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authorZhao Yakui <yakui.zhao@intel.com>2008-06-24 18:01:09 +0800
committerAndi Kleen <andi@basil.nowhere.org>2008-07-16 23:27:05 +0200
commitda5e09a1b3e5a9fc0b15a3feb64e921ccc55ba74 (patch)
tree382a75c1180e458df826ef4efbc191f3f71275c1 /drivers/acpi/processor_idle.c
parentc1e3b377ad48febba6f91b8ae42c44ee4d4ab45e (diff)
ACPI : Create "idle=nomwait" bootparam
"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>
Diffstat (limited to 'drivers/acpi/processor_idle.c')
-rw-r--r--drivers/acpi/processor_idle.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index c75c7ace8c13..d592dbb1d12a 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -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");