projects / linux-2.6-block.git / blame
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|---|---|---|
| 4b95f135 JP |
1 | |
| 2 | Subsystem Trace Points: power | |
| 3 | ||
| 4 | The power tracing system captures events related to power transitions | |
| 5 | within the kernel. Broadly speaking there are three major subheadings: | |
| 6 | ||
| 7 | o Power state switch which reports events related to suspend (S-states), | |
| 8 | cpuidle (C-states) and cpufreq (P-states) | |
| 9 | o System clock related changes | |
| 10 | o Power domains related changes and transitions | |
| 11 | ||
| 12 | This document describes what each of the tracepoints is and why they | |
| 13 | might be useful. | |
| 14 | ||
| 15 | Cf. include/trace/events/power.h for the events definitions. | |
| 16 | ||
| 17 | 1. Power state switch events | |
| 18 | ============================ | |
| 19 | ||
| 43720bd6 | 20 | 1.1 Trace API |
| 4b95f135 JP |
21 | ----------------- |
| 22 | ||
| 23 | A 'cpu' event class gathers the CPU-related events: cpuidle and | |
| 24 | cpufreq. | |
| 25 | ||
| 26 | cpu_idle "state=%lu cpu_id=%lu" | |
| 27 | cpu_frequency "state=%lu cpu_id=%lu" | |
| 28 | ||
| 29 | A suspend event is used to indicate the system going in and out of the | |
| 30 | suspend mode: | |
| 31 | ||
| 32 | machine_suspend "state=%lu" | |
| 33 | ||
| 34 | ||
| 35 | Note: the value of '-1' or '4294967295' for state means an exit from the current state, | |
| 36 | i.e. trace_cpu_idle(4, smp_processor_id()) means that the system | |
| 37 | enters the idle state 4, while trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()) | |
| 38 | means that the system exits the previous idle state. | |
| 39 | ||
| 40 | The event which has 'state=4294967295' in the trace is very important to the user | |
| 41 | space tools which are using it to detect the end of the current state, and so to | |
| 42 | correctly draw the states diagrams and to calculate accurate statistics etc. | |
| 43 | ||
| 4b95f135 JP |
44 | 2. Clocks events |
| 45 | ================ | |
| 46 | The clock events are used for clock enable/disable and for | |
| 47 | clock rate change. | |
| 48 | ||
| 49 | clock_enable "%s state=%lu cpu_id=%lu" | |
| 50 | clock_disable "%s state=%lu cpu_id=%lu" | |
| 51 | clock_set_rate "%s state=%lu cpu_id=%lu" | |
| 52 | ||
| 53 | The first parameter gives the clock name (e.g. "gpio1_iclk"). | |
| 54 | The second parameter is '1' for enable, '0' for disable, the target | |
| 55 | clock rate for set_rate. | |
| 56 | ||
| 57 | 3. Power domains events | |
| 58 | ======================= | |
| 59 | The power domain events are used for power domains transitions | |
| 60 | ||
| 61 | power_domain_target "%s state=%lu cpu_id=%lu" | |
| 62 | ||
| 63 | The first parameter gives the power domain name (e.g. "mpu_pwrdm"). | |
| 64 | The second parameter is the power domain target state. | |
| 65 |