Re: [PATCH v4 0/2] cpufreq: CPPC: add autonomous mode boot parameter support

[Sumit Gupta]

On 22/06/26 14:58, Sumit Gupta wrote:
> On 19/06/26 14:59, Pierre Gondois wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On 6/18/26 07:28, Viresh Kumar wrote:
> > > On 16-06-26, 18:22, Sumit Gupta wrote:
> > > > The dependency it was waiting on, the "cpufreq: Set policy->min and
> > > > max as real QoS constraints" series, is now in linux-pm (linux-next).
> > > > I rebased on top and verified autonomous mode works as expected, and
> > > > it applies cleanly on the current linux-next.
> > > >
> > > > The [1] reference in patch 2/2 points to v2 of that series; the merged
> > > > version is v3 [2].
> > > >
> > > > If there are no further comments, please consider acking and queuing
> > > > this for the next cycle.
> > > I was waiting for CPPC reviewers to provide some feedback.i
> > >
> > > Jie / Lifeng / Pierre ?
> > I think the patchset has the same issue described at:
> >
> > https://lore.kernel.org/all/86780f97-29ee-4a72-b311-38c89434b707@xxxxxxx/ 
> >
> >
> > I don't know if this is important to other persons,
> > but IMO it would be preferable to have a solution to this issue
> > before adding more functionalities relying on registers that are left
> > in an unknown state.
> >
> > If there are any other opinion ?
>
> The concern is valid, but this isn't a new gap. The registers the boot
> parameter programs are already writable via existing sysfs:
>  - auto_sel via auto_select
>  - EPP via energy_performance_preference_val
> So userspace can already leave these in a non-default state across
> unload / CPU hotplug in mainline. The boot parameter just sets the
> same registers at boot via the same paths.
>
> I am already working on the save/restore change we discussed on
> the ospm_nominal_perf thread, as a dedicated follow-up grouping
> all OSPM-set registers (ospm_nominal_perf, auto_sel, EPP) together.
> I think doing it once uniformly is cleaner.
>
> Both features are already under review, so my preference is to take
> them first and add the save/restore on top, rather than merging it
> first and respinning both features under it. Either order works for me
> if you and the maintainers prefer infra-first.
>
> Thanks,
> Sumit

I have sent v5 of the autonomous mode series [1] with a small fix.

Also posted patch [3] to preserve OSPM set regs across hotplug/unload.
It applies on top of [1] & [2] (both not yet merged).

[1]
  [PATCH v5 0/2] cpufreq: CPPC: add autonomous mode boot parameter support
https://lore.kernel.org/lkml/20260623080652.3353386-1-sumitg@xxxxxxxxxx/

[2]
  [PATCH v5] ACPI: CPPC: Add ospm_nominal_perf support
https://lore.kernel.org/lkml/20260615185934.2383514-1-sumitg@xxxxxxxxxx/

[3]
  [PATCH] cpufreq: CPPC: Preserve OSPM-set registers across hotplug and 
unload
https://lore.kernel.org/lkml/20260623095403.3407436-1-sumitg@xxxxxxxxxx/

Thanks,
Sumit