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ACPI: Processor native C-states using MWAIT

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Intel processors starting with the Core Duo support
support processor native C-state using the MWAIT instruction.
Refer: Intel Architecture Software Developer's Manual
http://www.intel.com/design/Pentium4/manuals/253668.htm

Platform firmware exports the support for Native C-state to OS using
ACPI _PDC and _CST methods.
Refer: Intel Processor Vendor-Specific ACPI: Interface Specification
http://www.intel.com/technology/iapc/acpi/downloads/302223.htm

With Processor Native C-state, we use 'MWAIT' instruction on the processor
to enter different C-states (C1, C2, C3).  We won't use the special IO
ports to enter C-state and no SMM mode etc required to enter C-state.
Overall this will mean better C-state support.

One major advantage of using MWAIT for all C-states is, with this and
"treat interrupt as break event" feature of MWAIT, we can now get accurate
timing for the time spent in C1, C2, ..  states.

Signed-off-by: Venkatesh Pallipadi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Len Brown <[email protected]>
This commit is contained in:
Venkatesh Pallipadi 2006-09-25 16:28:13 -07:00 • committed by Len Brown
commit 991528d734
8 changed files with 242 additions and 56 deletions
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2
include/asm-i386/processor.h
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@ -306,6 +306,8 @@ static inline void __mwait(unsigned long eax, unsigned long ecx)
: :"a" (eax), "c" (ecx));
}
extern void mwait_idle_with_hints(unsigned long eax, unsigned long ecx);
/* from system description table in BIOS. Mostly for MCA use, but
others may find it useful. */
extern unsigned int machine_id;