trace/coresight/coresight.rst

2 Coresight - HW Assisted Tracing on ARM
11 Coresight is an umbrella of technologies allowing for the debugging of ARM
24 flows through the coresight system (via ATB bus) using links that are connecting
25 the emanating source to a sink(s).  Sinks serve as endpoints to the coresight
28 host without fear of filling up the onboard coresight memory buffer.
30 At typical coresight system would look like this::
85 a way to aggregate and distribute signals between CoreSight components.
87 The coresight framework provides a central point to represent, configure and
88 manage coresight devices on a platform.  This first implementation centers on
133 See ``Documentation/devicetree/bindings/arm/arm,coresight-*.yaml`` for details.
142 The coresight framework provides a central point to represent, configure and
143 manage coresight devices on a platform.  Any coresight compliant device can
154 show up under /sys/bus/coresight/devices, as showns here for a TC2 platform::
156     root:~# ls /sys/bus/coresight/devices/
203 The devices that appear on the "coresight" bus were named the same as their
209     root:~# ls /sys/bus/coresight/devices/
235     root:~# ls /sys/bus/coresight/devices/
247 Each CoreSight component has a ``connections`` directory which will contain
248 links to other CoreSight components. This allows the user to explore the trace
257   linaro-developer:~# ls - l /sys/bus/coresight/devices/etm0/connections
264   linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel2/connections
274   linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel0/connections
283   linaro-developer:~# ls -l /sys/bus/coresight/devices/tmc_etf0/connections
291   linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel4/connections
299   linaro-developer:~# ls -l /sys/bus/coresight/devices/replicator0/connections
307   linaro-developer:~# ls -l /sys/bus/coresight/devices/tmc_etr0/connections
318 via the CTM. See (Documentation/trace/coresight/coresight-ect.rst)
322   linaro-developer:~# ls -l /sys/bus/coresight/devices/cti_sys0/connections
333 There are two ways to use the Coresight framework:
336 2. interacting directly with the Coresight devices using the sysFS interface.
339 requires a deep understanding of the Coresight HW.  The following sections
345 Before trace collection can start, a coresight sink needs to be identified.
350     root:/sys/bus/coresight/devices# ls
353     root:/sys/bus/coresight/devices# ls 20010000.etb
355     root:/sys/bus/coresight/devices# echo 1 > 20010000.etb/enable_sink
356     root:/sys/bus/coresight/devices# cat 20010000.etb/enable_sink
358     root:/sys/bus/coresight/devices#
365     root:/sys/bus/coresight/devices# echo 1 > 2201c000.ptm/enable_source
366     root:/sys/bus/coresight/devices# cat 2201c000.ptm/enable_source
368     root:/sys/bus/coresight/devices# cat 20010000.etb/status
377     root:/sys/bus/coresight/devices#
381     root:/sys/bus/coresight/devices# echo 0 > 2201c000.ptm/enable_source
382     root:/sys/bus/coresight/devices#
386     root:/sys/bus/coresight/devices# dd if=/dev/20010000.etb \
391     root:/sys/bus/coresight/devices#
397 wealth of possibilities that coresight provides.
453 Coresight tracers are represented using the Perf framework's Performance
456 scheduled.  When configured in a system, Coresight PMUs will be listed when
470 A Coresight PMU works the same way as any other PMU, i.e the name of the PMU is
472 Coresight system will typically have more than one sink, the name of the sink to
480 On older kernels, this may need to be found from the list of coresight devices,
481 available under ($SYSFS)/bus/coresight/devices/::
483 	root:~# ls /sys/bus/coresight/devices/
496 More information on the above and other example on how to use Coresight with
601        :ref:`ETM_MODE_BB <coresight-branch-broadcast>`
610        see :ref:`trace/coresight/coresight-config:Using Configurations in perf`
613        :ref:`trace/coresight/coresight-config:Using Configurations in perf`
620        <coresight-cycle-accurate>`
623        <coresight-return-stack>`
626        <coresight-timestamp>`
639 As with any other CoreSight component, specifics about the STM tracer can be
642     root@genericarmv8:~# ls /sys/bus/coresight/devices/stm0
650     root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/tmc_etf0/enable_sink
651     root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/stm0/enable_source
671 (Documentation/trace/coresight/coresight-ect.rst) [#fourth]_.
673 CoreSight System Configuration
676 CoreSight components can be complex devices with many programming options.
680 A CoreSight System Configuration manager is provided to allow these complex programming
684 (Documentation/trace/coresight/coresight-config.rst) [#fifth]_.
687 .. [#first] Documentation/ABI/testing/sysfs-bus-coresight-devices-stm
693 .. [#fourth] Documentation/trace/coresight/coresight-ect.rst
695 .. [#fifth] Documentation/trace/coresight/coresight-config.rst