Adding upstream version 2.8.0+dfsg.upstream/2.8.0+dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 30 insertions, 0 deletions

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+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.