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author | Jean Pihet <j-pihet@ti.com> | 2011-01-05 19:49:02 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2011-01-05 21:25:29 +0100 |
commit | 4b95f135f606c87e4056b6d7fd3c5781c818858b (patch) | |
tree | fb2ca090436141cd1c2641ab313e14e564a92afe /Documentation/trace | |
parent | 938cfed18bec2c7361f37efc954712a7cc42c353 (diff) | |
download | linux-4b95f135f606c87e4056b6d7fd3c5781c818858b.tar.bz2 |
tools, perf: Documentation for the power events API
Provides documentation for the following:
- the new power trace API,
- the old (legacy) power trace API,
- the DEPRECATED Kconfig option usage.
Signed-off-by: Jean Pihet <j-pihet@ti.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: trenn@suse.de
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: linux-pm@lists.linux-foundation.org
LKML-Reference: <1294253342-29056-3-git-send-email-j-pihet@ti.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/trace')
-rw-r--r-- | Documentation/trace/events-power.txt | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/Documentation/trace/events-power.txt b/Documentation/trace/events-power.txt new file mode 100644 index 000000000000..96d87b67fe37 --- /dev/null +++ b/Documentation/trace/events-power.txt @@ -0,0 +1,90 @@ + + Subsystem Trace Points: power + +The power tracing system captures events related to power transitions +within the kernel. Broadly speaking there are three major subheadings: + + o Power state switch which reports events related to suspend (S-states), + cpuidle (C-states) and cpufreq (P-states) + o System clock related changes + o Power domains related changes and transitions + +This document describes what each of the tracepoints is and why they +might be useful. + +Cf. include/trace/events/power.h for the events definitions. + +1. Power state switch events +============================ + +1.1 New trace API +----------------- + +A 'cpu' event class gathers the CPU-related events: cpuidle and +cpufreq. + +cpu_idle "state=%lu cpu_id=%lu" +cpu_frequency "state=%lu cpu_id=%lu" + +A suspend event is used to indicate the system going in and out of the +suspend mode: + +machine_suspend "state=%lu" + + +Note: the value of '-1' or '4294967295' for state means an exit from the current state, +i.e. trace_cpu_idle(4, smp_processor_id()) means that the system +enters the idle state 4, while trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()) +means that the system exits the previous idle state. + +The event which has 'state=4294967295' in the trace is very important to the user +space tools which are using it to detect the end of the current state, and so to +correctly draw the states diagrams and to calculate accurate statistics etc. + +1.2 DEPRECATED trace API +------------------------ + +A new Kconfig option CONFIG_EVENT_POWER_TRACING_DEPRECATED with the default value of +'y' has been created. This allows the legacy trace power API to be used conjointly +with the new trace API. +The Kconfig option, the old trace API (in include/trace/events/power.h) and the +old trace points will disappear in a future release (namely 2.6.41). + +power_start "type=%lu state=%lu cpu_id=%lu" +power_frequency "type=%lu state=%lu cpu_id=%lu" +power_end "cpu_id=%lu" + +The 'type' parameter takes one of those macros: + . POWER_NONE = 0, + . POWER_CSTATE = 1, /* C-State */ + . POWER_PSTATE = 2, /* Fequency change or DVFS */ + +The 'state' parameter is set depending on the type: + . Target C-state for type=POWER_CSTATE, + . Target frequency for type=POWER_PSTATE, + +power_end is used to indicate the exit of a state, corresponding to the latest +power_start event. + +2. Clocks events +================ +The clock events are used for clock enable/disable and for +clock rate change. + +clock_enable "%s state=%lu cpu_id=%lu" +clock_disable "%s state=%lu cpu_id=%lu" +clock_set_rate "%s state=%lu cpu_id=%lu" + +The first parameter gives the clock name (e.g. "gpio1_iclk"). +The second parameter is '1' for enable, '0' for disable, the target +clock rate for set_rate. + +3. Power domains events +======================= +The power domain events are used for power domains transitions + +power_domain_target "%s state=%lu cpu_id=%lu" + +The first parameter gives the power domain name (e.g. "mpu_pwrdm"). +The second parameter is the power domain target state. + |