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Diffstat (limited to 'Documentation/trace/coresight/coresight.rst')
| -rw-r--r-- | Documentation/trace/coresight/coresight.rst | 112 |
1 files changed, 84 insertions, 28 deletions
diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst index 1ec8dc35b1d8..806699871b80 100644 --- a/Documentation/trace/coresight/coresight.rst +++ b/Documentation/trace/coresight/coresight.rst @@ -130,7 +130,7 @@ Misc: Device Tree Bindings -------------------- -See Documentation/devicetree/bindings/arm/coresight.txt for details. +See ``Documentation/devicetree/bindings/arm/arm,coresight-*.yaml`` for details. As of this writing drivers for ITM, STMs and CTIs are not provided but are expected to be added as the solution matures. @@ -339,7 +339,8 @@ 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: +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 @@ -446,7 +447,8 @@ wealth of possibilities that coresight provides. Instruction 0 0x8026B588 E8BD8000 true LDM sp!,{pc} Timestamp Timestamp: 17107041535 -2) Using perf framework: +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 @@ -460,49 +462,44 @@ queried by the perf command line tool: 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. -On newer kernels the available sinks are listed in sysFS under +provided along with configuration options within forward slashes '/' (see +`Config option formats`_). + +Advanced Perf framework usage +----------------------------- + +Sink selection +~~~~~~~~~~~~~~ + +An appropriate sink will be selected automatically for use with Perf, but since +there will typically be more than one sink, the name of the sink to use may be +specified as a special config option prefixed with '@'. + +The available sinks are listed in sysFS under ($SYSFS)/bus/event_source/devices/cs_etm/sinks/:: root@localhost:/sys/bus/event_source/devices/cs_etm/sinks# ls tmc_etf0 tmc_etr0 tpiu0 -On older kernels, this may need to be found from the list of coresight devices, -available under ($SYSFS)/bus/coresight/devices/:: - - root:~# ls /sys/bus/coresight/devices/ - etm0 etm1 etm2 etm3 etm4 etm5 funnel0 - funnel1 funnel2 replicator0 stm0 tmc_etf0 tmc_etr0 tpiu0 root@linaro-nano:~# perf record -e cs_etm/@tmc_etr0/u --per-thread program -As mentioned above in section "Device Naming scheme", the names of the devices could -look different from what is used in the example above. One must use the device names -as it appears under the sysFS. - -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 [#third]_. -2.1) AutoFDO analysis using the perf tools: +AutoFDO analysis using the perf tools +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ perf can be used to record and analyze trace of programs. Execution can be recorded using 'perf record' with the cs_etm event, specifying the name of the sink to record to, e.g:: - perf record -e cs_etm/@tmc_etr0/u --per-thread + perf record -e cs_etm//u --per-thread The 'perf report' and 'perf script' commands can be used to analyze execution, synthesizing instruction and branch events from the instruction trace. @@ -513,7 +510,8 @@ The --itrace option controls the type and frequency of synthesized events Note that only 64-bit programs are currently supported - further work is required to support instruction decode of 32-bit Arm programs. -2.2) Tracing PID +Tracing PID +~~~~~~~~~~~ The kernel can be built to write the PID value into the PE ContextID registers. For a kernel running at EL1, the PID is stored in CONTEXTIDR_EL1. A PE may @@ -547,7 +545,7 @@ wants to trace PIDs for both host and guest, the two configs "contextid1" and Generating coverage files for Feedback Directed Optimization: AutoFDO ---------------------------------------------------------------------- +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 'perf inject' accepts the --itrace option in which case tracing data is removed and replaced with the synthesized events. e.g. @@ -565,7 +563,7 @@ sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tuto Bubble sorting array of 30000 elements 5910 ms - $ perf record -e cs_etm/@tmc_etr0/u --per-thread taskset -c 2 ./sort + $ perf record -e cs_etm//u --per-thread taskset -c 2 ./sort Bubble sorting array of 30000 elements 12543 ms [ perf record: Woken up 35 times to write data ] @@ -578,6 +576,49 @@ sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tuto Bubble sorting array of 30000 elements 5806 ms +Config option formats +~~~~~~~~~~~~~~~~~~~~~ + +The following strings can be provided between // on the perf command line to enable various options. +They are also listed in the folder /sys/bus/event_source/devices/cs_etm/format/ + +.. list-table:: + :header-rows: 1 + + * - Option + - Description + * - branch_broadcast + - Session local version of the system wide setting: + :ref:`ETM_MODE_BB <coresight-branch-broadcast>` + * - contextid + - See `Tracing PID`_ + * - contextid1 + - See `Tracing PID`_ + * - contextid2 + - See `Tracing PID`_ + * - configid + - Selection for a custom configuration. This is an implementation detail and not used directly, + see :ref:`trace/coresight/coresight-config:Using Configurations in perf` + * - preset + - Override for parameters in a custom configuration, see + :ref:`trace/coresight/coresight-config:Using Configurations in perf` + * - sinkid + - Hashed version of the string to select a sink, automatically set when using the @ notation. + This is an internal implementation detail and is not used directly, see `Using perf + framework`_. + * - cycacc + - Session local version of the system wide setting: :ref:`ETMv4_MODE_CYCACC + <coresight-cycle-accurate>` + * - retstack + - Session local version of the system wide setting: :ref:`ETM_MODE_RETURNSTACK + <coresight-return-stack>` + * - timestamp + - Session local version of the system wide setting: :ref:`ETMv4_MODE_TIMESTAMP + <coresight-timestamp>` + * - cc_threshold + - Cycle count threshold value. If nothing is provided here or the provided value is 0, then the + default value i.e 0x100 will be used. If provided value is less than minimum cycles threshold + value, as indicated via TRCIDR3.CCITMIN, then the minimum value will be used instead. How to use the STM module ------------------------- @@ -620,6 +661,19 @@ channels on the CTM (Cross Trigger Matrix). A separate documentation file is provided to explain the use of these devices. (Documentation/trace/coresight/coresight-ect.rst) [#fourth]_. +CoreSight System Configuration +------------------------------ + +CoreSight components can be complex devices with many programming options. +Furthermore, components can be programmed to interact with each other across the +complete system. + +A CoreSight System Configuration manager is provided to allow these complex programming +configurations to be selected and used easily from perf and sysfs. + +See the separate document for further information. +(Documentation/trace/coresight/coresight-config.rst) [#fifth]_. + .. [#first] Documentation/ABI/testing/sysfs-bus-coresight-devices-stm @@ -628,3 +682,5 @@ A separate documentation file is provided to explain the use of these devices. .. [#third] https://github.com/Linaro/perf-opencsd .. [#fourth] Documentation/trace/coresight/coresight-ect.rst + +.. [#fifth] Documentation/trace/coresight/coresight-config.rst |