Re: [BUG] Lunar Lake: 400 MHz after s2idle; PL1 Tau affects reproduction and recovery

[Mario Limonciello <mario.limonciello@amd.com>]

On 10/5/26 02:16, Scrimas wrote:
> On Mon, 7 Sep 2026 12:00:37 -0400, Sandor Nagy wrote:
>> My ThinkPad X1 Carbon Gen 13 intermittently resumes from long s2idle
>> suspends with all eight CPUs stuck around 400 MHz.
> 
> Same symptom here on a different OEM and a different SKU, so this does
> not look Lenovo-specific:
> 
>    Samsung Galaxy Book5 Pro 360 (NP960QHA)
>    Intel Core Ultra 7 256V (Lunar Lake), BIOS P17ALY.390.260616.03
>    Kernel 7.2.9 (CachyOS), intel_pstate active, HWP, s2idle only
>    platform_profile=performance, EPP=performance, on battery
>    PL1 34 W (MSR and MMIO), Tau 27983872 us (same value as your X1C13)
>    thermald not running
> 
> I log 60 s of turbostat and the xe GT throttle reasons after every
> resume. Over 2026-10-02..05: 13 resumes after sleeps of 1.5 h or less
> had no 400 MHz samples at all. The one resume after an 8.9 h s2idle
> had all cores at 400 MHz for the first ~9 s of the log (the log
> starts ~1 s after "PM: suspend exit"):
> 
>    Busy%  Bzy_MHz  PkgTmp  GFXMHz  PkgWatt
>    16.37   400     25      400     2.38
>    73.94   400     26      400     3.23
>    49.75   400     27      400     2.87
>    ...    (6 more samples at 400 MHz, 2.8-3.2 W)
>    40.94   480     28      400     3.04
>    37.83  3557     39      400    10.57
> 
> During exactly those seconds, gt0/freq0/throttle/reasons reported
> "pl1", then "none". So the package was being power-limited while
> drawing ~3 W against a 34 W PL1, at 25-28 C. That matches your
> energy-averaging hypothesis.
> 
> Ruled out on this machine:
> - ACPI _PPC: booted with processor.ignore_ppc=1, and scaling_max_freq
>    stayed at 4.7 GHz during the episode.
> - Thermal: package_throttle_count did not change during the window.
> 
> I have not captured MSR 0x19C bits 10-11 yet.
> 
> Thanks,
> Scrimas

If this is anything like the similar issue that was reported on some AMD 
systems; try unplugging and plugging back in the power adapter while in 
the bad state.

If it's already unplugged, plug it in and then unplug it again.

Does that help?