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79d7c3dca9
Although it's neat to avoid the suffix for the typical case of a
single PMU, it means systems with multiple CMN instances end up with
inconsistent naming. I think it also breaks perf tool's "uncore alias"
logic if the common instance prefix is also the full name of one.
Avoid any surprises by not trying to be clever and simply numbering
every instance, even when it might technically prove redundant.
Fixes: 0ba64770a2 ("perf: Add Arm CMN-600 PMU driver")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/649a2281233f193d59240b13ed91b57337c77b32.1611839564.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
66 lines
3.0 KiB
ReStructuredText
66 lines
3.0 KiB
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=============================
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Arm Coherent Mesh Network PMU
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=============================
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CMN-600 is a configurable mesh interconnect consisting of a rectangular
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grid of crosspoints (XPs), with each crosspoint supporting up to two
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device ports to which various AMBA CHI agents are attached.
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CMN implements a distributed PMU design as part of its debug and trace
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functionality. This consists of a local monitor (DTM) at every XP, which
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counts up to 4 event signals from the connected device nodes and/or the
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XP itself. Overflow from these local counters is accumulated in up to 8
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global counters implemented by the main controller (DTC), which provides
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overall PMU control and interrupts for global counter overflow.
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PMU events
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----------
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The PMU driver registers a single PMU device for the whole interconnect,
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see /sys/bus/event_source/devices/arm_cmn_0. Multi-chip systems may link
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more than one CMN together via external CCIX links - in this situation,
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each mesh counts its own events entirely independently, and additional
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PMU devices will be named arm_cmn_{1..n}.
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Most events are specified in a format based directly on the TRM
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definitions - "type" selects the respective node type, and "eventid" the
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event number. Some events require an additional occupancy ID, which is
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specified by "occupid".
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* Since RN-D nodes do not have any distinct events from RN-I nodes, they
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are treated as the same type (0xa), and the common event templates are
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named "rnid_*".
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* The cycle counter is treated as a synthetic event belonging to the DTC
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node ("type" == 0x3, "eventid" is ignored).
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* XP events also encode the port and channel in the "eventid" field, to
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match the underlying pmu_event0_id encoding for the pmu_event_sel
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register. The event templates are named with prefixes to cover all
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permutations.
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By default each event provides an aggregate count over all nodes of the
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given type. To target a specific node, "bynodeid" must be set to 1 and
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"nodeid" to the appropriate value derived from the CMN configuration
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(as defined in the "Node ID Mapping" section of the TRM).
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Watchpoints
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-----------
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The PMU can also count watchpoint events to monitor specific flit
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traffic. Watchpoints are treated as a synthetic event type, and like PMU
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events can be global or targeted with a particular XP's "nodeid" value.
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Since the watchpoint direction is otherwise implicit in the underlying
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register selection, separate events are provided for flit uploads and
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downloads.
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The flit match value and mask are passed in config1 and config2 ("val"
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and "mask" respectively). "wp_dev_sel", "wp_chn_sel", "wp_grp" and
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"wp_exclusive" are specified per the TRM definitions for dtm_wp_config0.
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Where a watchpoint needs to match fields from both match groups on the
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REQ or SNP channel, it can be specified as two events - one for each
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group - with the same nonzero "combine" value. The count for such a
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pair of combined events will be attributed to the primary match.
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Watchpoint events with a "combine" value of 0 are considered independent
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and will count individually.
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