[PATCH v4 0/2] cpufreq: CPPC: add autonomous mode boot parameter support

[Sumit Gupta]

This series adds a kernel boot parameter 'cppc_cpufreq.auto_sel_mode'
to enable CPPC autonomous performance selection on all CPUs at system
startup, avoiding per-CPU sysfs scripting at every boot.

When autonomous mode is enabled, the hardware automatically adjusts
CPU performance based on workload demands using Energy Performance
Preference (EPP) hints.

Patch 1: Sets CPPC Enable Register for both OS-driven and autonomous
CPPC control modes. It can be applied independently of patch 2.

Patch 2: Adds the auto_sel_mode boot parameter with three modes:
  - performance (or 1):         override EPP to performance (0x0)
  - balance_performance (or 2): override EPP to balance_performance (0x80)
  - default_epp (or 3):         preserve EPP value programmed by
                                BIOS/firmware

Patch 2 depends on Pierre's series [4] ("cpufreq: Set policy->min and
max as real QoS constraints") so that policy->min/max set during
cppc_cpufreq_cpu_init() are not overridden by cpufreq_set_policy().

v3[3] -> v4:
- Add 'balance_performance' mode which sets EPP to 0x80.
- Add CPPC_EPP_BALANCE_PERFORMANCE_PREF (0x80) constant in cppc_acpi.h.
- Clean up EPP mode selection with switch + boolean flag in cpu_init.
- Use local variable for kp->arg in auto_sel_mode_set/get to avoid
  repeated casts.

Sumit Gupta (2):
  cpufreq: CPPC: Set CPPC Enable register in cpu_init
  cpufreq: CPPC: add autonomous mode boot parameter support

 .../admin-guide/kernel-parameters.txt         |  20 +++
 drivers/cpufreq/cppc_cpufreq.c                | 154 +++++++++++++++++-
 include/acpi/cppc_acpi.h                      |   1 +
 3 files changed, 170 insertions(+), 5 deletions(-)

[1] v1: https://lore.kernel.org/lkml/20260317151053.2361475-1-sumitg@xxxxxxxxxx/
[2] v2: https://lore.kernel.org/lkml/20260424201814.230071-1-sumitg@xxxxxxxxxx/
[3] v3: https://lore.kernel.org/lkml/20260515122624.1920637-1-sumitg@xxxxxxxxxx/
[4] https://lore.kernel.org/lkml/20260511135538.522653-1-pierre.gondois@xxxxxxx/

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2.34.1