From 5153e57bf8b371d75c35fe37928bbd88a1b4bbe8 Mon Sep 17 00:00:00 2001 From: Mike Leach Date: Mon, 18 May 2020 12:02:25 -0600 Subject: coresight: docs: Add information about the topology representations Update the CoreSight documents to describe the new connections directory and the links between CoreSight devices in this directory. Signed-off-by: Mike Leach Signed-off-by: Mathieu Poirier Link: https://lore.kernel.org/r/20200518180242.7916-7-mathieu.poirier@linaro.org Signed-off-by: Greg Kroah-Hartman --- Documentation/trace/coresight/coresight-ect.rst | 5 +- Documentation/trace/coresight/coresight.rst | 85 +++++++++++++++++++++++++ 2 files changed, 89 insertions(+), 1 deletion(-) (limited to 'Documentation/trace/coresight') diff --git a/Documentation/trace/coresight/coresight-ect.rst b/Documentation/trace/coresight/coresight-ect.rst index ecc1e57012ef..50a5623d5d4f 100644 --- a/Documentation/trace/coresight/coresight-ect.rst +++ b/Documentation/trace/coresight/coresight-ect.rst @@ -72,7 +72,7 @@ capable of generating or using trigger signals.:: >$ ls /sys/bus/coresight/devices/etm0/cti_cpu0 channels ctmid enable nr_trigger_cons mgmt power powered regs - subsystem triggers0 triggers1 uevent + connections subsystem triggers0 triggers1 uevent *Key file items are:-* * ``enable``: enables/disables the CTI. Read to determine current state. @@ -88,6 +88,9 @@ capable of generating or using trigger signals.:: * ``channels``: Contains the channel API - CTI main programming interface. * ``regs``: Gives access to the raw programmable CTI regs. * ``mgmt``: the standard CoreSight management registers. + * ``connections``: Links to connected *CoreSight* devices. The number of + links can be 0 to ``nr_trigger_cons``. Actual number given by ``nr_links`` + in this directory. triggers directories diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst index 108600ee1e12..0b73acb44efa 100644 --- a/Documentation/trace/coresight/coresight.rst +++ b/Documentation/trace/coresight/coresight.rst @@ -241,6 +241,91 @@ to the newer scheme, to give a confirmation that what you see on your system is not unexpected. One must use the "names" as they appear on the system under specified locations. +Topology Representation +----------------------- + +Each CoreSight component has a ``connections`` directory which will contain +links to other CoreSight components. This allows the user to explore the trace +topology and for larger systems, determine the most appropriate sink for a +given source. The connection information can also be used to establish +which CTI devices are connected to a given component. This directory contains a +``nr_links`` attribute detailing the number of links in the directory. + +For an ETM source, in this case ``etm0`` on a Juno platform, a typical +arrangement will be:: + + linaro-developer:~# ls - l /sys/bus/coresight/devices/etm0/connections + cti_cpu0 -> ../../../23020000.cti/cti_cpu0 + nr_links + out:0 -> ../../../230c0000.funnel/funnel2 + +Following the out port to ``funnel2``:: + + linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel2/connections + in:0 -> ../../../23040000.etm/etm0 + in:1 -> ../../../23140000.etm/etm3 + in:2 -> ../../../23240000.etm/etm4 + in:3 -> ../../../23340000.etm/etm5 + nr_links + out:0 -> ../../../20040000.funnel/funnel0 + +And again to ``funnel0``:: + + linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel0/connections + in:0 -> ../../../220c0000.funnel/funnel1 + in:1 -> ../../../230c0000.funnel/funnel2 + nr_links + out:0 -> ../../../20010000.etf/tmc_etf0 + +Finding the first sink ``tmc_etf0``. This can be used to collect data +as a sink, or as a link to propagate further along the chain:: + + linaro-developer:~# ls -l /sys/bus/coresight/devices/tmc_etf0/connections + cti_sys0 -> ../../../20020000.cti/cti_sys0 + in:0 -> ../../../20040000.funnel/funnel0 + nr_links + out:0 -> ../../../20150000.funnel/funnel4 + +via ``funnel4``:: + + linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel4/connections + in:0 -> ../../../20010000.etf/tmc_etf0 + in:1 -> ../../../20140000.etf/tmc_etf1 + nr_links + out:0 -> ../../../20120000.replicator/replicator0 + +and a ``replicator0``:: + + linaro-developer:~# ls -l /sys/bus/coresight/devices/replicator0/connections + in:0 -> ../../../20150000.funnel/funnel4 + nr_links + out:0 -> ../../../20030000.tpiu/tpiu0 + out:1 -> ../../../20070000.etr/tmc_etr0 + +Arriving at the final sink in the chain, ``tmc_etr0``:: + + linaro-developer:~# ls -l /sys/bus/coresight/devices/tmc_etr0/connections + cti_sys0 -> ../../../20020000.cti/cti_sys0 + in:0 -> ../../../20120000.replicator/replicator0 + nr_links + +As described below, when using sysfs it is sufficient to enable a sink and +a source for successful trace. The framework will correctly enable all +intermediate links as required. + +Note: ``cti_sys0`` appears in two of the connections lists above. +CTIs can connect to multiple devices and are arranged in a star topology +via the CTM. See (:doc:`coresight-ect`) [#fourth]_ for further details. +Looking at this device we see 4 connections:: + + linaro-developer:~# ls -l /sys/bus/coresight/devices/cti_sys0/connections + nr_links + stm0 -> ../../../20100000.stm/stm0 + tmc_etf0 -> ../../../20010000.etf/tmc_etf0 + tmc_etr0 -> ../../../20070000.etr/tmc_etr0 + tpiu0 -> ../../../20030000.tpiu/tpiu0 + + How to use the tracer modules ----------------------------- -- cgit v1.2.3