Techwizz/kernel-fxtec-pro1x
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

tools, perf: Documentation for the power events API

Browse source 
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>
This commit is contained in:
Jean Pihet 2011-01-05 19:49:02 +01:00 committed by Ingo Molnar
parent 938cfed18b
commit 4b95f135f6
1 changed files with 90 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

90
Documentation/trace/events-power.txt Normal file
View file

@ -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.