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docs: perf: Add description for StarFive's StarLink PMU

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StarFive StarLink PMU support monitoring L3 memory system PMU events.
Add documentation to describe StarFive StarLink PMU support and it's
usage.

Signed-off-by: Ji Sheng Teoh <jisheng.teoh@starfivetech.com>
Link: https://lore.kernel.org/r/20240229072720.3987876-4-jisheng.teoh@starfivetech.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ji Sheng Teoh 2024-02-29 15:27:19 +08:00 committed by Will Deacon
parent 66461b43b0
commit 49925c1c5a
2 changed files with 47 additions and 0 deletions
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Documentation/admin-guide/perf/index.rst
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@ -13,6 +13,7 @@ Performance monitor support
imx-ddr
qcom_l2_pmu
qcom_l3_pmu
starfive_starlink_pmu
arm-ccn
arm-cmn
xgene-pmu

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Documentation/admin-guide/perf/starfive_starlink_pmu.rst Normal file
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@ -0,0 +1,46 @@
================================================
StarFive StarLink Performance Monitor Unit (PMU)
================================================
StarFive StarLink Performance Monitor Unit (PMU) exists within the
StarLink Coherent Network on Chip (CNoC) that connects multiple CPU
clusters with an L3 memory system.
The uncore PMU supports overflow interrupt, up to 16 programmable 64bit
event counters, and an independent 64bit cycle counter.
The PMU can only be accessed via Memory Mapped I/O and are common to the
cores connected to the same PMU.
Driver exposes supported PMU events in sysfs "events" directory under::
/sys/bus/event_source/devices/starfive_starlink_pmu/events/
Driver exposes cpu used to handle PMU events in sysfs "cpumask" directory
under::
/sys/bus/event_source/devices/starfive_starlink_pmu/cpumask/
Driver describes the format of config (event ID) in sysfs "format" directory
under::
/sys/bus/event_source/devices/starfive_starlink_pmu/format/
Example of perf usage::
$ perf list
starfive_starlink_pmu/cycles/ [Kernel PMU event]
starfive_starlink_pmu/read_hit/ [Kernel PMU event]
starfive_starlink_pmu/read_miss/ [Kernel PMU event]
starfive_starlink_pmu/read_request/ [Kernel PMU event]
starfive_starlink_pmu/release_request/ [Kernel PMU event]
starfive_starlink_pmu/write_hit/ [Kernel PMU event]
starfive_starlink_pmu/write_miss/ [Kernel PMU event]
starfive_starlink_pmu/write_request/ [Kernel PMU event]
starfive_starlink_pmu/writeback/ [Kernel PMU event]
$ perf stat -a -e /starfive_starlink_pmu/cycles/ sleep 1
Sampling is not supported. As a result, "perf record" is not supported.
Attaching to a task is not supported, only system-wide counting is supported.