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/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)