path: root/Documentation/trace/coresight.txt
diff options
Diffstat (limited to 'Documentation/trace/coresight.txt')
1 files changed, 35 insertions, 2 deletions
diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
index 0a5c3290e732..a33c88cd5d1d 100644
--- a/Documentation/trace/coresight.txt
+++ b/Documentation/trace/coresight.txt
@@ -190,8 +190,8 @@ expected to be accessed and controlled using those entries.
Last but not least, "struct module *owner" is expected to be set to reflect
the information carried in "THIS_MODULE".
-How to use
+How to use the tracer modules
Before trace collection can start, a coresight sink needs to be identify.
There is no limit on the amount of sinks (nor sources) that can be enabled at
@@ -297,3 +297,36 @@ Info Tracing enabled
Instruction 13570831 0x8026B584 E28DD00C false ADD sp,sp,#0xc
Instruction 0 0x8026B588 E8BD8000 true LDM sp!,{pc}
Timestamp Timestamp: 17107041535
+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
+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
+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