[PATCH v4 0/8] Enhanced autonomous selection and improvements

[Sumit Gupta <sumitg@nvidia.com>]

This patch series enhances the ACPI CPPC CPUFREQ driver with
comprehensive support for autonomous performance selection, expanded
runtime control interfaces and improvements.

It adds support for below:
- Expose sysfs to read/write the Minimum/Maximum Performance Registers
  using frequency (kHz), with internal conversion to performance values.
  Also, update the policy min/max accordingly.
    /sys/.../cpufreq/policy*/min_perf and max_perf

- Expose sysfs to read/write the Performance Limited Register.
    /sys/.../cpufreq/policy*/perf_limited

- When toggling autonomous selection, synchronize the policy limits
  by updating the policy min/max.

- System-wide autonomous mode configuration via 'auto_sel_mode' boot
  parameter. Mode can be switched dynamically on individual CPUs.

- Generic sysfs helper functions to reduce code duplication.

The patches are grouped as below:
- Patch 1, 2 & 3: Improvements. Can be applied independently.
- Patch 4: Sysfs to update min/max_perf. Can be applied independently.
- Patch 5: Sysfs to update perf_limited. Can be applied independently.
- Patch 6: add sysfs documentation. Depends on 'Patch 4 and 5'.
- Patch 7: sync policy min/max with auto_select. Depends on 'Patch 4'.
- Patch 8: Boot Parameter Support. Depends on 'Patch 4 and 7'.

---
v3[3] -> v4:
- patch1: changed param order for show/store and moved them above use.
- patch3: write epp and auto_sel registers independently. 
- patch4:
  - move mutex define outside macro.
  - return EOPNOTSUPP error also to the caller to handle appropriately.
  - change min/max_perf sysfs to accept freq, convert to perf internally
- patch6:
  - update dates and corrected names in description.
  - remove dependency of min/max_perf on auto_sel.
  - add info about highest_perf and lowest_perf interfaces.
  - update info about min/max_perf interface to read/write freq in kHz.

v2[2] -> v3:
- drop changes to rename exisiting APIs.
- add new 'patch 1' with generic helpers for sysfs show/store.
- used guard(mutex)() in place of mutex_lock/unlock.
- update kernel-parameters text to 'enable if supported by hardware'.
- disable auto_sel for all cpus if one fails in auto_sel_mode.
- use min/max_perf values if set from bootloader.
- general code improvements, error handling and reduced redundancies.

v1[1] -> v2:
- Move CPC register set sysfs from acpi_cppc to cpufreq directory.
- No sysfs to set auto_sel and epp. They were merged from diff series.
- Remove 'cppc_cpufreq_epp' instance of the 'cppc_cpufreq' driver.
- Synchronize perf_min/max with policy min/max.
- Update policy min/max Toggling auto_select.
- add sysfs to update the perf_limited register.

Sumit Gupta (8):
  cpufreq: CPPC: Add generic helpers for sysfs show/store
  ACPI: CPPC: Add cppc_get_perf() API to read performance controls
  ACPI: CPPC: extend APIs to support auto_sel and epp
  ACPI: CPPC: add APIs and sysfs interface for min/max_perf
  ACPI: CPPC: add APIs and sysfs interface for perf_limited register
  cpufreq: CPPC: Add sysfs for min/max_perf and perf_limited
  cpufreq: CPPC: update policy min/max when toggling auto_select
  cpufreq: CPPC: add autonomous mode boot parameter support

 .../ABI/testing/sysfs-devices-system-cpu      |  46 ++
 .../admin-guide/kernel-parameters.txt         |  12 +
 drivers/acpi/cppc_acpi.c                      | 196 +++++++-
 drivers/cpufreq/cppc_cpufreq.c                | 425 ++++++++++++++++--
 include/acpi/cppc_acpi.h                      |  39 +-
 5 files changed, 676 insertions(+), 42 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/

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2.34.1