Re: [PATCH v7 0/3] ACPI / cpufreq: CPPC: Add ospm_nominal_perf support

[Rafael J. Wysocki (Intel)]

On Fri, Aug 7, 2026 at 11:49 PM Sumit Gupta <sumitg@xxxxxxxxxx> wrote:
>
> 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 for its power and thermal
> decisions.
>
>  - Patch 1: adds cppc_set_ospm_nominal_perf() and
>    cppc_ospm_nominal_perf_supported().
>
>  - Patch 2: adds the per-policy ospm_nominal_freq attribute in kHz, and
>    tracks the register in the OSPM-set save/restore table. The register
>    cannot be read back, so the attribute is write-only.
>
>  - Patch 3: reflects the OSPM nominal in the cpufreq policy, so that
>    boost and the frequency limits stay consistent with the register.
>
> This series applies on top of the following series, which provides the
> save/restore table that patch 2 hooks into:
>   cpufreq: CPPC: Preserve OSPM-set registers across hotplug and unload
>   https://lore.kernel.org/lkml/20260806200857.601152-1-sumitg@xxxxxxxxxx/
>
> v6[6] -> v7:
>  - Split patch 1 into an ACPI patch and a cpufreq patch.
>  - Patch 1:
>    - drop cppc_get_ospm_nominal_perf(), as the register is write-only.
>    - add cppc_ospm_nominal_perf_supported(), sharing the setter's
>      writable check via the new cpc_reg_writable() helper.
>  - Patch 2:
>    - make ospm_nominal_freq write-only, and track the requested value
>      in software instead of reading the register back.
>    - place the register before auto_sel in the save/restore table.
>  - Patch 3:
>    - rename *_reflect_nominal() to *_update_nominal_limits().
>    - do not fail the sysfs write when cppc_cpufreq_update_nominal_limits()
>      fails to update the QoS limit.
>    - skip the limit update while boost is enabled.
>    - make cppc_cpufreq_effective_nominal() take the value from the
>      software-tracked state, so it returns it directly and cannot fail.
>    - init() checks cppc_ospm_nominal_perf_supported() directly, instead
>      of using cppc_cpufreq_effective_nominal().
>
> 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      |  24 ++++
>  drivers/acpi/cppc_acpi.c                      |  48 ++++++-
>  drivers/cpufreq/cppc_cpufreq.c                | 135 +++++++++++++++++-
>  include/acpi/cppc_acpi.h                      |  10 ++
>  4 files changed, 208 insertions(+), 9 deletions(-)
>
> v6: https://lore.kernel.org/lkml/20260717215330.2215058-1-sumitg@xxxxxxxxxx/
> v5: https://lore.kernel.org/lkml/20260615185934.2383514-1-sumitg@xxxxxxxxxx/
> v4: https://lore.kernel.org/lkml/20260527194626.185286-1-sumitg@xxxxxxxxxx/
> v3: https://lore.kernel.org/lkml/20260514194822.1841748-1-sumitg@xxxxxxxxxx/
> v2: https://lore.kernel.org/lkml/20260430142430.755437-1-sumitg@xxxxxxxxxx/
> v1: https://lore.kernel.org/lkml/20260427051823.280419-1-sumitg@xxxxxxxxxx/

Dear CPPC cpufreq driver reviewers, please let me know what you think.

This is not going to go in without any comments from anyone, as far as
I'm concerned.

Thanks!