From da5e09a1b3e5a9fc0b15a3feb64e921ccc55ba74 Mon Sep 17 00:00:00 2001 From: Zhao Yakui Date: Tue, 24 Jun 2008 18:01:09 +0800 Subject: 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 Signed-off-by: Li Shaohua Signed-off-by: Len Brown Signed-off-by: Andi Kleen --- drivers/acpi/processor_core.c | 13 +++++++++++++ drivers/acpi/processor_idle.c | 6 +++++- 2 files changed, 18 insertions(+), 1 deletion(-) (limited to 'drivers/acpi') diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c index 9a803f85ccf..4e1bb89fd6c 100644 --- a/drivers/acpi/processor_core.c +++ b/drivers/acpi/processor_core.c @@ -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)) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index c75c7ace8c1..d592dbb1d12 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"); -- cgit v1.2.3