From 991528d7348667924176f3e29addea0675298944 Mon Sep 17 00:00:00 2001 From: Venkatesh Pallipadi Date: Mon, 25 Sep 2006 16:28:13 -0700 Subject: ACPI: Processor native C-states using MWAIT 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 Signed-off-by: Andrew Morton Signed-off-by: Len Brown --- include/asm-i386/processor.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/asm-i386') diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h index 2277127696d..e0ddca94d50 100644 --- a/include/asm-i386/processor.h +++ b/include/asm-i386/processor.h @@ -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; -- cgit v1.2.3