[PATCH v10 0/3] ACPI / cpufreq: CPPC: Add ospm_nominal_perf support

[Sumit Gupta <sumitg@nvidia.com>]

This series adds support for the OSPM Nominal Performance register
(ACPI 6.6, Section 8.4.6.1.2.6) to the CPPC ACPI and cpufreq drivers.

Unlike the read-only Nominal Performance register, OSPM Nominal
Performance is writable and lets OSPM request a nominal level below
the platform-reported nominal. The platform treats performance above
this level as boost and below as throttle.

 - Patch 1: adds ACPI helpers to write the register and to check that
   the platform supports it.

 - Patch 2: adds the per-policy ospm_nominal_freq attribute in kHz. The
   value is kept across CPU hotplug and suspend/resume. The register
   cannot be read back, so a read returns the last value written.

 - Patch 3: uses the OSPM nominal as the maximum frequency while boost
   is off. Lowering the nominal creates a boost range on a platform
   that has none, and boost can then be enabled.

These are patches 6-8 of v9. Patches 1-5 of v9 are queued in for 7.5,
and this series applies on top of them.

v9 -> v10:
 - Drop v9 patches 1-5, as they are queued for 7.5.
 - Patch 1: when the register shares an access unit with Performance
   Limited, keep it reserved in the SystemMemory overlap validation, as
   it is write-only. (Sashiko)

Sumit Gupta (3):
  ACPI: CPPC: Add ospm_nominal_perf support
  cpufreq: CPPC: Add ospm_nominal_freq attribute
  cpufreq: CPPC: Reflect the OSPM nominal in boost and limits

 .../ABI/testing/sysfs-devices-system-cpu      |  31 ++++
 drivers/acpi/cppc_acpi.c                      |  56 ++++++
 drivers/cpufreq/cppc_cpufreq.c                | 173 +++++++++++++++++-
 include/acpi/cppc_acpi.h                      |  10 +
 4 files changed, 260 insertions(+), 10 deletions(-)

v8: https://lore.kernel.org/lkml/20261030172745.2045743-1-sumitg@nvidia.com/
v9: https://lore.kernel.org/lkml/20261106193304.3347374-1-sumitg@nvidia.com/

base-commit: 22f2a52b46d52df66cf0a5efe4d22296810cbcee
-- 
2.34.1