CPU C-state storange on Panasonic TOUGH BOOK CF-R9

[Andriy Gapon]

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.

-- 
Andriy Gapon