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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
parentc1e3b377ad48febba6f91b8ae42c44ee4d4ab45e (diff)
downloadlinux-da5e09a1b3e5a9fc0b15a3feb64e921ccc55ba74.tar.bz2
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>
-rw-r--r--Documentation/kernel-parameters.txt3
-rw-r--r--arch/ia64/kernel/process.c2
-rw-r--r--arch/x86/kernel/process.c11
-rw-r--r--drivers/acpi/processor_core.c13
-rw-r--r--drivers/acpi/processor_idle.c6
-rw-r--r--include/asm-ia64/processor.h1
-rw-r--r--include/asm-x86/processor.h1
7 files changed, 35 insertions, 2 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 65db7f4711aa..5e497d16fb51 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -818,7 +818,7 @@ and is between 256 and 4096 characters. It is defined in the file
See Documentation/ide/ide.txt.
idle= [X86]
- Format: idle=poll or idle=mwait, idle=halt
+ Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
Poll forces a polling idle loop that can slightly improves the performance
of waking up a idle CPU, but will use a lot of power and make the system
run hot. Not recommended.
@@ -828,6 +828,7 @@ and is between 256 and 4096 characters. It is defined in the file
as idle=poll.
idle=halt. Halt is forced to be used for CPU idle.
In such case C2/C3 won't be used again.
+ idle=nomwait. Disable mwait for CPU C-states
ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
Claim all unknown PCI IDE storage controllers.
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 612b3c4a0603..3ab8373103ec 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -57,6 +57,8 @@ unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
unsigned long idle_halt;
EXPORT_SYMBOL(idle_halt);
+unsigned long idle_nomwait;
+EXPORT_SYMBOL(idle_nomwait);
void
ia64_do_show_stack (struct unw_frame_info *info, void *arg)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 7fc729498760..4d629c62f4f8 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -11,6 +11,8 @@
unsigned long idle_halt;
EXPORT_SYMBOL(idle_halt);
+unsigned long idle_nomwait;
+EXPORT_SYMBOL(idle_nomwait);
struct kmem_cache *task_xstate_cachep;
@@ -340,6 +342,15 @@ static int __init idle_setup(char *str)
pm_idle = default_idle;
idle_halt = 1;
return 0;
+ } else if (!strcmp(str, "nomwait")) {
+ /*
+ * If the boot option of "idle=nomwait" is added,
+ * it means that mwait will be disabled for CPU C2/C3
+ * states. In such case it won't touch the variable
+ * of boot_option_idle_override.
+ */
+ idle_nomwait = 1;
+ return 0;
} else
return -1;
diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index 9a803f85ccfe..4e1bb89fd6c3 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 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");
diff --git a/include/asm-ia64/processor.h b/include/asm-ia64/processor.h
index f36e28a5f61e..f88fa054d01d 100644
--- a/include/asm-ia64/processor.h
+++ b/include/asm-ia64/processor.h
@@ -764,6 +764,7 @@ prefetchw (const void *x)
extern unsigned long boot_option_idle_override;
extern unsigned long idle_halt;
+extern unsigned long idle_nomwait;
#endif /* !__ASSEMBLY__ */
diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h
index bc221623248e..55402d2ab938 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -728,6 +728,7 @@ extern void select_idle_routine(const struct cpuinfo_x86 *c);
extern unsigned long boot_option_idle_override;
extern unsigned long idle_halt;
+extern unsigned long idle_nomwait;
extern void enable_sep_cpu(void);
extern int sysenter_setup(void);