Re: [BUG] intel_pstate: CPU frequencies miscalculated/incorrectly detected on Arrow Lake hardware

[srinivas pandruvada <srinivas.pandruvada@linux.intel.com>]

On Fri, 2025-12-05 at 20:28 +0100, Rafael J. Wysocki wrote:
> On Fri, Dec 5, 2025 at 8:11 PM srinivas pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
> > 
> > Hi Aaron,
> > 
> > On Wed, 2025-12-03 at 11:38 -0600, Aaron Rainbolt wrote:
> > > On Wed, 26 Nov 2025 17:00:31 -0600
> > > Aaron Rainbolt <arainbolt@kfocus.org> wrote:
> > > 
> > > 
> > > 
> > ...
> > 
> > 
> > 
> > There are too many platforms here, don't have time to get to all.
> > So
> > let's focus on one first.
> > 
> > ## Clevo | X580WNT-G  | Ultra 9 275HX | 6.18.0-061800rc7-generic
> > 
> > Summary:
> > There is no scaling factor related issue as reported before on
> > ASROCK
> > platform before. The achieved maximum frequencies are correct.
> > 
> > The base_freq display is wrong (see below because of BIOS config).
> > The cpuinfo_max_freq wrong display is not related to scaling factor
> > but
> > something else
> > 
> > 
> > To check, I need dump of:
> > m=$(getconf _NPROCESSORS_ONLN); for ((i=0; i<m; i++)); do echo
> > CPU$i;
> > sudo rdmsr -p $i 0x771;  sudo rdmsr -p $i 0x774; done
> > 
> > But I expect them to match the acpi_cppc/highest_perf, which is
> > showing
> > 3.9GHz.
> > 
> > What command you to report " M-Test  . Id"?
> > 
> > I think some busy 100% workload running on a single CPU.
> > 
> > 
> > 
> > Analsis:
> > 
> > Intel® Core™ Ultra 9 Processor 275HX
> > 8+16 no HT
> > Performance-core Base Frequency : 2.7 GHz
> > Efficient-core Base Frequency : 2.1 GHz
> > 
> > 
> > P-cores: 0-7
> > Nominal freq: 2700
> > Nominal perf: 43
> > Scaling : ~1.6 (correct)
> > 
> > E-cores:
> > 8-
> > Nominal freq: 2100
> > Nominal perf: 29
> > Scaling : ~1.38 (close to 1.4 so there will be some rounding issue)
> > 
> > So,  this is not related to scaling factor as before like on ASROCK
> > 
> > 
> > The P-cores under report `base_frequency` and `cpuinfo_max_freq`.
> > 
> > - FAIL: With Turbo ON or off, the claimed `base_freqency` (B-Claim)
> > of
> > 2000000 does
> >   NOT match the Intel spec (B-Spec) of 2700000.
> > 
> > From CPPC:
> > 
> > /sys/devices/system/cpu/cpu0/acpi_cppc/guaranteed_perf:32
> > The base freq reported by cpufreq: 3200/1.6 = 2000
> > 
> > 
> > 
> > 
> > - FAIL: With Turbo off, the claimed `cpuinfo_max_freq` (M-Claim) of
> > 2000000 does
> >   NOT match the Intel spec (M-Spec) of 2700000.
> > 
> > We don’t depend on ACPI CPPC to achieve the measured value. When
> > you
> > are busy you are getting 2700, so the behavior is correct as the
> > per
> > the CPU spec.
> > 
> > 
> > 
> > - FAIL: With Turbo ON, the claimed `cpuinfo_max_freq` (M-Claim) of
> > 3900000 does
> >   NOT match the Intel spec (M-Spec) of 5400000.
> > 
> > ACPI CPPC also tells 3.9 GHz as max. But we don’t depend on it.
> 
> But we depend on HWP_CAP.highest_perf == CPPC.highest_perf (because
> the CPPC value comes from HWP).

That's why asked for dump of MSRs above. This should match CPPC value.
But seems setting HWP_REQ.max_perf=61 or 62 on P-core still results in
5.4 Ghz.

Thanks,
Srinivas