perf: Add Arm CMN-600 PMU driver

Initial driver for PMU event counting on the Arm CMN-600 interconnect.
CMN sports an obnoxiously complex distributed PMU system as part of
its debug and trace features, which can do all manner of things like
sampling, cross-triggering and generating CoreSight trace. This driver
covers the PMU functionality, plus the relevant aspects of watchpoints
for simply counting matching flits.

Tested-by: Tsahi Zidenberg <tsahee@amazon.com>
Tested-by: Tuan Phan <tuanphan@os.amperecomputing.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

2 files changed, 66 insertions, 0 deletions

diff --git a/Documentation/admin-guide/perf/arm-cmn.rst b/Documentation/admin-guide/perf/arm-cmn.rst
new file mode 100644
index 000000000000..0e4809346014
--- /dev/null
+++ b/Documentation/admin-guide/perf/arm-cmn.rst
@@ -0,0 +1,65 @@
+=============================
+Arm Coherent Mesh Network PMU
+=============================
+
+CMN-600 is a configurable mesh interconnect consisting of a rectangular
+grid of crosspoints (XPs), with each crosspoint supporting up to two
+device ports to which various AMBA CHI agents are attached.
+
+CMN implements a distributed PMU design as part of its debug and trace
+functionality. This consists of a local monitor (DTM) at every XP, which
+counts up to 4 event signals from the connected device nodes and/or the
+XP itself. Overflow from these local counters is accumulated in up to 8
+global counters implemented by the main controller (DTC), which provides
+overall PMU control and interrupts for global counter overflow.
+
+PMU events
+----------
+
+The PMU driver registers a single PMU device for the whole interconnect,
+see /sys/bus/event_source/devices/arm_cmn. Multi-chip systems may link
+more than one CMN together via external CCIX links - in this situation,
+each mesh counts its own events entirely independently, and additional
+PMU devices will be named arm_cmn_{1..n}.
+
+Most events are specified in a format based directly on the TRM
+definitions - "type" selects the respective node type, and "eventid" the
+event number. Some events require an additional occupancy ID, which is
+specified by "occupid".
+
+* Since RN-D nodes do not have any distinct events from RN-I nodes, they
+  are treated as the same type (0xa), and the common event templates are
+  named "rnid_*".
+
+* The cycle counter is treated as a synthetic event belonging to the DTC
+  node ("type" == 0x3, "eventid" is ignored).
+
+* XP events also encode the port and channel in the "eventid" field, to
+  match the underlying pmu_event0_id encoding for the pmu_event_sel
+  register. The event templates are named with prefixes to cover all
+  permutations.
+
+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).
+
+Watchpoints
+-----------
+
+The PMU can also count watchpoint events to monitor specific flit
+traffic. Watchpoints are treated as a synthetic event type, and like PMU
+events can be global or targeted with a particular XP's "nodeid" value.
+Since the watchpoint direction is otherwise implicit in the underlying
+register selection, separate events are provided for flit uploads and
+downloads.
+
+The flit match value and mask are passed in config1 and config2 ("val"
+and "mask" respectively). "wp_dev_sel", "wp_chn_sel", "wp_grp" and
+"wp_exclusive" are specified per the TRM definitions for dtm_wp_config0.
+Where a watchpoint needs to match fields from both match groups on the
+REQ or SNP channel, it can be specified as two events - one for each
+group - with the same nonzero "combine" value. The count for such a
+pair of combined events will be attributed to the primary match.
+Watchpoint events with a "combine" value of 0 are considered independent
+and will count individually.
diff --git a/Documentation/admin-guide/perf/index.rst b/Documentation/admin-guide/perf/index.rst
index 47c99f40cc16..5a8f2529a033 100644
--- a/Documentation/admin-guide/perf/index.rst
+++ b/Documentation/admin-guide/perf/index.rst
@@ -12,6 +12,7 @@ Performance monitor support
    qcom_l2_pmu
    qcom_l3_pmu
    arm-ccn
+   arm-cmn
    xgene-pmu
    arm_dsu_pmu
    thunderx2-pmu