1Activity Monitors 2================= 3 4FEAT_AMUv1 of the Armv8-A architecture introduces the Activity Monitors 5extension. This extension describes the architecture for the Activity Monitor 6Unit (|AMU|), an optional non-invasive component for monitoring core events 7through a set of 64-bit counters. 8 9When the ``ENABLE_AMU=1`` build option is provided, Trusted Firmware-A sets up 10the |AMU| prior to its exit from EL3, and will save and restore architected 11|AMU| counters as necessary upon suspend and resume. 12 13Auxiliary counters 14------------------ 15 16FEAT_AMUv1 describes a set of implementation-defined auxiliary counters (also 17known as group 1 counters), controlled by the ``ENABLE_AMU_AUXILIARY_COUNTERS`` 18build option. 19 20As a security precaution, Trusted Firmware-A does not enable these by default. 21Instead, platforms may configure their auxiliary counters through one of two 22possible mechanisms: 23 24- |FCONF|, controlled by the ``ENABLE_AMU_FCONF`` build option. 25- A platform implementation of the ``plat_amu_topology`` function (the default). 26 27See :ref:`Activity Monitor Unit (AMU) Bindings` for documentation on the |FCONF| 28device tree bindings. 29 30-------------- 31 32*Copyright (c) 2021, Arm Limited. All rights reserved.* 33