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authorAnshuman Khandual <anshuman.khandual@arm.com>2021-04-05 19:43:06 +0300
committerMathieu Poirier <mathieu.poirier@linaro.org>2021-04-07 01:05:38 +0300
commit4af432186122bb274b76e7ac549073122c41d2fb (patch)
treed3848105036be3da56d8ab8b01f079d22fac68f9 /Documentation/trace
parentb20f34aec776f4c735cd3a899e9bc3333463848a (diff)
downloadlinux-4af432186122bb274b76e7ac549073122c41d2fb.tar.xz
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: Anshuman Khandual <anshuman.khandual@arm.com> [ Split from the TRBE driver patch ] Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Link: https://lore.kernel.org/r/20210405164307.1720226-20-suzuki.poulose@arm.com Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
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+.. 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