Documentation: hisi-pmu: Add introduction to HiSilicon V3 PMU

Some of HiSilicon V3 PMU hardware is divided into parts to fulfill the
job of monitoring specific parts of a device.  Add description on that
as well as the newly added ext option for L3C PMU.

Acked-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Yushan Wang <wangyushan12@huawei.com>
Reviewed-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/Documentation/admin-guide/perf/hisi-pmu.rst b/Documentation/admin-guide/perf/hisi-pmu.rst
index 8df048c26498..c4c2cbbf88cb 100644
--- a/Documentation/admin-guide/perf/hisi-pmu.rst
+++ b/Documentation/admin-guide/perf/hisi-pmu.rst
@@ -124,6 +124,39 @@ channel with this option. The current supported channels are as follows:
 7. tt_en: NoC PMU supports counting only transactions that have tracetag set
 if this option is set. See the 2nd list for more information about tracetag.
 
+For HiSilicon uncore PMU v3 whose identifier is 0x40, some uncore PMUs are
+further divided into parts for finer granularity of tracing, each part has its
+own dedicated PMU, and all such PMUs together cover the monitoring job of events
+on particular uncore device. Such PMUs are described in sysfs with name format
+slightly changed::
+
+/sys/bus/event_source/devices/hisi_sccl{X}_<l3c{Y}_{Z}/ddrc{Y}_{Z}/noc{Y}_{Z}>
+
+Z is the sub-id, indicating different PMUs for part of hardware device.
+
+Usage of most PMUs with different sub-ids are identical. Specially, L3C PMU
+provides ``ext`` option to allow exploration of even finer granual statistics
+of L3C PMU.  L3C PMU driver uses that as hint of termination when delivering
+perf command to hardware:
+
+- ext=0: Default, could be used with event names.
+- ext=1 and ext=2: Must be used with event codes, event names are not supported.
+
+An example of perf command could be::
+
+  $# perf stat -a -e hisi_sccl0_l3c1_0/rd_spipe/ sleep 5
+
+or::
+
+  $# perf stat -a -e hisi_sccl0_l3c1_0/event=0x1,ext=1/ sleep 5
+
+As above, ``hisi_sccl0_l3c1_0`` locates PMU of Super CPU CLuster 0, L3 cache 1
+pipe0.
+
+First command locates the first part of L3C since ``ext=0`` is implied by
+default. Second command issues the counting on another part of L3C with the
+event ``0x1``.
+
 Users could configure IDs to count data come from specific CCL/ICL, by setting
 srcid_cmd & srcid_msk, and data desitined for specific CCL/ICL by setting
 tgtid_cmd & tgtid_msk. A set bit in srcid_msk/tgtid_msk means the PMU will not