Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 87bf4d68 authored by Mathieu Poirier's avatar Mathieu Poirier Committed by Jonathan Corbet
Browse files

coresight: Grouping all perf tools oriented section together 



This patch groups together section pertaining to the perf tools.  That way
everything is at the same place rather than spread out.

Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent f29816b4

Documentation/trace/coresight.txt

+36 −36
Original line number Diff line number Diff line
@@ -345,42 +345,7 @@ More information on the above and other example on how to use Coresight with 
the perf tools can be found in the "HOWTO.md" file of the openCSD gitHub

repository [3].



How to use the STM module

-------------------------



Using the System Trace Macrocell module is the same as the tracers - the only

difference is that clients are driving the trace capture rather

than the program flow through the code.



As with any other CoreSight component, specifics about the STM tracer can be

found in sysfs with more information on each entry being found in [1]:



root@genericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm

enable_source   hwevent_select  port_enable     subsystem       uevent

hwevent_enable  mgmt            port_select     traceid

root@genericarmv8:~#



Like any other source a sink needs to be identified and the STM enabled before

being used:



root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink

root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source



From there user space applications can request and use channels using the devfs

interface provided for that purpose by the generic STM API:



root@genericarmv8:~# ls -l /dev/20100000.stm

crw-------    1 root     root       10,  61 Jan  3 18:11 /dev/20100000.stm

root@genericarmv8:~#



Details on how to use the generic STM API can be found here [2].



[1]. Documentation/ABI/testing/sysfs-bus-coresight-devices-stm

[2]. Documentation/trace/stm.txt





Using perf tools

----------------

2.1) AutoFDO analysis using the perf tools:



perf can be used to record and analyze trace of programs.
@@ -428,3 +393,38 @@ sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tuto 
	$ taskset -c 2 ./sort_autofdo

	Bubble sorting array of 30000 elements

	5806 ms





How to use the STM module

-------------------------



Using the System Trace Macrocell module is the same as the tracers - the only

difference is that clients are driving the trace capture rather

than the program flow through the code.



As with any other CoreSight component, specifics about the STM tracer can be

found in sysfs with more information on each entry being found in [1]:



root@genericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm

enable_source   hwevent_select  port_enable     subsystem       uevent

hwevent_enable  mgmt            port_select     traceid

root@genericarmv8:~#



Like any other source a sink needs to be identified and the STM enabled before

being used:



root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink

root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source



From there user space applications can request and use channels using the devfs

interface provided for that purpose by the generic STM API:



root@genericarmv8:~# ls -l /dev/20100000.stm

crw-------    1 root     root       10,  61 Jan  3 18:11 /dev/20100000.stm

root@genericarmv8:~#



Details on how to use the generic STM API can be found here [2].



[1]. Documentation/ABI/testing/sysfs-bus-coresight-devices-stm

[2]. Documentation/trace/stm.txt

[3]. https://github.com/Linaro/perf-opencsd