fenrus75
Intel Tiger Lake (TGL) 1165G7: PowerTOP Frequency stats: Some Cores Stuck at 400MHz
When using powertop 2.15 with an Intel 1165G7 (tgl / Tiger Lake) laptop (Lenovo IdeaPad Slim 9i 14ITL5), some CPU cores (0 to 3) become "stuck" at 400MHz (i.e., they cannot change frequency after lowering to 400MHz). This was noticed using Kernels 6.10.x and 6.11-rc5 on Arch and Fedora 40 or 41 beta while profiling power usage with s-tui and tuning power settings (platform profile and EPP values with active intel_pstate driver and powersave governor) via TLP. (Also, the thermald service was present and active.)
Generally, only two of the four cores will get stuck when PowerTOP is open and on the "Frequency stats" section. All other cores scale in frequency as they should. If PowerTOP is NOT used the problem never manifests. The frequency lock issue only occurs when the "Frequency stats" section is shown in PowerTOP and a core clocks below about 1100MHz. Additionally, only select cores seem get stuck at frequencies below 1000MHz (mostly 400MHz but sometimes 800MHz). HT logical "cores" DO NOT exhibit this issue; only real, physical cores (0 to 3) seem to be affected. Closing PowerTOP does NOT fix this issue. Only a system reboot will fix the locked-to-400MHz clock issue. Interestingly, MS Windows systems seemed to have had this problem too (some cores or all cores stuck at 400MHz), so there may still be firmware issues that PowerTOP triggers with Tiger Lake platforms (and possibly others like Alderlake which has had this issue on Windows too).
Comparing with an Intel 11900T 11th Gen. (rkl / Rocket Lake) system (35W TDP desktop CPU), I observed no issues with core frequency while using PowerTOP with the exact same software stack and conditions as the 1165G7 laptop, so this issue seems limited to Tiger Lake 11th Gen CPUs.
