/*
 * Copyright (C) 2015 Imagination Technologies
 * Author: Alex Smith <alex.smith@imgtec.com>
 *
 * 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;  either version 2 of the  License, or (at your
 * option) any later version.
 */

#include "vdso.h"

#include <linux/compiler.h>
#include <linux/irqchip/mips-gic.h>
#include <linux/time.h>

#include <asm/clocksource.h>
#include <asm/io.h>
#include <asm/mips-cm.h>
#include <asm/unistd.h>
#include <asm/vdso.h>

static __always_inline int do_realtime_coarse(struct timespec *ts,
                                              const union mips_vdso_data *data)
{
        u32 start_seq;

        do {
                start_seq = vdso_data_read_begin(data);

                ts->tv_sec = data->xtime_sec;
                ts->tv_nsec = data->xtime_nsec >> data->cs_shift;
        } while (vdso_data_read_retry(data, start_seq));

        return 0;
}

static __always_inline int do_monotonic_coarse(struct timespec *ts,
                                               const union mips_vdso_data *data)
{
        u32 start_seq;
        u32 to_mono_sec;
        u32 to_mono_nsec;

        do {
                start_seq = vdso_data_read_begin(data);

                ts->tv_sec = data->xtime_sec;
                ts->tv_nsec = data->xtime_nsec >> data->cs_shift;

                to_mono_sec = data->wall_to_mono_sec;
                to_mono_nsec = data->wall_to_mono_nsec;
        } while (vdso_data_read_retry(data, start_seq));

        ts->tv_sec += to_mono_sec;
        timespec_add_ns(ts, to_mono_nsec);

        return 0;
}

#ifdef CONFIG_CSRC_R4K

static __always_inline u64 read_r4k_count(void)
{
        unsigned int count;

        __asm__ __volatile__(
        "       .set push\n"
        "       .set mips32r2\n"
        "       rdhwr   %0, $2\n"
        "       .set pop\n"
        : "=r" (count));

        return count;
}

#endif

#ifdef CONFIG_CLKSRC_MIPS_GIC

static __always_inline u64 read_gic_count(const union mips_vdso_data *data)
{
        void __iomem *gic = get_gic(data);
        u32 hi, hi2, lo;

        do {
                hi = __raw_readl(gic + GIC_UMV_SH_COUNTER_63_32_OFS);
                lo = __raw_readl(gic + GIC_UMV_SH_COUNTER_31_00_OFS);
                hi2 = __raw_readl(gic + GIC_UMV_SH_COUNTER_63_32_OFS);
        } while (hi2 != hi);

        return (((u64)hi) << 32) + lo;
}

#endif

static __always_inline u64 get_ns(const union mips_vdso_data *data)
{
        u64 cycle_now, delta, nsec;

        switch (data->clock_mode) {
#ifdef CONFIG_CSRC_R4K
        case VDSO_CLOCK_R4K:
                cycle_now = read_r4k_count();
                break;
#endif
#ifdef CONFIG_CLKSRC_MIPS_GIC
        case VDSO_CLOCK_GIC:
                cycle_now = read_gic_count(data);
                break;
#endif
        default:
                return 0;
        }

        delta = (cycle_now - data->cs_cycle_last) & data->cs_mask;

        nsec = (delta * data->cs_mult) + data->xtime_nsec;
        nsec >>= data->cs_shift;

        return nsec;
}

static __always_inline int do_realtime(struct timespec *ts,
                                       const union mips_vdso_data *data)
{
        u32 start_seq;
        u64 ns;

        do {
                start_seq = vdso_data_read_begin(data);

                if (data->clock_mode == VDSO_CLOCK_NONE)
                        return -ENOSYS;

                ts->tv_sec = data->xtime_sec;
                ns = get_ns(data);
        } while (vdso_data_read_retry(data, start_seq));

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

        return 0;
}

static __always_inline int do_monotonic(struct timespec *ts,
                                        const union mips_vdso_data *data)
{
        u32 start_seq;
        u64 ns;
        u32 to_mono_sec;
        u32 to_mono_nsec;

        do {
                start_seq = vdso_data_read_begin(data);

                if (data->clock_mode == VDSO_CLOCK_NONE)
                        return -ENOSYS;

                ts->tv_sec = data->xtime_sec;
                ns = get_ns(data);

                to_mono_sec = data->wall_to_mono_sec;
                to_mono_nsec = data->wall_to_mono_nsec;
        } while (vdso_data_read_retry(data, start_seq));

        ts->tv_sec += to_mono_sec;
        ts->tv_nsec = 0;
        timespec_add_ns(ts, ns + to_mono_nsec);

        return 0;
}

#ifdef CONFIG_MIPS_CLOCK_VSYSCALL

/*
 * This is behind the ifdef so that we don't provide the symbol when there's no
 * possibility of there being a usable clocksource, because there's nothing we
 * can do without it. When libc fails the symbol lookup it should fall back on
 * the standard syscall path.
 */
int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
        const union mips_vdso_data *data = get_vdso_data();
        struct timespec ts;
        int ret;

        ret = do_realtime(&ts, data);
        if (ret)
                return ret;

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

        if (tz) {
                tz->tz_minuteswest = data->tz_minuteswest;
                tz->tz_dsttime = data->tz_dsttime;
        }

        return 0;
}

#endif /* CONFIG_CLKSRC_MIPS_GIC */

int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
{
        const union mips_vdso_data *data = get_vdso_data();
        int ret;

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

        /* If we return -ENOSYS libc should fall back to a syscall. */
        return ret;
}