/*
 *  arch/s390/kernel/vtime.c
 *    Virtual cpu timer based timer functions.
 *
 *  S390 version
 *    Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Jan Glauber <jan.glauber@de.ibm.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/types.h>
#include <linux/timex.h>
#include <linux/notifier.h>
#include <linux/kernel_stat.h>
#include <linux/rcupdate.h>
#include <linux/posix-timers.h>

#include <asm/s390_ext.h>
#include <asm/timer.h>
#include <asm/irq_regs.h>
#include <asm/cputime.h>

static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer);

DEFINE_PER_CPU(struct s390_idle_data, s390_idle);

static inline __u64 get_vtimer(void)
{
        __u64 timer;

        asm volatile("STPT %0" : "=m" (timer));
        return timer;
}

static inline void set_vtimer(__u64 expires)
{
        __u64 timer;

        asm volatile ("  STPT %0\n"  /* Store current cpu timer value */
                      "  SPT %1"     /* Set new value immediatly afterwards */
                      : "=m" (timer) : "m" (expires) );
        S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
        S390_lowcore.last_update_timer = expires;
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
static void do_account_vtime(struct task_struct *tsk, int hardirq_offset)
{
        struct thread_info *ti = task_thread_info(tsk);
        __u64 timer, clock, user, system, steal;

        timer = S390_lowcore.last_update_timer;
        clock = S390_lowcore.last_update_clock;
        asm volatile ("  STPT %0\n"    /* Store current cpu timer value */
                      "  STCK %1"      /* Store current tod clock value */
                      : "=m" (S390_lowcore.last_update_timer),
                        "=m" (S390_lowcore.last_update_clock) );
        S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
        S390_lowcore.steal_timer += S390_lowcore.last_update_clock - clock;

        user = S390_lowcore.user_timer - ti->user_timer;
        S390_lowcore.steal_timer -= user;
        ti->user_timer = S390_lowcore.user_timer;
        account_user_time(tsk, user, user);

        system = S390_lowcore.system_timer - ti->system_timer;
        S390_lowcore.steal_timer -= system;
        ti->system_timer = S390_lowcore.system_timer;
        account_system_time(tsk, hardirq_offset, system, system);

        steal = S390_lowcore.steal_timer;
        if ((s64) steal > 0) {
                S390_lowcore.steal_timer = 0;
                account_steal_time(steal);
        }
}

void account_vtime(struct task_struct *prev, struct task_struct *next)
{
        struct thread_info *ti;

        do_account_vtime(prev, 0);
        ti = task_thread_info(prev);
        ti->user_timer = S390_lowcore.user_timer;
        ti->system_timer = S390_lowcore.system_timer;
        ti = task_thread_info(next);
        S390_lowcore.user_timer = ti->user_timer;
        S390_lowcore.system_timer = ti->system_timer;
}

void account_process_tick(struct task_struct *tsk, int user_tick)
{
        do_account_vtime(tsk, HARDIRQ_OFFSET);
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void account_system_vtime(struct task_struct *tsk)
{
        struct thread_info *ti = task_thread_info(tsk);
        __u64 timer, system;

        timer = S390_lowcore.last_update_timer;
        S390_lowcore.last_update_timer = get_vtimer();
        S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

        system = S390_lowcore.system_timer - ti->system_timer;
        S390_lowcore.steal_timer -= system;
        ti->system_timer = S390_lowcore.system_timer;
        account_system_time(tsk, 0, system, system);
}
EXPORT_SYMBOL_GPL(account_system_vtime);

void vtime_start_cpu(void)
{
        struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
        struct vtimer_queue *vq = &__get_cpu_var(virt_cpu_timer);
        __u64 idle_time, expires;

        /* Account time spent with enabled wait psw loaded as idle time. */
        idle_time = S390_lowcore.int_clock - idle->idle_enter;
        account_idle_time(idle_time);
        S390_lowcore.steal_timer +=
                idle->idle_enter - S390_lowcore.last_update_clock;
        S390_lowcore.last_update_clock = S390_lowcore.int_clock;

        /* Account system time spent going idle. */
        S390_lowcore.system_timer += S390_lowcore.last_update_timer - vq->idle;
        S390_lowcore.last_update_timer = S390_lowcore.async_enter_timer;

        /* Restart vtime CPU timer */
        if (vq->do_spt) {
                /* Program old expire value but first save progress. */
                expires = vq->idle - S390_lowcore.async_enter_timer;
                expires += get_vtimer();
                set_vtimer(expires);
        } else {
                /* Don't account the CPU timer delta while the cpu was idle. */
                vq->elapsed -= vq->idle - S390_lowcore.async_enter_timer;
        }

        idle->sequence++;
        smp_wmb();
        idle->idle_time += idle_time;
        idle->idle_enter = 0ULL;
        idle->idle_count++;
        smp_wmb();
        idle->sequence++;
}

void vtime_stop_cpu(void)
{
        struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
        struct vtimer_queue *vq = &__get_cpu_var(virt_cpu_timer);
        psw_t psw;

        /* Wait for external, I/O or machine check interrupt. */
        psw.mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_IO | PSW_MASK_EXT;

        /* Check if the CPU timer needs to be reprogrammed. */
        if (vq->do_spt) {
                __u64 vmax = VTIMER_MAX_SLICE;
                /*
                 * The inline assembly is equivalent to
                 *      vq->idle = get_cpu_timer();
                 *      set_cpu_timer(VTIMER_MAX_SLICE);
                 *      idle->idle_enter = get_clock();
                 *      __load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT |
                 *                         PSW_MASK_IO | PSW_MASK_EXT);
                 * The difference is that the inline assembly makes sure that
                 * the last three instruction are stpt, stck and lpsw in that
                 * order. This is done to increase the precision.
                 */
                asm volatile(
#ifndef CONFIG_64BIT
                        "       basr    1,0\n"
                        "0:     ahi     1,1f-0b\n"
                        "       st      1,4(%2)\n"
#else /* CONFIG_64BIT */
                        "       larl    1,1f\n"
                        "       stg     1,8(%2)\n"
#endif /* CONFIG_64BIT */
                        "       stpt    0(%4)\n"
                        "       spt     0(%5)\n"
                        "       stck    0(%3)\n"
#ifndef CONFIG_64BIT
                        "       lpsw    0(%2)\n"
#else /* CONFIG_64BIT */
                        "       lpswe   0(%2)\n"
#endif /* CONFIG_64BIT */
                        "1:"
                        : "=m" (idle->idle_enter), "=m" (vq->idle)
                        : "a" (&psw), "a" (&idle->idle_enter),
                          "a" (&vq->idle), "a" (&vmax), "m" (vmax), "m" (psw)
                        : "memory", "cc", "1");
        } else {
                /*
                 * The inline assembly is equivalent to
                 *      vq->idle = get_cpu_timer();
                 *      idle->idle_enter = get_clock();
                 *      __load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT |
                 *                         PSW_MASK_IO | PSW_MASK_EXT);
                 * The difference is that the inline assembly makes sure that
                 * the last three instruction are stpt, stck and lpsw in that
                 * order. This is done to increase the precision.
                 */
                asm volatile(
#ifndef CONFIG_64BIT
                        "       basr    1,0\n"
                        "0:     ahi     1,1f-0b\n"
                        "       st      1,4(%2)\n"
#else /* CONFIG_64BIT */
                        "       larl    1,1f\n"
                        "       stg     1,8(%2)\n"
#endif /* CONFIG_64BIT */
                        "       stpt    0(%4)\n"
                        "       stck    0(%3)\n"
#ifndef CONFIG_64BIT
                        "       lpsw    0(%2)\n"
#else /* CONFIG_64BIT */
                        "       lpswe   0(%2)\n"
#endif /* CONFIG_64BIT */
                        "1:"
                        : "=m" (idle->idle_enter), "=m" (vq->idle)
                        : "a" (&psw), "a" (&idle->idle_enter),
                          "a" (&vq->idle), "m" (psw)
                        : "memory", "cc", "1");
        }
}

cputime64_t s390_get_idle_time(int cpu)
{
        struct s390_idle_data *idle;
        unsigned long long now, idle_time, idle_enter;
        unsigned int sequence;

        idle = &per_cpu(s390_idle, cpu);

        now = get_clock();
repeat:
        sequence = idle->sequence;
        smp_rmb();
        if (sequence & 1)
                goto repeat;
        idle_time = 0;
        idle_enter = idle->idle_enter;
        if (idle_enter != 0ULL && idle_enter < now)
                idle_time = now - idle_enter;
        smp_rmb();
        if (idle->sequence != sequence)
                goto repeat;
        return idle_time;
}

/*
 * Sorted add to a list. List is linear searched until first bigger
 * element is found.
 */
static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
{
        struct vtimer_list *event;

        list_for_each_entry(event, head, entry) {
                if (event->expires > timer->expires) {
                        list_add_tail(&timer->entry, &event->entry);
                        return;
                }
        }
        list_add_tail(&timer->entry, head);
}

/*
 * Do the callback functions of expired vtimer events.
 * Called from within the interrupt handler.
 */
static void do_callbacks(struct list_head *cb_list)
{
        struct vtimer_queue *vq;
        struct vtimer_list *event, *tmp;

        if (list_empty(cb_list))
                return;

        vq = &__get_cpu_var(virt_cpu_timer);

        list_for_each_entry_safe(event, tmp, cb_list, entry) {
                list_del_init(&event->entry);
                (event->function)(event->data);
                if (event->interval) {
                        /* Recharge interval timer */
                        event->expires = event->interval + vq->elapsed;
                        spin_lock(&vq->lock);
                        list_add_sorted(event, &vq->list);
                        spin_unlock(&vq->lock);
                }
        }
}

/*
 * Handler for the virtual CPU timer.
 */
static void do_cpu_timer_interrupt(__u16 error_code)
{
        struct vtimer_queue *vq;
        struct vtimer_list *event, *tmp;
        struct list_head cb_list;       /* the callback queue */
        __u64 elapsed, next;

        INIT_LIST_HEAD(&cb_list);
        vq = &__get_cpu_var(virt_cpu_timer);

        /* walk timer list, fire all expired events */
        spin_lock(&vq->lock);

        elapsed = vq->elapsed + (vq->timer - S390_lowcore.async_enter_timer);
        BUG_ON((s64) elapsed < 0);
        vq->elapsed = 0;
        list_for_each_entry_safe(event, tmp, &vq->list, entry) {
                if (event->expires < elapsed)
                        /* move expired timer to the callback queue */
                        list_move_tail(&event->entry, &cb_list);
                else
                        event->expires -= elapsed;
        }
        spin_unlock(&vq->lock);

        vq->do_spt = list_empty(&cb_list);
        do_callbacks(&cb_list);

        /* next event is first in list */
        next = VTIMER_MAX_SLICE;
        spin_lock(&vq->lock);
        if (!list_empty(&vq->list)) {
                event = list_first_entry(&vq->list, struct vtimer_list, entry);
                next = event->expires;
        } else
                vq->do_spt = 0;
        spin_unlock(&vq->lock);
        /*
         * To improve precision add the time spent by the
         * interrupt handler to the elapsed time.
         * Note: CPU timer counts down and we got an interrupt,
         *       the current content is negative
         */
        elapsed = S390_lowcore.async_enter_timer - get_vtimer();
        set_vtimer(next - elapsed);
        vq->timer = next - elapsed;
        vq->elapsed = elapsed;
}

void init_virt_timer(struct vtimer_list *timer)
{
        timer->function = NULL;
        INIT_LIST_HEAD(&timer->entry);
}
EXPORT_SYMBOL(init_virt_timer);

static inline int vtimer_pending(struct vtimer_list *timer)
{
        return (!list_empty(&timer->entry));
}

/*
 * this function should only run on the specified CPU
 */
static void internal_add_vtimer(struct vtimer_list *timer)
{
        struct vtimer_queue *vq;
        unsigned long flags;
        __u64 left, expires;

        vq = &per_cpu(virt_cpu_timer, timer->cpu);
        spin_lock_irqsave(&vq->lock, flags);

        BUG_ON(timer->cpu != smp_processor_id());

        if (list_empty(&vq->list)) {
                /* First timer on this cpu, just program it. */
                list_add(&timer->entry, &vq->list);
                set_vtimer(timer->expires);
                vq->timer = timer->expires;
                vq->elapsed = 0;
        } else {
                /* Check progress of old timers. */
                expires = timer->expires;
                left = get_vtimer();
                if (likely((s64) expires < (s64) left)) {
                        /* The new timer expires before the current timer. */
                        set_vtimer(expires);
                        vq->elapsed += vq->timer - left;
                        vq->timer = expires;
                } else {
                        vq->elapsed += vq->timer - left;
                        vq->timer = left;
                }
                /* Insert new timer into per cpu list. */
                timer->expires += vq->elapsed;
                list_add_sorted(timer, &vq->list);
        }

        spin_unlock_irqrestore(&vq->lock, flags);
        /* release CPU acquired in prepare_vtimer or mod_virt_timer() */
        put_cpu();
}

static inline void prepare_vtimer(struct vtimer_list *timer)
{
        BUG_ON(!timer->function);
        BUG_ON(!timer->expires || timer->expires > VTIMER_MAX_SLICE);
        BUG_ON(vtimer_pending(timer));
        timer->cpu = get_cpu();
}

/*
 * add_virt_timer - add an oneshot virtual CPU timer
 */
void add_virt_timer(void *new)
{
        struct vtimer_list *timer;

        timer = (struct vtimer_list *)new;
        prepare_vtimer(timer);
        timer->interval = 0;
        internal_add_vtimer(timer);
}
EXPORT_SYMBOL(add_virt_timer);

/*
 * add_virt_timer_int - add an interval virtual CPU timer
 */
void add_virt_timer_periodic(void *new)
{
        struct vtimer_list *timer;

        timer = (struct vtimer_list *)new;
        prepare_vtimer(timer);
        timer->interval = timer->expires;
        internal_add_vtimer(timer);
}
EXPORT_SYMBOL(add_virt_timer_periodic);

int __mod_vtimer(struct vtimer_list *timer, __u64 expires, int periodic)
{
        struct vtimer_queue *vq;
        unsigned long flags;
        int cpu;

        BUG_ON(!timer->function);
        BUG_ON(!expires || expires > VTIMER_MAX_SLICE);

        if (timer->expires == expires && vtimer_pending(timer))
                return 1;

        cpu = get_cpu();
        vq = &per_cpu(virt_cpu_timer, cpu);

        /* disable interrupts before test if timer is pending */
        spin_lock_irqsave(&vq->lock, flags);

        /* if timer isn't pending add it on the current CPU */
        if (!vtimer_pending(timer)) {
                spin_unlock_irqrestore(&vq->lock, flags);

                if (periodic)
                        timer->interval = expires;
                else
                        timer->interval = 0;
                timer->expires = expires;
                timer->cpu = cpu;
                internal_add_vtimer(timer);
                return 0;
        }

        /* check if we run on the right CPU */
        BUG_ON(timer->cpu != cpu);

        list_del_init(&timer->entry);
        timer->expires = expires;
        if (periodic)
                timer->interval = expires;

        /* the timer can't expire anymore so we can release the lock */
        spin_unlock_irqrestore(&vq->lock, flags);
        internal_add_vtimer(timer);
        return 1;
}

/*
 * If we change a pending timer the function must be called on the CPU
 * where the timer is running on.
 *
 * returns whether it has modified a pending timer (1) or not (0)
 */
int mod_virt_timer(struct vtimer_list *timer, __u64 expires)
{
        return __mod_vtimer(timer, expires, 0);
}
EXPORT_SYMBOL(mod_virt_timer);

/*
 * If we change a pending timer the function must be called on the CPU
 * where the timer is running on.
 *
 * returns whether it has modified a pending timer (1) or not (0)
 */
int mod_virt_timer_periodic(struct vtimer_list *timer, __u64 expires)
{
        return __mod_vtimer(timer, expires, 1);
}
EXPORT_SYMBOL(mod_virt_timer_periodic);

/*
 * delete a virtual timer
 *
 * returns whether the deleted timer was pending (1) or not (0)
 */
int del_virt_timer(struct vtimer_list *timer)
{
        unsigned long flags;
        struct vtimer_queue *vq;

        /* check if timer is pending */
        if (!vtimer_pending(timer))
                return 0;

        vq = &per_cpu(virt_cpu_timer, timer->cpu);
        spin_lock_irqsave(&vq->lock, flags);

        /* we don't interrupt a running timer, just let it expire! */
        list_del_init(&timer->entry);

        spin_unlock_irqrestore(&vq->lock, flags);
        return 1;
}
EXPORT_SYMBOL(del_virt_timer);

/*
 * Start the virtual CPU timer on the current CPU.
 */
void init_cpu_vtimer(void)
{
        struct vtimer_queue *vq;

        /* initialize per cpu vtimer structure */
        vq = &__get_cpu_var(virt_cpu_timer);
        INIT_LIST_HEAD(&vq->list);
        spin_lock_init(&vq->lock);

        /* enable cpu timer interrupts */
        __ctl_set_bit(0,10);
}

void __init vtime_init(void)
{
        /* request the cpu timer external interrupt */
        if (register_external_interrupt(0x1005, do_cpu_timer_interrupt))
                panic("Couldn't request external interrupt 0x1005");

        /* Enable cpu timer interrupts on the boot cpu. */
        init_cpu_vtimer();
}