[Xen-devel] why are deep cstates disabled?

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

I'm trying to get deep C states to work on my Dell D630
running a Core 2 Duo (Merom) T7300.

The output of "xm debug-key c" implies that the processor
supports C3, but max_cstate is set to 1.

Digging through the code and adding some debug printk's,
I see that max_cstate is being changed from 7 to 1 by
cpuidle_disable_deep_cstate(), which was added at
c/s 19549.

Am I reading correctly from:
http://lists.xensource.com/archives/html/xen-devel/2009-04/msg00490.html
that if a platform has no HPET (or it is disabled), no
deep C power states are permitted?

My D630 has no HPET... or at least there is no indication
in the BIOS menu that there is an HPET.

I tried setting "hpetbroadcast" and dom0 boot fails.

Is there any way to get C3 working on my box or am
I out of luck?

Thanks,
Dan


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