Merge branch 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6

* 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6:
  intel_idle: native hardware cpuidle driver for latest Intel processors
  ACPI: acpi_idle: touch TS_POLLING only in the non-MWAIT case
  acpi_pad: uses MONITOR/MWAIT, so it doesn't need to clear TS_POLLING
  sched: clarify commment for TS_POLLING
  ACPI: allow a native cpuidle driver to displace ACPI
  cpuidle: make cpuidle_curr_driver static
  cpuidle: add cpuidle_unregister_driver() error check
  cpuidle: fail to register if !CONFIG_CPU_IDLE

14 files changed, 538 insertions, 42 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 33047a605438..13608bd2e791 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2887,6 +2887,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git
 S:      Maintained
 F:      drivers/input/
 
+INTEL IDLE DRIVER
+M:      Len Brown <lenb@kernel.org>
+L:      linux-pm@lists.linux-foundation.org
+T:      git git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6.git
+S:      Supported
+F:      drivers/idle/intel_idle.c
+
 INTEL FRAMEBUFFER DRIVER (excluding 810 and 815)
 M:      Maik Broemme <mbroemme@plusserver.de>
 L:      linux-fbdev@vger.kernel.org
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 62ba9400cc43..f0b6e5dbc5a0 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -239,8 +239,8 @@ static inline struct thread_info *current_thread_info(void)
 #define TS_USEDFPU              0x0001  /* FPU was used by this task
                                            this quantum (SMP) */
 #define TS_COMPAT               0x0002  /* 32bit syscall active (64BIT)*/
-#define TS_POLLING              0x0004  /* true if in idle loop
-                                           and not sleeping */
+#define TS_POLLING              0x0004  /* idle task polling need_resched,
+                                           skip sending interrupt */
 #define TS_RESTORE_SIGMASK      0x0008  /* restore signal mask in do_signal() */
 
 #define tsk_is_polling(t) (task_thread_info(t)->status & TS_POLLING)
diff --git a/drivers/Makefile b/drivers/Makefile
index f42a03029b7c..91874e048552 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_PCI)		+= pci/
 obj-$(CONFIG_PARISC)            += parisc/
 obj-$(CONFIG_RAPIDIO)           += rapidio/
 obj-y                           += video/
+obj-y                           += idle/
 obj-$(CONFIG_ACPI)              += acpi/
 obj-$(CONFIG_SFI)               += sfi/
 # PnP must come after ACPI since it will eventually need to check if acpi
@@ -91,7 +92,6 @@ obj-$(CONFIG_EISA)		+= eisa/
 obj-y                           += lguest/
 obj-$(CONFIG_CPU_FREQ)          += cpufreq/
 obj-$(CONFIG_CPU_IDLE)          += cpuidle/
-obj-y                           += idle/
 obj-$(CONFIG_MMC)               += mmc/
 obj-$(CONFIG_MEMSTICK)          += memstick/
 obj-$(CONFIG_NEW_LEDS)          += leds/
diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index f169e516a1af..d269a8f3329c 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -172,13 +172,6 @@ static int power_saving_thread(void *data)
 
                 do_sleep = 0;
 
-                current_thread_info()->status &= ~TS_POLLING;
-                /*
-                 * TS_POLLING-cleared state must be visible before we test
-                 * NEED_RESCHED:
-                 */
-                smp_mb();
-
                 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
 
                 while (!need_resched()) {
@@ -209,8 +202,6 @@ static int power_saving_thread(void *data)
                         }
                 }
 
-                current_thread_info()->status |= TS_POLLING;
-
                 /*
                  * current sched_rt has threshold for rt task running time.
                  * When a rt task uses 95% CPU time, the rt thread will be
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 5675d9747e87..b1034a9ada4e 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -616,7 +616,8 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
         acpi_processor_get_limit_info(pr);
 
 
-        acpi_processor_power_init(pr, device);
+        if (cpuidle_get_driver() == &acpi_idle_driver)
+                acpi_processor_power_init(pr, device);
 
         pr->cdev = thermal_cooling_device_register("Processor", device,
                                                 &processor_cooling_ops);
@@ -920,9 +921,14 @@ static int __init acpi_processor_init(void)
         if (!acpi_processor_dir)
                 return -ENOMEM;
 #endif
-        result = cpuidle_register_driver(&acpi_idle_driver);
-        if (result < 0)
-                goto out_proc;
+
+        if (!cpuidle_register_driver(&acpi_idle_driver)) {
+                printk(KERN_DEBUG "ACPI: %s registered with cpuidle\n",
+                        acpi_idle_driver.name);
+        } else {
+                printk(KERN_DEBUG "ACPI: acpi_idle yielding to %s",
+                        cpuidle_get_driver()->name);
+        }
 
         result = acpi_bus_register_driver(&acpi_processor_driver);
         if (result < 0)
@@ -941,7 +947,6 @@ static int __init acpi_processor_init(void)
 out_cpuidle:
         cpuidle_unregister_driver(&acpi_idle_driver);
 
-out_proc:
 #ifdef CONFIG_ACPI_PROCFS
         remove_proc_entry(ACPI_PROCESSOR_CLASS, acpi_root_dir);
 #endif
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 13c6cb703f1d..2e8c27d48f2b 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -872,6 +872,7 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
                 return(acpi_idle_enter_c1(dev, state));
 
         local_irq_disable();
+
         if (cx->entry_method != ACPI_CSTATE_FFH) {
                 current_thread_info()->status &= ~TS_POLLING;
                 /*
@@ -879,12 +880,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
                  * NEED_RESCHED:
                  */
                 smp_mb();
-        }
 
-        if (unlikely(need_resched())) {
-                current_thread_info()->status |= TS_POLLING;
-                local_irq_enable();
-                return 0;
+                if (unlikely(need_resched())) {
+                        current_thread_info()->status |= TS_POLLING;
+                        local_irq_enable();
+                        return 0;
+                }
         }
 
         /*
@@ -911,7 +912,8 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
         sched_clock_idle_wakeup_event(idle_time_ns);
 
         local_irq_enable();
-        current_thread_info()->status |= TS_POLLING;
+        if (cx->entry_method != ACPI_CSTATE_FFH)
+                current_thread_info()->status |= TS_POLLING;
 
         cx->usage++;
 
@@ -962,6 +964,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
         }
 
         local_irq_disable();
+
         if (cx->entry_method != ACPI_CSTATE_FFH) {
                 current_thread_info()->status &= ~TS_POLLING;
                 /*
@@ -969,12 +972,12 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
                  * NEED_RESCHED:
                  */
                 smp_mb();
-        }
 
-        if (unlikely(need_resched())) {
-                current_thread_info()->status |= TS_POLLING;
-                local_irq_enable();
-                return 0;
+                if (unlikely(need_resched())) {
+                        current_thread_info()->status |= TS_POLLING;
+                        local_irq_enable();
+                        return 0;
+                }
         }
 
         acpi_unlazy_tlb(smp_processor_id());
@@ -1028,7 +1031,8 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
         sched_clock_idle_wakeup_event(idle_time_ns);
 
         local_irq_enable();
-        current_thread_info()->status |= TS_POLLING;
+        if (cx->entry_method != ACPI_CSTATE_FFH)
+                current_thread_info()->status |= TS_POLLING;
 
         cx->usage++;
 
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 12fdd3987a36..199488576a05 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -156,7 +156,7 @@ int cpuidle_enable_device(struct cpuidle_device *dev)
 
         if (dev->enabled)
                 return 0;
-        if (!cpuidle_curr_driver || !cpuidle_curr_governor)
+        if (!cpuidle_get_driver() || !cpuidle_curr_governor)
                 return -EIO;
         if (!dev->state_count)
                 return -EINVAL;
@@ -207,7 +207,7 @@ void cpuidle_disable_device(struct cpuidle_device *dev)
 {
         if (!dev->enabled)
                 return;
-        if (!cpuidle_curr_driver || !cpuidle_curr_governor)
+        if (!cpuidle_get_driver() || !cpuidle_curr_governor)
                 return;
 
         dev->enabled = 0;
@@ -271,10 +271,11 @@ static int __cpuidle_register_device(struct cpuidle_device *dev)
 {
         int ret;
         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
+        struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 
         if (!sys_dev)
                 return -EINVAL;
-        if (!try_module_get(cpuidle_curr_driver->owner))
+        if (!try_module_get(cpuidle_driver->owner))
                 return -EINVAL;
 
         init_completion(&dev->kobj_unregister);
@@ -284,7 +285,7 @@ static int __cpuidle_register_device(struct cpuidle_device *dev)
         per_cpu(cpuidle_devices, dev->cpu) = dev;
         list_add(&dev->device_list, &cpuidle_detected_devices);
         if ((ret = cpuidle_add_sysfs(sys_dev))) {
-                module_put(cpuidle_curr_driver->owner);
+                module_put(cpuidle_driver->owner);
                 return ret;
         }
 
@@ -325,6 +326,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device);
 void cpuidle_unregister_device(struct cpuidle_device *dev)
 {
         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
+        struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 
         if (dev->registered == 0)
                 return;
@@ -340,7 +342,7 @@ void cpuidle_unregister_device(struct cpuidle_device *dev)
 
         cpuidle_resume_and_unlock();
 
-        module_put(cpuidle_curr_driver->owner);
+        module_put(cpuidle_driver->owner);
 }
 
 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
diff --git a/drivers/cpuidle/cpuidle.h b/drivers/cpuidle/cpuidle.h
index 9476ba33ee2c..33e50d556f17 100644
--- a/drivers/cpuidle/cpuidle.h
+++ b/drivers/cpuidle/cpuidle.h
@@ -9,7 +9,6 @@
 
 /* For internal use only */
 extern struct cpuidle_governor *cpuidle_curr_governor;
-extern struct cpuidle_driver *cpuidle_curr_driver;
 extern struct list_head cpuidle_governors;
 extern struct list_head cpuidle_detected_devices;
 extern struct mutex cpuidle_lock;
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 2257004fe33d..fd1601e3d125 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -14,7 +14,7 @@
 
 #include "cpuidle.h"
 
-struct cpuidle_driver *cpuidle_curr_driver;
+static struct cpuidle_driver *cpuidle_curr_driver;
 DEFINE_SPINLOCK(cpuidle_driver_lock);
 
 /**
@@ -40,13 +40,25 @@ int cpuidle_register_driver(struct cpuidle_driver *drv)
 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 
 /**
+ * cpuidle_get_driver - return the current driver
+ */
+struct cpuidle_driver *cpuidle_get_driver(void)
+{
+        return cpuidle_curr_driver;
+}
+EXPORT_SYMBOL_GPL(cpuidle_get_driver);
+
+/**
  * cpuidle_unregister_driver - unregisters a driver
  * @drv: the driver
  */
 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 {
-        if (!drv)
+        if (drv != cpuidle_curr_driver) {
+                WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
+                        drv->name);
                 return;
+        }
 
         spin_lock(&cpuidle_driver_lock);
         cpuidle_curr_driver = NULL;
diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
index 0ba9c8b8ee74..0310ffaec9df 100644
--- a/drivers/cpuidle/sysfs.c
+++ b/drivers/cpuidle/sysfs.c
@@ -47,10 +47,11 @@ static ssize_t show_current_driver(struct sysdev_class *class,
                                    char *buf)
 {
         ssize_t ret;
+        struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 
         spin_lock(&cpuidle_driver_lock);
-        if (cpuidle_curr_driver)
-                ret = sprintf(buf, "%s\n", cpuidle_curr_driver->name);
+        if (cpuidle_driver)
+                ret = sprintf(buf, "%s\n", cpuidle_driver->name);
         else
                 ret = sprintf(buf, "none\n");
         spin_unlock(&cpuidle_driver_lock);
diff --git a/drivers/idle/Kconfig b/drivers/idle/Kconfig
index f15e90a453d1..fb5c5186d4aa 100644
--- a/drivers/idle/Kconfig
+++ b/drivers/idle/Kconfig
@@ -1,3 +1,14 @@
+config INTEL_IDLE
+        tristate "Cpuidle Driver for Intel Processors"
+        depends on CPU_IDLE
+        depends on X86
+        depends on CPU_SUP_INTEL
+        depends on EXPERIMENTAL
+        help
+          Enable intel_idle, a cpuidle driver that includes knowledge of
+          native Intel hardware idle features.  The acpi_idle driver
+          can be configured at the same time, in order to handle
+          processors intel_idle does not support.
 
 menu "Memory power savings"
 depends on X86_64
diff --git a/drivers/idle/Makefile b/drivers/idle/Makefile
index 5f68fc377e21..23d295cf10f2 100644
--- a/drivers/idle/Makefile
+++ b/drivers/idle/Makefile
@@ -1,2 +1,3 @@
 obj-$(CONFIG_I7300_IDLE)                        += i7300_idle.o
+obj-$(CONFIG_INTEL_IDLE)                        += intel_idle.o
 
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
new file mode 100755
index 000000000000..54f0fb4cd5d2
--- /dev/null
+++ b/drivers/idle/intel_idle.c
@@ -0,0 +1,461 @@
+/*
+ * intel_idle.c - native hardware idle loop for modern Intel processors
+ *
+ * Copyright (c) 2010, Intel Corporation.
+ * Len Brown <len.brown@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*
+ * intel_idle is a cpuidle driver that loads on specific Intel processors
+ * in lieu of the legacy ACPI processor_idle driver.  The intent is to
+ * make Linux more efficient on these processors, as intel_idle knows
+ * more than ACPI, as well as make Linux more immune to ACPI BIOS bugs.
+ */
+
+/*
+ * Design Assumptions
+ *
+ * All CPUs have same idle states as boot CPU
+ *
+ * Chipset BM_STS (bus master status) bit is a NOP
+ *      for preventing entry into deep C-stats
+ */
+
+/*
+ * Known limitations
+ *
+ * The driver currently initializes for_each_online_cpu() upon modprobe.
+ * It it unaware of subsequent processors hot-added to the system.
+ * This means that if you boot with maxcpus=n and later online
+ * processors above n, those processors will use C1 only.
+ *
+ * ACPI has a .suspend hack to turn off deep c-statees during suspend
+ * to avoid complications with the lapic timer workaround.
+ * Have not seen issues with suspend, but may need same workaround here.
+ *
+ * There is currently no kernel-based automatic probing/loading mechanism
+ * if the driver is built as a module.
+ */
+
+/* un-comment DEBUG to enable pr_debug() statements */
+#define DEBUG
+
+#include <linux/kernel.h>
+#include <linux/cpuidle.h>
+#include <linux/clockchips.h>
+#include <linux/hrtimer.h>      /* ktime_get_real() */
+#include <trace/events/power.h>
+#include <linux/sched.h>
+
+#define INTEL_IDLE_VERSION "0.4"
+#define PREFIX "intel_idle: "
+
+#define MWAIT_SUBSTATE_MASK     (0xf)
+#define MWAIT_CSTATE_MASK       (0xf)
+#define MWAIT_SUBSTATE_SIZE     (4)
+#define MWAIT_MAX_NUM_CSTATES   8
+#define CPUID_MWAIT_LEAF (5)
+#define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1)
+#define CPUID5_ECX_INTERRUPT_BREAK      (0x2)
+
+static struct cpuidle_driver intel_idle_driver = {
+        .name = "intel_idle",
+        .owner = THIS_MODULE,
+};
+/* intel_idle.max_cstate=0 disables driver */
+static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1;
+static int power_policy = 7; /* 0 = max perf; 15 = max powersave */
+
+static unsigned int substates;
+static int (*choose_substate)(int);
+
+/* Reliable LAPIC Timer States, bit 1 for C1 etc.  */
+static unsigned int lapic_timer_reliable_states;
+
+static struct cpuidle_device *intel_idle_cpuidle_devices;
+static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state);
+
+static struct cpuidle_state *cpuidle_state_table;
+
+/*
+ * States are indexed by the cstate number,
+ * which is also the index into the MWAIT hint array.
+ * Thus C0 is a dummy.
+ */
+static struct cpuidle_state nehalem_cstates[MWAIT_MAX_NUM_CSTATES] = {
+        { /* MWAIT C0 */ },
+        { /* MWAIT C1 */
+                .name = "NHM-C1",
+                .desc = "MWAIT 0x00",
+                .driver_data = (void *) 0x00,
+                .flags = CPUIDLE_FLAG_TIME_VALID,
+                .exit_latency = 3,
+                .power_usage = 1000,
+                .target_residency = 6,
+                .enter = &intel_idle },
+        { /* MWAIT C2 */
+                .name = "NHM-C3",
+                .desc = "MWAIT 0x10",
+                .driver_data = (void *) 0x10,
+                .flags = CPUIDLE_FLAG_TIME_VALID,
+                .exit_latency = 20,
+                .power_usage = 500,
+                .target_residency = 80,
+                .enter = &intel_idle },
+        { /* MWAIT C3 */
+                .name = "NHM-C6",
+                .desc = "MWAIT 0x20",
+                .driver_data = (void *) 0x20,
+                .flags = CPUIDLE_FLAG_TIME_VALID,
+                .exit_latency = 200,
+                .power_usage = 350,
+                .target_residency = 800,
+                .enter = &intel_idle },
+};
+
+static struct cpuidle_state atom_cstates[MWAIT_MAX_NUM_CSTATES] = {
+        { /* MWAIT C0 */ },
+        { /* MWAIT C1 */
+                .name = "ATM-C1",
+                .desc = "MWAIT 0x00",
+                .driver_data = (void *) 0x00,
+                .flags = CPUIDLE_FLAG_TIME_VALID,
+                .exit_latency = 1,
+                .power_usage = 1000,
+                .target_residency = 4,
+                .enter = &intel_idle },
+        { /* MWAIT C2 */
+                .name = "ATM-C2",
+                .desc = "MWAIT 0x10",
+                .driver_data = (void *) 0x10,
+                .flags = CPUIDLE_FLAG_TIME_VALID,
+                .exit_latency = 20,
+                .power_usage = 500,
+                .target_residency = 80,
+                .enter = &intel_idle },
+        { /* MWAIT C3 */ },
+        { /* MWAIT C4 */
+                .name = "ATM-C4",
+                .desc = "MWAIT 0x30",
+                .driver_data = (void *) 0x30,
+                .flags = CPUIDLE_FLAG_TIME_VALID,
+                .exit_latency = 100,
+                .power_usage = 250,
+                .target_residency = 400,
+                .enter = &intel_idle },
+        { /* MWAIT C5 */ },
+        { /* MWAIT C6 */
+                .name = "ATM-C6",
+                .desc = "MWAIT 0x40",
+                .driver_data = (void *) 0x40,
+                .flags = CPUIDLE_FLAG_TIME_VALID,
+                .exit_latency = 200,
+                .power_usage = 150,
+                .target_residency = 800,
+                .enter = NULL },        /* disabled */
+};
+
+/*
+ * choose_tunable_substate()
+ *
+ * Run-time decision on which C-state substate to invoke
+ * If power_policy = 0, choose shallowest substate (0)
+ * If power_policy = 15, choose deepest substate
+ * If power_policy = middle, choose middle substate etc.
+ */
+static int choose_tunable_substate(int cstate)
+{
+        unsigned int num_substates;
+        unsigned int substate_choice;
+
+        power_policy &= 0xF;    /* valid range: 0-15 */
+        cstate &= 7;    /* valid range: 0-7 */
+
+        num_substates = (substates >> ((cstate) * 4)) & MWAIT_SUBSTATE_MASK;
+
+        if (num_substates <= 1)
+                return 0;
+
+        substate_choice = ((power_policy + (power_policy + 1) *
+                                (num_substates - 1)) / 16);
+
+        return substate_choice;
+}
+
+/*
+ * choose_zero_substate()
+ */
+static int choose_zero_substate(int cstate)
+{
+        return 0;
+}
+
+/**
+ * intel_idle
+ * @dev: cpuidle_device
+ * @state: cpuidle state
+ *
+ */
+static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state)
+{
+        unsigned long ecx = 1; /* break on interrupt flag */
+        unsigned long eax = (unsigned long)cpuidle_get_statedata(state);
+        unsigned int cstate;
+        ktime_t kt_before, kt_after;
+        s64 usec_delta;
+        int cpu = smp_processor_id();
+
+        cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
+
+        eax = eax + (choose_substate)(cstate);
+
+        local_irq_disable();
+
+        if (!(lapic_timer_reliable_states & (1 << (cstate))))
+                clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
+
+        kt_before = ktime_get_real();
+
+        stop_critical_timings();
+#ifndef MODULE
+        trace_power_start(POWER_CSTATE, (eax >> 4) + 1);
+#endif
+        if (!need_resched()) {
+
+                __monitor((void *)&current_thread_info()->flags, 0, 0);
+                smp_mb();
+                if (!need_resched())
+                        __mwait(eax, ecx);
+        }
+
+        start_critical_timings();
+
+        kt_after = ktime_get_real();
+        usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
+
+        local_irq_enable();
+
+        if (!(lapic_timer_reliable_states & (1 << (cstate))))
+                clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
+
+        return usec_delta;
+}
+
+/*
+ * intel_idle_probe()
+ */
+static int intel_idle_probe(void)
+{
+        unsigned int eax, ebx, ecx, edx;
+
+        if (max_cstate == 0) {
+                pr_debug(PREFIX "disabled\n");
+                return -EPERM;
+        }
+
+        if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+                return -ENODEV;
+
+        if (!boot_cpu_has(X86_FEATURE_MWAIT))
+                return -ENODEV;
+
+        if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
+                return -ENODEV;
+
+        cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
+
+        if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
+                !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
+                        return -ENODEV;
+#ifdef DEBUG
+        if (substates == 0)     /* can over-ride via modparam */
+#endif
+                substates = edx;
+
+        pr_debug(PREFIX "MWAIT substates: 0x%x\n", substates);
+
+        if (boot_cpu_has(X86_FEATURE_ARAT))     /* Always Reliable APIC Timer */
+                lapic_timer_reliable_states = 0xFFFFFFFF;
+
+        if (boot_cpu_data.x86 != 6)     /* family 6 */
+                return -ENODEV;
+
+        switch (boot_cpu_data.x86_model) {
+
+        case 0x1A:      /* Core i7, Xeon 5500 series */
+        case 0x1E:      /* Core i7 and i5 Processor - Lynnfield Jasper Forest */
+        case 0x1F:      /* Core i7 and i5 Processor - Nehalem */
+        case 0x2E:      /* Nehalem-EX Xeon */
+                lapic_timer_reliable_states = (1 << 1);  /* C1 */
+
+        case 0x25:      /* Westmere */
+        case 0x2C:      /* Westmere */
+                cpuidle_state_table = nehalem_cstates;
+                choose_substate = choose_tunable_substate;
+                break;
+
+        case 0x1C:      /* 28 - Atom Processor */
+                lapic_timer_reliable_states = (1 << 2) | (1 << 1); /* C2, C1 */
+                cpuidle_state_table = atom_cstates;
+                choose_substate = choose_zero_substate;
+                break;
+#ifdef FUTURE_USE
+        case 0x17:      /* 23 - Core 2 Duo */
+                lapic_timer_reliable_states = (1 << 2) | (1 << 1); /* C2, C1 */
+#endif
+
+        default:
+                pr_debug(PREFIX "does not run on family %d model %d\n",
+                        boot_cpu_data.x86, boot_cpu_data.x86_model);
+                return -ENODEV;
+        }
+
+        pr_debug(PREFIX "v" INTEL_IDLE_VERSION
+                " model 0x%X\n", boot_cpu_data.x86_model);
+
+        pr_debug(PREFIX "lapic_timer_reliable_states 0x%x\n",
+                lapic_timer_reliable_states);
+        return 0;
+}
+
+/*
+ * intel_idle_cpuidle_devices_uninit()
+ * unregister, free cpuidle_devices
+ */
+static void intel_idle_cpuidle_devices_uninit(void)
+{
+        int i;
+        struct cpuidle_device *dev;
+
+        for_each_online_cpu(i) {
+                dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
+                cpuidle_unregister_device(dev);
+        }
+
+        free_percpu(intel_idle_cpuidle_devices);
+        return;
+}
+/*
+ * intel_idle_cpuidle_devices_init()
+ * allocate, initialize, register cpuidle_devices
+ */
+static int intel_idle_cpuidle_devices_init(void)
+{
+        int i, cstate;
+        struct cpuidle_device *dev;
+
+        intel_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
+        if (intel_idle_cpuidle_devices == NULL)
+                return -ENOMEM;
+
+        for_each_online_cpu(i) {
+                dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
+
+                dev->state_count = 1;
+
+                for (cstate = 1; cstate < MWAIT_MAX_NUM_CSTATES; ++cstate) {
+                        int num_substates;
+
+                        if (cstate > max_cstate) {
+                                printk(PREFIX "max_cstate %d reached\n",
+                                        max_cstate);
+                                break;
+                        }
+
+                        /* does the state exist in CPUID.MWAIT? */
+                        num_substates = (substates >> ((cstate) * 4))
+                                                & MWAIT_SUBSTATE_MASK;
+                        if (num_substates == 0)
+                                continue;
+                        /* is the state not enabled? */
+                        if (cpuidle_state_table[cstate].enter == NULL) {
+                                /* does the driver not know about the state? */
+                                if (*cpuidle_state_table[cstate].name == '\0')
+                                        pr_debug(PREFIX "unaware of model 0x%x"
+                                                " MWAIT %d please"
+                                                " contact lenb@kernel.org",
+                                        boot_cpu_data.x86_model, cstate);
+                                continue;
+                        }
+
+                        if ((cstate > 2) &&
+                                !boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
+                                mark_tsc_unstable("TSC halts in idle"
+                                        " states deeper than C2");
+
+                        dev->states[dev->state_count] = /* structure copy */
+                                cpuidle_state_table[cstate];
+
+                        dev->state_count += 1;
+                }
+
+                dev->cpu = i;
+                if (cpuidle_register_device(dev)) {
+                        pr_debug(PREFIX "cpuidle_register_device %d failed!\n",
+                                 i);
+                        intel_idle_cpuidle_devices_uninit();
+                        return -EIO;
+                }
+        }
+
+        return 0;
+}
+
+
+static int __init intel_idle_init(void)
+{
+        int retval;
+
+        retval = intel_idle_probe();
+        if (retval)
+                return retval;
+
+        retval = cpuidle_register_driver(&intel_idle_driver);
+        if (retval) {
+                printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
+                        cpuidle_get_driver()->name);
+                return retval;
+        }
+
+        retval = intel_idle_cpuidle_devices_init();
+        if (retval) {
+                cpuidle_unregister_driver(&intel_idle_driver);
+                return retval;
+        }
+
+        return 0;
+}
+
+static void __exit intel_idle_exit(void)
+{
+        intel_idle_cpuidle_devices_uninit();
+        cpuidle_unregister_driver(&intel_idle_driver);
+
+        return;
+}
+
+module_init(intel_idle_init);
+module_exit(intel_idle_exit);
+
+module_param(power_policy, int, 0644);
+module_param(max_cstate, int, 0444);
+#ifdef DEBUG
+module_param(substates, int, 0444);
+#endif
+
+MODULE_AUTHOR("Len Brown <len.brown@intel.com>");
+MODULE_DESCRIPTION("Cpuidle driver for Intel Hardware v" INTEL_IDLE_VERSION);
+MODULE_LICENSE("GPL");
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index dcf77fa826b5..55215cce5005 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -125,6 +125,7 @@ struct cpuidle_driver {
 #ifdef CONFIG_CPU_IDLE
 
 extern int cpuidle_register_driver(struct cpuidle_driver *drv);
+struct cpuidle_driver *cpuidle_get_driver(void);
 extern void cpuidle_unregister_driver(struct cpuidle_driver *drv);
 extern int cpuidle_register_device(struct cpuidle_device *dev);
 extern void cpuidle_unregister_device(struct cpuidle_device *dev);
@@ -137,16 +138,17 @@ extern void cpuidle_disable_device(struct cpuidle_device *dev);
 #else
 
 static inline int cpuidle_register_driver(struct cpuidle_driver *drv)
-{return 0;}
+{return -ENODEV; }
+static inline struct cpuidle_driver *cpuidle_get_driver(void) {return NULL; }
 static inline void cpuidle_unregister_driver(struct cpuidle_driver *drv) { }
 static inline int cpuidle_register_device(struct cpuidle_device *dev)
-{return 0;}
+{return -ENODEV; }
 static inline void cpuidle_unregister_device(struct cpuidle_device *dev) { }
 
 static inline void cpuidle_pause_and_lock(void) { }
 static inline void cpuidle_resume_and_unlock(void) { }
 static inline int cpuidle_enable_device(struct cpuidle_device *dev)
-{return 0;}
+{return -ENODEV; }
 static inline void cpuidle_disable_device(struct cpuidle_device *dev) { }
 
 #endif