[Patch 0/5] Support Autonomous Selection mode in cppc_cpufreq

Sumit Gupta
2025-02-11T10:38:00Z

This patchset supports the Autonomous Performance Level Selection mode
in the cppc_cpufreq driver. The feature is part of the existing CPPC
specification and already present in Intel and AMD specific pstate
cpufreq drivers. The patchset adds the support in generic acpi cppc
cpufreq driver.

It adds a new 'cppc_cpufreq_epp' instance of the 'cppc_cpufreq' driver
for supporting the Autonomous Performance Level Selection and Energy
Performance Preference (EPP).
Autonomous selection will get enabled during boot if 'cppc_auto_sel'
boot argument is passed or the 'Autonomous Selection Enable' register
is already set before kernel boot. When enabled, the hardware is
allowed to autonomously select the CPU frequency within the min and
max perf boundaries using the Engergy Performance Preference hints.
The EPP values range from '0x0'(performance preference) to '0xFF'
(energy efficiency preference).

It also exposes the acpi_cppc sysfs nodes to update the epp, auto_sel
and {min|max_perf} registers for changing the hints to hardware for
Autonomous selection.

In a followup patch, plan to add support to dynamically switch the
cpufreq driver instance from 'cppc_cpufreq_epp' to 'cppc_cpufreq' and
vice-versa without reboot.

The patches are divided into below groups:
- Patch [1-2]: Improvements. Can be applied independently.
- Patch [3-4]: sysfs store nodes for Auto mode. Depend on Patch [1-2].
- Patch [5]: Support for 'cppc_cpufreq_epp'. Uses a macro from [3].

Sumit Gupta (5):
ACPI: CPPC: add read perf ctrls api and rename few existing
ACPI: CPPC: expand macro to create store acpi_cppc sysfs node
ACPI: CPPC: support updating epp, auto_sel and {min|max_perf} from
sysfs
Documentation: ACPI: add autonomous mode ctrls info in cppc_sysfs.txt
cpufreq: CPPC: Add cppc_cpufreq_epp instance for Autonomous mode

Documentation/admin-guide/acpi/cppc_sysfs.rst | 28 ++
.../admin-guide/kernel-parameters.txt | 11 +
drivers/acpi/cppc_acpi.c | 311 ++++++++++++++++--
drivers/cpufreq/cppc_cpufreq.c | 260 ++++++++++++++-
include/acpi/cppc_acpi.h | 19 +-
5 files changed, 572 insertions(+), 57 deletions(-)

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2.25.1