| Maximum Power Mitigation Mechanism (MPMM) |
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| |MPMM| is an optional microarchitectural power management mechanism supported by |
| some Arm Armv9-A cores, beginning with the Cortex-X2, Cortex-A710 and |
| Cortex-A510 cores. This mechanism detects and limits high-activity events to |
| assist in |SoC| processor power domain dynamic power budgeting and limit the |
| triggering of whole-rail (i.e. clock chopping) responses to overcurrent |
| conditions. |
| |
| |MPMM| is enabled on a per-core basis by the EL3 runtime firmware. The presence |
| of |MPMM| cannot be determined at runtime by the firmware, and therefore the |
| platform must expose this information through one of two possible mechanisms: |
| |
| - |FCONF|, controlled by the ``ENABLE_MPMM_FCONF`` build option. |
| - A platform implementation of the ``plat_mpmm_topology`` function (the |
| default). |
| |
| See :ref:`Maximum Power Mitigation Mechanism (MPMM) Bindings` for documentation |
| on the |FCONF| device tree bindings. |
| |
| .. warning:: |
| |
| |MPMM| exposes gear metrics through the auxiliary |AMU| counters. An |
| external power controller can use these metrics to budget SoC power by |
| limiting the number of cores that can execute higher-activity workloads or |
| switching to a different DVFS operating point. When this is the case, the |
| |AMU| counters that make up the |MPMM| gears must be enabled by the EL3 |
| runtime firmware - please see :ref:`Activity Monitor Auxiliary Counters` for |
| documentation on enabling auxiliary |AMU| counters. |