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ACPI : Create "idle=nomwait" bootparam

Browse source 
"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 <[email protected]>
Signed-off-by: Li Shaohua <[email protected]>
Signed-off-by: Len Brown <[email protected]>
Signed-off-by: Andi Kleen <[email protected]>
This commit is contained in:
Zhao Yakui 2008-06-24 18:01:09 +08:00 • committed by Andi Kleen
commit da5e09a1b3
7 changed files with 35 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

13
drivers/acpi/processor_core.c
View file

@ -265,7 +265,20 @@ static int acpi_processor_set_pdc(struct acpi_processor *pr)
if (!pdc_in)
return status;
if (idle_nomwait) {
/*
* If mwait is disabled for CPU C-states, the C2C3_FFH access
* mode will be disabled in the parameter of _PDC object.
* Of course C1_FFH access mode will also be disabled.
*/
union acpi_object *obj;
u32 *buffer = NULL;
obj = pdc_in->pointer;
buffer = (u32 *)(obj->buffer.pointer);
buffer[2] &= ~(ACPI_PDC_C_C2C3_FFH | ACPI_PDC_C_C1_FFH);
}
status = acpi_evaluate_object(pr->handle, "_PDC", pdc_in, NULL);
if (ACPI_FAILURE(status))

6
drivers/acpi/processor_idle.c
View file

@ -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");