/*
 *  cpuidle-pseries - idle state cpuidle driver.
 *  Adapted from drivers/idle/intel_idle.c and
 *  drivers/acpi/processor_idle.c
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/cpuidle.h>
#include <linux/cpu.h>
#include <linux/notifier.h>

#include <asm/paca.h>
#include <asm/reg.h>
#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/runlatch.h>
#include <asm/plpar_wrappers.h>

struct cpuidle_driver pseries_idle_driver = {
        .name             = "pseries_idle",
        .owner            = THIS_MODULE,
};

static int max_idle_state;
static struct cpuidle_state *cpuidle_state_table;
static u64 snooze_timeout;
static bool snooze_timeout_en;

static inline void idle_loop_prolog(unsigned long *in_purr)
{
        ppc64_runlatch_off();
        *in_purr = mfspr(SPRN_PURR);
        /*
         * Indicate to the HV that we are idle. Now would be
         * a good time to find other work to dispatch.
         */
        get_lppaca()->idle = 1;
}

static inline void idle_loop_epilog(unsigned long in_purr)
{
        u64 wait_cycles;

        wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
        wait_cycles += mfspr(SPRN_PURR) - in_purr;
        get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
        get_lppaca()->idle = 0;

        if (irqs_disabled())
                local_irq_enable();
        ppc64_runlatch_on();
}

static int snooze_loop(struct cpuidle_device *dev,
                        struct cpuidle_driver *drv,
                        int index)
{
        unsigned long in_purr;
        u64 snooze_exit_time;

        idle_loop_prolog(&in_purr);
        local_irq_enable();
        set_thread_flag(TIF_POLLING_NRFLAG);
        snooze_exit_time = get_tb() + snooze_timeout;

        while (!need_resched()) {
                HMT_low();
                HMT_very_low();
                if (snooze_timeout_en && get_tb() > snooze_exit_time)
                        break;
        }

        HMT_medium();
        clear_thread_flag(TIF_POLLING_NRFLAG);
        smp_mb();

        idle_loop_epilog(in_purr);

        return index;
}

static void check_and_cede_processor(void)
{
        /*
         * Ensure our interrupt state is properly tracked,
         * also checks if no interrupt has occurred while we
         * were soft-disabled
         */
        if (prep_irq_for_idle()) {
                cede_processor();
#ifdef CONFIG_TRACE_IRQFLAGS
                /* Ensure that H_CEDE returns with IRQs on */
                if (WARN_ON(!(mfmsr() & MSR_EE)))
                        __hard_irq_enable();
#endif
        }
}

static int dedicated_cede_loop(struct cpuidle_device *dev,
                                struct cpuidle_driver *drv,
                                int index)
{
        unsigned long in_purr;

        idle_loop_prolog(&in_purr);
        get_lppaca()->donate_dedicated_cpu = 1;

        HMT_medium();
        check_and_cede_processor();

        get_lppaca()->donate_dedicated_cpu = 0;

        idle_loop_epilog(in_purr);

        return index;
}

static int shared_cede_loop(struct cpuidle_device *dev,
                        struct cpuidle_driver *drv,
                        int index)
{
        unsigned long in_purr;

        idle_loop_prolog(&in_purr);

        /*
         * Yield the processor to the hypervisor.  We return if
         * an external interrupt occurs (which are driven prior
         * to returning here) or if a prod occurs from another
         * processor. When returning here, external interrupts
         * are enabled.
         */
        check_and_cede_processor();

        idle_loop_epilog(in_purr);

        return index;
}

/*
 * States for dedicated partition case.
 */
static struct cpuidle_state dedicated_states[] = {
        { /* Snooze */
                .name = "snooze",
                .desc = "snooze",
                .exit_latency = 0,
                .target_residency = 0,
                .enter = &snooze_loop },
        { /* CEDE */
                .name = "CEDE",
                .desc = "CEDE",
                .exit_latency = 10,
                .target_residency = 100,
                .enter = &dedicated_cede_loop },
};

/*
 * States for shared partition case.
 */
static struct cpuidle_state shared_states[] = {
        { /* Shared Cede */
                .name = "Shared Cede",
                .desc = "Shared Cede",
                .exit_latency = 0,
                .target_residency = 0,
                .enter = &shared_cede_loop },
};

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

        if (dev && cpuidle_get_driver()) {
                switch (action) {
                case CPU_ONLINE:
                case CPU_ONLINE_FROZEN:
                        cpuidle_pause_and_lock();
                        cpuidle_enable_device(dev);
                        cpuidle_resume_and_unlock();
                        break;

                case CPU_DEAD:
                case CPU_DEAD_FROZEN:
                        cpuidle_pause_and_lock();
                        cpuidle_disable_device(dev);
                        cpuidle_resume_and_unlock();
                        break;

                default:
                        return NOTIFY_DONE;
                }
        }
        return NOTIFY_OK;
}

static struct notifier_block setup_hotplug_notifier = {
        .notifier_call = pseries_cpuidle_add_cpu_notifier,
};

/*
 * pseries_cpuidle_driver_init()
 */
static int pseries_cpuidle_driver_init(void)
{
        int idle_state;
        struct cpuidle_driver *drv = &pseries_idle_driver;

        drv->state_count = 0;

        for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
                /* Is the state not enabled? */
                if (cpuidle_state_table[idle_state].enter == NULL)
                        continue;

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

                drv->state_count += 1;
        }

        return 0;
}

/*
 * pseries_idle_probe()
 * Choose state table for shared versus dedicated partition
 */
static int pseries_idle_probe(void)
{

        if (cpuidle_disable != IDLE_NO_OVERRIDE)
                return -ENODEV;

        if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
                if (lppaca_shared_proc(get_lppaca())) {
                        cpuidle_state_table = shared_states;
                        max_idle_state = ARRAY_SIZE(shared_states);
                } else {
                        cpuidle_state_table = dedicated_states;
                        max_idle_state = ARRAY_SIZE(dedicated_states);
                }
        } else
                return -ENODEV;

        if (max_idle_state > 1) {
                snooze_timeout_en = true;
                snooze_timeout = cpuidle_state_table[1].target_residency *
                                 tb_ticks_per_usec;
        }
        return 0;
}

static int __init pseries_processor_idle_init(void)
{
        int retval;

        retval = pseries_idle_probe();
        if (retval)
                return retval;

        pseries_cpuidle_driver_init();
        retval = cpuidle_register(&pseries_idle_driver, NULL);
        if (retval) {
                printk(KERN_DEBUG "Registration of pseries driver failed.\n");
                return retval;
        }

        register_cpu_notifier(&setup_hotplug_notifier);
        printk(KERN_DEBUG "pseries_idle_driver registered\n");
        return 0;
}

device_initcall(pseries_processor_idle_init);