linux-kernel - Re: [PATCH v2] cpufreq: intel_pstate: Add Icelake servers support in no-HWP mode

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Date:   Tue, 7 Sep 2021 13:16:10 -0700
From:   Doug Smythies <dsmythies@...us.net>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Giovanni Gherdovich <ggherdovich@...e.cz>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Len Brown <lenb@...nel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dsmythies <dsmythies@...us.net>
Subject: Re: [PATCH v2] cpufreq: intel_pstate: Add Icelake servers support in
 no-HWP mode

Hi Srinivas, Thank you for your reply.

On Tue, Sep 7, 2021 at 9:01 AM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
> On Tue, 2021-09-07 at 08:45 -0700, Doug Smythies wrote:
>>
> > Recent ASUS BIOS updates have changed the default system
> > response for this old thread, rendering "intel_pstate=no_hwp"
> > useless.
> >
> > It also raises a question: If BIOS has forced HWP, then how do we
> > prevent the acpi-cpufreq driver from being used? Read on.
>
> Does BIOS has option to enable Intel speed shift with no legacy
> support?
> Then this option will not populate ACPI _PSS table.

The option is there no matter what.
I have tried every variation of legacy or no legacy that
I can find. Currently:
Current boot mode:   UEFI Firmware mode
SecureBoot:          disabled

>
> >
> > On Fri, May 14, 2021 at 3:12 PM Doug Smythies <dsmythies@...us.net>
> > wrote:
> > >
> > > On Fri, May 14, 2021 at 1:33 PM Giovanni Gherdovich <
> > > ggherdovich@...e.cz> wrote:
> > > > On Fri, 2021-05-14 at 08:31 -0700, Doug Smythies wrote:
> > ...
> > > >
...
> > Previous correspondence was with BIOS version 1003. There have been 3
> > BIOS
> > releases since then (at least that I know of), 2103, 2201, 2301, and
> > all of them
> > have changed the behaviour of the "Auto" setting for Intel Speed
> > Shift
> > Technology BIOS setting, forcing it on upon transfer of control to
> > the OS.
> >
> > Where with "intel_pstate=no_hwp" one used to get 0 for MSR_PM_ENABLE
> > (0x770) they now get 1.
>
> So they are forcing Out of band OOB mode.
> Does bit 8 or 18 in MSR 0x1aa is set?

No.

Here is the output from my msr reader/decoder program.
Kernel 5.14 (unpatched).
intel_pstate=disable
BIOS setting "Auto" for Intel Speed Shift,
Driver: acpi-cpufreq

doug@s19:~$ sudo c/msr-decoder
How many CPUs?: 12
8.) 0x198: IA32_PERF_STATUS     : CPU 0-11 :  45 :  45 :  45 :  45 :
45 :  45 :  45 :  45 :  45 :  45 :  45 :  45 :
B.) 0x770: IA32_PM_ENABLE: 1 : HWP enable
1.) 0x19C: IA32_THERM_STATUS: 88450000
2.) 0x1AA: MSR_MISC_PWR_MGMT: 401CC0 EIST enabled Coordination enabled
OOB Bit 8 reset OOB Bit 18 reset
3.) 0x1B1: IA32_PACKAGE_THERM_STATUS: 88410000
4.) 0x64F: MSR_CORE_PERF_LIMIT_REASONS: 0
A.) 0x1FC: MSR_POWER_CTL: 3C005D : C1E disable : EEO disable : RHO disable
5.) 0x771: IA32_HWP_CAPABILITIES (performance): 10B2930 : high 48 :
guaranteed 41 : efficient 11 : lowest 1
6.) 0x774: IA32_HWP_REQUEST:    CPU 0-11 :
    raw: 80003001 : 80003001 : 80003001 : 80003001 : 80003001 :
80003001 : 80003001 : 80003001 : 80003001 : 80003001 : 80003001 :
80003001 :
    min:        1 :        1 :        1 :        1 :        1 :
1 :        1 :        1 :        1 :        1 :        1 :        1 :
    max:       48 :       48 :       48 :       48 :       48 :
48 :       48 :       48 :       48 :       48 :       48 :       48 :
    des:        0 :        0 :        0 :        0 :        0 :
0 :        0 :        0 :        0 :        0 :        0 :        0 :
    epp:      128 :      128 :      128 :      128 :      128 :
128 :      128 :      128 :      128 :      128 :      128 :      128
:
    act:        0 :        0 :        0 :        0 :        0 :
0 :        0 :        0 :        0 :        0 :        0 :        0 :
7.) 0x777: IA32_HWP_STATUS: 0 : high 0 : guaranteed 0 : efficient 0 : lowest 0

...

... Doug