| 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. |
| |
| Auxiliary counters |
| ------------------ |
| |
| FEAT_AMUv1 describes a set of implementation-defined auxiliary counters (also |
| known as group 1 counters), controlled by the ``ENABLE_AMU_AUXILIARY_COUNTERS`` |
| build option. |
| |
| As a security precaution, Trusted Firmware-A does not enable these by default. |
| Instead, platforms may configure their auxiliary counters through one of two |
| possible mechanisms: |
| |
| - |FCONF|, controlled by the ``ENABLE_AMU_FCONF`` build option. |
| - A platform implementation of the ``plat_amu_topology`` function (the default). |
| |
| See :ref:`Activity Monitor Unit (AMU) Bindings` for documentation on the |FCONF| |
| device tree bindings. |
| |
| -------------- |
| |
| *Copyright (c) 2021, Arm Limited. All rights reserved.* |
