[Deepin-Kernel-SIG] [linux 6.18.y] [FROMLIST] ACPI: CPPC: Add support for CPPC v4

[Avenger-285714]

CPPC v4 (ACPI 6.6, Section 8.4.6) adds two optional entries to the _CPC package:

1. OSPM Nominal Performance (8.4.6.1.2.6): A write-only register that lets OSPM inform the platform what it considers nominal performance. The platform classifies performance above this level as boost and below as throttle for its power/thermal decisions.

2. Resource Priority (8.4.6.1.2.7): A Package of Resource Priority Register Descriptor sub-packages that allow OSPM to set relative priority among processors for shared resources (boost, throttle, L2/L3 cache, memory bandwidth). Parsing the full structure is not yet supported; such entries are marked as unsupported.

Add v4 _CPC table parsing (25 entries) and update REG_OPTIONAL to mark the two new registers as optional.

Reviewed-by: Mario Limonciello (AMD) superm1@kernel.org
Reviewed-by: Pierre Gondois pierre.gondois@arm.com
Link: https://patch.msgid.link/20260527194626.185286-2-sumitg@nvidia.com

Link: https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?h=linux-next&id=71e1815113f7e37e7e39ed69526cd7d399e5a0c9

Summary by Sourcery

Add support for ACPI CPPC v4 _CPC packages while remaining backward compatible with earlier revisions.

New Features:

• Support CPPC v4 _CPC packages including the two new OSPM Nominal Performance and Resource Priority entries.

Enhancements:

• Relax CPPC _CPC package validation to treat v4 as the new baseline for future supersets and cap higher revisions to the v4 layout.
• Extend the optional-register bitmap and maximum CPC register entries to cover the additional CPPC v3/v4 fields.
• Gracefully handle unsupported Resource Priority packages by marking them as unsupported and logging a debug message.

[sourcery-ai]

Reviewer's Guide

Adds CPPC v4 support to ACPI CPPC parsing, including handling two new optional _CPC entries (OSPM Nominal Performance and Resource Priority), updating revision/entry-count validation, and extending register metadata and limits while treating Resource Priority as currently unsupported.

Flow diagram for CPPC revision and entry-count handling in acpi_cppc_processor_probe

flowchart TD
    A[Start acpi_cppc_processor_probe] --> B[Read cpc_rev and num_ent]
    B --> C{cpc_rev == CPPC_V2_REV
    and num_ent != CPPC_V2_NUM_ENT}
    C -->|yes| Z[pr_debug and goto out_free]
    C -->|no| D{cpc_rev == CPPC_V3_REV
    and num_ent != CPPC_V3_NUM_ENT}
    D -->|yes| Z
    D -->|no| E{cpc_rev == CPPC_V4_REV
    and num_ent != CPPC_V4_NUM_ENT}
    E -->|yes| Z
    E -->|no| F{cpc_rev > CPPC_V4_REV
    and num_ent <= CPPC_V4_NUM_ENT}
    F -->|yes| Z
    F -->|no| G{cpc_rev > CPPC_V4_REV}
    G -->|yes| H[Set num_ent = CPPC_V4_NUM_ENT
and cpc_rev = CPPC_V4_REV]
    G -->|no| I[Keep existing num_ent and cpc_rev]
    H --> J[Set cpc_ptr->num_entries = num_ent]
    I --> J
    J --> K[Continue CPPC parsing]
    Z --> L[Exit acpi_cppc_processor_probe]

Loading

File-Level Changes

Change	Details	Files
Extend CPPC revision and entry-count handling to support CPPC v4 _CPC packages.	Introduce CPPC_V4_REV and CPPC_V4_NUM_ENT constants for the new revision and its expected 25 entries Update the _CPC package validation logic to treat v4 as the current baseline and ensure future revisions are proper supersets of v4 Clamp revisions greater than v4 down to v4 and cap the parsed entry count at the v4 number of entries	drivers/acpi/cppc_acpi.c include/acpi/cppc_acpi.h
Add new CPPC register indices for the v4-only entries and increase internal limits.	Extend the cppc_regs enum with OSPM_NOMINAL_PERF and RESOURCE_PRIORITY indices at the end Increase MAX_CPC_REG_ENT to cover the additional registers introduced in later CPPC revisions	include/acpi/cppc_acpi.h
Adjust optional-register bitmask and implement stub handling for Resource Priority entries in _CPC.	Modify the REG_OPTIONAL bitmask so that the new CPPC v4 registers are treated as optional When a RESOURCE_PRIORITY entry appears as a package, log a debug message, mark it as unsupported, and store a dummy integer value instead of rejecting _CPC parsing	drivers/acpi/cppc_acpi.c

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[sourcery-ai]

Hey - I've left some high level feedback:

• The REG_OPTIONAL bitmap is now a larger magic constant (0x7FC7D0); consider expressing it in terms of BIT() and the enum cppc_regs indices so it’s obvious which fields are optional and easier to maintain when adding future CPPC fields.
• For the RESOURCE_PRIORITY package you synthesize an ACPI_TYPE_INTEGER with value 0 to mark it unsupported; it might be clearer and safer to either leave the type unset/invalid or introduce a dedicated “unsupported” representation so later code cannot mistake this for a legitimate integer-valued register.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The REG_OPTIONAL bitmap is now a larger magic constant (0x7FC7D0); consider expressing it in terms of BIT() and the enum cppc_regs indices so it’s obvious which fields are optional and easier to maintain when adding future CPPC fields.
- For the RESOURCE_PRIORITY package you synthesize an ACPI_TYPE_INTEGER with value 0 to mark it unsupported; it might be clearer and safer to either leave the type unset/invalid or introduce a dedicated “unsupported” representation so later code cannot mistake this for a legitimate integer-valued register.

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[Copilot]

Pull request overview

Adds ACPI CPPC v4 (_CPC revision 4) awareness to the CPPC ACPI library, extending the parsed register set to include the two new optional v4 entries while keeping behavior compatible with older revisions.

Changes:

• Add CPPC v4 revision/entry-count definitions and extend the CPC register index enum for the two new v4 fields.
• Update _CPC package validation/capping logic to treat v4 as the baseline for future supersets.
• Treat the v4 “Resource Priority” package as unsupported for now (mark unsupported and log a debug message).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
include/acpi/cppc_acpi.h	Adds CPPC v4 constants, extends register enumeration, and bumps max CPC register entries to fit v4 layout.
drivers/acpi/cppc_acpi.c	Updates optional-register bitmap, relaxes validation for v4 supersets, and adds handling for the v4 Resource Priority package type.

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