[mirror_ubuntu-zesty-kernel.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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */
#define pr_fmt(fmt) "ACPI: " fmt

#include <linux/module.h>
#include <linux/acpi.h>
#include <linux/dmi.h>
#include <linux/sched.h>       /* need_resched() */
#include <linux/tick.h>
#include <linux/cpuidle.h>
#include <acpi/processor.h>

/*
 * Include the apic definitions for x86 to have the APIC timer related defines
 * available also for UP (on SMP it gets magically included via linux/smp.h).
 * asm/acpi.h is not an option, as it would require more include magic. Also
 * creating an empty asm-ia64/apic.h would just trade pest vs. cholera.
 */
#ifdef CONFIG_X86
#include <asm/apic.h>
#endif

#define ACPI_PROCESSOR_CLASS            "processor"
#define _COMPONENT              ACPI_PROCESSOR_COMPONENT
ACPI_MODULE_NAME("processor_idle");

static unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER;
module_param(max_cstate, uint, 0000);
static unsigned int nocst __read_mostly;
module_param(nocst, uint, 0000);
static int bm_check_disable __read_mostly;
module_param(bm_check_disable, uint, 0000);

static unsigned int latency_factor __read_mostly = 2;
module_param(latency_factor, uint, 0644);

static DEFINE_PER_CPU(struct cpuidle_device *, acpi_cpuidle_device);

struct cpuidle_driver acpi_idle_driver = {
        .name =         "acpi_idle",
        .owner =        THIS_MODULE,
};

#ifdef CONFIG_ACPI_PROCESSOR_CSTATE
static
DEFINE_PER_CPU(struct acpi_processor_cx * [CPUIDLE_STATE_MAX], acpi_cstate);

static int disabled_by_idle_boot_param(void)
{
        return boot_option_idle_override == IDLE_POLL ||
                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.
 *
 * To skip this limit, boot/load with a large max_cstate limit.
 */
static int set_max_cstate(const struct dmi_system_id *id)
{
        if (max_cstate > ACPI_PROCESSOR_MAX_POWER)
                return 0;

        pr_notice("%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;
}

static const struct dmi_system_id processor_power_dmi_table[] = {
        { 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},
        { set_max_cstate, "Pavilion zv5000", {
          DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
          DMI_MATCH(DMI_PRODUCT_NAME,"Pavilion zv5000 (DS502A#ABA)")},
         (void *)1},
        { set_max_cstate, "Asus L8400B", {
          DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
          DMI_MATCH(DMI_PRODUCT_NAME,"L8400B series Notebook PC")},
         (void *)1},
        {},
};


/*
 * Callers should disable interrupts before the call and enable
 * interrupts after return.
 */
static void acpi_safe_halt(void)
{
        if (!tif_need_resched()) {
                safe_halt();
                local_irq_disable();
        }
}

#ifdef ARCH_APICTIMER_STOPS_ON_C3

/*
 * Some BIOS implementations switch to C3 in the published C2 state.
 * This seems to be a common problem on AMD boxen, but other vendors
 * are affected too. We pick the most conservative approach: we assume
 * that the local APIC stops in both C2 and C3.
 */
static void lapic_timer_check_state(int state, struct acpi_processor *pr,
                                   struct acpi_processor_cx *cx)
{
        struct acpi_processor_power *pwr = &pr->power;
        u8 type = local_apic_timer_c2_ok ? ACPI_STATE_C3 : ACPI_STATE_C2;

        if (cpu_has(&cpu_data(pr->id), X86_FEATURE_ARAT))
                return;

        if (amd_e400_c1e_detected)
                type = ACPI_STATE_C1;

        /*
         * Check, if one of the previous states already marked the lapic
         * unstable
         */
        if (pwr->timer_broadcast_on_state < state)
                return;

        if (cx->type >= type)
                pr->power.timer_broadcast_on_state = state;
}

static void __lapic_timer_propagate_broadcast(void *arg)
{
        struct acpi_processor *pr = (struct acpi_processor *) arg;

        if (pr->power.timer_broadcast_on_state < INT_MAX)
                tick_broadcast_enable();
        else
                tick_broadcast_disable();
}

static void lapic_timer_propagate_broadcast(struct acpi_processor *pr)
{
        smp_call_function_single(pr->id, __lapic_timer_propagate_broadcast,
                                 (void *)pr, 1);
}

/* Power(C) State timer broadcast control */
static void lapic_timer_state_broadcast(struct acpi_processor *pr,
                                       struct acpi_processor_cx *cx,
                                       int broadcast)
{
        int state = cx - pr->power.states;

        if (state >= pr->power.timer_broadcast_on_state) {
                if (broadcast)
                        tick_broadcast_enter();
                else
                        tick_broadcast_exit();
        }
}

#else

static void lapic_timer_check_state(int state, struct acpi_processor *pr,
                                   struct acpi_processor_cx *cstate) { }
static void lapic_timer_propagate_broadcast(struct acpi_processor *pr) { }
static void lapic_timer_state_broadcast(struct acpi_processor *pr,
                                       struct acpi_processor_cx *cx,
                                       int broadcast)
{
}

#endif

#if defined(CONFIG_X86)
static void tsc_check_state(int state)
{
        switch (boot_cpu_data.x86_vendor) {
        case X86_VENDOR_AMD:
        case X86_VENDOR_INTEL:
                /*
                 * AMD Fam10h TSC will tick in all
                 * C/P/S0/S1 states when this bit is set.
                 */
                if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
                        return;

                /*FALL THROUGH*/
        default:
                /* TSC could halt in idle, so notify users */
                if (state > ACPI_STATE_C1)
                        mark_tsc_unstable("TSC halts in idle");
        }
}
#else
static void tsc_check_state(int state) { return; }
#endif

static int acpi_processor_get_power_info_fadt(struct acpi_processor *pr)
{

        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_gbl_FADT.flags & ACPI_FADT_C2_MP_SUPPORTED))
                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_gbl_FADT.c2_latency;
        pr->power.states[ACPI_STATE_C3].latency = acpi_gbl_FADT.c3_latency;

        /*
         * FADT specified C2 latency must be less than or equal to
         * 100 microseconds.
         */
        if (acpi_gbl_FADT.c2_latency > ACPI_PROCESSOR_MAX_C2_LATENCY) {
                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                        "C2 latency too large [%d]\n", acpi_gbl_FADT.c2_latency));
                /* invalidate C2 */
                pr->power.states[ACPI_STATE_C2].address = 0;
        }

        /*
         * FADT supplied C3 latency must be less than or equal to
         * 1000 microseconds.
         */
        if (acpi_gbl_FADT.c3_latency > ACPI_PROCESSOR_MAX_C3_LATENCY) {
                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                        "C3 latency too large [%d]\n", acpi_gbl_FADT.c3_latency));
                /* invalidate C3 */
                pr->power.states[ACPI_STATE_C3].address = 0;
        }

        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;
                pr->power.states[ACPI_STATE_C1].entry_method = ACPI_CSTATE_HALT;
        }
        /* 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;
        u64 count;
        int current_count;
        int i, ret = 0;
        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) {
                pr_err("not enough elements in _CST\n");
                ret = -EFAULT;
                goto end;
        }

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

        /* Validate number of power states. */
        if (count < 1 || count != cst->package.count - 1) {
                pr_err("count given by _CST is not valid\n");
                ret = -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.entry_method = ACPI_CSTATE_SYSTEMIO;
                if (reg->space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) {
                        if (acpi_processor_ffh_cstate_probe
                                        (pr->id, &cx, reg) == 0) {
                                cx.entry_method = 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.
                                 * Otherwise, ignore this info and continue.
                                 */
                                cx.entry_method = ACPI_CSTATE_HALT;
                                snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
                        } else {
                                continue;
                        }
                        if (cx.type == ACPI_STATE_C1 &&
                            (boot_option_idle_override == IDLE_NOMWAIT)) {
                                /*
                                 * 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.
                                 * When the option of idle=nomwait is added,
                                 * the C1 entry_method type should be
                                 * 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);
                }

                if (cx.type == ACPI_STATE_C1) {
                        cx.valid = 1;
                }

                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;

                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)) {
                        pr_warn("Limiting number of power states to max (%d)\n",
                                ACPI_PROCESSOR_MAX_POWER);
                        pr_warn("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)
                ret = -EFAULT;

      end:
        kfree(buffer.pointer);

        return ret;
}

static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
                                           struct acpi_processor_cx *cx)
{
        static int bm_check_flag = -1;
        static int bm_control_flag = -1;


        if (!cx->address)
                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 == -1) {
                /* 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;
                bm_control_flag = pr->flags.bm_control;
        } else {
                pr->flags.bm_check = bm_check_flag;
                pr->flags.bm_control = bm_control_flag;
        }

        if (pr->flags.bm_check) {
                if (!pr->flags.bm_control) {
                        if (pr->flags.has_cst != 1) {
                                /* bus mastering control is necessary */
                                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                        "C3 support requires BM control\n"));
                                return;
                        } else {
                                /* Here we enter C3 without bus mastering */
                                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                        "C3 support without BM control\n"));
                        }
                }
        } else {
                /*
                 * WBINVD should be set in fadt, for C3 state to be
                 * supported on when bm_check is not required.
                 */
                if (!(acpi_gbl_FADT.flags & ACPI_FADT_WBINVD)) {
                        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                                          "Cache invalidation should work properly"
                                          " for C3 to be enabled on SMP systems\n"));
                        return;
                }
        }

        /*
         * 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;

        /*
         * On older chipsets, BM_RLD needs to be set
         * in order for Bus Master activity to wake the
         * system from C3.  Newer chipsets handle DMA
         * during C3 automatically and BM_RLD is a NOP.
         * In either case, the proper way to
         * handle BM_RLD is to set it and leave it set.
         */
        acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_RLD, 1);

        return;
}

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

        pr->power.timer_broadcast_on_state = INT_MAX;

        for (i = 1; i < ACPI_PROCESSOR_MAX_POWER && i <= max_cstate; 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:
                        if (!cx->address)
                                break;
                        cx->valid = 1;
                        break;

                case ACPI_STATE_C3:
                        acpi_processor_power_verify_c3(pr, cx);
                        break;
                }
                if (!cx->valid)
                        continue;

                lapic_timer_check_state(i, pr, cx);
                tsc_check_state(cx->type);
                working++;
        }

        lapic_timer_propagate_broadcast(pr);

        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);

        /*
         * 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;
}

/**
 * acpi_idle_bm_check - checks if bus master activity was detected
 */
static int acpi_idle_bm_check(void)
{
        u32 bm_status = 0;

        if (bm_check_disable)
                return 0;

        acpi_read_bit_register(ACPI_BITREG_BUS_MASTER_STATUS, &bm_status);
        if (bm_status)
                acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_STATUS, 1);
        /*
         * 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))
                        bm_status = 1;
        }
        return bm_status;
}

/**
 * acpi_idle_do_entry - enter idle state using the appropriate method
 * @cx: cstate data
 *
 * Caller disables interrupt before call and enables interrupt after return.
 */
static void acpi_idle_do_entry(struct acpi_processor_cx *cx)
{
        if (cx->entry_method == ACPI_CSTATE_FFH) {
                /* Call into architectural FFH based C-state */
                acpi_processor_ffh_cstate_enter(cx);
        } else if (cx->entry_method == ACPI_CSTATE_HALT) {
                acpi_safe_halt();
        } else {
                /* IO port based C-state */
                inb(cx->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. */
                inl(acpi_gbl_FADT.xpm_timer_block.address);
        }
}

/**
 * acpi_idle_play_dead - enters an ACPI state for long-term idle (i.e. off-lining)
 * @dev: the target CPU
 * @index: the index of suggested state
 */
static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
{
        struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);

        ACPI_FLUSH_CPU_CACHE();

        while (1) {

                if (cx->entry_method == ACPI_CSTATE_HALT)
                        safe_halt();
                else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) {
                        inb(cx->address);
                        /* See comment in acpi_idle_do_entry() */
                        inl(acpi_gbl_FADT.xpm_timer_block.address);
                } else
                        return -ENODEV;
        }

        /* Never reached */
        return 0;
}

static bool acpi_idle_fallback_to_c1(struct acpi_processor *pr)
{
        return IS_ENABLED(CONFIG_HOTPLUG_CPU) && !pr->flags.has_cst &&
                !(acpi_gbl_FADT.flags & ACPI_FADT_C2_MP_SUPPORTED);
}

static int c3_cpu_count;
static DEFINE_RAW_SPINLOCK(c3_lock);

/**
 * acpi_idle_enter_bm - enters C3 with proper BM handling
 * @pr: Target processor
 * @cx: Target state context
 * @timer_bc: Whether or not to change timer mode to broadcast
 */
static void acpi_idle_enter_bm(struct acpi_processor *pr,
                               struct acpi_processor_cx *cx, bool timer_bc)
{
        acpi_unlazy_tlb(smp_processor_id());

        /*
         * Must be done before busmaster disable as we might need to
         * access HPET !
         */
        if (timer_bc)
                lapic_timer_state_broadcast(pr, cx, 1);

        /*
         * disable bus master
         * bm_check implies we need ARB_DIS
         * bm_control implies whether we can do ARB_DIS
         *
         * That leaves a case where bm_check is set and bm_control is
         * not set. In that case we cannot do much, we enter C3
         * without doing anything.
         */
        if (pr->flags.bm_control) {
                raw_spin_lock(&c3_lock);
                c3_cpu_count++;
                /* Disable bus master arbitration when all CPUs are in C3 */
                if (c3_cpu_count == num_online_cpus())
                        acpi_write_bit_register(ACPI_BITREG_ARB_DISABLE, 1);
                raw_spin_unlock(&c3_lock);
        }

        acpi_idle_do_entry(cx);

        /* Re-enable bus master arbitration */
        if (pr->flags.bm_control) {
                raw_spin_lock(&c3_lock);
                acpi_write_bit_register(ACPI_BITREG_ARB_DISABLE, 0);
                c3_cpu_count--;
                raw_spin_unlock(&c3_lock);
        }

        if (timer_bc)
                lapic_timer_state_broadcast(pr, cx, 0);
}

static int acpi_idle_enter(struct cpuidle_device *dev,
                           struct cpuidle_driver *drv, int index)
{
        struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
        struct acpi_processor *pr;

        pr = __this_cpu_read(processors);
        if (unlikely(!pr))
                return -EINVAL;

        if (cx->type != ACPI_STATE_C1) {
                if (acpi_idle_fallback_to_c1(pr) && num_online_cpus() > 1) {
                        index = CPUIDLE_DRIVER_STATE_START;
                        cx = per_cpu(acpi_cstate[index], dev->cpu);
                } else if (cx->type == ACPI_STATE_C3 && pr->flags.bm_check) {
                        if (cx->bm_sts_skip || !acpi_idle_bm_check()) {
                                acpi_idle_enter_bm(pr, cx, true);
                                return index;
                        } else if (drv->safe_state_index >= 0) {
                                index = drv->safe_state_index;
                                cx = per_cpu(acpi_cstate[index], dev->cpu);
                        } else {
                                acpi_safe_halt();
                                return -EBUSY;
                        }
                }
        }

        lapic_timer_state_broadcast(pr, cx, 1);

        if (cx->type == ACPI_STATE_C3)
                ACPI_FLUSH_CPU_CACHE();

        acpi_idle_do_entry(cx);

        lapic_timer_state_broadcast(pr, cx, 0);

        return index;
}

static void acpi_idle_enter_freeze(struct cpuidle_device *dev,
                                   struct cpuidle_driver *drv, int index)
{
        struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);

        if (cx->type == ACPI_STATE_C3) {
                struct acpi_processor *pr = __this_cpu_read(processors);

                if (unlikely(!pr))
                        return;

                if (pr->flags.bm_check) {
                        acpi_idle_enter_bm(pr, cx, false);
                        return;
                } else {
                        ACPI_FLUSH_CPU_CACHE();
                }
        }
        acpi_idle_do_entry(cx);
}

/**
 * acpi_processor_setup_cpuidle_cx - prepares and configures CPUIDLE
 * device i.e. per-cpu data
 *
 * @pr: the ACPI processor
 * @dev : the cpuidle device
 */
static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
                                           struct cpuidle_device *dev)
{
        int i, count = CPUIDLE_DRIVER_STATE_START;
        struct acpi_processor_cx *cx;

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

        if (pr->flags.power == 0) {
                return -EINVAL;
        }

        if (!dev)
                return -EINVAL;

        dev->cpu = pr->id;

        if (max_cstate == 0)
                max_cstate = 1;

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

                if (!cx->valid)
                        continue;

                per_cpu(acpi_cstate[count], dev->cpu) = cx;

                count++;
                if (count == CPUIDLE_STATE_MAX)
                        break;
        }

        if (!count)
                return -EINVAL;

        return 0;
}

/**
 * acpi_processor_setup_cpuidle states- prepares and configures cpuidle
 * global state data i.e. idle routines
 *
 * @pr: the ACPI processor
 */
static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
{
        int i, count = CPUIDLE_DRIVER_STATE_START;
        struct acpi_processor_cx *cx;
        struct cpuidle_state *state;
        struct cpuidle_driver *drv = &acpi_idle_driver;

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

        if (pr->flags.power == 0)
                return -EINVAL;

        drv->safe_state_index = -1;
        for (i = CPUIDLE_DRIVER_STATE_START; i < CPUIDLE_STATE_MAX; i++) {
                drv->states[i].name[0] = '\0';
                drv->states[i].desc[0] = '\0';
        }

        if (max_cstate == 0)
                max_cstate = 1;

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

                if (!cx->valid)
                        continue;

                state = &drv->states[count];
                snprintf(state->name, CPUIDLE_NAME_LEN, "C%d", i);
                strncpy(state->desc, cx->desc, CPUIDLE_DESC_LEN);
                state->exit_latency = cx->latency;
                state->target_residency = cx->latency * latency_factor;
                state->enter = acpi_idle_enter;

                state->flags = 0;
                if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2) {
                        state->enter_dead = acpi_idle_play_dead;
                        drv->safe_state_index = count;
                }
                /*
                 * Halt-induced C1 is not good for ->enter_freeze, because it
                 * re-enables interrupts on exit.  Moreover, C1 is generally not
                 * particularly interesting from the suspend-to-idle angle, so
                 * avoid C1 and the situations in which we may need to fall back
                 * to it altogether.
                 */
                if (cx->type != ACPI_STATE_C1 && !acpi_idle_fallback_to_c1(pr))
                        state->enter_freeze = acpi_idle_enter_freeze;

                count++;
                if (count == CPUIDLE_STATE_MAX)
                        break;
        }

        drv->state_count = count;

        if (!count)
                return -EINVAL;

        return 0;
}

static inline void acpi_processor_cstate_first_run_checks(void)
{
        acpi_status status;
        static int first_run;

        if (first_run)
                return;
        dmi_check_system(processor_power_dmi_table);
        max_cstate = acpi_processor_cstate_check(max_cstate);
        if (max_cstate < ACPI_C_STATES_MAX)
                pr_notice("ACPI: processor limited to max C-state %d\n",
                          max_cstate);
        first_run++;

        if (acpi_gbl_FADT.cst_control && !nocst) {
                status = acpi_os_write_port(acpi_gbl_FADT.smi_command,
                                            acpi_gbl_FADT.cst_control, 8);
                if (ACPI_FAILURE(status))
                        ACPI_EXCEPTION((AE_INFO, status,
                                        "Notifying BIOS of _CST ability failed"));
        }
}
#else

static inline int disabled_by_idle_boot_param(void) { return 0; }
static inline void acpi_processor_cstate_first_run_checks(void) { }
static int acpi_processor_get_power_info(struct acpi_processor *pr)
{
        return -ENODEV;
}

static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
                                           struct cpuidle_device *dev)
{
        return -EINVAL;
}

static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
{
        return -EINVAL;
}

#endif /* CONFIG_ACPI_PROCESSOR_CSTATE */

int acpi_processor_hotplug(struct acpi_processor *pr)
{
        int ret = 0;
        struct cpuidle_device *dev;

        if (disabled_by_idle_boot_param())
                return 0;

        if (nocst)
                return -ENODEV;

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

        dev = per_cpu(acpi_cpuidle_device, pr->id);
        cpuidle_pause_and_lock();
        cpuidle_disable_device(dev);
        acpi_processor_get_power_info(pr);
        if (pr->flags.power) {
                acpi_processor_setup_cpuidle_cx(pr, dev);
                ret = cpuidle_enable_device(dev);
        }
        cpuidle_resume_and_unlock();

        return ret;
}

int acpi_processor_cst_has_changed(struct acpi_processor *pr)
{
        int cpu;
        struct acpi_processor *_pr;
        struct cpuidle_device *dev;

        if (disabled_by_idle_boot_param())
                return 0;

        if (nocst)
                return -ENODEV;

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

        /*
         * FIXME:  Design the ACPI notification to make it once per
         * system instead of once per-cpu.  This condition is a hack
         * to make the code that updates C-States be called once.
         */

        if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) {

                /* Protect against cpu-hotplug */
                get_online_cpus();
                cpuidle_pause_and_lock();

                /* Disable all cpuidle devices */
                for_each_online_cpu(cpu) {
                        _pr = per_cpu(processors, cpu);
                        if (!_pr || !_pr->flags.power_setup_done)
                                continue;
                        dev = per_cpu(acpi_cpuidle_device, cpu);
                        cpuidle_disable_device(dev);
                }

                /* Populate Updated C-state information */
                acpi_processor_get_power_info(pr);
                acpi_processor_setup_cpuidle_states(pr);

                /* Enable all cpuidle devices */
                for_each_online_cpu(cpu) {
                        _pr = per_cpu(processors, cpu);
                        if (!_pr || !_pr->flags.power_setup_done)
                                continue;
                        acpi_processor_get_power_info(_pr);
                        if (_pr->flags.power) {
                                dev = per_cpu(acpi_cpuidle_device, cpu);
                                acpi_processor_setup_cpuidle_cx(_pr, dev);
                                cpuidle_enable_device(dev);
                        }
                }
                cpuidle_resume_and_unlock();
                put_online_cpus();
        }

        return 0;
}

static int acpi_processor_registered;

int acpi_processor_power_init(struct acpi_processor *pr)
{
        int retval;
        struct cpuidle_device *dev;

        if (disabled_by_idle_boot_param())
                return 0;

        acpi_processor_cstate_first_run_checks();

        if (!acpi_processor_get_power_info(pr))
                pr->flags.power_setup_done = 1;

        /*
         * 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) {
                /* Register acpi_idle_driver if not already registered */
                if (!acpi_processor_registered) {
                        acpi_processor_setup_cpuidle_states(pr);
                        retval = cpuidle_register_driver(&acpi_idle_driver);
                        if (retval)
                                return retval;
                        pr_debug("%s registered with cpuidle\n",
                                 acpi_idle_driver.name);
                }

                dev = kzalloc(sizeof(*dev), GFP_KERNEL);
                if (!dev)
                        return -ENOMEM;
                per_cpu(acpi_cpuidle_device, pr->id) = dev;

                acpi_processor_setup_cpuidle_cx(pr, dev);

                /* Register per-cpu cpuidle_device. Cpuidle driver
                 * must already be registered before registering device
                 */
                retval = cpuidle_register_device(dev);
                if (retval) {
                        if (acpi_processor_registered == 0)
                                cpuidle_unregister_driver(&acpi_idle_driver);
                        return retval;
                }
                acpi_processor_registered++;
        }
        return 0;
}

int acpi_processor_power_exit(struct acpi_processor *pr)
{
        struct cpuidle_device *dev = per_cpu(acpi_cpuidle_device, pr->id);

        if (disabled_by_idle_boot_param())
                return 0;

        if (pr->flags.power) {
                cpuidle_unregister_device(dev);
                acpi_processor_registered--;
                if (acpi_processor_registered == 0)
                        cpuidle_unregister_driver(&acpi_idle_driver);
        }

        pr->flags.power_setup_done = 0;
        return 0;
}