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 312fe77764a48cba9fb04e000fc2dffeba7fa978..65db7f4711aa431c5310c68e5b0e172e2cce7b0f 100644 (file)
--- 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
+                       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 @@ and is between 256 and 4096 characters. It is defined in the file
                        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 fabaf08d9a695bbb088951da7e96af4a9b640443..612b3c4a0603405cce665d94b0d32f0051486b85 100644 (file)
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -55,6 +55,8 @@ void (*ia64_mark_idle)(int);
 
 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 7dceea947232f5739b7844c10ba9c2b22f336e95..7fc729498760262770863695b5c7bde802acdd0e 100644 (file)
--- 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 @@ static int __init idle_setup(char *str)
                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 0fc310e7dfd6eb4cc7b1cdcec87a6da778ce338f..c75c7ace8c1322c767a71e6e096ae3e4302ac694 100644 (file)
--- 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)

diff --git a/include/asm-ia64/processor.h b/include/asm-ia64/processor.h
index 6aff126fc07ea31802ec249613e9237c16472875..f36e28a5f61ea6630fd7b83338b3ab5cb474b4c3 100644 (file)
--- a/include/asm-ia64/processor.h
+++ b/include/asm-ia64/processor.h
@@ -763,6 +763,7 @@ prefetchw (const void *x)
 #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 7f738270459276a305758ac8a3edce974b1985ba..bc221623248e5e3771d301b4e299d540348b19f0 100644 (file)
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -727,6 +727,7 @@ extern int                  force_mwait;
 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);