SKL BOOT FAILURE unless idle=nomwait (was Re: PROBLEM: Cpufreq constantly keeps frequency at maximum on 4.5-rc4)

Since this is about cpuidle, I'll also mention that this hardware
requires idle=nomwait on the command line, otherwise the kernel will not
boot.

Arto,

A boot failure is even more disruptive than bad P-state and C-state choices!
Please tell us more about it.

What c-states are used when you use "idle=nomwait"?
you can see them this way:

grep . /sys/devices/system/cpu/cpu0/cpuidle/*/*

Please boot with intel_idle.max_cstate=0

If that also boots, please again show the available c-states via the grep above.

Does it happen if you use default cmdline,
but edit intel_idle.c to comment out c8 and c9 support?

Please run
# turbostat --debug | tee ts.out 2>&1
and send ts.out to show the deepest idle state that this system can
actually enter.

thanks,
Len Brown, Intel Open Source Technology Center