diff options
author | Pawel Moll <pawel.moll@arm.com> | 2014-07-22 18:32:59 +0100 |
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committer | Arnd Bergmann <arnd@arndb.de> | 2014-07-23 22:14:43 +0200 |
commit | a33b0daab73a0e08cc04459dd44b0121a8e8f81b (patch) | |
tree | e7c432add19822871a057313264825c85e9cdf80 /Documentation/arm | |
parent | 779ae55bd8ee63f2ba35a0ec15f033e512e706ee (diff) |
bus: ARM CCN PMU driver
Driver providing perf backend for ARM Cache Coherent Network
interconnect. Supports counting all hardware events and crosspoint
watchpoints.
Currently works with CCN-504 only, although there should be
no changes required for CCN-508 (just impossible to test it now).
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'Documentation/arm')
-rw-r--r-- | Documentation/arm/CCN.txt | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/arm/CCN.txt b/Documentation/arm/CCN.txt new file mode 100644 index 00000000000..0632b3aad83 --- /dev/null +++ b/Documentation/arm/CCN.txt @@ -0,0 +1,52 @@ +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. All crosspoint events require "xp" (index), +"port" (device port number) and "vc" (virtual channel ID) and +"dir" (direction). Watchpoints (special "event" value 0xfe) also +require 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. + +Example of perf tool use: + +/ # perf list | grep ccn + ccn/cycles/ [Kernel PMU event] +<...> + ccn/xp_valid_flit/ [Kernel PMU event] +<...> + +/ # perf stat -C 0 -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. Also notice that only single cpu is being selected +("-C 0") - this is because perf framework does not support +"non-CPU related" counters (yet?) so system-wide session ("-a") +would try (and in most cases fail) to set up the same event +per each CPU. |