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Diffstat (limited to 'Documentation/trace/coresight.txt')
| -rw-r--r-- | Documentation/trace/coresight.txt | 103 |
1 files changed, 75 insertions, 28 deletions
diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt index 6f0120c3a4f1..efbc832146e7 100644 --- a/Documentation/trace/coresight.txt +++ b/Documentation/trace/coresight.txt @@ -187,13 +187,19 @@ that can be performed on them (see "struct coresight_ops"). The specific to that component only. "Implementation defined" customisations are expected to be accessed and controlled using those entries. -Last but not least, "struct module *owner" is expected to be set to reflect -the information carried in "THIS_MODULE". How to use the tracer modules ----------------------------- -Before trace collection can start, a coresight sink needs to be identify. +There are two ways to use the Coresight framework: 1) using the perf cmd line +tools and 2) interacting directly with the Coresight devices using the sysFS +interface. Preference is given to the former as using the sysFS interface +requires a deep understanding of the Coresight HW. The following sections +provide details on using both methods. + +1) Using the sysFS interface: + +Before trace collection can start, a coresight sink needs to be identified. There is no limit on the amount of sinks (nor sources) that can be enabled at any given moment. As a generic operation, all device pertaining to the sink class will have an "active" entry in sysfs: @@ -298,42 +304,48 @@ Instruction 13570831 0x8026B584 E28DD00C false ADD Instruction 0 0x8026B588 E8BD8000 true LDM sp!,{pc} Timestamp Timestamp: 17107041535 -How to use the STM module -------------------------- +2) Using perf framework: -Using the System Trace Macrocell module is the same as the tracers - the only -difference is that clients are driving the trace capture rather -than the program flow through the code. +Coresight tracers are represented using the Perf framework's Performance +Monitoring Unit (PMU) abstraction. As such the perf framework takes charge of +controlling when tracing gets enabled based on when the process of interest is +scheduled. When configured in a system, Coresight PMUs will be listed when +queried by the perf command line tool: -As with any other CoreSight component, specifics about the STM tracer can be -found in sysfs with more information on each entry being found in [1]: + linaro@linaro-nano:~$ ./perf list pmu -root@genericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm -enable_source hwevent_select port_enable subsystem uevent -hwevent_enable mgmt port_select traceid -root@genericarmv8:~# + List of pre-defined events (to be used in -e): -Like any other source a sink needs to be identified and the STM enabled before -being used: + cs_etm// [Kernel PMU event] -root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink -root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source + linaro@linaro-nano:~$ -From there user space applications can request and use channels using the devfs -interface provided for that purpose by the generic STM API: +Regardless of the number of tracers available in a system (usually equal to the +amount of processor cores), the "cs_etm" PMU will be listed only once. -root@genericarmv8:~# ls -l /dev/20100000.stm -crw------- 1 root root 10, 61 Jan 3 18:11 /dev/20100000.stm -root@genericarmv8:~# +A Coresight PMU works the same way as any other PMU, i.e the name of the PMU is +listed along with configuration options within forward slashes '/'. Since a +Coresight system will typically have more than one sink, the name of the sink to +work with needs to be specified as an event option. Names for sink to choose +from are listed in sysFS under ($SYSFS)/bus/coresight/devices: -Details on how to use the generic STM API can be found here [2]. + root@linaro-nano:~# ls /sys/bus/coresight/devices/ + 20010000.etf 20040000.funnel 20100000.stm 22040000.etm + 22140000.etm 230c0000.funnel 23240000.etm 20030000.tpiu + 20070000.etr 20120000.replicator 220c0000.funnel + 23040000.etm 23140000.etm 23340000.etm -[1]. Documentation/ABI/testing/sysfs-bus-coresight-devices-stm -[2]. Documentation/trace/stm.txt + root@linaro-nano:~# perf record -e cs_etm/@20070000.etr/u --per-thread program +The syntax within the forward slashes '/' is important. The '@' character +tells the parser that a sink is about to be specified and that this is the sink +to use for the trace session. -Using perf tools ----------------- +More information on the above and other example on how to use Coresight with +the perf tools can be found in the "HOWTO.md" file of the openCSD gitHub +repository [3]. + +2.1) AutoFDO analysis using the perf tools: perf can be used to record and analyze trace of programs. @@ -381,3 +393,38 @@ sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tuto $ taskset -c 2 ./sort_autofdo Bubble sorting array of 30000 elements 5806 ms + + +How to use the STM module +------------------------- + +Using the System Trace Macrocell module is the same as the tracers - the only +difference is that clients are driving the trace capture rather +than the program flow through the code. + +As with any other CoreSight component, specifics about the STM tracer can be +found in sysfs with more information on each entry being found in [1]: + +root@genericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm +enable_source hwevent_select port_enable subsystem uevent +hwevent_enable mgmt port_select traceid +root@genericarmv8:~# + +Like any other source a sink needs to be identified and the STM enabled before +being used: + +root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink +root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source + +From there user space applications can request and use channels using the devfs +interface provided for that purpose by the generic STM API: + +root@genericarmv8:~# ls -l /dev/20100000.stm +crw------- 1 root root 10, 61 Jan 3 18:11 /dev/20100000.stm +root@genericarmv8:~# + +Details on how to use the generic STM API can be found here [2]. + +[1]. Documentation/ABI/testing/sysfs-bus-coresight-devices-stm +[2]. Documentation/trace/stm.rst +[3]. https://github.com/Linaro/perf-opencsd |