19cf75647SChris KayActivity Monitors 29cf75647SChris Kay================= 39cf75647SChris Kay 49cf75647SChris KayFEAT_AMUv1 of the Armv8-A architecture introduces the Activity Monitors 59cf75647SChris Kayextension. This extension describes the architecture for the Activity Monitor 69cf75647SChris KayUnit (|AMU|), an optional non-invasive component for monitoring core events 79cf75647SChris Kaythrough a set of 64-bit counters. 89cf75647SChris Kay 99cf75647SChris KayWhen the ``ENABLE_AMU=1`` build option is provided, Trusted Firmware-A sets up 109cf75647SChris Kaythe |AMU| prior to its exit from EL3, and will save and restore architected 119cf75647SChris Kay|AMU| counters as necessary upon suspend and resume. 129cf75647SChris Kay 13*742ca230SChris KayAuxiliary counters 14*742ca230SChris Kay------------------ 15*742ca230SChris Kay 16*742ca230SChris KayFEAT_AMUv1 describes a set of implementation-defined auxiliary counters (also 17*742ca230SChris Kayknown as group 1 counters), controlled by the ``ENABLE_AMU_AUXILIARY_COUNTERS`` 18*742ca230SChris Kaybuild option. 19*742ca230SChris Kay 20*742ca230SChris KayAs a security precaution, Trusted Firmware-A does not enable these by default. 21*742ca230SChris KayInstead, platforms may configure their auxiliary counters through one of two 22*742ca230SChris Kaypossible mechanisms: 23*742ca230SChris Kay 24*742ca230SChris Kay- |FCONF|, controlled by the ``ENABLE_AMU_FCONF`` build option. 25*742ca230SChris Kay- A platform implementation of the ``plat_amu_topology`` function (the default). 26*742ca230SChris Kay 27*742ca230SChris KaySee :ref:`Activity Monitor Unit (AMU) Bindings` for documentation on the |FCONF| 28*742ca230SChris Kaydevice tree bindings. 29*742ca230SChris Kay 309cf75647SChris Kay-------------- 319cf75647SChris Kay 329cf75647SChris Kay*Copyright (c) 2021, Arm Limited. All rights reserved.* 33