// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2005-2017 Andes Technology Corporation

#include <linux/compiler.h>
#include <linux/hrtimer.h>
#include <linux/time.h>
#include <asm/io.h>
#include <asm/barrier.h>
#include <asm/bug.h>
#include <asm/page.h>
#include <asm/unistd.h>
#include <asm/vdso_datapage.h>
#include <asm/vdso_timer_info.h>
#include <asm/asm-offsets.h>

#define X(x) #x
#define Y(x) X(x)

extern struct vdso_data *__get_datapage(void);
extern struct vdso_data *__get_timerpage(void);

static notrace unsigned int __vdso_read_begin(const struct vdso_data *vdata)
{
        u32 seq;
repeat:
        seq = READ_ONCE(vdata->seq_count);
        if (seq & 1) {
                cpu_relax();
                goto repeat;
        }
        return seq;
}

static notrace unsigned int vdso_read_begin(const struct vdso_data *vdata)
{
        unsigned int seq;

        seq = __vdso_read_begin(vdata);

        smp_rmb();              /* Pairs with smp_wmb in vdso_write_end */
        return seq;
}

static notrace int vdso_read_retry(const struct vdso_data *vdata, u32 start)
{
        smp_rmb();              /* Pairs with smp_wmb in vdso_write_begin */
        return vdata->seq_count != start;
}

static notrace long clock_gettime_fallback(clockid_t _clkid,
                                           struct __kernel_old_timespec *_ts)
{
        register struct __kernel_old_timespec *ts asm("$r1") = _ts;
        register clockid_t clkid asm("$r0") = _clkid;
        register long ret asm("$r0");

        asm volatile ("movi     $r15, %3\n"
                      "syscall  0x0\n"
                      :"=r" (ret)
                      :"r"(clkid), "r"(ts), "i"(__NR_clock_gettime)
                      :"$r15", "memory");

        return ret;
}

static notrace int do_realtime_coarse(struct __kernel_old_timespec *ts,
                                      struct vdso_data *vdata)
{
        u32 seq;

        do {
                seq = vdso_read_begin(vdata);

                ts->tv_sec = vdata->xtime_coarse_sec;
                ts->tv_nsec = vdata->xtime_coarse_nsec;

        } while (vdso_read_retry(vdata, seq));
        return 0;
}

static notrace int do_monotonic_coarse(struct __kernel_old_timespec *ts,
                                       struct vdso_data *vdata)
{
        u32 seq;
        u64 ns;

        do {
                seq = vdso_read_begin(vdata);

                ts->tv_sec = vdata->xtime_coarse_sec + vdata->wtm_clock_sec;
                ns = vdata->xtime_coarse_nsec + vdata->wtm_clock_nsec;

        } while (vdso_read_retry(vdata, seq));

        ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
        ts->tv_nsec = ns;

        return 0;
}

static notrace inline u64 vgetsns(struct vdso_data *vdso)
{
        u32 cycle_now;
        u32 cycle_delta;
        u32 *timer_cycle_base;

        timer_cycle_base =
            (u32 *) ((char *)__get_timerpage() + vdso->cycle_count_offset);
        cycle_now = readl_relaxed(timer_cycle_base);
        if (true == vdso->cycle_count_down)
                cycle_now = ~(*timer_cycle_base);
        cycle_delta = cycle_now - (u32) vdso->cs_cycle_last;
        return ((u64) cycle_delta & vdso->cs_mask) * vdso->cs_mult;
}

static notrace int do_realtime(struct __kernel_old_timespec *ts, struct vdso_data *vdata)
{
        unsigned count;
        u64 ns;
        do {
                count = vdso_read_begin(vdata);
                ts->tv_sec = vdata->xtime_clock_sec;
                ns = vdata->xtime_clock_nsec;
                ns += vgetsns(vdata);
                ns >>= vdata->cs_shift;
        } while (vdso_read_retry(vdata, count));

        ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
        ts->tv_nsec = ns;

        return 0;
}

static notrace int do_monotonic(struct __kernel_old_timespec *ts, struct vdso_data *vdata)
{
        u64 ns;
        u32 seq;

        do {
                seq = vdso_read_begin(vdata);

                ts->tv_sec = vdata->xtime_clock_sec;
                ns = vdata->xtime_clock_nsec;
                ns += vgetsns(vdata);
                ns >>= vdata->cs_shift;

                ts->tv_sec += vdata->wtm_clock_sec;
                ns += vdata->wtm_clock_nsec;

        } while (vdso_read_retry(vdata, seq));

        ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
        ts->tv_nsec = ns;

        return 0;
}

notrace int __vdso_clock_gettime(clockid_t clkid, struct __kernel_old_timespec *ts)
{
        struct vdso_data *vdata;
        int ret = -1;

        vdata = __get_datapage();
        if (vdata->cycle_count_offset == EMPTY_REG_OFFSET)
                return clock_gettime_fallback(clkid, ts);

        switch (clkid) {
        case CLOCK_REALTIME_COARSE:
                ret = do_realtime_coarse(ts, vdata);
                break;
        case CLOCK_MONOTONIC_COARSE:
                ret = do_monotonic_coarse(ts, vdata);
                break;
        case CLOCK_REALTIME:
                ret = do_realtime(ts, vdata);
                break;
        case CLOCK_MONOTONIC:
                ret = do_monotonic(ts, vdata);
                break;
        default:
                break;
        }

        if (ret)
                ret = clock_gettime_fallback(clkid, ts);

        return ret;
}

static notrace int clock_getres_fallback(clockid_t _clk_id,
                                          struct __kernel_old_timespec *_res)
{
        register clockid_t clk_id asm("$r0") = _clk_id;
        register struct __kernel_old_timespec *res asm("$r1") = _res;
        register int ret asm("$r0");

        asm volatile ("movi     $r15, %3\n"
                      "syscall  0x0\n"
                      :"=r" (ret)
                      :"r"(clk_id), "r"(res), "i"(__NR_clock_getres)
                      :"$r15", "memory");

        return ret;
}

notrace int __vdso_clock_getres(clockid_t clk_id, struct __kernel_old_timespec *res)
{
        struct vdso_data *vdata = __get_datapage();

        if (res == NULL)
                return 0;
        switch (clk_id) {
        case CLOCK_REALTIME:
        case CLOCK_MONOTONIC:
        case CLOCK_MONOTONIC_RAW:
                res->tv_sec = 0;
                res->tv_nsec = vdata->hrtimer_res;
                break;
        case CLOCK_REALTIME_COARSE:
        case CLOCK_MONOTONIC_COARSE:
                res->tv_sec = 0;
                res->tv_nsec = CLOCK_COARSE_RES;
                break;
        default:
                return clock_getres_fallback(clk_id, res);
        }
        return 0;
}

static notrace inline int gettimeofday_fallback(struct __kernel_old_timeval *_tv,
                                                struct timezone *_tz)
{
        register struct __kernel_old_timeval *tv asm("$r0") = _tv;
        register struct timezone *tz asm("$r1") = _tz;
        register int ret asm("$r0");

        asm volatile ("movi     $r15, %3\n"
                      "syscall  0x0\n"
                      :"=r" (ret)
                      :"r"(tv), "r"(tz), "i"(__NR_gettimeofday)
                      :"$r15", "memory");

        return ret;
}

notrace int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{
        struct __kernel_old_timespec ts;
        struct vdso_data *vdata;
        int ret;

        vdata = __get_datapage();

        if (vdata->cycle_count_offset == EMPTY_REG_OFFSET)
                return gettimeofday_fallback(tv, tz);

        ret = do_realtime(&ts, vdata);

        if (tv) {
                tv->tv_sec = ts.tv_sec;
                tv->tv_usec = ts.tv_nsec / 1000;
        }
        if (tz) {
                tz->tz_minuteswest = vdata->tz_minuteswest;
                tz->tz_dsttime = vdata->tz_dsttime;
        }

        return ret;
}