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

[Pierre Gondois <pierre.gondois@arm.com>]

Hello Sumit,

I have some small comments on the 2 patchsets, but not much
I think. I had some issue to apply this patchset on top of:

[PATCH v5 0/4] cpufreq: CPPC: Preserve OSPM-set registers across hotplug 
and unload

Also, I think it would be nice to rebase it on top of Christan's serie:
https://lore.kernel.org/all/20260916162805.1039247-1-christian.loehle@arm.com/

Regards,

Pierre


On 8/7/26 23:48, Sumit Gupta 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@nvidia.com/
>
> 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@nvidia.com/
> v5:https://lore.kernel.org/lkml/20260615185934.2383514-1-sumitg@nvidia.com/
> v4:https://lore.kernel.org/lkml/20260527194626.185286-1-sumitg@nvidia.com/
> v3:https://lore.kernel.org/lkml/20260514194822.1841748-1-sumitg@nvidia.com/
> v2:https://lore.kernel.org/lkml/20260430142430.755437-1-sumitg@nvidia.com/
> v1:https://lore.kernel.org/lkml/20260427051823.280419-1-sumitg@nvidia.com/
>