[Bug 105949] System stall on Supermicro SKL boards on drm-tip

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105949

--- Comment #7 from Imre Deak <imre.deak at intel.com> ---
(In reply to Dmitry Ermilov from comment #6)
> > Or is there another scenario which you refer to as "can't be booted"?
> Yes, the third scenario is SM boards can't boot at all without
> "intel_pstate=disable i915.enable_rc6=0 intel_idle.max_cstate=1".
> We plan to check which exact option among these helps to boot. 
> Actually this (the 3rd) scenario is the one we wanted to bring to you.
> Presence of the warning is just an observation, I'm not sure if it's
> relevant.

If you're using the system without a display then I'm guessing the presence of
this error shouldn't cause a boot failure.

> > In the case where booting without the error messages, is there some other issue you see (system stall reported on bug 105949)?
> Yes, it's bug 105955. Generally at first we came across bug 105955. And
> after some experiments we discovered the problem described in the current
> bug.

Ok, so the lag happens even without the CDCLK PLL enabling issues reported
here.

> > Did you try to bisect the problem causing the above error messages (noting that you need several boots for each bisect step)?
> Not yet. To get the ball rolling we can try to revert
> https://patchwork.freedesktop.org/patch/65235/. 

That one re-enabled display C (DC) states. Another way to test if DC states
cause the problem is to boot with i915.enable_dc=0 kernel parameter.

> > Specifically there's been a recent related WA, could you try if the problem persists reverting that on top of drm-tip?
> Sure. Thank you.
> 
> Regards,
> Dmitry

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