From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- Documentation/arm/CCN.txt | 52 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 Documentation/arm/CCN.txt (limited to 'Documentation/arm/CCN.txt') diff --git a/Documentation/arm/CCN.txt b/Documentation/arm/CCN.txt new file mode 100644 index 000000000..0632b3aad --- /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. -- cgit v1.2.3-54-g00ecf