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authorMike Leach <mike.leach@linaro.org>2020-05-18 21:02:25 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-05-19 17:31:16 +0300
commit5153e57bf8b371d75c35fe37928bbd88a1b4bbe8 (patch)
treea89452273828260fb397200dd393284292b3a409 /Documentation/trace/coresight
parent73274abb6557c934d4e1c852fe078c73b38eb114 (diff)
downloadlinux-5153e57bf8b371d75c35fe37928bbd88a1b4bbe8.tar.xz
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 <mike.leach@linaro.org> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Link: https://lore.kernel.org/r/20200518180242.7916-7-mathieu.poirier@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/trace/coresight')
-rw-r--r--Documentation/trace/coresight/coresight-ect.rst5
-rw-r--r--Documentation/trace/coresight/coresight.rst85
2 files changed, 89 insertions, 1 deletions
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<N> 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
+ <file details> cti_cpu0 -> ../../../23020000.cti/cti_cpu0
+ <file details> nr_links
+ <file details> out:0 -> ../../../230c0000.funnel/funnel2
+
+Following the out port to ``funnel2``::
+
+ linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel2/connections
+ <file details> in:0 -> ../../../23040000.etm/etm0
+ <file details> in:1 -> ../../../23140000.etm/etm3
+ <file details> in:2 -> ../../../23240000.etm/etm4
+ <file details> in:3 -> ../../../23340000.etm/etm5
+ <file details> nr_links
+ <file details> out:0 -> ../../../20040000.funnel/funnel0
+
+And again to ``funnel0``::
+
+ linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel0/connections
+ <file details> in:0 -> ../../../220c0000.funnel/funnel1
+ <file details> in:1 -> ../../../230c0000.funnel/funnel2
+ <file details> nr_links
+ <file details> 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
+ <file details> cti_sys0 -> ../../../20020000.cti/cti_sys0
+ <file details> in:0 -> ../../../20040000.funnel/funnel0
+ <file details> nr_links
+ <file details> out:0 -> ../../../20150000.funnel/funnel4
+
+via ``funnel4``::
+
+ linaro-developer:~# ls -l /sys/bus/coresight/devices/funnel4/connections
+ <file details> in:0 -> ../../../20010000.etf/tmc_etf0
+ <file details> in:1 -> ../../../20140000.etf/tmc_etf1
+ <file details> nr_links
+ <file details> out:0 -> ../../../20120000.replicator/replicator0
+
+and a ``replicator0``::
+
+ linaro-developer:~# ls -l /sys/bus/coresight/devices/replicator0/connections
+ <file details> in:0 -> ../../../20150000.funnel/funnel4
+ <file details> nr_links
+ <file details> out:0 -> ../../../20030000.tpiu/tpiu0
+ <file details> 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
+ <file details> cti_sys0 -> ../../../20020000.cti/cti_sys0
+ <file details> in:0 -> ../../../20120000.replicator/replicator0
+ <file details> 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
+ <file details> nr_links
+ <file details> stm0 -> ../../../20100000.stm/stm0
+ <file details> tmc_etf0 -> ../../../20010000.etf/tmc_etf0
+ <file details> tmc_etr0 -> ../../../20070000.etr/tmc_etr0
+ <file details> tpiu0 -> ../../../20030000.tpiu/tpiu0
+
+
How to use the tracer modules
-----------------------------