1*54fd6939SJiyong ParkActivity Monitors 2*54fd6939SJiyong Park================= 3*54fd6939SJiyong Park 4*54fd6939SJiyong ParkFEAT_AMUv1 of the Armv8-A architecture introduces the Activity Monitors 5*54fd6939SJiyong Parkextension. This extension describes the architecture for the Activity Monitor 6*54fd6939SJiyong ParkUnit (|AMU|), an optional non-invasive component for monitoring core events 7*54fd6939SJiyong Parkthrough a set of 64-bit counters. 8*54fd6939SJiyong Park 9*54fd6939SJiyong ParkWhen the ``ENABLE_AMU=1`` build option is provided, Trusted Firmware-A sets up 10*54fd6939SJiyong Parkthe |AMU| prior to its exit from EL3, and will save and restore architected 11*54fd6939SJiyong Park|AMU| counters as necessary upon suspend and resume. 12*54fd6939SJiyong Park 13*54fd6939SJiyong Park.. _Activity Monitor Auxiliary Counters: 14*54fd6939SJiyong Park 15*54fd6939SJiyong ParkAuxiliary counters 16*54fd6939SJiyong Park------------------ 17*54fd6939SJiyong Park 18*54fd6939SJiyong ParkFEAT_AMUv1 describes a set of implementation-defined auxiliary counters (also 19*54fd6939SJiyong Parkknown as group 1 counters), controlled by the ``ENABLE_AMU_AUXILIARY_COUNTERS`` 20*54fd6939SJiyong Parkbuild option. 21*54fd6939SJiyong Park 22*54fd6939SJiyong ParkAs a security precaution, Trusted Firmware-A does not enable these by default. 23*54fd6939SJiyong ParkInstead, platforms may configure their auxiliary counters through one of two 24*54fd6939SJiyong Parkpossible mechanisms: 25*54fd6939SJiyong Park 26*54fd6939SJiyong Park- |FCONF|, controlled by the ``ENABLE_AMU_FCONF`` build option. 27*54fd6939SJiyong Park- A platform implementation of the ``plat_amu_topology`` function (the default). 28*54fd6939SJiyong Park 29*54fd6939SJiyong ParkSee :ref:`Activity Monitor Unit (AMU) Bindings` for documentation on the |FCONF| 30*54fd6939SJiyong Parkdevice tree bindings. 31*54fd6939SJiyong Park 32*54fd6939SJiyong Park-------------- 33*54fd6939SJiyong Park 34*54fd6939SJiyong Park*Copyright (c) 2021, Arm Limited. All rights reserved.* 35