[PATCH] notifiers: fix blocking_notifier_call_chain() scalability

[linux/fpc-iii.git] / drivers / acpi / processor_idle.c

/*
 * processor_idle - idle state submodule to the ACPI processor driver
 *
 *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
 *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *  Copyright (C) 2004, 2005 Dominik Brodowski <linux@brodo.de>
 *  Copyright (C) 2004  Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
 *                      - Added processor hotplug support
 *  Copyright (C) 2005  Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *                      - Added support for C3 on SMP
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or (at
 *  your option) any later version.
 *
 *  This program is distributed in the hope that 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.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/acpi.h>
#include <linux/dmi.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>        /* need_resched() */
#include <linux/latency.h>

#include <asm/io.h>
#include <asm/uaccess.h>

#include <acpi/acpi_bus.h>
#include <acpi/processor.h>

#define ACPI_PROCESSOR_COMPONENT        0x01000000
#define ACPI_PROCESSOR_CLASS            "processor"
#define ACPI_PROCESSOR_DRIVER_NAME      "ACPI Processor Driver"
#define _COMPONENT              ACPI_PROCESSOR_COMPONENT
ACPI_MODULE_NAME("acpi_processor")
#define ACPI_PROCESSOR_FILE_POWER       "power"
#define US_TO_PM_TIMER_TICKS(t)         ((t * (PM_TIMER_FREQUENCY/1000)) / 1000)
#define C2_OVERHEAD                     4       /* 1us (3.579 ticks per us) */
#define C3_OVERHEAD                     4       /* 1us (3.579 ticks per us) */
static void (*pm_idle_save) (void) __read_mostly;
module_param(max_cstate, uint, 0644);

static unsigned int nocst __read_mostly;
module_param(nocst, uint, 0000);

/*
 * bm_history -- bit-mask with a bit per jiffy of bus-master activity
 * 1000 HZ: 0xFFFFFFFF: 32 jiffies = 32ms
 * 800 HZ: 0xFFFFFFFF: 32 jiffies = 40ms
 * 100 HZ: 0x0000000F: 4 jiffies = 40ms
 * reduce history for more aggressive entry into C3
 */
static unsigned int bm_history __read_mostly =
    (HZ >= 800 ? 0xFFFFFFFF : ((1U << (HZ / 25)) - 1));
module_param(bm_history, uint, 0644);
/* --------------------------------------------------------------------------
                                Power Management
   -------------------------------------------------------------------------- */

/*
 * IBM ThinkPad R40e crashes mysteriously when going into C2 or C3.
 * For now disable this. Probably a bug somewhere else.
 *
 * To skip this limit, boot/load with a large max_cstate limit.
 */
static int set_max_cstate(struct dmi_system_id *id)
{
        if (max_cstate > ACPI_PROCESSOR_MAX_POWER)
                return 0;

        printk(KERN_NOTICE PREFIX "%s detected - limiting to C%ld max_cstate."
               " Override with \"processor.max_cstate=%d\"\n", id->ident,
               (long)id->driver_data, ACPI_PROCESSOR_MAX_POWER + 1);

        max_cstate = (long)id->driver_data;

        return 0;
}

/* Actually this shouldn't be __cpuinitdata, would be better to fix the
   callers to only run once -AK */
static struct dmi_system_id __cpuinitdata processor_power_dmi_table[] = {
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET70WW")}, (void *)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET60WW")}, (void *)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET43WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET45WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET47WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET50WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET52WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET55WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET56WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET59WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET60WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET61WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET62WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET64WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET65WW") }, (void*)1},
        { set_max_cstate, "IBM ThinkPad R40e", {
          DMI_MATCH(DMI_BIOS_VENDOR,"IBM"),
          DMI_MATCH(DMI_BIOS_VERSION,"1SET68WW") }, (void*)1},
        { set_max_cstate, "Medion 41700", {
          DMI_MATCH(DMI_BIOS_VENDOR,"Phoenix Technologies LTD"),
          DMI_MATCH(DMI_BIOS_VERSION,"R01-A1J")}, (void *)1},
        { set_max_cstate, "Clevo 5600D", {
          DMI_MATCH(DMI_BIOS_VENDOR,"Phoenix Technologies LTD"),
          DMI_MATCH(DMI_BIOS_VERSION,"SHE845M0.86C.0013.D.0302131307")},
         (void *)2},
        {},
};

static inline u32 ticks_elapsed(u32 t1, u32 t2)
{
        if (t2 >= t1)
                return (t2 - t1);
        else if (!acpi_fadt.tmr_val_ext)
                return (((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
        else
                return ((0xFFFFFFFF - t1) + t2);
}

static void
acpi_processor_power_activate(struct acpi_processor *pr,
                              struct acpi_processor_cx *new)
{
        struct acpi_processor_cx *old;

        if (!pr || !new)
                return;

        old = pr->power.state;

        if (old)
                old->promotion.count = 0;
        new->demotion.count = 0;

        /* Cleanup from old state. */
        if (old) {
                switch (old->type) {
                case ACPI_STATE_C3:
                        /* Disable bus master reload */
                        if (new->type != ACPI_STATE_C3 && pr->flags.bm_check)
                                acpi_set_register(ACPI_BITREG_BUS_MASTER_RLD, 0,
                                                  ACPI_MTX_DO_NOT_LOCK);
                        break;
                }
        }

        /* Prepare to use new state. */
        switch (new->type) {
        case ACPI_STATE_C3:
                /* Enable bus master reload */
                if (old->type != ACPI_STATE_C3 && pr->flags.bm_check)
                        acpi_set_register(ACPI_BITREG_BUS_MASTER_RLD, 1,
                                          ACPI_MTX_DO_NOT_LOCK);
                break;
        }

        pr->power.state = new;

        return;
}

static void acpi_safe_halt(void)
{
        current_thread_info()->status &= ~TS_POLLING;
        /*
         * TS_POLLING-cleared state must be visible before we
         * test NEED_RESCHED:
         */
        smp_mb();
        if (!need_resched())
                safe_halt();
        current_thread_info()->status |= TS_POLLING;
}

static atomic_t c3_cpu_count;

/* Common C-state entry for C2, C3, .. */
static void acpi_cstate_enter(struct acpi_processor_cx *cstate)
{
        if (cstate->space_id == ACPI_CSTATE_FFH) {
                /* Call into architectural FFH based C-state */
                acpi_processor_ffh_cstate_enter(cstate);
        } else {
                int unused;
                /* IO port based C-state */
                inb(cstate->address);
                /* Dummy wait op - must do something useless after P_LVL2 read
                   because chipsets cannot guarantee that STPCLK# signal
                   gets asserted in time to freeze execution properly. */
                unused = inl(acpi_fadt.xpm_tmr_blk.address);
        }
}

static void acpi_processor_idle(void)
{
        struct acpi_processor *pr = NULL;
        struct acpi_processor_cx *cx = NULL;
        struct acpi_processor_cx *next_state = NULL;
        int sleep_ticks = 0;
        u32 t1, t2 = 0;

        pr = processors[smp_processor_id()];
        if (!pr)
                return;

        /*
         * Interrupts must be disabled during bus mastering calculations and
         * for C2/C3 transitions.
         */
        local_irq_disable();

        /*
         * Check whether we truly need to go idle, or should
         * reschedule:
         */
        if (unlikely(need_resched())) {
                local_irq_enable();
                return;
        }

        cx = pr->power.state;
        if (!cx) {
                if (pm_idle_save)
                        pm_idle_save();
                else
                        acpi_safe_halt();
                return;
        }

        /*
         * Check BM Activity
         * -----------------
         * Check for bus mastering activity (if required), record, and check
         * for demotion.
         */
        if (pr->flags.bm_check) {
                u32 bm_status = 0;
                unsigned long diff = jiffies - pr->power.bm_check_timestamp;

                if (diff > 31)
                        diff = 31;

                pr->power.bm_activity <<= diff;

                acpi_get_register(ACPI_BITREG_BUS_MASTER_STATUS,
                                  &bm_status, ACPI_MTX_DO_NOT_LOCK);
                if (bm_status) {
                        pr->power.bm_activity |= 0x1;
                        acpi_set_register(ACPI_BITREG_BUS_MASTER_STATUS,
                                          1, ACPI_MTX_DO_NOT_LOCK);
                }
                /*
                 * PIIX4 Erratum #18: Note that BM_STS doesn't always reflect
                 * the true state of bus mastering activity; forcing us to
                 * manually check the BMIDEA bit of each IDE channel.
                 */
                else if (errata.piix4.bmisx) {
                        if ((inb_p(errata.piix4.bmisx + 0x02) & 0x01)
                            || (inb_p(errata.piix4.bmisx + 0x0A) & 0x01))
                                pr->power.bm_activity |= 0x1;
                }

                pr->power.bm_check_timestamp = jiffies;

                /*
                 * If bus mastering is or was active this jiffy, demote
                 * to avoid a faulty transition.  Note that the processor
                 * won't enter a low-power state during this call (to this
                 * function) but should upon the next.
                 *
                 * TBD: A better policy might be to fallback to the demotion
                 *      state (use it for this quantum only) istead of
                 *      demoting -- and rely on duration as our sole demotion
                 *      qualification.  This may, however, introduce DMA
                 *      issues (e.g. floppy DMA transfer overrun/underrun).
                 */
                if ((pr->power.bm_activity & 0x1) &&
                    cx->demotion.threshold.bm) {
                        local_irq_enable();
                        next_state = cx->demotion.state;
                        goto end;
                }
        }

#ifdef CONFIG_HOTPLUG_CPU
        /*
         * Check for P_LVL2_UP flag before entering C2 and above on
         * an SMP system. We do it here instead of doing it at _CST/P_LVL
         * detection phase, to work cleanly with logical CPU hotplug.
         */
        if ((cx->type != ACPI_STATE_C1) && (num_online_cpus() > 1) && 
            !pr->flags.has_cst && !acpi_fadt.plvl2_up)
                cx = &pr->power.states[ACPI_STATE_C1];
#endif

        /*
         * Sleep:
         * ------
         * Invoke the current Cx state to put the processor to sleep.
         */
        if (cx->type == ACPI_STATE_C2 || cx->type == ACPI_STATE_C3) {
                current_thread_info()->status &= ~TS_POLLING;
                /*
                 * TS_POLLING-cleared state must be visible before we
                 * test NEED_RESCHED:
                 */
                smp_mb();
                if (need_resched()) {
                        current_thread_info()->status |= TS_POLLING;
                        local_irq_enable();
                        return;
                }
        }

        switch (cx->type) {

        case ACPI_STATE_C1:
                /*
                 * Invoke C1.
                 * Use the appropriate idle routine, the one that would
                 * be used without acpi C-states.
                 */
                if (pm_idle_save)
                        pm_idle_save();
                else
                        acpi_safe_halt();

                /*
                 * TBD: Can't get time duration while in C1, as resumes
                 *      go to an ISR rather than here.  Need to instrument
                 *      base interrupt handler.
                 */
                sleep_ticks = 0xFFFFFFFF;
                break;

        case ACPI_STATE_C2:
                /* Get start time (ticks) */
                t1 = inl(acpi_fadt.xpm_tmr_blk.address);
                /* Invoke C2 */
                acpi_cstate_enter(cx);
                /* Get end time (ticks) */
                t2 = inl(acpi_fadt.xpm_tmr_blk.address);

#ifdef CONFIG_GENERIC_TIME
                /* TSC halts in C2, so notify users */
                mark_tsc_unstable();
#endif
                /* Re-enable interrupts */
                local_irq_enable();
                current_thread_info()->status |= TS_POLLING;
                /* Compute time (ticks) that we were actually asleep */
                sleep_ticks =
                    ticks_elapsed(t1, t2) - cx->latency_ticks - C2_OVERHEAD;
                break;

        case ACPI_STATE_C3:

                if (pr->flags.bm_check) {
                        if (atomic_inc_return(&c3_cpu_count) ==
                            num_online_cpus()) {
                                /*
                                 * All CPUs are trying to go to C3
                                 * Disable bus master arbitration
                                 */
                                acpi_set_register(ACPI_BITREG_ARB_DISABLE, 1,
                                                  ACPI_MTX_DO_NOT_LOCK);
                        }
                } else {
                        /* SMP with no shared cache... Invalidate cache  */
                        ACPI_FLUSH_CPU_CACHE();
                }

                /* Get start time (ticks) */
                t1 = inl(acpi_fadt.xpm_tmr_blk.address);
                /* Invoke C3 */
                acpi_cstate_enter(cx);
                /* Get end time (ticks) */
                t2 = inl(acpi_fadt.xpm_tmr_blk.address);
                if (pr->flags.bm_check) {
                        /* Enable bus master arbitration */
                        atomic_dec(&c3_cpu_count);
                        acpi_set_register(ACPI_BITREG_ARB_DISABLE, 0,
                                          ACPI_MTX_DO_NOT_LOCK);
                }

#ifdef CONFIG_GENERIC_TIME
                /* TSC halts in C3, so notify users */
                mark_tsc_unstable();
#endif
                /* Re-enable interrupts */
                local_irq_enable();
                current_thread_info()->status |= TS_POLLING;
                /* Compute time (ticks) that we were actually asleep */
                sleep_ticks =
                    ticks_elapsed(t1, t2) - cx->latency_ticks - C3_OVERHEAD;
                break;

        default:
                local_irq_enable();
                return;
        }
        cx->usage++;
        if ((cx->type != ACPI_STATE_C1) && (sleep_ticks > 0))
                cx->time += sleep_ticks;

        next_state = pr->power.state;

#ifdef CONFIG_HOTPLUG_CPU
        /* Don't do promotion/demotion */
        if ((cx->type == ACPI_STATE_C1) && (num_online_cpus() > 1) &&
            !pr->flags.has_cst && !acpi_fadt.plvl2_up) {
                next_state = cx;
                goto end;
        }
#endif

        /*
         * Promotion?
         * ----------
         * Track the number of longs (time asleep is greater than threshold)
         * and promote when the count threshold is reached.  Note that bus
         * mastering activity may prevent promotions.
         * Do not promote above max_cstate.
         */
        if (cx->promotion.state &&
            ((cx->promotion.state - pr->power.states) <= max_cstate)) {
                if (sleep_ticks > cx->promotion.threshold.ticks &&
                  cx->promotion.state->latency <= system_latency_constraint()) {
                        cx->promotion.count++;
                        cx->demotion.count = 0;
                        if (cx->promotion.count >=
                            cx->promotion.threshold.count) {
                                if (pr->flags.bm_check) {
                                        if (!
                                            (pr->power.bm_activity & cx->
                                             promotion.threshold.bm)) {
                                                next_state =
                                                    cx->promotion.state;
                                                goto end;
                                        }
                                } else {
                                        next_state = cx->promotion.state;
                                        goto end;
                                }
                        }
                }
        }

        /*
         * Demotion?
         * ---------
         * Track the number of shorts (time asleep is less than time threshold)
         * and demote when the usage threshold is reached.
         */
        if (cx->demotion.state) {
                if (sleep_ticks < cx->demotion.threshold.ticks) {
                        cx->demotion.count++;
                        cx->promotion.count = 0;
                        if (cx->demotion.count >= cx->demotion.threshold.count) {
                                next_state = cx->demotion.state;
                                goto end;
                        }
                }
        }

      end:
        /*
         * Demote if current state exceeds max_cstate
         * or if the latency of the current state is unacceptable
         */
        if ((pr->power.state - pr->power.states) > max_cstate ||
                pr->power.state->latency > system_latency_constraint()) {
                if (cx->demotion.state)
                        next_state = cx->demotion.state;
        }

        /*
         * New Cx State?
         * -------------
         * If we're going to start using a new Cx state we must clean up
         * from the previous and prepare to use the new.
         */
        if (next_state != pr->power.state)
                acpi_processor_power_activate(pr, next_state);
}

static int acpi_processor_set_power_policy(struct acpi_processor *pr)
{
        unsigned int i;
        unsigned int state_is_set = 0;
        struct acpi_processor_cx *lower = NULL;
        struct acpi_processor_cx *higher = NULL;
        struct acpi_processor_cx *cx;


        if (!pr)
                return -EINVAL;

        /*
         * This function sets the default Cx state policy (OS idle handler).
         * Our scheme is to promote quickly to C2 but more conservatively
         * to C3.  We're favoring C2  for its characteristics of low latency
         * (quick response), good power savings, and ability to allow bus
         * mastering activity.  Note that the Cx state policy is completely
         * customizable and can be altered dynamically.
         */

        /* startup state */
        for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
                cx = &pr->power.states[i];
                if (!cx->valid)
                        continue;

                if (!state_is_set)
                        pr->power.state = cx;
                state_is_set++;
                break;
        }

        if (!state_is_set)
                return -ENODEV;

        /* demotion */
        for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
                cx = &pr->power.states[i];
                if (!cx->valid)
                        continue;

                if (lower) {
                        cx->demotion.state = lower;
                        cx->demotion.threshold.ticks = cx->latency_ticks;
                        cx->demotion.threshold.count = 1;
                        if (cx->type == ACPI_STATE_C3)
                                cx->demotion.threshold.bm = bm_history;
                }

                lower = cx;
        }

        /* promotion */
        for (i = (ACPI_PROCESSOR_MAX_POWER - 1); i > 0; i--) {
                cx = &pr->power.states[i];
                if (!cx->valid)
                        continue;

                if (higher) {
                        cx->promotion.state = higher;
                        cx->promotion.threshold.ticks = cx->latency_ticks;
                        if (cx->type >= ACPI_STATE_C2)
                                cx->promotion.threshold.count = 4;
                        else
                                cx->promotion.threshold.count = 10;
                        if (higher->type == ACPI_STATE_C3)
                                cx->promotion.threshold.bm = bm_history;
                }

                higher = cx;
        }

        return 0;
}

static int acpi_processor_get_power_info_fadt(struct acpi_processor *pr)
{

        if (!pr)
                return -EINVAL;

        if (!pr->pblk)
                return -ENODEV;

        /* if info is obtained from pblk/fadt, type equals state */
        pr->power.states[ACPI_STATE_C2].type = ACPI_STATE_C2;
        pr->power.states[ACPI_STATE_C3].type = ACPI_STATE_C3;

#ifndef CONFIG_HOTPLUG_CPU
        /*
         * Check for P_LVL2_UP flag before entering C2 and above on
         * an SMP system. 
         */
        if ((num_online_cpus() > 1) && !acpi_fadt.plvl2_up)
                return -ENODEV;
#endif

        /* determine C2 and C3 address from pblk */
        pr->power.states[ACPI_STATE_C2].address = pr->pblk + 4;
        pr->power.states[ACPI_STATE_C3].address = pr->pblk + 5;

        /* determine latencies from FADT */
        pr->power.states[ACPI_STATE_C2].latency = acpi_fadt.plvl2_lat;
        pr->power.states[ACPI_STATE_C3].latency = acpi_fadt.plvl3_lat;

        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                          "lvl2[0x%08x] lvl3[0x%08x]\n",
                          pr->power.states[ACPI_STATE_C2].address,
                          pr->power.states[ACPI_STATE_C3].address));

        return 0;
}

static int acpi_processor_get_power_info_default(struct acpi_processor *pr)
{
        if (!pr->power.states[ACPI_STATE_C1].valid) {
                /* set the first C-State to C1 */
                /* all processors need to support C1 */
                pr->power.states[ACPI_STATE_C1].type = ACPI_STATE_C1;
                pr->power.states[ACPI_STATE_C1].valid = 1;
        }
        /* the C0 state only exists as a filler in our array */
        pr->power.states[ACPI_STATE_C0].valid = 1;
        return 0;
}

static int acpi_processor_get_power_info_cst(struct acpi_processor *pr)
{
        acpi_status status = 0;
        acpi_integer count;
        int current_count;
        int i;
        struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
        union acpi_object *cst;


        if (nocst)
                return -ENODEV;

        current_count = 0;

        status = acpi_evaluate_object(pr->handle, "_CST", NULL, &buffer);
        if (ACPI_FAILURE(status)) {
                ACPI_DEBUG_PRINT((ACPI_DB_INFO, "No _CST, giving up\n"));
                return -ENODEV;
        }

        cst = buffer.pointer;

        /* There must be at least 2 elements */
        if (!cst || (cst->type != ACPI_TYPE_PACKAGE) || cst->package.count < 2) {
                printk(KERN_ERR PREFIX "not enough elements in _CST\n");
                status = -EFAULT;
                goto end;
        }

        count = cst->package.elements[0].integer.value;

        /* Validate number of power states. */
        if (count < 1 || count != cst->package.count - 1) {
                printk(KERN_ERR PREFIX "count given by _CST is not valid\n");
                status = -EFAULT;
                goto end;
        }

        /* Tell driver that at least _CST is supported. */
        pr->flags.has_cst = 1;

        for (i = 1; i <= count; i++) {
                union acpi_object *element;
                union acpi_object *obj;
                struct acpi_power_register *reg;
                struct acpi_processor_cx cx;

                memset(&cx, 0, sizeof(cx));

                element = &(cst->package.elements[i]);
                if (element->type != ACPI_TYPE_PACKAGE)
                        continue;

                if (element->package.count != 4)
                        continue;

                obj = &(element->package.elements[0]);

                if (obj->type != ACPI_TYPE_BUFFER)
                        continue;

                reg = (struct acpi_power_register *)obj->buffer.pointer;

                if (reg->space_id != ACPI_ADR_SPACE_SYSTEM_IO &&
                    (reg->space_id != ACPI_ADR_SPACE_FIXED_HARDWARE))
                        continue;

                /* There should be an easy way to extract an integer... */
                obj = &(element->package.elements[1]);
                if (obj->type != ACPI_TYPE_INTEGER)
                        continue;

                cx.type = obj->integer.value;
                /*
                 * Some buggy BIOSes won't list C1 in _CST -
                 * Let acpi_processor_get_power_info_default() handle them later
                 */
                if (i == 1 && cx.type != ACPI_STATE_C1)
                        current_count++;

                cx.address = reg->address;
                cx.index = current_count + 1;

                cx.space_id = ACPI_CSTATE_SYSTEMIO;
                if (reg->space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) {
                        if (acpi_processor_ffh_cstate_probe
                                        (pr->id, &cx, reg) == 0) {
                                cx.space_id = ACPI_CSTATE_FFH;
                        } else if (cx.type != ACPI_STATE_C1) {
                                /*
                                 * C1 is a special case where FIXED_HARDWARE
                                 * can be handled in non-MWAIT way as well.
                                 * In that case, save this _CST entry info.
                                 * That is, we retain space_id of SYSTEM_IO for
                                 * halt based C1.
                                 * Otherwise, ignore this info and continue.
                                 */
                                continue;
                        }
                }

                obj = &(element->package.elements[2]);
                if (obj->type != ACPI_TYPE_INTEGER)
                        continue;

                cx.latency = obj->integer.value;

                obj = &(element->package.elements[3]);
                if (obj->type != ACPI_TYPE_INTEGER)
                        continue;

                cx.power = obj->integer.value;

                current_count++;
                memcpy(&(pr->power.states[current_count]), &cx, sizeof(cx));

                /*
                 * We support total ACPI_PROCESSOR_MAX_POWER - 1
                 * (From 1 through ACPI_PROCESSOR_MAX_POWER - 1)
                 */
                if (current_count >= (ACPI_PROCESSOR_MAX_POWER - 1)) {
                        printk(KERN_WARNING
                               "Limiting number of power states to max (%d)\n",
                               ACPI_PROCESSOR_MAX_POWER);
                        printk(KERN_WARNING
                               "Please increase ACPI_PROCESSOR_MAX_POWER if needed.\n");
                        break;
                }
        }

        ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Found %d power states\n",
                          current_count));

        /* Validate number of power states discovered */
        if (current_count < 2)
                status = -EFAULT;

      end:
        kfree(buffer.pointer);

        return status;
}

static void acpi_processor_power_verify_c2(struct acpi_processor_cx *cx)
{

        if (!cx->address)
                return;

        /*
         * C2 latency must be less than or equal to 100
         * microseconds.
         */
        else if (cx->latency > ACPI_PROCESSOR_MAX_C2_LATENCY) {
                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                  "latency too large [%d]\n", cx->latency));
                return;
        }

        /*
         * Otherwise we've met all of our C2 requirements.
         * Normalize the C2 latency to expidite policy
         */
        cx->valid = 1;
        cx->latency_ticks = US_TO_PM_TIMER_TICKS(cx->latency);

        return;
}

static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
                                           struct acpi_processor_cx *cx)
{
        static int bm_check_flag;


        if (!cx->address)
                return;

        /*
         * C3 latency must be less than or equal to 1000
         * microseconds.
         */
        else if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY) {
                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                  "latency too large [%d]\n", cx->latency));
                return;
        }

        /*
         * PIIX4 Erratum #18: We don't support C3 when Type-F (fast)
         * DMA transfers are used by any ISA device to avoid livelock.
         * Note that we could disable Type-F DMA (as recommended by
         * the erratum), but this is known to disrupt certain ISA
         * devices thus we take the conservative approach.
         */
        else if (errata.piix4.fdma) {
                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                  "C3 not supported on PIIX4 with Type-F DMA\n"));
                return;
        }

        /* All the logic here assumes flags.bm_check is same across all CPUs */
        if (!bm_check_flag) {
                /* Determine whether bm_check is needed based on CPU  */
                acpi_processor_power_init_bm_check(&(pr->flags), pr->id);
                bm_check_flag = pr->flags.bm_check;
        } else {
                pr->flags.bm_check = bm_check_flag;
        }

        if (pr->flags.bm_check) {
                /* bus mastering control is necessary */
                if (!pr->flags.bm_control) {
                        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                          "C3 support requires bus mastering control\n"));
                        return;
                }
        } else {
                /*
                 * WBINVD should be set in fadt, for C3 state to be
                 * supported on when bm_check is not required.
                 */
                if (acpi_fadt.wb_invd != 1) {
                        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                          "Cache invalidation should work properly"
                                          " for C3 to be enabled on SMP systems\n"));
                        return;
                }
                acpi_set_register(ACPI_BITREG_BUS_MASTER_RLD,
                                  0, ACPI_MTX_DO_NOT_LOCK);
        }

        /*
         * Otherwise we've met all of our C3 requirements.
         * Normalize the C3 latency to expidite policy.  Enable
         * checking of bus mastering status (bm_check) so we can
         * use this in our C3 policy
         */
        cx->valid = 1;
        cx->latency_ticks = US_TO_PM_TIMER_TICKS(cx->latency);

        return;
}

static int acpi_processor_power_verify(struct acpi_processor *pr)
{
        unsigned int i;
        unsigned int working = 0;

#ifdef ARCH_APICTIMER_STOPS_ON_C3
        int timer_broadcast = 0;
        cpumask_t mask = cpumask_of_cpu(pr->id);
        on_each_cpu(switch_ipi_to_APIC_timer, &mask, 1, 1);
#endif

        for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
                struct acpi_processor_cx *cx = &pr->power.states[i];

                switch (cx->type) {
                case ACPI_STATE_C1:
                        cx->valid = 1;
                        break;

                case ACPI_STATE_C2:
                        acpi_processor_power_verify_c2(cx);
#ifdef ARCH_APICTIMER_STOPS_ON_C3
                        /* Some AMD systems fake C3 as C2, but still
                           have timer troubles */
                        if (cx->valid && 
                                boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
                                timer_broadcast++;
#endif
                        break;

                case ACPI_STATE_C3:
                        acpi_processor_power_verify_c3(pr, cx);
#ifdef ARCH_APICTIMER_STOPS_ON_C3
                        if (cx->valid)
                                timer_broadcast++;
#endif
                        break;
                }

                if (cx->valid)
                        working++;
        }

#ifdef ARCH_APICTIMER_STOPS_ON_C3
        if (timer_broadcast)
                on_each_cpu(switch_APIC_timer_to_ipi, &mask, 1, 1);
#endif

        return (working);
}

static int acpi_processor_get_power_info(struct acpi_processor *pr)
{
        unsigned int i;
        int result;


        /* NOTE: the idle thread may not be running while calling
         * this function */

        /* Zero initialize all the C-states info. */
        memset(pr->power.states, 0, sizeof(pr->power.states));

        result = acpi_processor_get_power_info_cst(pr);
        if (result == -ENODEV)
                result = acpi_processor_get_power_info_fadt(pr);

        if (result)
                return result;

        acpi_processor_get_power_info_default(pr);

        pr->power.count = acpi_processor_power_verify(pr);

        /*
         * Set Default Policy
         * ------------------
         * Now that we know which states are supported, set the default
         * policy.  Note that this policy can be changed dynamically
         * (e.g. encourage deeper sleeps to conserve battery life when
         * not on AC).
         */
        result = acpi_processor_set_power_policy(pr);
        if (result)
                return result;

        /*
         * if one state of type C2 or C3 is available, mark this
         * CPU as being "idle manageable"
         */
        for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
                if (pr->power.states[i].valid) {
                        pr->power.count = i;
                        if (pr->power.states[i].type >= ACPI_STATE_C2)
                                pr->flags.power = 1;
                }
        }

        return 0;
}

int acpi_processor_cst_has_changed(struct acpi_processor *pr)
{
        int result = 0;


        if (!pr)
                return -EINVAL;

        if (nocst) {
                return -ENODEV;
        }

        if (!pr->flags.power_setup_done)
                return -ENODEV;

        /* Fall back to the default idle loop */
        pm_idle = pm_idle_save;
        synchronize_sched();    /* Relies on interrupts forcing exit from idle. */

        pr->flags.power = 0;
        result = acpi_processor_get_power_info(pr);
        if ((pr->flags.power == 1) && (pr->flags.power_setup_done))
                pm_idle = acpi_processor_idle;

        return result;
}

/* proc interface */

static int acpi_processor_power_seq_show(struct seq_file *seq, void *offset)
{
        struct acpi_processor *pr = seq->private;
        unsigned int i;


        if (!pr)
                goto end;

        seq_printf(seq, "active state:            C%zd\n"
                   "max_cstate:              C%d\n"
                   "bus master activity:     %08x\n"
                   "maximum allowed latency: %d usec\n",
                   pr->power.state ? pr->power.state - pr->power.states : 0,
                   max_cstate, (unsigned)pr->power.bm_activity,
                   system_latency_constraint());

        seq_puts(seq, "states:\n");

        for (i = 1; i <= pr->power.count; i++) {
                seq_printf(seq, "   %cC%d:                  ",
                           (&pr->power.states[i] ==
                            pr->power.state ? '*' : ' '), i);

                if (!pr->power.states[i].valid) {
                        seq_puts(seq, "<not supported>\n");
                        continue;
                }

                switch (pr->power.states[i].type) {
                case ACPI_STATE_C1:
                        seq_printf(seq, "type[C1] ");
                        break;
                case ACPI_STATE_C2:
                        seq_printf(seq, "type[C2] ");
                        break;
                case ACPI_STATE_C3:
                        seq_printf(seq, "type[C3] ");
                        break;
                default:
                        seq_printf(seq, "type[--] ");
                        break;
                }

                if (pr->power.states[i].promotion.state)
                        seq_printf(seq, "promotion[C%zd] ",
                                   (pr->power.states[i].promotion.state -
                                    pr->power.states));
                else
                        seq_puts(seq, "promotion[--] ");

                if (pr->power.states[i].demotion.state)
                        seq_printf(seq, "demotion[C%zd] ",
                                   (pr->power.states[i].demotion.state -
                                    pr->power.states));
                else
                        seq_puts(seq, "demotion[--] ");

                seq_printf(seq, "latency[%03d] usage[%08d] duration[%020llu]\n",
                           pr->power.states[i].latency,
                           pr->power.states[i].usage,
                           pr->power.states[i].time);
        }

      end:
        return 0;
}

static int acpi_processor_power_open_fs(struct inode *inode, struct file *file)
{
        return single_open(file, acpi_processor_power_seq_show,
                           PDE(inode)->data);
}

static const struct file_operations acpi_processor_power_fops = {
        .open = acpi_processor_power_open_fs,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
};

#ifdef CONFIG_SMP
static void smp_callback(void *v)
{
        /* we already woke the CPU up, nothing more to do */
}

/*
 * This function gets called when a part of the kernel has a new latency
 * requirement.  This means we need to get all processors out of their C-state,
 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 * wakes them all right up.
 */
static int acpi_processor_latency_notify(struct notifier_block *b,
                unsigned long l, void *v)
{
        smp_call_function(smp_callback, NULL, 0, 1);
        return NOTIFY_OK;
}

static struct notifier_block acpi_processor_latency_notifier = {
        .notifier_call = acpi_processor_latency_notify,
};
#endif

int __cpuinit acpi_processor_power_init(struct acpi_processor *pr,
                              struct acpi_device *device)
{
        acpi_status status = 0;
        static int first_run;
        struct proc_dir_entry *entry = NULL;
        unsigned int i;


        if (!first_run) {
                dmi_check_system(processor_power_dmi_table);
                if (max_cstate < ACPI_C_STATES_MAX)
                        printk(KERN_NOTICE
                               "ACPI: processor limited to max C-state %d\n",
                               max_cstate);
                first_run++;
#ifdef CONFIG_SMP
                register_latency_notifier(&acpi_processor_latency_notifier);
#endif
        }

        if (!pr)
                return -EINVAL;

        if (acpi_fadt.cst_cnt && !nocst) {
                status =
                    acpi_os_write_port(acpi_fadt.smi_cmd, acpi_fadt.cst_cnt, 8);
                if (ACPI_FAILURE(status)) {
                        ACPI_EXCEPTION((AE_INFO, status,
                                        "Notifying BIOS of _CST ability failed"));
                }
        }

        acpi_processor_get_power_info(pr);

        /*
         * Install the idle handler if processor power management is supported.
         * Note that we use previously set idle handler will be used on
         * platforms that only support C1.
         */
        if ((pr->flags.power) && (!boot_option_idle_override)) {
                printk(KERN_INFO PREFIX "CPU%d (power states:", pr->id);
                for (i = 1; i <= pr->power.count; i++)
                        if (pr->power.states[i].valid)
                                printk(" C%d[C%d]", i,
                                       pr->power.states[i].type);
                printk(")\n");

                if (pr->id == 0) {
                        pm_idle_save = pm_idle;
                        pm_idle = acpi_processor_idle;
                }
        }

        /* 'power' [R] */
        entry = create_proc_entry(ACPI_PROCESSOR_FILE_POWER,
                                  S_IRUGO, acpi_device_dir(device));
        if (!entry)
                return -EIO;
        else {
                entry->proc_fops = &acpi_processor_power_fops;
                entry->data = acpi_driver_data(device);
                entry->owner = THIS_MODULE;
        }

        pr->flags.power_setup_done = 1;

        return 0;
}

int acpi_processor_power_exit(struct acpi_processor *pr,
                              struct acpi_device *device)
{

        pr->flags.power_setup_done = 0;

        if (acpi_device_dir(device))
                remove_proc_entry(ACPI_PROCESSOR_FILE_POWER,
                                  acpi_device_dir(device));

        /* Unregister the idle handler when processor #0 is removed. */
        if (pr->id == 0) {
                pm_idle = pm_idle_save;

                /*
                 * We are about to unload the current idle thread pm callback
                 * (pm_idle), Wait for all processors to update cached/local
                 * copies of pm_idle before proceeding.
                 */
                cpu_idle_wait();
#ifdef CONFIG_SMP
                unregister_latency_notifier(&acpi_processor_latency_notifier);
#endif
        }

        return 0;
}