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authorRobin Murphy <robin.murphy@arm.com>2018-02-15 18:51:41 +0000
committerArnd Bergmann <arnd@arndb.de>2018-03-06 17:26:15 +0100
commit1888d3ddc3d6a2511be86045cfb2e7ea5fc67c44 (patch)
tree5d0a27771cb8a0f15028d7cc7d663c1dda9ceb4b /Documentation/perf
parent661e50bc853209e41a5c14a290ca4decc43cbfd1 (diff)
drivers/bus: Move Arm CCN PMU driver
The arm-ccn driver is purely a perf driver for the CCN PMU, not a bus driver in the sense of the other residents of drivers/bus/, so let's move it to the appropriate place for SoC PMU drivers. Not to mention moving the documentation accordingly as well. Acked-by: Pawel Moll <pawel.moll@arm.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'Documentation/perf')
-rw-r--r--Documentation/perf/arm-ccn.txt59
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diff --git a/Documentation/perf/arm-ccn.txt b/Documentation/perf/arm-ccn.txt
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+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.