MPMM is a core-specific microarchitectural feature. It has been present
in every Arm core since the Cortex-A510 and has been implemented in
exactly the same way. Despite that, it is enabled more like an
architectural feature with a top level enable flag. This utilised the
identical implementation.
This duality has left MPMM in an awkward place, where its enablement
should be generic, like an architectural feature, but since it is not,
it should also be core-specific if it ever changes. One choice to do
this has been through the device tree.
This has worked just fine so far, however, recent implementations expose
a weakness in that this is rather slow - the device tree has to be read,
there's a long call stack of functions with many branches, and system
registers are read. In the hot path of PSCI CPU powerdown, this has a
significant and measurable impact. Besides it being a rather large
amount of code that is difficult to understand.
Since MPMM is a microarchitectural feature, its correct placement is in
the reset function. The essence of the current enablement is to write
CPUPPMCR_EL3.MPMM_EN if CPUPPMCR_EL3.MPMMPINCTL == 0. Replacing the C
enablement with an assembly macro in each CPU's reset function achieves
the same effect with just a single close branch and a grand total of 6
instructions (versus the old 2 branches and 32 instructions).
Having done this, the device tree entry becomes redundant. Should a core
that doesn't support MPMM arise, this can cleanly be handled in the
reset function. As such, the whole ENABLE_MPMM_FCONF and platform hooks
mechanisms become obsolete and are removed.
Change-Id: I1d0475b21a1625bb3519f513ba109284f973ffdf
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Document bindings for TB_FW_CONFIG that are common between platforms.
Since the information this device tree type contains pertains to
firmware specific properties, we do not expect that the document will
cover all uses, nor do we promise backward compatiblity.
Change-Id: I0e850c13b77cc62940ab5020a15bf8e503568ed8
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
MPMM - the Maximum Power Mitigation Mechanism - is an optional
microarchitectural feature present on some Armv9-A cores, introduced
with the Cortex-X2, Cortex-A710 and Cortex-A510 cores.
MPMM allows the SoC firmware to detect and limit 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.
This feature is enabled via the `ENABLE_MPMM` build option.
Configuration can be done via FCONF by enabling `ENABLE_MPMM_FCONF`, or
by via the plaform-implemented `plat_mpmm_topology` function.
Change-Id: I77da82808ad4744ece8263f0bf215c5a091c3167
Signed-off-by: Chris Kay <chris.kay@arm.com>
This change makes AMU auxiliary counters configurable on a per-core
basis, controlled by `ENABLE_AMU_AUXILIARY_COUNTERS`.
Auxiliary counters can be described via the `HW_CONFIG` device tree if
the `ENABLE_AMU_FCONF` build option is enabled, or the platform must
otherwise implement the `plat_amu_topology` function.
A new phandle property for `cpu` nodes (`amu`) has been introduced to
the `HW_CONFIG` specification to allow CPUs to describe the view of
their own AMU:
```
cpu0: cpu@0 {
...
amu = <&cpu0_amu>;
};
```
Multiple cores may share an `amu` handle if they implement the
same set of auxiliary counters.
AMU counters are described for one or more AMUs through the use of a new
`amus` node:
```
amus {
cpu0_amu: amu-0 {
#address-cells = <1>;
#size-cells = <0>;
counter@0 {
reg = <0>;
enable-at-el3;
};
counter@n {
reg = <n>;
...
};
};
};
```
This structure describes the **auxiliary** (group 1) AMU counters.
Architected counters have architecturally-defined behaviour, and as
such do not require DTB entries.
These `counter` nodes support two properties:
- The `reg` property represents the counter register index.
- The presence of the `enable-at-el3` property determines whether
the firmware should enable the counter prior to exiting EL3.
Change-Id: Ie43aee010518c5725a3b338a4899b0857caf4c28
Signed-off-by: Chris Kay <chris.kay@arm.com>
Updated the document for BL1 and BL2 boot flow to capture
below changes made in FCONF
1. Loading of fw_config and tb_fw_config images by BL1.
2. Population of fw_config and tb_fw_config by BL2.
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: Ifea5c61d520ff1de834c279ce1759b53448303ba
Complete the documentation with information on how to write a DTS for
fconf. This patch adds the bindings information for dynamic
configuration properties.
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
Change-Id: Ic6d9f927df53bb87315c23ec5a8943d0c3258d45
