Messages in this thread | | | Subject | Re: [PATCH 2/3] coresight: Add section for integration with the perf tools | From | Randy Dunlap <> | Date | Mon, 16 Apr 2018 12:48:28 -0700 |
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On 04/16/2018 12:35 PM, Mathieu Poirier wrote: > Adding a section that document how to use the Coresight framework and > drivers from the perf tools. > > Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> > --- > Documentation/trace/coresight.txt | 50 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 50 insertions(+) > > diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt > index 710c75b6c73f..8caae8050a60 100644 > --- a/Documentation/trace/coresight.txt > +++ b/Documentation/trace/coresight.txt > @@ -187,9 +187,18 @@ 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. > > + > How to use the tracer modules > ----------------------------- > > +There is two ways to use the Coresight framework: 1) using the perf cmd line
There are two ways
> +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 identify.
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 > @@ -295,6 +304,47 @@ Instruction 13570831 0x8026B584 E28DD00C false ADD > Instruction 0 0x8026B588 E8BD8000 true LDM sp!,{pc} > Timestamp Timestamp: 17107041535 > > +2) Using perf framework: > + > +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: > + > + linaro@linaro-nano:~$ ./perf list pmu > + > + List of pre-defined events (to be used in -e): > + > + cs_etm// [Kernel PMU event] > + > + linaro@linaro-nano:~$ > + > +Regardless of the number of tracers available in a system (usually equal to the > +amount of processor core), the "cs_etm" PMU will be listed only once.
? cores),
> + > +A Coresight PMU works the same way as any other PMUs, i.e the name of the PMU is
any other PMU, i.e.
> +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: > + > + 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 > + > + 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 IP
Can we get away from using "IP" and call it a device or (hardware) module or something more descriptive?
> +to use for the trace session. > + > +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].
-- ~Randy
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