/*
 * Copyright 2015 Mentor Graphics Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2 of the
 * License.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/compiler.h>
#include <linux/hrtimer.h>
#include <linux/time.h>
#include <asm/barrier.h>
#include <asm/bug.h>
#include <asm/cp15.h>
#include <asm/page.h>
#include <asm/unistd.h>
#include <asm/vdso_datapage.h>

#ifndef CONFIG_AEABI
#error This code depends on AEABI system call conventions
#endif

extern struct vdso_data *__get_datapage(void);

static notrace u32 __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 u32 vdso_read_begin(const struct vdso_data *vdata)
{
        u32 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 timespec *_ts)
{
        register struct timespec *ts asm("r1") = _ts;
        register clockid_t clkid asm("r0") = _clkid;
        register long ret asm ("r0");
        register long nr asm("r7") = __NR_clock_gettime;

        asm volatile(
        "       swi #0\n"
        : "=r" (ret)
        : "r" (clkid), "r" (ts), "r" (nr)
        : "memory");

        return ret;
}

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

        do {
                seq = vdso_read_begin(vdata);

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

                tomono.tv_sec = vdata->wtm_clock_sec;
                tomono.tv_nsec = vdata->wtm_clock_nsec;

        } while (vdso_read_retry(vdata, seq));

        ts->tv_sec += tomono.tv_sec;
        timespec_add_ns(ts, tomono.tv_nsec);

        return 0;
}

#ifdef CONFIG_ARM_ARCH_TIMER

static notrace u64 get_ns(struct vdso_data *vdata)
{
        u64 cycle_delta;
        u64 cycle_now;
        u64 nsec;

        isb();
        cycle_now = read_sysreg(CNTVCT);

        cycle_delta = (cycle_now - vdata->cs_cycle_last) & vdata->cs_mask;

        nsec = (cycle_delta * vdata->cs_mult) + vdata->xtime_clock_snsec;
        nsec >>= vdata->cs_shift;

        return nsec;
}

static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
{
        u64 nsecs;
        u32 seq;

        do {
                seq = vdso_read_begin(vdata);

                if (!vdata->tk_is_cntvct)
                        return -1;

                ts->tv_sec = vdata->xtime_clock_sec;
                nsecs = get_ns(vdata);

        } while (vdso_read_retry(vdata, seq));

        ts->tv_nsec = 0;
        timespec_add_ns(ts, nsecs);

        return 0;
}

static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
{
        struct timespec tomono;
        u64 nsecs;
        u32 seq;

        do {
                seq = vdso_read_begin(vdata);

                if (!vdata->tk_is_cntvct)
                        return -1;

                ts->tv_sec = vdata->xtime_clock_sec;
                nsecs = get_ns(vdata);

                tomono.tv_sec = vdata->wtm_clock_sec;
                tomono.tv_nsec = vdata->wtm_clock_nsec;

        } while (vdso_read_retry(vdata, seq));

        ts->tv_sec += tomono.tv_sec;
        ts->tv_nsec = 0;
        timespec_add_ns(ts, nsecs + tomono.tv_nsec);

        return 0;
}

#else /* CONFIG_ARM_ARCH_TIMER */

static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
{
        return -1;
}

static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
{
        return -1;
}

#endif /* CONFIG_ARM_ARCH_TIMER */

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

        vdata = __get_datapage();

        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 long gettimeofday_fallback(struct timeval *_tv,
                                          struct timezone *_tz)
{
        register struct timezone *tz asm("r1") = _tz;
        register struct timeval *tv asm("r0") = _tv;
        register long ret asm ("r0");
        register long nr asm("r7") = __NR_gettimeofday;

        asm volatile(
        "       swi #0\n"
        : "=r" (ret)
        : "r" (tv), "r" (tz), "r" (nr)
        : "memory");

        return ret;
}

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

        vdata = __get_datapage();

        ret = do_realtime(&ts, vdata);
        if (ret)
                return gettimeofday_fallback(tv, tz);

        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;
}

/* Avoid unresolved references emitted by GCC */

void __aeabi_unwind_cpp_pr0(void)
{
}

void __aeabi_unwind_cpp_pr1(void)
{
}

void __aeabi_unwind_cpp_pr2(void)
{
}