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authorZhao Yakui <yakui.zhao@intel.com>2008-06-24 17:58:53 +0800
committerAndi Kleen <andi@basil.nowhere.org>2008-07-16 23:27:05 +0200
commitc1e3b377ad48febba6f91b8ae42c44ee4d4ab45e (patch)
tree7893e4226f52c4001150066f544415c1b17741f5 /drivers/acpi
parent5b53496a5ad79e91052f72761a7c5516b069bc99 (diff)
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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>
Diffstat (limited to 'drivers/acpi')
-rw-r--r--drivers/acpi/processor_idle.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 0fc310e7dfd6..c75c7ace8c13 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 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr)
} 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 @@ int __cpuinit acpi_processor_power_init(struct acpi_processor *pr,
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)
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