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

Punit Agrawal
2025-12-03T11:04:24Z

Hi Sudeep,

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

> On Wed, Nov 05, 2025 at 11:49:38AM +0000, Punit Agrawal wrote:
>> 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?
>>
>
> I can create one but that is not strictly necessary. As mentioned in the
> cover letter, the only dependency is on value of SCMI_PROTOCOL_TELEMETRY
> ins `scmi_std_protocol` enumeration. Just add one and you must be able to
> compile the series independent of Cristian series.

Thanks, I managed to get the patches building. Looking forward to the
series progressing. If possible, do keep me in the loop for future
updates.