| Message ID | 1523981287-15370-3-git-send-email-mathieu.poirier@linaro.org |
|---|---|
| State | Accepted |
| Commit | f29816b496f1024ec491203e9f3f6c6c924faf39 |
| Headers | show |
| Series | coresight: Refresh documenation | expand |
On 04/17/18 09:08, 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> Acked-by: Randy Dunlap <rdunlap@infradead.org> Thanks. > --- > Documentation/trace/coresight.txt | 52 ++++++++++++++++++++++++++++++++++++++- > 1 file changed, 51 insertions(+), 1 deletion(-) > > diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt > index 710c75b6c73f..ab0d0f2d5cec 100644 > --- a/Documentation/trace/coresight.txt > +++ b/Documentation/trace/coresight.txt > @@ -187,10 +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. > > + > 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: > @@ -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 cores), the "cs_etm" PMU will be listed only once. > + > +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: > + > + 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 sink > +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]. > + > How to use the STM module > ------------------------- > > -- ~Randy
diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt index 710c75b6c73f..ab0d0f2d5cec 100644 --- a/Documentation/trace/coresight.txt +++ b/Documentation/trace/coresight.txt @@ -187,10 +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. + 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: @@ -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 cores), the "cs_etm" PMU will be listed only once. + +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: + + 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 sink +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]. + How to use the STM module -------------------------
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 | 52 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 51 insertions(+), 1 deletion(-) -- 2.7.4