docs(amu): add AMU documentation
This change adds some documentation on the AMU and its purpose. This is
expanded on in later patches.
Change-Id: If2834676790938d8da5ea2ceba37b674f6cc0f01
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/docs/components/activity-monitors.rst b/docs/components/activity-monitors.rst
new file mode 100644
index 0000000..57d81f8
--- /dev/null
+++ b/docs/components/activity-monitors.rst
@@ -0,0 +1,15 @@
+Activity Monitors
+=================
+
+FEAT_AMUv1 of the Armv8-A architecture introduces the Activity Monitors
+extension. This extension describes the architecture for the Activity Monitor
+Unit (|AMU|), an optional non-invasive component for monitoring core events
+through a set of 64-bit counters.
+
+When the ``ENABLE_AMU=1`` build option is provided, Trusted Firmware-A sets up
+the |AMU| prior to its exit from EL3, and will save and restore architected
+|AMU| counters as necessary upon suspend and resume.
+
+--------------
+
+*Copyright (c) 2021, Arm Limited. All rights reserved.*
diff --git a/docs/components/index.rst b/docs/components/index.rst
index f349d8d..e467516 100644
--- a/docs/components/index.rst
+++ b/docs/components/index.rst
@@ -7,6 +7,7 @@
:numbered:
spd/index
+ activity-monitors
arm-sip-service
debugfs-design
exception-handling
diff --git a/docs/global_substitutions.txt b/docs/global_substitutions.txt
index 24ac830..a70f15e 100644
--- a/docs/global_substitutions.txt
+++ b/docs/global_substitutions.txt
@@ -1,5 +1,7 @@
.. |AArch32| replace:: :term:`AArch32`
.. |AArch64| replace:: :term:`AArch64`
+.. |AMU| replace:: :term:`AMU`
+.. |AMUs| replace:: :term:`AMUs <AMU>`
.. |API| replace:: :term:`API`
.. |BTI| replace:: :term:`BTI`
.. |CoT| replace:: :term:`CoT`
diff --git a/docs/glossary.rst b/docs/glossary.rst
index f4912f5..a062319 100644
--- a/docs/glossary.rst
+++ b/docs/glossary.rst
@@ -15,6 +15,10 @@
AArch64
64-bit execution state of the ARMv8 ISA
+ AMU
+ Activity Monitor Unit, a hardware monitoring unit introduced by FEAT_AMUv1
+ that exposes CPU core runtime metrics as a set of counter registers.
+
API
Application Programming Interface