Re: [PATCH v2 0/2] ACPI: CPPC: Add CPPC v4 support (ACPI 6.6)

[Rafael J. Wysocki]

On Thu, Apr 30, 2026 at 4:25 PM Sumit Gupta <sumitg@xxxxxxxxxx> wrote:
>
> Add initial kernel support for CPPC v4 (ACPI 6.6, Section 8.4.6),
> which extends the _CPC package from 23 to 25 entries with two
> optional fields:
>
>   - OSPM Nominal Performance (8.4.6.1.2.6): register used by OSPM
>     to tell the platform what it considers nominal. The platform
>     classifies performance above this as boost and below as
>     throttle for power/thermal decisions.
>
>   - Resource Priority (8.4.6.1.2.7): Package of Resource Priority
>     Register Descriptor sub-packages. Full parsing is not yet
>     implemented; such entries are marked as unsupported.
>
> Patch 1: Add v4 _CPC parsing - validate the 25-entry layout,
> handle the Resource Priority package, and mark the two new
> registers optional.
>
> Patch 2: Add acpi_cppc/ospm_nominal_perf as a read-write sysfs
> attribute, and initialize it to the platform nominal value
> during cppc_cpufreq policy init.
>
> ---
> v1[1] -> v2:
> - Patch 1: added Reviewed-by from Mario Limonciello.
> - Patch 2:
>   - Make ospm_nominal_perf sysfs read-write; cache last write in
>     cpc_desc and skip redundant register writes.
>   - Validate input in cppc_set_ospm_nominal_perf.
>
> Sumit Gupta (2):
>   ACPI: CPPC: Add support for CPPC v4
>   ACPI: CPPC: Add ospm_nominal_perf support
>
>  drivers/acpi/cppc_acpi.c       | 93 +++++++++++++++++++++++++++++++---
>  drivers/cpufreq/cppc_cpufreq.c | 10 ++++
>  include/acpi/cppc_acpi.h       | 14 ++++-
>  3 files changed, 109 insertions(+), 8 deletions(-)
>
> [1] https://lore.kernel.org/lkml/20260427051823.280419-1-sumitg@xxxxxxxxxx/
>
> --

Can you please see the sashiko.dev feedback on this set:

https://sashiko.dev/#/patchset/20260430142430.755437-1-sumitg%40nvidia.com

and let me know what you think?  Especially regarding the second patch?