ACPI power management with SCMI on RdN2 platforms
Through the RDN2 infrastructure developed at ARM it is possible to set up a test environment
in order to verify sending SCMI commands within AML power methods.
This code lays the groundwork for testing and validating the ACPI power management features
(device frequency scaling, device power management, power capping) implemented on top
of the SCMI protocols.
To set up the platform the steps described in
https://gitlab.arm.com/arm-reference-solutions/arm-reference-solutions-docs/-/tree/master/docs/infra/rdn2
should be followed.
The release tag currently used to carry out the experiment is:
https://gitlab.arm.com/arm-reference-solutions/arm-reference-solutions-docs/-/blob/master/docs/infra/releases/RD-INFRA-2022.08.18/release_note.rst
The test carried out is the buildroot boot, as described in:
https://gitlab.arm.com/arm-reference-solutions/arm-reference-solutions-docs/-/blob/master/docs/infra/common/buildroot-boot.rst
The code that implements the testbench is split into three components, edk2-platform, scp and arm-TF.
They should be applied on top of the code pulled by the RD-infrastructure with the release tag provided
above (2022.08.18).
The scp patch
adds:
the MHU2 non-secure channel required by OSPM to communicate to the SCP over PCC
a virtual power domain to control power states
SCMI agent to handle MHU2 communication
The EDK2 patches
add:
PCCT table
DMA PL330 PSx power methods (and PCC opregion)
The ARM-TF patch
is a hack required to make MHU2 protocol work on the FVP.
Boostrapping the platform through the buildroot test for rdn2 should trigger a power state change
for DMA PL330, proving that the SCMI command sent in the PS3 method was executed and received
by the SCP. The power domain in the SCP is a virtual one so it does nothing to handle the state
transition but that’s enough to verify the flow is working from ACPI power methods into SCP.