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stm class: Document the stm_ftrace 

This patch adds a description to the stm_ftrace device source, an
interface for collecting Ftrace's function trace information via
STM devices.

Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
This commit is contained in:
Chunyan Zhang 2017-03-23 14:13:25 +08:00 committed by Alexander Shishkin
parent 71c488f32b
commit 39fccd2fc3
1 changed files with 12 additions and 1 deletions
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13
Documentation/trace/stm.txt
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@ -83,7 +83,7 @@ by writing the name of the desired stm device there, for example:
$ echo dummy_stm.0 > /sys/class/stm_source/console/stm_source_link
For examples on how to use stm_source interface in the kernel, refer
to stm_console or stm_heartbeat drivers.
to stm_console, stm_heartbeat or stm_ftrace drivers.
Each stm_source device will need to assume a master and a range of
channels, depending on how many channels it requires. These are
@ -107,5 +107,16 @@ console in the STP stream, create a "console" policy entry (see the
beginning of this text on how to do that). When initialized, it will
consume one channel.
stm_ftrace
==========
This is another "stm_source" device, once the stm_ftrace has been
linked with an stm device, and if "function" tracer is enabled,
function address and parent function address which Ftrace subsystem
would store into ring buffer will be exported via the stm device at
the same time.
Currently only Ftrace "function" tracer is supported.
[1] https://software.intel.com/sites/default/files/managed/d3/3c/intel-th-developer-manual.pdf
[2] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0444b/index.html