Re: [PATCH 0/8] firmware: arm_scmi: Refactoring and enablement of ACPI PCC transport

Punit Agrawal
2025-11-05T11:49:42Z

Hi Sudeep,

Sudeep Holla <sudeep.holla@arm.com> writes:

> The SCMI can be utilized in systems using either the FDT or ACPI specification.
> While FDT-based systems can natively use SCMI, ACPI-based systems often
> need to abstract the functionality provided by SCMI under ASL methods.
> So far, there has been no need to support SCMI natively on ACPI systems.
>
> However, with the addition of a few new protocols such as Powercap and Telemetry,
> which lack abstractions in the ACPI specification, there is now a need to
> run SCMI natively for those use cases.
>
> This patch series introduces ACPI PCC transport support for the Arm SCMI
> framework, alongside several foundational refactors and enhancements to
> achieve firmware-node neutrality between Device Tree (DT) and ACPI systems.
>
> The key changes include:
>
> 1. ACPI/DT abstraction and fwnode transition
>
> Converted the core SCMI code to use `fwnode_handle` instead of DT-specific
> structures, ensuring seamless operation across both ACPI and DT
> environments. All property lookups, child enumeration, and device
> association paths have been updated accordingly.
>
> 2. Unified transport registration for ACPI and DT
>
> Extended the SCMI transport driver macros to support ACPI match tables,
> enabling transports to probe using ACPI device IDs while maintaining
> backward compatibility with DT-only systems.
>
> 3. Protocol device initialization and refactoring
>
> Refactored the protocol device creation and validation logic into a new
> helper for improved readability and maintainability. Enhanced the
> initialization logic to handle ACPI-based SCMI devices without explicit
> child fwnodes.
>
> 4. Introduction of ACPI PCC transport
>
> Added a new SCMI transport driver leveraging ACPI PCCT (Platform
> Communications Channel Table) subspaces via the Linux PCC mailbox
> framework. This enables SCMI communication over PCC on ACPI-based
> platforms.
>
> Collectively, these changes lay the groundwork for robust SCMI operation on
> ACPI platforms, achieving near parity with DT systems where applicable,
> while enabling the new PCC transport path for firmware communication.

I was interested in taking a closer look at the patches here but they
have a dependency on support for the telemetry protocol patches. I get a
compile error.

I was wondering if you have a branch with the dependencies included. Are
the v1 telemetry support patches[0] the right version to be using?

Thanks,
Punit

[0] https://lore.kernel.org/all/20250925203554.482371-1-cristian.marussi@arm.com/ …