/*
 * SiFive HiFive1 AON (Always On Domain) for QEMU.
 *
 * Copyright (c) 2022 SiFive, Inc. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2 or later, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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 "qemu/osdep.h"
#include "qemu/timer.h"
#include "qemu/log.h"
#include "hw/irq.h"
#include "hw/registerfields.h"
#include "hw/misc/sifive_e_aon.h"
#include "qapi/visitor.h"
#include "qapi/error.h"
#include "sysemu/watchdog.h"
#include "hw/qdev-properties.h"

REG32(AON_WDT_WDOGCFG, 0x0)
    FIELD(AON_WDT_WDOGCFG, SCALE, 0, 4)
    FIELD(AON_WDT_WDOGCFG, RSVD0, 4, 4)
    FIELD(AON_WDT_WDOGCFG, RSTEN, 8, 1)
    FIELD(AON_WDT_WDOGCFG, ZEROCMP, 9, 1)
    FIELD(AON_WDT_WDOGCFG, RSVD1, 10, 2)
    FIELD(AON_WDT_WDOGCFG, EN_ALWAYS, 12, 1)
    FIELD(AON_WDT_WDOGCFG, EN_CORE_AWAKE, 13, 1)
    FIELD(AON_WDT_WDOGCFG, RSVD2, 14, 14)
    FIELD(AON_WDT_WDOGCFG, IP0, 28, 1)
    FIELD(AON_WDT_WDOGCFG, RSVD3, 29, 3)
REG32(AON_WDT_WDOGCOUNT, 0x8)
    FIELD(AON_WDT_WDOGCOUNT, VALUE, 0, 31)
REG32(AON_WDT_WDOGS, 0x10)
REG32(AON_WDT_WDOGFEED, 0x18)
REG32(AON_WDT_WDOGKEY, 0x1c)
REG32(AON_WDT_WDOGCMP0, 0x20)

static void sifive_e_aon_wdt_update_wdogcount(SiFiveEAONState *r)
{
    int64_t now;
    if (FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, EN_ALWAYS) == 0 &&
        FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, EN_CORE_AWAKE) == 0) {
        return;
    }

    now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
    r->wdogcount += muldiv64(now - r->wdog_restart_time,
                             r->wdogclk_freq, NANOSECONDS_PER_SECOND);

    /* Clean the most significant bit. */
    r->wdogcount &= R_AON_WDT_WDOGCOUNT_VALUE_MASK;
    r->wdog_restart_time = now;
}

static void sifive_e_aon_wdt_update_state(SiFiveEAONState *r)
{
    uint16_t wdogs;
    bool cmp_signal = false;
    sifive_e_aon_wdt_update_wdogcount(r);
    wdogs = (uint16_t)(r->wdogcount >>
                           FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, SCALE));

    if (wdogs >= r->wdogcmp0) {
        cmp_signal = true;
        if (FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, ZEROCMP) == 1) {
            r->wdogcount = 0;
            wdogs = 0;
        }
    }

    if (cmp_signal) {
        if (FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, RSTEN) == 1) {
            watchdog_perform_action();
        }
        r->wdogcfg = FIELD_DP32(r->wdogcfg, AON_WDT_WDOGCFG, IP0, 1);
    }

    qemu_set_irq(r->wdog_irq, FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, IP0));

    if (wdogs < r->wdogcmp0 &&
        (FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, EN_ALWAYS) == 1 ||
         FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, EN_CORE_AWAKE) == 1)) {
        int64_t next = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        next += muldiv64((r->wdogcmp0 - wdogs) <<
                         FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, SCALE),
                         NANOSECONDS_PER_SECOND, r->wdogclk_freq);
        timer_mod(r->wdog_timer, next);
    } else {
        timer_mod(r->wdog_timer, INT64_MAX);
    }
}

/*
 * Callback used when the timer set using timer_mod expires.
 */
static void sifive_e_aon_wdt_expired_cb(void *opaque)
{
    SiFiveEAONState *r = SIFIVE_E_AON(opaque);
    sifive_e_aon_wdt_update_state(r);
}

static uint64_t
sifive_e_aon_wdt_read(void *opaque, hwaddr addr, unsigned int size)
{
    SiFiveEAONState *r = SIFIVE_E_AON(opaque);

    switch (addr) {
    case A_AON_WDT_WDOGCFG:
        return r->wdogcfg;
    case A_AON_WDT_WDOGCOUNT:
        sifive_e_aon_wdt_update_wdogcount(r);
        return r->wdogcount;
    case A_AON_WDT_WDOGS:
        sifive_e_aon_wdt_update_wdogcount(r);
        return r->wdogcount >>
               FIELD_EX32(r->wdogcfg,
                          AON_WDT_WDOGCFG,
                          SCALE);
    case A_AON_WDT_WDOGFEED:
        return 0;
    case A_AON_WDT_WDOGKEY:
        return r->wdogunlock;
    case A_AON_WDT_WDOGCMP0:
        return r->wdogcmp0;
    default:
        qemu_log_mask(LOG_GUEST_ERROR, "%s: bad read: addr=0x%x\n",
                      __func__, (int)addr);
    }

    return 0;
}

static void
sifive_e_aon_wdt_write(void *opaque, hwaddr addr,
                       uint64_t val64, unsigned int size)
{
    SiFiveEAONState *r = SIFIVE_E_AON(opaque);
    uint32_t value = val64;

    switch (addr) {
    case A_AON_WDT_WDOGCFG: {
        uint8_t new_en_always;
        uint8_t new_en_core_awake;
        uint8_t old_en_always;
        uint8_t old_en_core_awake;
        if (r->wdogunlock == 0) {
            return;
        }

        new_en_always = FIELD_EX32(value, AON_WDT_WDOGCFG, EN_ALWAYS);
        new_en_core_awake = FIELD_EX32(value, AON_WDT_WDOGCFG, EN_CORE_AWAKE);
        old_en_always = FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG, EN_ALWAYS);
        old_en_core_awake = FIELD_EX32(r->wdogcfg, AON_WDT_WDOGCFG,
                                       EN_CORE_AWAKE);

        if ((old_en_always ||
             old_en_core_awake) == 1 &&
            (new_en_always ||
             new_en_core_awake) == 0) {
            sifive_e_aon_wdt_update_wdogcount(r);
        } else if ((old_en_always ||
                    old_en_core_awake) == 0 &&
                   (new_en_always ||
                    new_en_core_awake) == 1) {
            r->wdog_restart_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        }
        r->wdogcfg = value;
        r->wdogunlock = 0;
        break;
    }
    case A_AON_WDT_WDOGCOUNT:
        if (r->wdogunlock == 0) {
            return;
        }
        r->wdogcount = value & R_AON_WDT_WDOGCOUNT_VALUE_MASK;
        r->wdog_restart_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        r->wdogunlock = 0;
        break;
    case A_AON_WDT_WDOGS:
        return;
    case A_AON_WDT_WDOGFEED:
        if (r->wdogunlock == 0) {
            return;
        }
        if (value == SIFIVE_E_AON_WDOGFEED) {
            r->wdogcount = 0;
            r->wdog_restart_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        }
        r->wdogunlock = 0;
        break;
    case A_AON_WDT_WDOGKEY:
        if (value == SIFIVE_E_AON_WDOGKEY) {
            r->wdogunlock = 1;
        }
        break;
    case A_AON_WDT_WDOGCMP0:
        if (r->wdogunlock == 0) {
            return;
        }
        r->wdogcmp0 = (uint16_t) value;
        r->wdogunlock = 0;
        break;
    default:
        qemu_log_mask(LOG_GUEST_ERROR, "%s: bad write: addr=0x%x v=0x%x\n",
                      __func__, (int)addr, (int)value);
    }
    sifive_e_aon_wdt_update_state(r);
}

static uint64_t
sifive_e_aon_read(void *opaque, hwaddr addr, unsigned int size)
{
    if (addr < SIFIVE_E_AON_RTC) {
        return sifive_e_aon_wdt_read(opaque, addr, size);
    } else if (addr < SIFIVE_E_AON_MAX) {
        qemu_log_mask(LOG_UNIMP, "%s: Unimplemented read: addr=0x%x\n",
                      __func__, (int)addr);
    } else {
        qemu_log_mask(LOG_GUEST_ERROR, "%s: bad read: addr=0x%x\n",
                      __func__, (int)addr);
    }
    return 0;
}

static void
sifive_e_aon_write(void *opaque, hwaddr addr,
                   uint64_t val64, unsigned int size)
{
    if (addr < SIFIVE_E_AON_RTC) {
        sifive_e_aon_wdt_write(opaque, addr, val64, size);
    } else if (addr < SIFIVE_E_AON_MAX) {
        qemu_log_mask(LOG_UNIMP, "%s: Unimplemented write: addr=0x%x\n",
                      __func__, (int)addr);
    } else {
        qemu_log_mask(LOG_GUEST_ERROR, "%s: bad write: addr=0x%x\n",
                      __func__, (int)addr);
    }
}

static const MemoryRegionOps sifive_e_aon_ops = {
    .read = sifive_e_aon_read,
    .write = sifive_e_aon_write,
    .endianness = DEVICE_NATIVE_ENDIAN,
    .impl = {
        .min_access_size = 4,
        .max_access_size = 4
    },
    .valid = {
        .min_access_size = 4,
        .max_access_size = 4
    }
};

static void sifive_e_aon_reset(DeviceState *dev)
{
    SiFiveEAONState *r = SIFIVE_E_AON(dev);

    r->wdogcfg = FIELD_DP32(r->wdogcfg, AON_WDT_WDOGCFG, RSTEN, 0);
    r->wdogcfg = FIELD_DP32(r->wdogcfg, AON_WDT_WDOGCFG, EN_ALWAYS, 0);
    r->wdogcfg = FIELD_DP32(r->wdogcfg, AON_WDT_WDOGCFG, EN_CORE_AWAKE, 0);
    r->wdogcmp0 = 0xbeef;

    sifive_e_aon_wdt_update_state(r);
}

static void sifive_e_aon_init(Object *obj)
{
    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
    SiFiveEAONState *r = SIFIVE_E_AON(obj);

    memory_region_init_io(&r->mmio, OBJECT(r), &sifive_e_aon_ops, r,
                          TYPE_SIFIVE_E_AON, SIFIVE_E_AON_MAX);
    sysbus_init_mmio(sbd, &r->mmio);

    /* watchdog timer */
    r->wdog_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
                                 sifive_e_aon_wdt_expired_cb, r);
    r->wdogclk_freq = SIFIVE_E_LFCLK_DEFAULT_FREQ;
    sysbus_init_irq(sbd, &r->wdog_irq);
}

static Property sifive_e_aon_properties[] = {
    DEFINE_PROP_UINT64("wdogclk-frequency", SiFiveEAONState, wdogclk_freq,
                       SIFIVE_E_LFCLK_DEFAULT_FREQ),
    DEFINE_PROP_END_OF_LIST(),
};

static void sifive_e_aon_class_init(ObjectClass *oc, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(oc);

    device_class_set_legacy_reset(dc, sifive_e_aon_reset);
    device_class_set_props(dc, sifive_e_aon_properties);
}

static const TypeInfo sifive_e_aon_info = {
    .name          = TYPE_SIFIVE_E_AON,
    .parent        = TYPE_SYS_BUS_DEVICE,
    .instance_size = sizeof(SiFiveEAONState),
    .instance_init = sifive_e_aon_init,
    .class_init    = sifive_e_aon_class_init,
};

static void sifive_e_aon_register_types(void)
{
    type_register_static(&sifive_e_aon_info);
}

type_init(sifive_e_aon_register_types)