Subject: ACPI: Add the boot option of "idle=halt" to use halt for CPU idle
From: Zhao Yakui <yakui.zhao@xxxxxxxxx>
If the boot option of "idle=halt" is added, OSPM will be forced to use
Halt for CPU idle. In such case CPU C-state won't be used again for CPU idle.
Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
---
Documentation/kernel-parameters.txt | 4 +++-
arch/x86/kernel/process.c | 3 +++
2 files changed, 6 insertions(+), 1 deletion(-)
Index: linux-2.6/arch/x86/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/process.c
+++ linux-2.6/arch/x86/kernel/process.c
@@ -6,6 +6,7 @@
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/pm.h>
+#include <asm/system.h>
struct kmem_cache *task_xstate_cachep;
@@ -169,6 +170,8 @@ static int __init idle_setup(char *str)
pm_idle = poll_idle;
} else if (!strcmp(str, "mwait"))
force_mwait = 1;
+ else if (!strcmp(str, "halt"))
+ pm_idle = default_idle;
else
return -1;
Index: linux-2.6/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.orig/Documentation/kernel-parameters.txt
+++ linux-2.6/Documentation/kernel-parameters.txt
@@ -785,7 +785,7 @@ and is between 256 and 4096 characters.
See Documentation/ide/ide.txt.
idle= [X86]
- Format: idle=poll or idle=mwait
+ Format: idle=poll or idle=mwait, idle = halt
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.
@@ -793,6 +793,8 @@ and is between 256 and 4096 characters.
to not use it because it doesn't save as much power as a normal idle
loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
as idle=poll.
+ idle = halt . Halt is forced to be used for CPU idle.
+ In such case C2/C3 won't be used again.
ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
Claim all unknown PCI IDE storage controllers.
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