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author | Robin Murphy <robin.murphy@arm.com> | 2018-02-15 18:51:41 +0000 |
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committer | Arnd Bergmann <arnd@arndb.de> | 2018-03-06 17:26:15 +0100 |
commit | 1888d3ddc3d6a2511be86045cfb2e7ea5fc67c44 (patch) | |
tree | 5d0a27771cb8a0f15028d7cc7d663c1dda9ceb4b /Documentation/perf | |
parent | 661e50bc853209e41a5c14a290ca4decc43cbfd1 (diff) | |
download | linux-stable-1888d3ddc3d6a2511be86045cfb2e7ea5fc67c44.tar.gz linux-stable-1888d3ddc3d6a2511be86045cfb2e7ea5fc67c44.tar.bz2 linux-stable-1888d3ddc3d6a2511be86045cfb2e7ea5fc67c44.zip |
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.txt | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/Documentation/perf/arm-ccn.txt b/Documentation/perf/arm-ccn.txt new file mode 100644 index 000000000000..15cdb7bc57c3 --- /dev/null +++ b/Documentation/perf/arm-ccn.txt @@ -0,0 +1,59 @@ +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. |