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[firefly-linux-kernel-4.4.55.git] / Documentation / trace / coresight.txt

diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
index 02361552a3eac314a68338c5638f4239ed0d28d7..a33c88cd5d1d62f3fb4e377090d3d75615242b55 100644 (file)
--- a/Documentation/trace/coresight.txt
+++ b/Documentation/trace/coresight.txt
@@ -14,8 +14,8 @@ document is concerned with the latter.
 HW assisted tracing is becoming increasingly useful when dealing with systems
 that have many SoCs and other components like GPU and DMA engines.  ARM has
 developed a HW assisted tracing solution by means of different components, each
-being added to a design at systhesis time to cater to specific tracing needs.
-Compoments are generally categorised as source, link and sinks and are
+being added to a design at synthesis time to cater to specific tracing needs.
+Components are generally categorised as source, link and sinks and are
 (usually) discovered using the AMBA bus.
 
 "Sources" generate a compressed stream representing the processor instruction
@@ -138,7 +138,7 @@ void coresight_unregister(struct coresight_device *csdev);
 
 The registering function is taking a "struct coresight_device *csdev" and
 register the device with the core framework.  The unregister function takes
-a reference to a "strut coresight_device", obtained at registration time.
+a reference to a "struct coresight_device", obtained at registration time.
 
 If everything goes well during the registration process the new devices will
 show up under /sys/bus/coresight/devices, as showns here for a TC2 platform:
@@ -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
+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