interconnect: Add interconnect_graph file to debugfs

The interconnect graphs can be difficult to understand and the current
"interconnect_summary" file doesn't even display links in any way.

Add a new "interconnect_graph" file to debugfs in the graphviz "dot"
format which describes interconnect providers, nodes and links.

The file is human-readable and can be visualized by piping through
graphviz. Example:

ssh $TARGET cat /sys/kernel/debug/interconnect/interconnect_graph \
	| dot -Tsvg > interconnect_graph.svg

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/Documentation/driver-api/interconnect.rst b/Documentation/driver-api/interconnect.rst
index cdeb5825f314..5ed4f57a6bac 100644
--- a/Documentation/driver-api/interconnect.rst
+++ b/Documentation/driver-api/interconnect.rst
@@ -91,3 +91,25 @@ Interconnect consumers are the clients which use the interconnect APIs to
 get paths between endpoints and set their bandwidth/latency/QoS requirements
 for these interconnect paths.  These interfaces are not currently
 documented.
+
+Interconnect debugfs interfaces
+-------------------------------
+
+Like several other subsystems interconnect will create some files for debugging
+and introspection. Files in debugfs are not considered ABI so application
+software shouldn't rely on format details change between kernel versions.
+
+``/sys/kernel/debug/interconnect/interconnect_summary``:
+
+Show all interconnect nodes in the system with their aggregated bandwidth
+request. Indented under each node show bandwidth requests from each device.
+
+``/sys/kernel/debug/interconnect/interconnect_graph``:
+
+Show the interconnect graph in the graphviz dot format. It shows all
+interconnect nodes and links in the system and groups together nodes from the
+same provider as subgraphs. The format is human-readable and can also be piped
+through dot to generate diagrams in many graphical formats::
+
+        $ cat /sys/kernel/debug/interconnect/interconnect_graph | \
+                dot -Tsvg > interconnect_graph.svg