[v6] Enhanced autonomous selection and improvements

[PATCH v6 0/9] Enhanced autonomous selection and improvements
Posted by Sumit Gupta 2 weeks, 4 days ago
As discussed in [6], v5 is split into two parts. This is part 1
(v5 patches 1-7) and can be applied independently. I will follow up
separately with part 2 (v5 patches 8-11).

This patch series adds sysfs interfaces for CPPC min_perf, max_perf,
and perf_limited registers, along with supporting ACPI APIs and
improvements for the cppc_cpufreq driver.

CPPC autonomous mode (auto_sel) enables hardware-driven CPU performance
scaling using Energy Performance Preference (EPP) hints. Currently,
there's limited runtime control and visibility into CPPC performance
registers.

This series addresses these gaps by:
1. Exposing min_perf/max_perf registers via sysfs (as frequency in kHz)
   to allow fine-grained performance bounds control in autonomous mode.
2. Exposing perf_limited register to detect and clear throttling events.

It also includes code improvements: generic sysfs helpers, struct
cleanup, new APIs for reading performance controls, and extended
epp_perf support.

The patches are grouped as below:
- Patch 1: Generic sysfs helpers (refactoring, independent).
- Patch 2-4: Code improvements (can be applied independently).
- Patch 5: Extend cppc_set_epp_perf for FFH/SystemMemory (independent).
- Patch 6-7: APIs and sysfs for min/max_perf, perf_limited (independent).
- Patch 8: ABI documentation (depends on patch 6-7).
- Patch 9: Update cached perf_ctrls on sysfs write (depends on patch 6).

---
v5[5] -> v6:
- Split patchset as described above.
- patch1: added CPPC_CPUFREQ_ATTR_RW_U64 macro for sysfs attributes.
- patch3: new patch to rename EPP constants for clarity.
- patch5: simplified else block in cppc_set_epp_perf().
- patch6: fallback to caps values if registers are uninitialized.
- patch7: use CPPC_CPUFREQ_ATTR_RW_U64 macro for perf_limited sysfs.
- patch9: new patch to update cached perf_ctrls on sysfs write.
- Renamed mutex to cppc_cpufreq_autonomous_lock.

Sumit Gupta (9):
  cpufreq: CPPC: Add generic helpers for sysfs show/store
  ACPI: CPPC: Clean up cppc_perf_caps and cppc_perf_ctrls structs
  ACPI: CPPC: Rename EPP constants for clarity
  ACPI: CPPC: Add cppc_get_perf() API to read performance controls
  ACPI: CPPC: Extend cppc_set_epp_perf() for FFH/SystemMemory
  ACPI: CPPC: add APIs and sysfs interface for min/max_perf
  ACPI: CPPC: add APIs and sysfs interface for perf_limited
  cpufreq: CPPC: Add sysfs for min/max_perf and perf_limited
  cpufreq: CPPC: Update cached perf_ctrls on sysfs write

 .../ABI/testing/sysfs-devices-system-cpu      |  44 ++++
 drivers/acpi/cppc_acpi.c                      | 206 +++++++++++++++-
 drivers/cpufreq/cppc_cpufreq.c                | 224 ++++++++++++++++--
 include/acpi/cppc_acpi.h                      |  46 +++-
 4 files changed, 491 insertions(+), 29 deletions(-)

[1] https://lore.kernel.org/lkml/20250211103737.447704-1-sumitg@nvidia.com/
[2] https://lore.kernel.org/lkml/20250823200121.1320197-1-sumitg@nvidia.com/
[3] https://lore.kernel.org/lkml/20251001150104.1275188-1-sumitg@nvidia.com/
[4] https://lore.kernel.org/lkml/20251105113844.4086250-1-sumitg@nvidia.com/
[5] https://lore.kernel.org/lkml/20251223121307.711773-1-sumitg@nvidia.com/
[6] https://lore.kernel.org/lkml/66f58f43-631b-40a0-8d42-4e90cd24b757@arm.com/

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