// SPDX-License-Identifier: GPL-2.0
/*
 *    Virtual cpu timer based timer functions.
 *
 *    Copyright IBM Corp. 2004, 2012
 *    Author(s): Jan Glauber <jan.glauber@de.ibm.com>
 */

#include <linux/kernel_stat.h>
#include <linux/sched/cputime.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/timex.h>
#include <linux/types.h>
#include <linux/time.h>

#include <asm/vtimer.h>
#include <asm/vtime.h>
#include <asm/cpu_mf.h>
#include <asm/smp.h>

#include "entry.h"

static void virt_timer_expire(void);

static LIST_HEAD(virt_timer_list);
static DEFINE_SPINLOCK(virt_timer_lock);
static atomic64_t virt_timer_current;
static atomic64_t virt_timer_elapsed;

DEFINE_PER_CPU(u64, mt_cycles[8]);
static DEFINE_PER_CPU(u64, mt_scaling_mult) = { 1 };
static DEFINE_PER_CPU(u64, mt_scaling_div) = { 1 };
static DEFINE_PER_CPU(u64, mt_scaling_jiffies);

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 imm. afterwards */
                : "=m" (timer) : "m" (expires));
        S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
        S390_lowcore.last_update_timer = expires;
}

static inline int virt_timer_forward(u64 elapsed)
{
        BUG_ON(!irqs_disabled());

        if (list_empty(&virt_timer_list))
                return 0;
        elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
        return elapsed >= atomic64_read(&virt_timer_current);
}

static void update_mt_scaling(void)
{
        u64 cycles_new[8], *cycles_old;
        u64 delta, fac, mult, div;
        int i;

        stcctm5(smp_cpu_mtid + 1, cycles_new);
        cycles_old = this_cpu_ptr(mt_cycles);
        fac = 1;
        mult = div = 0;
        for (i = 0; i <= smp_cpu_mtid; i++) {
                delta = cycles_new[i] - cycles_old[i];
                div += delta;
                mult *= i + 1;
                mult += delta * fac;
                fac *= i + 1;
        }
        div *= fac;
        if (div > 0) {
                /* Update scaling factor */
                __this_cpu_write(mt_scaling_mult, mult);
                __this_cpu_write(mt_scaling_div, div);
                memcpy(cycles_old, cycles_new,
                       sizeof(u64) * (smp_cpu_mtid + 1));
        }
        __this_cpu_write(mt_scaling_jiffies, jiffies_64);
}

static inline u64 update_tsk_timer(unsigned long *tsk_vtime, u64 new)
{
        u64 delta;

        delta = new - *tsk_vtime;
        *tsk_vtime = new;
        return delta;
}


static inline u64 scale_vtime(u64 vtime)
{
        u64 mult = __this_cpu_read(mt_scaling_mult);
        u64 div = __this_cpu_read(mt_scaling_div);

        if (smp_cpu_mtid)
                return vtime * mult / div;
        return vtime;
}

static void account_system_index_scaled(struct task_struct *p, u64 cputime,
                                        enum cpu_usage_stat index)
{
        p->stimescaled += cputime_to_nsecs(scale_vtime(cputime));
        account_system_index_time(p, cputime_to_nsecs(cputime), index);
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
static int do_account_vtime(struct task_struct *tsk)
{
        u64 timer, clock, user, guest, system, hardirq, softirq, steal;

        timer = S390_lowcore.last_update_timer;
        clock = S390_lowcore.last_update_clock;
        asm volatile(
                "       stpt    %0\n"   /* Store current cpu timer value */
#ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES
                "       stckf   %1"     /* Store current tod clock value */
#else
                "       stck    %1"     /* Store current tod clock value */
#endif
                : "=m" (S390_lowcore.last_update_timer),
                  "=m" (S390_lowcore.last_update_clock));
        clock = S390_lowcore.last_update_clock - clock;
        timer -= S390_lowcore.last_update_timer;

        if (hardirq_count())
                S390_lowcore.hardirq_timer += timer;
        else
                S390_lowcore.system_timer += timer;

        /* Update MT utilization calculation */
        if (smp_cpu_mtid &&
            time_after64(jiffies_64, this_cpu_read(mt_scaling_jiffies)))
                update_mt_scaling();

        /* Calculate cputime delta */
        user = update_tsk_timer(&tsk->thread.user_timer,
                                READ_ONCE(S390_lowcore.user_timer));
        guest = update_tsk_timer(&tsk->thread.guest_timer,
                                 READ_ONCE(S390_lowcore.guest_timer));
        system = update_tsk_timer(&tsk->thread.system_timer,
                                  READ_ONCE(S390_lowcore.system_timer));
        hardirq = update_tsk_timer(&tsk->thread.hardirq_timer,
                                   READ_ONCE(S390_lowcore.hardirq_timer));
        softirq = update_tsk_timer(&tsk->thread.softirq_timer,
                                   READ_ONCE(S390_lowcore.softirq_timer));
        S390_lowcore.steal_timer +=
                clock - user - guest - system - hardirq - softirq;

        /* Push account value */
        if (user) {
                account_user_time(tsk, cputime_to_nsecs(user));
                tsk->utimescaled += cputime_to_nsecs(scale_vtime(user));
        }

        if (guest) {
                account_guest_time(tsk, cputime_to_nsecs(guest));
                tsk->utimescaled += cputime_to_nsecs(scale_vtime(guest));
        }

        if (system)
                account_system_index_scaled(tsk, system, CPUTIME_SYSTEM);
        if (hardirq)
                account_system_index_scaled(tsk, hardirq, CPUTIME_IRQ);
        if (softirq)
                account_system_index_scaled(tsk, softirq, CPUTIME_SOFTIRQ);

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

        return virt_timer_forward(user + guest + system + hardirq + softirq);
}

void vtime_task_switch(struct task_struct *prev)
{
        do_account_vtime(prev);
        prev->thread.user_timer = S390_lowcore.user_timer;
        prev->thread.guest_timer = S390_lowcore.guest_timer;
        prev->thread.system_timer = S390_lowcore.system_timer;
        prev->thread.hardirq_timer = S390_lowcore.hardirq_timer;
        prev->thread.softirq_timer = S390_lowcore.softirq_timer;
        S390_lowcore.user_timer = current->thread.user_timer;
        S390_lowcore.guest_timer = current->thread.guest_timer;
        S390_lowcore.system_timer = current->thread.system_timer;
        S390_lowcore.hardirq_timer = current->thread.hardirq_timer;
        S390_lowcore.softirq_timer = current->thread.softirq_timer;
}

/*
 * In s390, accounting pending user time also implies
 * accounting system time in order to correctly compute
 * the stolen time accounting.
 */
void vtime_flush(struct task_struct *tsk)
{
        if (do_account_vtime(tsk))
                virt_timer_expire();
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void vtime_account_irq_enter(struct task_struct *tsk)
{
        u64 timer;

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

        if ((tsk->flags & PF_VCPU) && (irq_count() == 0))
                S390_lowcore.guest_timer += timer;
        else if (hardirq_count())
                S390_lowcore.hardirq_timer += timer;
        else if (in_serving_softirq())
                S390_lowcore.softirq_timer += timer;
        else
                S390_lowcore.system_timer += timer;

        virt_timer_forward(timer);
}
EXPORT_SYMBOL_GPL(vtime_account_irq_enter);

void vtime_account_system(struct task_struct *tsk)
__attribute__((alias("vtime_account_irq_enter")));
EXPORT_SYMBOL_GPL(vtime_account_system);

/*
 * 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 *tmp;

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

/*
 * Handler for expired virtual CPU timer.
 */
static void virt_timer_expire(void)
{
        struct vtimer_list *timer, *tmp;
        unsigned long elapsed;
        LIST_HEAD(cb_list);

        /* walk timer list, fire all expired timers */
        spin_lock(&virt_timer_lock);
        elapsed = atomic64_read(&virt_timer_elapsed);
        list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
                if (timer->expires < elapsed)
                        /* move expired timer to the callback queue */
                        list_move_tail(&timer->entry, &cb_list);
                else
                        timer->expires -= elapsed;
        }
        if (!list_empty(&virt_timer_list)) {
                timer = list_first_entry(&virt_timer_list,
                                         struct vtimer_list, entry);
                atomic64_set(&virt_timer_current, timer->expires);
        }
        atomic64_sub(elapsed, &virt_timer_elapsed);
        spin_unlock(&virt_timer_lock);

        /* Do callbacks and recharge periodic timers */
        list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
                list_del_init(&timer->entry);
                timer->function(timer->data);
                if (timer->interval) {
                        /* Recharge interval timer */
                        timer->expires = timer->interval +
                                atomic64_read(&virt_timer_elapsed);
                        spin_lock(&virt_timer_lock);
                        list_add_sorted(timer, &virt_timer_list);
                        spin_unlock(&virt_timer_lock);
                }
        }
}

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);
}

static void internal_add_vtimer(struct vtimer_list *timer)
{
        if (list_empty(&virt_timer_list)) {
                /* First timer, just program it. */
                atomic64_set(&virt_timer_current, timer->expires);
                atomic64_set(&virt_timer_elapsed, 0);
                list_add(&timer->entry, &virt_timer_list);
        } else {
                /* Update timer against current base. */
                timer->expires += atomic64_read(&virt_timer_elapsed);
                if (likely((s64) timer->expires <
                           (s64) atomic64_read(&virt_timer_current)))
                        /* The new timer expires before the current timer. */
                        atomic64_set(&virt_timer_current, timer->expires);
                /* Insert new timer into the list. */
                list_add_sorted(timer, &virt_timer_list);
        }
}

static void __add_vtimer(struct vtimer_list *timer, int periodic)
{
        unsigned long flags;

        timer->interval = periodic ? timer->expires : 0;
        spin_lock_irqsave(&virt_timer_lock, flags);
        internal_add_vtimer(timer);
        spin_unlock_irqrestore(&virt_timer_lock, flags);
}

/*
 * add_virt_timer - add a oneshot virtual CPU timer
 */
void add_virt_timer(struct vtimer_list *timer)
{
        __add_vtimer(timer, 0);
}
EXPORT_SYMBOL(add_virt_timer);

/*
 * add_virt_timer_int - add an interval virtual CPU timer
 */
void add_virt_timer_periodic(struct vtimer_list *timer)
{
        __add_vtimer(timer, 1);
}
EXPORT_SYMBOL(add_virt_timer_periodic);

static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
{
        unsigned long flags;
        int rc;

        BUG_ON(!timer->function);

        if (timer->expires == expires && vtimer_pending(timer))
                return 1;
        spin_lock_irqsave(&virt_timer_lock, flags);
        rc = vtimer_pending(timer);
        if (rc)
                list_del_init(&timer->entry);
        timer->interval = periodic ? expires : 0;
        timer->expires = expires;
        internal_add_vtimer(timer);
        spin_unlock_irqrestore(&virt_timer_lock, flags);
        return rc;
}

/*
 * 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);

/*
 * 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;

        if (!vtimer_pending(timer))
                return 0;
        spin_lock_irqsave(&virt_timer_lock, flags);
        list_del_init(&timer->entry);
        spin_unlock_irqrestore(&virt_timer_lock, flags);
        return 1;
}
EXPORT_SYMBOL(del_virt_timer);

/*
 * Start the virtual CPU timer on the current CPU.
 */
void vtime_init(void)
{
        /* set initial cpu timer */
        set_vtimer(VTIMER_MAX_SLICE);
        /* Setup initial MT scaling values */
        if (smp_cpu_mtid) {
                __this_cpu_write(mt_scaling_jiffies, jiffies);
                __this_cpu_write(mt_scaling_mult, 1);
                __this_cpu_write(mt_scaling_div, 1);
                stcctm5(smp_cpu_mtid + 1, this_cpu_ptr(mt_cycles));
        }
}