Messages in this thread | | | Subject | Re: [PATCH v2] cpufreq: intel_pstate: Add Icelake servers support in no-HWP mode | From | Srinivas Pandruvada <> | Date | Fri, 14 May 2021 19:58:44 -0700 |
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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 > > > >
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