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ACPI : Create "idle=nomwait" bootparam

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"idle=nomwait" disables the use of the MWAIT
instruction from both C1 (C1_FFH) and deeper (C2C3_FFH)
C-states.

When MWAIT is unavailable, the BIOS and OS generally
negotiate to use the HALT instruction for C1,
and use IO accesses for deeper C-states.

This option is useful for power and performance
comparisons, and also to work around BIOS bugs
where broken MWAIT support is advertised.

http://bugzilla.kernel.org/show_bug.cgi?id=10807
http://bugzilla.kernel.org/show_bug.cgi?id=10914

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
This commit is contained in:
Zhao Yakui
2008-06-24 18:01:09 +08:00
committed by Andi Kleen
parent c1e3b377ad
commit da5e09a1b3
7 changed files with 35 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/acpi/processor_idle.c
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@ -957,13 +957,17 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr)
} else {
continue;
}
if (cx.type == ACPI_STATE_C1 && idle_halt) {
if (cx.type == ACPI_STATE_C1 &&
(idle_halt || idle_nomwait)) {
/*
* In most cases the C1 space_id obtained from
* _CST object is FIXED_HARDWARE access mode.
* But when the option of idle=halt is added,
* the entry_method type should be changed from
* CSTATE_FFH to CSTATE_HALT.
* When the option of idle=nomwait is added,
* the C1 entry_method type should be
* CSTATE_HALT.
*/
cx.entry_method = ACPI_CSTATE_HALT;
snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");