Commit bcc5834f authored by James Clark's avatar James Clark Committed by Suzuki K Poulose
Browse files

Documentation: coresight: Turn numbered subsections into real subsections 



This is to allow them to be referenced in a later commit. There was
also a mistake where sysFS was introduced as section 2, but numbered
as section 1. And vice versa for 'Using perf framework'. This can't
happen with unnumbered sections.

Signed-off-by: default avatarJames Clark <james.clark@arm.com>
Reviewed-by: default avatarMike Leach <mike.leach@linaro.org>
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220511144601.2257870-3-james.clark@arm.com
parent 2d693ed4

Documentation/trace/coresight/coresight.rst

+12 −5
Original line number Diff line number Diff line
@@ -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.