ACPI: Create "idle=halt" bootparam
"idle=halt" limits the idle loop to using
the halt instruction. No MWAIT, no IO accesses,
no C-states deeper than C1.
If something is broken in the idle code,
"idle=halt" is a less severe workaround
than "idle=poll" which disables all power savings.
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 312fe77..65db7f4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -818,7 +818,7 @@
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.
@@ -826,6 +826,8 @@
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.
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index fabaf08..612b3c4 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -55,6 +55,8 @@
unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
+unsigned long idle_halt;
+EXPORT_SYMBOL(idle_halt);
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 7dceea9..7fc7294 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -7,6 +7,10 @@
#include <linux/module.h>
#include <linux/pm.h>
#include <linux/clockchips.h>
+#include <asm/system.h>
+
+unsigned long idle_halt;
+EXPORT_SYMBOL(idle_halt);
struct kmem_cache *task_xstate_cachep;
@@ -325,7 +329,18 @@
pm_idle = poll_idle;
} else if (!strcmp(str, "mwait"))
force_mwait = 1;
- else
+ else if (!strcmp(str, "halt")) {
+ /*
+ * When the boot option of idle=halt is added, halt is
+ * forced to be used for CPU idle. In such case CPU C2/C3
+ * won't be used again.
+ * To continue to load the CPU idle driver, don't touch
+ * the boot_option_idle_override.
+ */
+ pm_idle = default_idle;
+ idle_halt = 1;
+ return 0;
+ } else
return -1;
boot_option_idle_override = 1;
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 0fc310e..c75c7ac 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -41,6 +41,7 @@
#include <linux/pm_qos_params.h>
#include <linux/clockchips.h>
#include <linux/cpuidle.h>
+#include <linux/cpuidle.h>
/*
* Include the apic definitions for x86 to have the APIC timer related defines
@@ -57,6 +58,7 @@
#include <acpi/acpi_bus.h>
#include <acpi/processor.h>
+#include <asm/processor.h>
#define ACPI_PROCESSOR_COMPONENT 0x01000000
#define ACPI_PROCESSOR_CLASS "processor"
@@ -955,6 +957,17 @@
} else {
continue;
}
+ if (cx.type == ACPI_STATE_C1 && idle_halt) {
+ /*
+ * 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.
+ */
+ cx.entry_method = ACPI_CSTATE_HALT;
+ snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
+ }
} else {
snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI IOPORT 0x%x",
cx.address);
@@ -1780,6 +1793,15 @@
return 0;
if (!first_run) {
+ if (idle_halt) {
+ /*
+ * When the boot option of "idle=halt" is added, halt
+ * is used for CPU IDLE.
+ * In such case C2/C3 is meaningless. So the max_cstate
+ * is set to one.
+ */
+ max_cstate = 1;
+ }
dmi_check_system(processor_power_dmi_table);
max_cstate = acpi_processor_cstate_check(max_cstate);
if (max_cstate < ACPI_C_STATES_MAX)
diff --git a/include/asm-ia64/processor.h b/include/asm-ia64/processor.h
index 6aff126..f36e28a 100644
--- a/include/asm-ia64/processor.h
+++ b/include/asm-ia64/processor.h
@@ -763,6 +763,7 @@
#define spin_lock_prefetch(x) prefetchw(x)
extern unsigned long boot_option_idle_override;
+extern unsigned long idle_halt;
#endif /* !__ASSEMBLY__ */
diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h
index 7f73827..bc22162 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -727,6 +727,7 @@
extern void select_idle_routine(const struct cpuinfo_x86 *c);
extern unsigned long boot_option_idle_override;
+extern unsigned long idle_halt;
extern void enable_sep_cpu(void);
extern int sysenter_setup(void);