From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
To: Giovanni Gherdovich <ggherdovich@suse.cz>,
Doug Smythies <dsmythies@telus.net>
Cc: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
Viresh Kumar <viresh.kumar@linaro.org>,
Len Brown <lenb@kernel.org>,
Linux PM list <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] cpufreq: intel_pstate: Add Icelake servers support in no-HWP mode
Date: Fri, 14 May 2021 19:58:44 -0700 [thread overview]
Message-ID: <214234be04103c37c09e4c1cdbcea4b4093e5aaf.camel@linux.intel.com> (raw)
In-Reply-To: <067ee60e47a0350d01f0c3f216c1032818044b36.camel@suse.cz>
On Fri, 2021-05-14 at 22:33 +0200, Giovanni Gherdovich wrote:
> On Fri, 2021-05-14 at 08:31 -0700, Doug Smythies wrote:
> > Hi All,
> >
> > Can I on-board to this patch or do you want me to submit another?
> > I want to add COMETLAKE (tested), as below:
> >
> > ... Doug
>
> Hello Doug!
>
> Wait, why you don't want to use HWP? It's such a fantastic
> technology!
>
> :) I'm just teasing you.
>
> More seriously:
>
> when COMETLAKE is not in that list, can you confirm that if you go
> into the
> BIOS config at boot, and disable HWP from there, then intel_pstate
> does *not* load?
>
> Does it say "intel_pstate: CPU model not supported" in the dmesg log?
>
> The control may be somewhere around "power mangement" in the BIOS
> config, and
> may be called "Enable/disable Intel Speed Shift".
>
> I'm asking because I've just checked on two Dell laptops, one Skylake
> and the
> other Kabylake, and the menu is there in the BIOS config to disable
> HWP,
> but if I disable it... nothing happens. "lscpu" shows all the hwp
> flags as usual:
>
> # lscpu | grep Flags | tr ' ' '\n' | grep hwp
> hwp
> hwp_notify
> hwp_act_window
> hwp_epp
>
> and turbostat gives me:
>
> # turbostat -Summary -i 1 : 2>&1 | grep MSR_PM_ENABLE
> cpu0: MSR_PM_ENABLE: 0x00000001 (HWP)
>
> Which is to say, on the Intel client machines I have, the firmware
> doesn't
> seem to be able to hide HWP from the OS. Buggy BIOS? Maybe, the fact
> of the
> matter is, I wouldn't need to add, say, KABYLAKE to that list, based
> on my
> experience.
When you disable in BIOS on these systems, it just hides HWP control
via ACPI CPC table. It doesn't disable HWP CPU feature.
Thanks,
Srinivas
>
> The other side of the issue is that, from my understanding, the
> preferred/supported way to disable HWP is to boot with
> intel_pstate=no_hwp,
> and that list is a sort of "known exceptions" that people really
> can't live
> without (it's mostly server CPUs, and mostly because of unfortunate
> firmware
> defaults). Otherwise you'd see the entire intel-family.h file in
> there.
>
>
> Cheers,
> Giovanni
>
> >
> > On Thu, May 13, 2021 at 6:21 AM Giovanni Gherdovich <
> > ggherdovich@suse.cz> wrote:
> > > Users may disable HWP in firmware, in which case intel_pstate
> > > wouldn't load
> > > unless the CPU model is explicitly supported.
> > >
> > > Add ICELAKE_X to the list of CPUs that can register intel_pstate
> > > while not
> > > advertising the HWP capability. Without this change, an ICELAKE_X
> > > in no-HWP
> > > mode could only use the acpi_cpufreq frequency scaling driver.
> > >
> > > See also commit d8de7a44e11f ("cpufreq: intel_pstate: Add Skylake
> > > servers
> > > support").
> > >
> > > Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
> > > ---
> > > This replaces
> > > https://lore.kernel.org/lkml/20210513075930.22657-1-ggherdovich@suse.cz
> > >
> > > drivers/cpufreq/intel_pstate.c | 1 +
> > > 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/cpufreq/intel_pstate.c
> > > b/drivers/cpufreq/intel_pstate.c
> > > index f0401064d7aa..28c9733e0dce 100644
> > > --- a/drivers/cpufreq/intel_pstate.c
> > > +++ b/drivers/cpufreq/intel_pstate.c
> > > @@ -2087,6 +2087,7 @@ static const struct x86_cpu_id
> > > intel_pstate_cpu_ids[] = {
> > > X86_MATCH(ATOM_GOLDMONT, core_funcs),
> > > X86_MATCH(ATOM_GOLDMONT_PLUS, core_funcs),
> > > X86_MATCH(SKYLAKE_X, core_funcs),
> > > + X86_MATCH(ICELAKE_X, core_funcs),
> > + X86_MATCH(COMETLAKE, core_funcs),
> > > {}
> > > };
> > > MODULE_DEVICE_TABLE(x86cpu, intel_pstate_cpu_ids);
> > > --
> > > 2.26.2
> > >
>
next prev parent reply other threads:[~2021-05-15 2:58 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 7:59 [PATCH] cpufreq: intel_pstate: Force intel_pstate to load when HWP disabled in firmware Giovanni Gherdovich
2021-05-13 9:24 ` Srinivas Pandruvada
2021-05-13 10:10 ` Giovanni Gherdovich
2021-05-13 11:03 ` Srinivas Pandruvada
2021-05-13 12:10 ` Giovanni Gherdovich
2021-05-13 13:20 ` [PATCH v2] cpufreq: intel_pstate: Add Icelake servers support in no-HWP mode Giovanni Gherdovich
2021-05-14 15:31 ` Doug Smythies
2021-05-14 20:33 ` Giovanni Gherdovich
2021-05-14 22:12 ` Doug Smythies
2021-09-07 15:45 ` Doug Smythies
2021-09-07 16:01 ` Srinivas Pandruvada
2021-09-07 20:16 ` Doug Smythies
2021-09-08 2:04 ` Srinivas Pandruvada
2021-09-08 3:43 ` Doug Smythies
2021-09-14 18:41 ` Doug Smythies
2021-09-15 9:38 ` Srinivas Pandruvada
2021-05-15 2:58 ` Srinivas Pandruvada [this message]
2021-05-17 15:26 ` Rafael J. Wysocki
2021-05-18 11:33 ` Giovanni Gherdovich
2021-05-19 5:37 ` Doug Smythies
2021-05-18 12:34 ` [PATCH v3 1/2] " Giovanni Gherdovich
2021-05-18 12:34 ` [PATCH v3 2/2] cpufreq: intel_pstate: Add Cometlake " Giovanni Gherdovich
2021-05-21 16:49 ` [PATCH v3 1/2] cpufreq: intel_pstate: Add Icelake servers " Rafael J. Wysocki
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