Temperature feedback and guardian state transition of IMC and PLLs around this large jump are shown in Fig.1.
After this jump, PLL repeatedly failed with GRUB_RESONANCE.
So I re-tuned PLL temperature bias around 17:00 in order to recover PLL lock.
The reason why temperature feedback of IMC has so large jump hasn't investigated yet.
Is it similar behaviour reported in klog30314?
If so, it is well known issue to be solved for long-term stable operation.
> Is it similar behaviour reported in klog30314?
Yes to the fact that PLL lock by guardian is prevented by the jump of IMC temperature feedback.
No to the reason why IMC temperature feedback jumped.
In the previous case, IMC guardian executed "clear history" because the feedback output became lager than software threshold. As a result, IMC temperature feedback jumped to 0ct. In this time temperature feedback jumped from ~-5000ct to ~-6000ct. So it's not due to "clear history".
In any case, PLL guardian must become to find a proper temperature bias on its own.