[Bug 98564] [drm:skl_set_power_well] *ERROR* power well 2 disable timeout

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=98564

--- Comment #4 from Imre Deak <imre.deak at intel.com> ---
(In reply to Jason A. Donenfeld from comment #3)
> (In reply to Imre Deak from comment #2)
> > We seem to clear all request bits so not sure what keeps PW#2 up. Is there
> > any KVM related option in your BIOS setup, could you try with disabling it
> > if so?
> 
> Disabling VT-x and VT-d in the BIOS have no effect.

I meant something AMT/KVM specific. If there is no such option in your BIOS or
some other bootup AMT setup, I'm not sure what keeps the KVM request active.
Normally this is used for remote control. If you don't need that it will only
result in increased power consumption (since PW#2 will be forced on).

> However, this error is not observed when restarting the system. Rather, it
> is only observed when cold booting.

Strange, no idea why the request would be cleared by a warm-reset. In any case
not much we can do about that, the request bit is only accessible for the Intel
ME and can be set/cleared arbitrarily at the back of the driver.

> > Also could you give a try to the following to increase the timeout and get
> > some debug info?:
> 
> Sure. The added message evaluates to:
> 
> [    0.735000] [drm:skl_set_power_well] *ERROR* power well 2 disable timeout
> (50000005 7000000f c0000000 50000005 050f0000 0000050f)

Thanks. So the KVM request bit is set and we can't clear it. In any case this
shouldn't cause other issues besides the increased power consumption, so I'll
convert the WARN to be a note.

Could you still read the following regs after a cold and a subsequent warm
reboot? (need intel-gpu-tools):

# intel_reg read 0x42314 0x45408

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