Andriy Gapon wrote:
> on 13/09/2010 20:07 Andriy Gapon said the following:
>> I am also going to take a look how Linux and OpenSolaris name the C-states.
> 
> Well, Linux does what you suggested, it uses index of a C-state as its name.
> There is one difference from our current code - if a C-state is skipped for 
> some
> reason, then its index is not re-used, but the entry is marked as non-valid.
> So, if we skip "C2" for some reason, then "C3" will become "C2".  Not so on 
> Linux.
> Also, they print a type/class of a C state using C1, C2, C3 and "--" for
> higher/unknown types.
> 
> Additionally, it seems that we do not currently have any support for 
> Functional
> Fixed Hardware (FFH) way of providing C states.  In this case _CST returns GAS
> of a register used to enter a C state with address space ID set to
> ACPI_ADR_SPACE_FIXED_HARDWARE (0x7f/127).  Such addresses should be handled 
> in a
> special way:
> ftp://download.intel.com/technology/IAPC/acpi/downloads/30222305.pdf
> 
> Currently we simply (and silently) ignore such _CST entries.
> I think that this should be useful (if not necessary) with mwait.

I added some FFHW support for ACPI P-states. You can see that in the
cpufreq code or in the speedstep driver.

-- 
Nate

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