter is '1' for enable, '0' fo
60 clock rate for set_rate.
61
62 3. Power domains events
63 =======================
64 The power domain events are used for power dom
65 ::
66
67 power_domain_target "%s state=%lu cpu_id=%
68
69 The first parameter gives the power domain nam
70 The second parameter is the power domain targe
71
72 4. PM QoS events
73 ================
74 The PM QoS events are used for QoS add/update/
75 target/flags update.
76 ::
77
78 pm_qos_update_target "action=%
79 pm_qos_update_flags "action=%
80
81 The first parameter gives the QoS action name
82 The second parameter is the previous QoS value
83 The third parameter is the current QoS value t
84
85 There are also events used for device PM QoS a
86 ::
87
88 dev_pm_qos_add_request "device=%
89 dev_pm_qos_update_request "device=%
90 dev_pm_qos_remove_request "device=%
91
92 The first parameter gives the device name whic
93 QoS requests.
94 The second parameter gives the request type (e
95 The third parameter is value to be added/updat
96
97 And, there are events used for CPU latency QoS
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
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