diff options
Diffstat (limited to 'Documentation/trace/coresight')
| -rw-r--r-- | Documentation/trace/coresight/coresight-etm4x-reference.rst | 17 | ||||
| -rw-r--r-- | Documentation/trace/coresight/coresight.rst | 58 |
2 files changed, 68 insertions, 7 deletions
diff --git a/Documentation/trace/coresight/coresight-etm4x-reference.rst b/Documentation/trace/coresight/coresight-etm4x-reference.rst index d25dfe86af9b..fb7578fd9372 100644 --- a/Documentation/trace/coresight/coresight-etm4x-reference.rst +++ b/Documentation/trace/coresight/coresight-etm4x-reference.rst @@ -650,13 +650,26 @@ Bit assignments shown below:- parameter is set this value is applied to the currently indexed address range. +.. _coresight-branch-broadcast: **bit (4):** ETM_MODE_BB **description:** - Set to enable branch broadcast if supported in hardware [IDR0]. + Set to enable branch broadcast if supported in hardware [IDR0]. The primary use for this feature + is when code is patched dynamically at run time and the full program flow may not be able to be + reconstructed using only conditional branches. + There is currently no support in Perf for supplying modified binaries to the decoder, so this + feature is only inteded to be used for debugging purposes or with a 3rd party tool. + + Choosing this option will result in a significant increase in the amount of trace generated - + possible danger of overflows, or fewer instructions covered. Note, that this option also + overrides any setting of :ref:`ETM_MODE_RETURNSTACK <coresight-return-stack>`, so where a branch + broadcast range overlaps a return stack range, return stacks will not be available for that + range. + +.. _coresight-cycle-accurate: **bit (5):** ETMv4_MODE_CYCACC @@ -678,6 +691,7 @@ Bit assignments shown below:- **description:** Set to enable virtual machine ID tracing if supported [IDR2]. +.. _coresight-timestamp: **bit (11):** ETMv4_MODE_TIMESTAMP @@ -685,6 +699,7 @@ Bit assignments shown below:- **description:** Set to enable timestamp generation if supported [IDR0]. +.. _coresight-return-stack: **bit (12):** ETM_MODE_RETURNSTACK diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst index a15571d96cc8..4a71ea6cb390 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 @@ -495,7 +497,11 @@ 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: +Advanced perf framework usage +----------------------------- + +AutoFDO analysis using the perf tools +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ perf can be used to record and analyze trace of programs. @@ -513,7 +519,8 @@ 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 +554,7 @@ 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. @@ -578,6 +585,45 @@ 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>` How to use the STM module ------------------------- |