Commit 4af43218 authored by Anshuman Khandual's avatar Anshuman Khandual Committed by Mathieu Poirier
Browse files

Documentation: trace: Add documentation for TRBE 



Add documentation for the  TRBE under trace/coresight.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Signed-off-by: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
[ Split from the TRBE driver patch ]
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20210405164307.1720226-20-suzuki.poulose@arm.com


Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
parent b20f34ae

Documentation/trace/coresight/coresight-trbe.rst

0 → 100644
+38 −0
Original line number Diff line number Diff line 
.. SPDX-License-Identifier: GPL-2.0



==============================

Trace Buffer Extension (TRBE).

==============================



    :Author:   Anshuman Khandual <anshuman.khandual@arm.com>

    :Date:     November 2020



Hardware Description

--------------------



Trace Buffer Extension (TRBE) is a percpu hardware which captures in system

memory, CPU traces generated from a corresponding percpu tracing unit. This

gets plugged in as a coresight sink device because the corresponding trace

generators (ETE), are plugged in as source device.



The TRBE is not compliant to CoreSight architecture specifications, but is

driven via the CoreSight driver framework to support the ETE (which is

CoreSight compliant) integration.



Sysfs files and directories

---------------------------



The TRBE devices appear on the existing coresight bus alongside the other

coresight devices::



	>$ ls /sys/bus/coresight/devices

	trbe0  trbe1  trbe2 trbe3



The ``trbe<N>`` named TRBEs are associated with a CPU.::



	>$ ls /sys/bus/coresight/devices/trbe0/

        align flag



*Key file items are:-*

   * ``align``: TRBE write pointer alignment

   * ``flag``: TRBE updates memory with access and dirty flags