/*
 *  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>

static ext_int_info_t ext_int_info_timer;
static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer);

#ifdef CONFIG_VIRT_CPU_ACCOUNTING
/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void account_process_tick(struct task_struct *tsk, int user_tick)
{
        cputime_t cputime;
        __u64 timer, clock;
        int rcu_user_flag;

        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_clock += S390_lowcore.last_update_clock - clock;

        cputime = S390_lowcore.user_timer >> 12;
        rcu_user_flag = cputime != 0;
        S390_lowcore.user_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
        account_user_time(tsk, cputime);

        cputime =  S390_lowcore.system_timer >> 12;
        S390_lowcore.system_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
        account_system_time(tsk, HARDIRQ_OFFSET, cputime);

        cputime = S390_lowcore.steal_clock;
        if ((__s64) cputime > 0) {
                cputime >>= 12;
                S390_lowcore.steal_clock -= cputime << 12;
                account_steal_time(tsk, cputime);
        }
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void account_vtime(struct task_struct *tsk)
{
        cputime_t cputime;
        __u64 timer;

        timer = S390_lowcore.last_update_timer;
        asm volatile ("  STPT %0"    /* Store current cpu timer value */
                      : "=m" (S390_lowcore.last_update_timer) );
        S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

        cputime = S390_lowcore.user_timer >> 12;
        S390_lowcore.user_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
        account_user_time(tsk, cputime);

        cputime =  S390_lowcore.system_timer >> 12;
        S390_lowcore.system_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
        account_system_time(tsk, 0, cputime);
}

/*
 * 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)
{
        cputime_t cputime;
        __u64 timer;

        timer = S390_lowcore.last_update_timer;
        asm volatile ("  STPT %0"    /* Store current cpu timer value */
                      : "=m" (S390_lowcore.last_update_timer) );
        S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

        cputime =  S390_lowcore.system_timer >> 12;
        S390_lowcore.system_timer -= cputime << 12;
        S390_lowcore.steal_clock -= cputime << 12;
        account_system_time(tsk, 0, cputime);
}
EXPORT_SYMBOL_GPL(account_system_vtime);

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;

        /* store expire time for this CPU timer */
        __get_cpu_var(virt_cpu_timer).to_expire = expires;
}
#else
static inline void set_vtimer(__u64 expires)
{
        S390_lowcore.last_update_timer = expires;
        asm volatile ("SPT %0" : : "m" (S390_lowcore.last_update_timer));

        /* store expire time for this CPU timer */
        __get_cpu_var(virt_cpu_timer).to_expire = expires;
}
#endif

void vtime_start_cpu_timer(void)
{
        struct vtimer_queue *vt_list;

        vt_list = &__get_cpu_var(virt_cpu_timer);

        /* CPU timer interrupt is pending, don't reprogramm it */
        if (vt_list->idle & 1LL<<63)
                return;

        if (!list_empty(&vt_list->list))
                set_vtimer(vt_list->idle);
}

void vtime_stop_cpu_timer(void)
{
        struct vtimer_queue *vt_list;

        vt_list = &__get_cpu_var(virt_cpu_timer);

        /* nothing to do */
        if (list_empty(&vt_list->list)) {
                vt_list->idle = VTIMER_MAX_SLICE;
                goto fire;
        }

        /* store the actual expire value */
        asm volatile ("STPT %0" : "=m" (vt_list->idle));

        /*
         * If the CPU timer is negative we don't reprogramm
         * it because we will get instantly an interrupt.
         */
        if (vt_list->idle & 1LL<<63)
                return;

        vt_list->offset += vt_list->to_expire - vt_list->idle;

        /*
         * We cannot halt the CPU timer, we just write a value that
         * nearly never expires (only after 71 years) and re-write
         * the stored expire value if we continue the timer
         */
 fire:
        set_vtimer(VTIMER_MAX_SLICE);
}

/*
 * 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 *vt_list;
        struct vtimer_list *event, *tmp;
        void (*fn)(unsigned long);
        unsigned long data;

        if (list_empty(cb_list))
                return;

        vt_list = &__get_cpu_var(virt_cpu_timer);

        list_for_each_entry_safe(event, tmp, cb_list, entry) {
                fn = event->function;
                data = event->data;
                fn(data);

                if (!event->interval)
                        /* delete one shot timer */
                        list_del_init(&event->entry);
                else {
                        /* move interval timer back to list */
                        spin_lock(&vt_list->lock);
                        list_del_init(&event->entry);
                        list_add_sorted(event, &vt_list->list);
                        spin_unlock(&vt_list->lock);
                }
        }
}

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

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

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

        if (vt_list->to_expire < VTIMER_MAX_SLICE)
                vt_list->offset += vt_list->to_expire;

        list_for_each_entry_safe(event, tmp, &vt_list->list, entry) {
                if (event->expires > vt_list->offset)
                        /* found first unexpired event, leave */
                        break;

                /* re-charge interval timer, we have to add the offset */
                if (event->interval)
                        event->expires = event->interval + vt_list->offset;

                /* move expired timer to the callback queue */
                list_move_tail(&event->entry, &cb_list);
        }
        spin_unlock(&vt_list->lock);
        do_callbacks(&cb_list);

        /* next event is first in list */
        spin_lock(&vt_list->lock);
        if (!list_empty(&vt_list->list)) {
                ptr = vt_list->list.next;
                event = list_entry(ptr, struct vtimer_list, entry);
                next = event->expires - vt_list->offset;

                /* add the expired time from this interrupt handler
                 * and the callback functions
                 */
                asm volatile ("STPT %0" : "=m" (delta));
                delta = 0xffffffffffffffffLL - delta + 1;
                vt_list->offset += delta;
                next -= delta;
        } else {
                vt_list->offset = 0;
                next = VTIMER_MAX_SLICE;
        }
        spin_unlock(&vt_list->lock);
        set_vtimer(next);
}

void init_virt_timer(struct vtimer_list *timer)
{
        timer->function = NULL;
        INIT_LIST_HEAD(&timer->entry);
        spin_lock_init(&timer->lock);
}
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)
{
        unsigned long flags;
        __u64 done;
        struct vtimer_list *event;
        struct vtimer_queue *vt_list;

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

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

        /* if list is empty we only have to set the timer */
        if (list_empty(&vt_list->list)) {
                /* reset the offset, this may happen if the last timer was
                 * just deleted by mod_virt_timer and the interrupt
                 * didn't happen until here
                 */
                vt_list->offset = 0;
                goto fire;
        }

        /* save progress */
        asm volatile ("STPT %0" : "=m" (done));

        /* calculate completed work */
        done = vt_list->to_expire - done + vt_list->offset;
        vt_list->offset = 0;

        list_for_each_entry(event, &vt_list->list, entry)
                event->expires -= done;

 fire:
        list_add_sorted(timer, &vt_list->list);

        /* get first element, which is the next vtimer slice */
        event = list_entry(vt_list->list.next, struct vtimer_list, entry);

        set_vtimer(event->expires);
        spin_unlock_irqrestore(&vt_list->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);

/*
 * If we change a pending timer the function must be called on the CPU
 * where the timer is running on, e.g. by smp_call_function_single()
 *
 * The original mod_timer adds the timer if it is not pending. For compatibility
 * we do the same. The timer will be added on the current CPU as a oneshot timer.
 *
 * returns whether it has modified a pending timer (1) or not (0)
 */
int mod_virt_timer(struct vtimer_list *timer, __u64 expires)
{
        struct vtimer_queue *vt_list;
        unsigned long flags;
        int cpu;

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

        /*
         * This is a common optimization triggered by the
         * networking code - if the timer is re-modified
         * to be the same thing then just return:
         */
        if (timer->expires == expires && vtimer_pending(timer))
                return 1;

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

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

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

        /* if timer isn't pending add it on the current CPU */
        if (!vtimer_pending(timer)) {
                spin_unlock_irqrestore(&vt_list->lock, flags);
                /* we do not activate an interval timer with mod_virt_timer */
                timer->interval = 0;
                timer->expires = expires;
                timer->cpu = cpu;
                internal_add_vtimer(timer);
                return 0;
        }

        list_del_init(&timer->entry);
        timer->expires = expires;

        /* also change the interval if we have an interval timer */
        if (timer->interval)
                timer->interval = expires;

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

/*
 * 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 *vt_list;

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

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

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

        /* last timer removed */
        if (list_empty(&vt_list->list)) {
                vt_list->to_expire = 0;
                vt_list->offset = 0;
        }

        spin_unlock_irqrestore(&vt_list->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 *vt_list;

        /* kick the virtual timer */
        S390_lowcore.exit_timer = VTIMER_MAX_SLICE;
        S390_lowcore.last_update_timer = VTIMER_MAX_SLICE;
        asm volatile ("SPT %0" : : "m" (S390_lowcore.last_update_timer));
        asm volatile ("STCK %0" : "=m" (S390_lowcore.last_update_clock));

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

        vt_list = &__get_cpu_var(virt_cpu_timer);
        INIT_LIST_HEAD(&vt_list->list);
        spin_lock_init(&vt_list->lock);
        vt_list->to_expire = 0;
        vt_list->offset = 0;
        vt_list->idle = 0;

}

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

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