1 files changed, 61 insertions, 0 deletions
diff --git a/Documentation/admin-guide/perf/arm-ccn.rst b/Documentation/admin-guide/perf/arm-ccn.rst
new file mode 100644
index 000000000000..832b0c64023a
--- /dev/null
+++ b/Documentation/admin-guide/perf/arm-ccn.rst
@@ -0,0 +1,61 @@
+==========================
+ARM Cache Coherent Network
+==========================
+
+CCN-504 is a ring-bus interconnect consisting of 11 crosspoints
+(XPs), with each crosspoint supporting up to two device ports,
+so nodes (devices) 0 and 1 are connected to crosspoint 0,
+nodes 2 and 3 to crosspoint 1 etc.
+
+PMU (perf) driver
+-----------------
+
+The CCN driver registers a perf PMU driver, which provides
+description of available events and configuration options
+in sysfs, see /sys/bus/event_source/devices/ccn*.
+
+The "format" directory describes format of the config, config1
+and config2 fields of the perf_event_attr structure. The "events"
+directory provides configuration templates for all documented
+events, that can be used with perf tool. For example "xp_valid_flit"
+is an equivalent of "type=0x8,event=0x4". Other parameters must be
+explicitly specified.
+
+For events originating from device, "node" defines its index.
+
+Crosspoint PMU events require "xp" (index), "bus" (bus number)
+and "vc" (virtual channel ID).
+
+Crosspoint watchpoint-based events (special "event" value 0xfe)
+require "xp" and "vc" as as above plus "port" (device port index),
+"dir" (transmit/receive direction), comparator values ("cmp_l"
+and "cmp_h") and "mask", being index of the comparator mask.
+
+Masks are defined separately from the event description
+(due to limited number of the config values) in the "cmp_mask"
+directory, with first 8 configurable by user and additional
+4 hardcoded for the most frequent use cases.
+
+Cycle counter is described by a "type" value 0xff and does
+not require any other settings.
+
+The driver also provides a "cpumask" sysfs attribute, which contains
+a single CPU ID, of the processor which will be used to handle all
+the CCN PMU events. It is recommended that the user space tools
+request the events on this processor (if not, the perf_event->cpu value
+will be overwritten anyway). In case of this processor being offlined,
+the events are migrated to another one and the attribute is updated.
+
+Example of perf tool use::
+
+  / # perf list | grep ccn
+    ccn/cycles/                                        [Kernel PMU event]
+  <...>
+    ccn/xp_valid_flit,xp=?,port=?,vc=?,dir=?/          [Kernel PMU event]
+  <...>
+
+  / # perf stat -a -e ccn/cycles/,ccn/xp_valid_flit,xp=1,port=0,vc=1,dir=1/ \
+                                                                         sleep 1
+
+The driver does not support sampling, therefore "perf record" will
+not work. Per-task (without "-a") perf sessions are not supported.