/*
 * 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>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <asm/cpu_device_id.h>
#include <asm/mwait.h>
#include <asm/msr.h>

#define INTEL_IDLE_VERSION "0.4"
#define PREFIX "intel_idle: "

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 unsigned int mwait_substates;

#define LAPIC_TIMER_ALWAYS_RELIABLE 0xFFFFFFFF
/* Reliable LAPIC Timer States, bit 1 for C1 etc.  */
static unsigned int lapic_timer_reliable_states = (1 << 1);      /* Default to only C1 */

struct idle_cpu {
        struct cpuidle_state *state_table;

        /*
         * Hardware C-state auto-demotion may not always be optimal.
         * Indicate which enable bits to clear here.
         */
        unsigned long auto_demotion_disable_flags;
};

static const struct idle_cpu *icpu;
static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
static int intel_idle(struct cpuidle_device *dev,
                        struct cpuidle_driver *drv, int index);
static int intel_idle_cpu_init(int cpu);

static struct cpuidle_state *cpuidle_state_table;

/*
 * Set this flag for states where the HW flushes the TLB for us
 * and so we don't need cross-calls to keep it consistent.
 * If this flag is set, SW flushes the TLB, so even if the
 * HW doesn't do the flushing, this flag is safe to use.
 */
#define CPUIDLE_FLAG_TLB_FLUSHED        0x10000

/*
 * 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 = "C1-NHM",
                .desc = "MWAIT 0x00",
                .flags = CPUIDLE_FLAG_TIME_VALID,
                .exit_latency = 3,
                .target_residency = 6,
                .enter = &intel_idle },
        { /* MWAIT C2 */
                .name = "C3-NHM",
                .desc = "MWAIT 0x10",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 20,
                .target_residency = 80,
                .enter = &intel_idle },
        { /* MWAIT C3 */
                .name = "C6-NHM",
                .desc = "MWAIT 0x20",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 200,
                .target_residency = 800,
                .enter = &intel_idle },
};

static struct cpuidle_state snb_cstates[MWAIT_MAX_NUM_CSTATES] = {
        { /* MWAIT C0 */ },
        { /* MWAIT C1 */
                .name = "C1-SNB",
                .desc = "MWAIT 0x00",
                .flags = CPUIDLE_FLAG_TIME_VALID,
                .exit_latency = 1,
                .target_residency = 1,
                .enter = &intel_idle },
        { /* MWAIT C2 */
                .name = "C3-SNB",
                .desc = "MWAIT 0x10",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 80,
                .target_residency = 211,
                .enter = &intel_idle },
        { /* MWAIT C3 */
                .name = "C6-SNB",
                .desc = "MWAIT 0x20",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 104,
                .target_residency = 345,
                .enter = &intel_idle },
        { /* MWAIT C4 */
                .name = "C7-SNB",
                .desc = "MWAIT 0x30",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 109,
                .target_residency = 345,
                .enter = &intel_idle },
};

static struct cpuidle_state ivb_cstates[MWAIT_MAX_NUM_CSTATES] = {
        { /* MWAIT C0 */ },
        { /* MWAIT C1 */
                .name = "C1-IVB",
                .desc = "MWAIT 0x00",
                .flags = CPUIDLE_FLAG_TIME_VALID,
                .exit_latency = 1,
                .target_residency = 1,
                .enter = &intel_idle },
        { /* MWAIT C2 */
                .name = "C3-IVB",
                .desc = "MWAIT 0x10",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 59,
                .target_residency = 156,
                .enter = &intel_idle },
        { /* MWAIT C3 */
                .name = "C6-IVB",
                .desc = "MWAIT 0x20",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 80,
                .target_residency = 300,
                .enter = &intel_idle },
        { /* MWAIT C4 */
                .name = "C7-IVB",
                .desc = "MWAIT 0x30",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 87,
                .target_residency = 300,
                .enter = &intel_idle },
};

static struct cpuidle_state atom_cstates[MWAIT_MAX_NUM_CSTATES] = {
        { /* MWAIT C0 */ },
        { /* MWAIT C1 */
                .name = "C1-ATM",
                .desc = "MWAIT 0x00",
                .flags = CPUIDLE_FLAG_TIME_VALID,
                .exit_latency = 1,
                .target_residency = 4,
                .enter = &intel_idle },
        { /* MWAIT C2 */
                .name = "C2-ATM",
                .desc = "MWAIT 0x10",
                .flags = CPUIDLE_FLAG_TIME_VALID,
                .exit_latency = 20,
                .target_residency = 80,
                .enter = &intel_idle },
        { /* MWAIT C3 */ },
        { /* MWAIT C4 */
                .name = "C4-ATM",
                .desc = "MWAIT 0x30",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 100,
                .target_residency = 400,
                .enter = &intel_idle },
        { /* MWAIT C5 */ },
        { /* MWAIT C6 */
                .name = "C6-ATM",
                .desc = "MWAIT 0x52",
                .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 140,
                .target_residency = 560,
                .enter = &intel_idle },
};

static long get_driver_data(int cstate)
{
        int driver_data;
        switch (cstate) {

        case 1: /* MWAIT C1 */
                driver_data = 0x00;
                break;
        case 2: /* MWAIT C2 */
                driver_data = 0x10;
                break;
        case 3: /* MWAIT C3 */
                driver_data = 0x20;
                break;
        case 4: /* MWAIT C4 */
                driver_data = 0x30;
                break;
        case 5: /* MWAIT C5 */
                driver_data = 0x40;
                break;
        case 6: /* MWAIT C6 */
                driver_data = 0x52;
                break;
        default:
                driver_data = 0x00;
        }
        return driver_data;
}

/**
 * intel_idle
 * @dev: cpuidle_device
 * @drv: cpuidle driver
 * @index: index of cpuidle state
 *
 * Must be called under local_irq_disable().
 */
static int intel_idle(struct cpuidle_device *dev,
                struct cpuidle_driver *drv, int index)
{
        unsigned long ecx = 1; /* break on interrupt flag */
        struct cpuidle_state *state = &drv->states[index];
        struct cpuidle_state_usage *state_usage = &dev->states_usage[index];
        unsigned long eax = (unsigned long)cpuidle_get_statedata(state_usage);
        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;

        /*
         * leave_mm() to avoid costly and often unnecessary wakeups
         * for flushing the user TLB's associated with the active mm.
         */
        if (state->flags & CPUIDLE_FLAG_TLB_FLUSHED)
                leave_mm(cpu);

        if (!(lapic_timer_reliable_states & (1 << (cstate))))
                clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);

        kt_before = ktime_get_real();

        stop_critical_timings();
        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);

        /* Update cpuidle counters */
        dev->last_residency = (int)usec_delta;

        return index;
}

static void __setup_broadcast_timer(void *arg)
{
        unsigned long reason = (unsigned long)arg;
        int cpu = smp_processor_id();

        reason = reason ?
                CLOCK_EVT_NOTIFY_BROADCAST_ON : CLOCK_EVT_NOTIFY_BROADCAST_OFF;

        clockevents_notify(reason, &cpu);
}

static int cpu_hotplug_notify(struct notifier_block *n,
                              unsigned long action, void *hcpu)
{
        int hotcpu = (unsigned long)hcpu;
        struct cpuidle_device *dev;

        switch (action & 0xf) {
        case CPU_ONLINE:

                if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE)
                        smp_call_function_single(hotcpu, __setup_broadcast_timer,
                                                 (void *)true, 1);

                /*
                 * Some systems can hotplug a cpu at runtime after
                 * the kernel has booted, we have to initialize the
                 * driver in this case
                 */
                dev = per_cpu_ptr(intel_idle_cpuidle_devices, hotcpu);
                if (!dev->registered)
                        intel_idle_cpu_init(hotcpu);

                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block cpu_hotplug_notifier = {
        .notifier_call = cpu_hotplug_notify,
};

static void auto_demotion_disable(void *dummy)
{
        unsigned long long msr_bits;

        rdmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits);
        msr_bits &= ~(icpu->auto_demotion_disable_flags);
        wrmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits);
}

static const struct idle_cpu idle_cpu_nehalem = {
        .state_table = nehalem_cstates,
        .auto_demotion_disable_flags = NHM_C1_AUTO_DEMOTE | NHM_C3_AUTO_DEMOTE,
};

static const struct idle_cpu idle_cpu_atom = {
        .state_table = atom_cstates,
};

static const struct idle_cpu idle_cpu_lincroft = {
        .state_table = atom_cstates,
        .auto_demotion_disable_flags = ATM_LNC_C6_AUTO_DEMOTE,
};

static const struct idle_cpu idle_cpu_snb = {
        .state_table = snb_cstates,
};

static const struct idle_cpu idle_cpu_ivb = {
        .state_table = ivb_cstates,
};

#define ICPU(model, cpu) \
        { X86_VENDOR_INTEL, 6, model, X86_FEATURE_MWAIT, (unsigned long)&cpu }

static const struct x86_cpu_id intel_idle_ids[] = {
        ICPU(0x1a, idle_cpu_nehalem),
        ICPU(0x1e, idle_cpu_nehalem),
        ICPU(0x1f, idle_cpu_nehalem),
        ICPU(0x25, idle_cpu_nehalem),
        ICPU(0x2c, idle_cpu_nehalem),
        ICPU(0x2e, idle_cpu_nehalem),
        ICPU(0x1c, idle_cpu_atom),
        ICPU(0x26, idle_cpu_lincroft),
        ICPU(0x2f, idle_cpu_nehalem),
        ICPU(0x2a, idle_cpu_snb),
        ICPU(0x2d, idle_cpu_snb),
        ICPU(0x3a, idle_cpu_ivb),
        {}
};
MODULE_DEVICE_TABLE(x86cpu, intel_idle_ids);

/*
 * intel_idle_probe()
 */
static int intel_idle_probe(void)
{
        unsigned int eax, ebx, ecx;
        const struct x86_cpu_id *id;

        if (max_cstate == 0) {
                pr_debug(PREFIX "disabled\n");
                return -EPERM;
        }

        id = x86_match_cpu(intel_idle_ids);
        if (!id) {
                if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
                    boot_cpu_data.x86 == 6)
                        pr_debug(PREFIX "does not run on family %d model %d\n",
                                boot_cpu_data.x86, boot_cpu_data.x86_model);
                return -ENODEV;
        }

        if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
                return -ENODEV;

        cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);

        if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
            !(ecx & CPUID5_ECX_INTERRUPT_BREAK) ||
            !mwait_substates)
                        return -ENODEV;

        pr_debug(PREFIX "MWAIT substates: 0x%x\n", mwait_substates);

        icpu = (const struct idle_cpu *)id->driver_data;
        cpuidle_state_table = icpu->state_table;

        if (boot_cpu_has(X86_FEATURE_ARAT))     /* Always Reliable APIC Timer */
                lapic_timer_reliable_states = LAPIC_TIMER_ALWAYS_RELIABLE;
        else
                on_each_cpu(__setup_broadcast_timer, (void *)true, 1);

        register_cpu_notifier(&cpu_hotplug_notifier);

        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_driver_init()
 * allocate, initialize cpuidle_states
 */
static int intel_idle_cpuidle_driver_init(void)
{
        int cstate;
        struct cpuidle_driver *drv = &intel_idle_driver;

        drv->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 = (mwait_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");

                drv->states[drv->state_count] = /* structure copy */
                        cpuidle_state_table[cstate];

                drv->state_count += 1;
        }

        if (icpu->auto_demotion_disable_flags)
                on_each_cpu(auto_demotion_disable, NULL, 1);

        return 0;
}


/*
 * intel_idle_cpu_init()
 * allocate, initialize, register cpuidle_devices
 * @cpu: cpu/core to initialize
 */
static int intel_idle_cpu_init(int cpu)
{
        int cstate;
        struct cpuidle_device *dev;

        dev = per_cpu_ptr(intel_idle_cpuidle_devices, cpu);

        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 = (mwait_substates >> ((cstate) * 4))
                        & MWAIT_SUBSTATE_MASK;
                if (num_substates == 0)
                        continue;
                /* is the state not enabled? */
                if (cpuidle_state_table[cstate].enter == NULL)
                        continue;

                dev->states_usage[dev->state_count].driver_data =
                        (void *)get_driver_data(cstate);

                dev->state_count += 1;
        }

        dev->cpu = cpu;

        if (cpuidle_register_device(dev)) {
                pr_debug(PREFIX "cpuidle_register_device %d failed!\n", cpu);
                intel_idle_cpuidle_devices_uninit();
                return -EIO;
        }

        if (icpu->auto_demotion_disable_flags)
                smp_call_function_single(cpu, auto_demotion_disable, NULL, 1);

        return 0;
}

static int __init intel_idle_init(void)
{
        int retval, i;

        /* Do not load intel_idle at all for now if idle= is passed */
        if (boot_option_idle_override != IDLE_NO_OVERRIDE)
                return -ENODEV;

        retval = intel_idle_probe();
        if (retval)
                return retval;

        intel_idle_cpuidle_driver_init();
        retval = cpuidle_register_driver(&intel_idle_driver);
        if (retval) {
                struct cpuidle_driver *drv = cpuidle_get_driver();
                printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
                        drv ? drv->name : "none");
                return retval;
        }

        intel_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
        if (intel_idle_cpuidle_devices == NULL)
                return -ENOMEM;

        for_each_online_cpu(i) {
                retval = intel_idle_cpu_init(i);
                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);


        if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE)
                on_each_cpu(__setup_broadcast_timer, (void *)false, 1);
        unregister_cpu_notifier(&cpu_hotplug_notifier);

        return;
}

module_init(intel_idle_init);
module_exit(intel_idle_exit);

module_param(max_cstate, int, 0444);

MODULE_AUTHOR("Len Brown <len.brown@intel.com>");
MODULE_DESCRIPTION("Cpuidle driver for Intel Hardware v" INTEL_IDLE_VERSION);
MODULE_LICENSE("GPL");