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AW: RE: RE: RE: [Xen-devel] No C-States any longer...

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: AW: RE: RE: RE: [Xen-devel] No C-States any longer...
From: Carsten Schiers <carsten@xxxxxxxxxx>
Date: Wed, 22 Jun 2011 13:36:18 +0200
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>> There is a comment in acpi_processor_get_power_info_default it is
>> said that all processors need to support C1 at least. So (hypothesis),
>> if my BIOS is not implemented as specified (neither _CST nor PBLK),
>>> shouldn't acpi_processor_get_power_info_default also bee called on my
>> machine? Is the code exiting too early?
>You can argue that point. It exits at current point because typical BIOS 
>provide either CST or valid FADT/PBLK info. Of course even when ACPI
>table is broken we can still make a valid C1 entry. But also note that even
>then such ACPI Cstate information is not gathered, the kernel always
>invokes hlt when system is idle which achieves the effect. :-)

After having had some discussion with Gigabyte, I am now sure that the BIOS
intentionally doesn't implement C-States at all. Gigabyte says, they iomplemeted
Cool'n'Quiet "instead". 

In don't share this point, as I think Spec does require either _CST or PBLK.
Nevertheless, I think to remember that

  - xenpm did only mention C0 and C1 in the past
  - but xenpm did so and does not any longer

Eventually, even if it's only cosmetic, something needs to be changed in order
to reflect that case by setting up C1 in such a case. I am sorry, but I was not
able to do it.

I simply bought a new board...

Thanks for everybodies help. If someone ever changes the code, I have some days
left to check it.


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