[PATCH] perf/arm-cmn: Add documentation for nodeid

[Zidenberg, Tsahi]

Document how nodeids could be calculated.

Signed-off-by: Tzachi Zidenberg <tsahee at amazon.com>
---
Documentation/admin-guide/perf/arm-cmn.rst | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/perf/arm-cmn.rst b/Documentation/admin-guide/perf/arm-cmn.rst
index 0e4809346014..a68f26531e4a 100644
--- a/Documentation/admin-guide/perf/arm-cmn.rst
+++ b/Documentation/admin-guide/perf/arm-cmn.rst
@@ -41,8 +41,14 @@ specified by "occupid".

By default each event provides an aggregate count over all nodes of the
given type. To target a specific node, "bynodeid" must be set to 1 and
-"nodeid" to the appropriate value derived from the CMN configuration
-(as defined in the "Node ID Mapping" section of the TRM).
+"nodeid" to the appropriate value derived from the CMN configuration.
+
+The CMN map is written to /sys/kernel/debug/arm-cmn/map.
+A nodeid could be calculated with this formulae:
+  node-id = d | (p << 2) | (y << 3) | (x << (3 + xybits))
+where:
+  x,y,p,d are node location as can be seen in the map
+  xybits is 2 for meshes <= 2*2, and 3 otherwise.

Watchpoints
-----------
-- 
2.16.5