RE: [PATCH] cpufreq: intel_pstate: Implement passive mode with HWP enabled

Doug Smythies
2020-08-02T15:17:48Z

Hi Rafael,

On 2020.07.19 04:43 Rafael J. Wysocki wrote:
> On Fri, Jul 17, 2020 at 3:37 PM Doug Smythies <dsmythies@telus.net> wrote:
> > On 2020.07.16 05:08 Rafael J. Wysocki wrote:
> > > On Wed, Jul 15, 2020 at 10:39 PM Doug Smythies <dsmythies@telus.net> wrote:
> > >> On 2020.07.14 11:16 Rafael J. Wysocki wrote:
> > >> >
> > >> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > >> ...
> > >> > Since the passive mode hasn't worked with HWP at all, and it is not going to
> > >> > the default for HWP systems anyway, I don't see any drawbacks related to making
> > >> > this change, so I would consider this as 5.9 material unless there are any
> > >> > serious objections.
> > >>
> > >> Good point.
> >
> > Actually, for those users that default to passive mode upon boot,
> > this would mean they would find themselves using this.
> > Also, it isn't obvious, from the typical "what driver and what governor"
> > inquiry.
>
> So the change in behavior is that after this patch
> intel_pstate=passive doesn't imply no_hwp any more.
>
> That's a very minor difference though and I'm not aware of any adverse
> effects it can cause on HWP systems anyway.

My point was, that it will now default to something where
testing has not been completed.

> The "what governor" is straightforward in the passive mode: that's
> whatever cpufreq governor has been selected.

I think you might have missed my point.
From the normal methods of inquiry one does not know
if HWP is being used or not. Why? Because with
or without HWP one gets the same answers under:

/sys/devices/system/cpu/cpu*/cpufreq/scaling_driver
/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

... Doug