[PATCH] X86: Cleanup idle= internal variables by getting rid of idle_halt idle_nomwait

[Thomas Renninger <trenn@suse.de>]

On Wednesday 03 November 2010 07:33:54 Len Brown wrote:
> On Tue, 2 Nov 2010, Thomas Renninger wrote:
> > 
...
> > Compare with:
> > arch/x86/kernel/process.c
> > and
> > drivers/acpi/processor_idle.c
> 
> idle=halt and idle=nomwait will not
> set boot_option_idle_override,
> so checking that option in intel_idle
> is a NOP for those incantations.
Indeed, thanks for looking closer at this.

> idle_setup() is a confusing mess.
I can't find better words.

> That function and all these idle workaround flags
> need to be re-whacked.
Whatabout this (compile tested (on x86_64/ia64)).
Adding lkml as this affects x86 core code.

Thanks,

    Thomas

--------------
X86: Cleanup idle= internal variables by getting rid of idle_halt idle_nomwait

Having four variables for the same thing:
  idle_halt, idle_nomwait, force_mwait and boot_option_idle_overrides
is rather confusing and unnecessary complex.

if idle= boot param is passed, only set up one variable:
boot_option_idle_overrides

Introduces following functional changes/fixes:
  - intel_idle driver does not register if any idle=xy
    boot param is passed.
  - processor_idle.c will also not register a cpuidle driver
    and get active if idle=halt is passed.
    Before a cpuidle driver with one (C1, halt) state got registered
    Now the default_idle function will be used which finally uses
    the same idle call to enter sleep state (safe_halt()), but
    without registering a whole cpuidle driver.

That means idle= param will always avoid cpuidle drivers to register
with one exception (same behavior as before):
idle=nomwait
may still register acpi_idle cpuidle driver, but C1 will not use
mwait, but hlt. This can be a workaround for IO based deeper sleep
states where C1 mwait causes problems.

Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: lenb@kernel.org
CC: linux-acpi@vger.kernel.org
CC: stable@kernel.org
CC: linux-pm@lists.linux-foundation.org

diff --git a/arch/ia64/include/asm/processor.h b/arch/ia64/include/asm/processor.h
index 348e44d..03afe79 100644
--- a/arch/ia64/include/asm/processor.h
+++ b/arch/ia64/include/asm/processor.h
@@ -717,8 +717,9 @@ prefetchw (const void *x)
 #define spin_lock_prefetch(x)	prefetchw(x)
 
 extern unsigned long boot_option_idle_override;
-extern unsigned long idle_halt;
-extern unsigned long idle_nomwait;
+
+enum idle_boot_override {IDLE_NO_OVERRIDE=0, IDLE_HALT, IDLE_FORCE_MWAIT,
+			 IDLE_NOMWAIT, IDLE_POLL};
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 16f1c7b..6d33c5c 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -53,12 +53,8 @@
 
 void (*ia64_mark_idle)(int);
 
-unsigned long boot_option_idle_override = 0;
+unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
 EXPORT_SYMBOL(boot_option_idle_override);
-unsigned long idle_halt;
-EXPORT_SYMBOL(idle_halt);
-unsigned long idle_nomwait;
-EXPORT_SYMBOL(idle_nomwait);
 void (*pm_idle) (void);
 EXPORT_SYMBOL(pm_idle);
 void (*pm_power_off) (void);
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index cae9c3c..b79bd98 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -762,10 +762,11 @@ extern void select_idle_routine(const struct cpuinfo_x86 *c);
 extern void init_c1e_mask(void);
 
 extern unsigned long		boot_option_idle_override;
-extern unsigned long		idle_halt;
-extern unsigned long		idle_nomwait;
 extern bool			c1e_detected;
 
+enum idle_boot_override {IDLE_NO_OVERRIDE=0, IDLE_HALT, IDLE_NOMWAIT,
+			 IDLE_POLL, IDLE_FORCE_MWAIT};
+
 extern void enable_sep_cpu(void);
 extern int sysenter_setup(void);
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 57d1868..b647215 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -22,11 +22,6 @@
 #include <asm/i387.h>
 #include <asm/debugreg.h>
 
-unsigned long idle_halt;
-EXPORT_SYMBOL(idle_halt);
-unsigned long idle_nomwait;
-EXPORT_SYMBOL(idle_nomwait);
-
 struct kmem_cache *task_xstate_cachep;
 EXPORT_SYMBOL_GPL(task_xstate_cachep);
 
@@ -328,7 +323,7 @@ long sys_execve(const char __user *name,
 /*
  * Idle related variables and functions
  */
-unsigned long boot_option_idle_override = 0;
+unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
 EXPORT_SYMBOL(boot_option_idle_override);
 
 /*
@@ -499,7 +494,6 @@ static void poll_idle(void)
  *
  * idle=mwait overrides this decision and forces the usage of mwait.
  */
-static int __cpuinitdata force_mwait;
 
 #define MWAIT_INFO			0x05
 #define MWAIT_ECX_EXTENDED_INFO		0x01
@@ -509,7 +503,7 @@ static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
 {
 	u32 eax, ebx, ecx, edx;
 
-	if (force_mwait)
+	if (boot_option_idle_override == IDLE_FORCE_MWAIT)
 		return 1;
 
 	if (c->cpuid_level < MWAIT_INFO)
@@ -629,9 +623,10 @@ static int __init idle_setup(char *str)
 	if (!strcmp(str, "poll")) {
 		printk("using polling idle threads.\n");
 		pm_idle = poll_idle;
-	} else if (!strcmp(str, "mwait"))
-		force_mwait = 1;
-	else if (!strcmp(str, "halt")) {
+		boot_option_idle_override = IDLE_POLL;
+	} else if (!strcmp(str, "mwait")) {
+		boot_option_idle_override = IDLE_FORCE_MWAIT;
+	} 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
@@ -640,8 +635,7 @@ static int __init idle_setup(char *str)
 		 * the boot_option_idle_override.
 		 */
 		pm_idle = default_idle;
-		idle_halt = 1;
-		return 0;
+		boot_option_idle_override = IDLE_HALT;
 	} else if (!strcmp(str, "nomwait")) {
 		/*
 		 * If the boot option of "idle=nomwait" is added,
@@ -649,12 +643,10 @@ static int __init idle_setup(char *str)
 		 * states. In such case it won't touch the variable
 		 * of boot_option_idle_override.
 		 */
-		idle_nomwait = 1;
-		return 0;
+		boot_option_idle_override = IDLE_NOMWAIT;
 	} else
 		return -1;
 
-	boot_option_idle_override = 1;
 	return 0;
 }
 early_param("idle", idle_setup);
diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index bec561c..3c1a2fe 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -23,7 +23,7 @@ static int set_no_mwait(const struct dmi_system_id *id)
 {
 	printk(KERN_NOTICE PREFIX "%s detected - "
 		"disabling mwait for CPU C-states\n", id->ident);
-	idle_nomwait = 1;
+	boot_option_idle_override = IDLE_NOMWAIT;
 	return 0;
 }
 
@@ -283,7 +283,7 @@ acpi_processor_eval_pdc(acpi_handle handle, struct acpi_object_list *pdc_in)
 {
 	acpi_status status = AE_OK;
 
-	if (idle_nomwait) {
+	if (boot_option_idle_override == IDLE_NOMWAIT) {
 		/*
 		 * If mwait is disabled for CPU C-states, the C2C3_FFH access
 		 * mode will be disabled in the parameter of _PDC object.
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index dcb38f8..eefd4aa 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -79,6 +79,13 @@ module_param(bm_check_disable, uint, 0000);
 static unsigned int latency_factor __read_mostly = 2;
 module_param(latency_factor, uint, 0644);
 
+static int disabled_by_idle_boot_param(void)
+{
+	return boot_option_idle_override == IDLE_POLL ||
+		boot_option_idle_override == IDLE_FORCE_MWAIT ||
+		boot_option_idle_override == IDLE_HALT;
+}
+
 /*
  * IBM ThinkPad R40e crashes mysteriously when going into C2 or C3.
  * For now disable this. Probably a bug somewhere else.
@@ -455,7 +462,7 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr)
 				continue;
 			}
 			if (cx.type == ACPI_STATE_C1 &&
-					(idle_halt || idle_nomwait)) {
+			    (boot_option_idle_override == IDLE_NOMWAIT)) {
 				/*
 				 * In most cases the C1 space_id obtained from
 				 * _CST object is FIXED_HARDWARE access mode.
@@ -1058,7 +1065,7 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr)
 {
 	int ret = 0;
 
-	if (boot_option_idle_override)
+	if (disabled_by_idle_boot_param())
 		return 0;
 
 	if (!pr)
@@ -1089,19 +1096,10 @@ int __cpuinit acpi_processor_power_init(struct acpi_processor *pr,
 	acpi_status status = 0;
 	static int first_run;
 
-	if (boot_option_idle_override)
+	if (disabled_by_idle_boot_param())
 		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)
@@ -1142,7 +1140,7 @@ int __cpuinit acpi_processor_power_init(struct acpi_processor *pr,
 int acpi_processor_power_exit(struct acpi_processor *pr,
 			      struct acpi_device *device)
 {
-	if (boot_option_idle_override)
+	if (disabled_by_idle_boot_param())
 		return 0;
 
 	cpuidle_unregister_device(&pr->power.dev);
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 41665d2..8e625de 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -410,6 +410,10 @@ static int __init intel_idle_init(void)
 {
 	int retval;
 
+	/* Do not load intel_idle at all for now if idle= is passed */
+	if (boot_option_idle_override != IDLE_NO_OVERRIDE)
+		return -ENODEV;
+
 	retval = intel_idle_probe();
 	if (retval)
 		return retval;