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SubjectRE: [RFC PATCH] cpufreq: add support for HiSilicon SoC HIP09
Date
Hi,

> From: Thanu Rangarajan <Thanu.Rangarajan@arm.com>
> Sent: Wednesday, May 6, 2020 1:58 PM
>
> Hi,
> ACPI CPPC already supports the notion of boost. Not sure we need any
> enhancements there.
>
> Regards,
> Thanu
>
> On 06/05/2020, 18:19, "Sudeep Holla" <sudeep.holla@arm.com> wrote:
>
> + Thanu, Souvik who work with ASWG
>
> On Wed, May 06, 2020 at 05:36:51PM +0800, Hanjun Guo wrote:
> > Hi Sudeep,
> >
> > On 2020/4/30 17:55, Sudeep Holla wrote:
> > > On Thu, Apr 30, 2020 at 02:19:59PM +0800, Xiongfeng Wang wrote:
> > > > HiSilicon SoC has a separate System Control Processor(SCP)
> dedicated for
> > > > clock frequency adjustment and has been using the cpufreq driver
> > > > 'cppc-cpufreq'. New HiSilicon SoC HIP09 add support for CPU Boost,
> but
> > > > ACPI CPPC doesn't support this. In HiSilicon SoC HIP09, each core has
> > > > its own clock domain. It is better for the core itself to adjust its
> > > > frequency when we require fast response. In this patch, we add a
> > > > separate cpufreq driver for HiSilicon SoC HIP09.
> > > >
> > >
> > > I disagree with this approach unless you have tried to extend the CPPC
> > > in ACPI to accommodate this boost feature you need. Until you show
> those
> > > efforts and disagreement to do that from ASWG, I am NACKing this
> approach.
> >
> > Unfortunately we are not in ASWG at now, could you please give some
> > help about extending CPPC in ACPI to support boost feature?
> >
>
> You may have to provide more details than the commit log for sure as I
> haven't understood the boost feature and what is missing in ACPI CPPC.

I would agree with Thanu here regarding the ACPI spec part - everything is already there.

It seems to me that the .set_boost is today not handled in cppc_cpufreq.c. In fact if a platform provides a value for Highest Performance which is different than Nominal Performance, then the entire range of performance is always requested, which works well for platforms which do boost enable/disable selection at hardware/firmware level.

.boost hook could potentially be useful in cppc_cpufreq.c for platforms which would manage the boost selection in software. But it would be good to keep a common implementation which can choose between "software-triggered or auto-boost" selection for different platforms.

Regards,
Souvik

>
> --
> Regards,
> Sudeep
>
>

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