// SPDX-License-Identifier: GPL-2.0

#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/goldfish.h>
#include <clocksource/timer-goldfish.h>

struct goldfish_timer {
        struct clocksource cs;
        struct clock_event_device ced;
        struct resource res;
        void __iomem *base;
};

static struct goldfish_timer *ced_to_gf(struct clock_event_device *ced)
{
        return container_of(ced, struct goldfish_timer, ced);
}

static struct goldfish_timer *cs_to_gf(struct clocksource *cs)
{
        return container_of(cs, struct goldfish_timer, cs);
}

static u64 goldfish_timer_read(struct clocksource *cs)
{
        struct goldfish_timer *timerdrv = cs_to_gf(cs);
        void __iomem *base = timerdrv->base;
        u32 time_low, time_high;
        u64 ticks;

        /*
         * time_low: get low bits of current time and update time_high
         * time_high: get high bits of time at last time_low read
         */
        time_low = gf_ioread32(base + TIMER_TIME_LOW);
        time_high = gf_ioread32(base + TIMER_TIME_HIGH);

        ticks = ((u64)time_high << 32) | time_low;

        return ticks;
}

static int goldfish_timer_set_oneshot(struct clock_event_device *evt)
{
        struct goldfish_timer *timerdrv = ced_to_gf(evt);
        void __iomem *base = timerdrv->base;

        gf_iowrite32(0, base + TIMER_ALARM_HIGH);
        gf_iowrite32(0, base + TIMER_ALARM_LOW);
        gf_iowrite32(1, base + TIMER_IRQ_ENABLED);

        return 0;
}

static int goldfish_timer_shutdown(struct clock_event_device *evt)
{
        struct goldfish_timer *timerdrv = ced_to_gf(evt);
        void __iomem *base = timerdrv->base;

        gf_iowrite32(0, base + TIMER_IRQ_ENABLED);

        return 0;
}

static int goldfish_timer_next_event(unsigned long delta,
                                     struct clock_event_device *evt)
{
        struct goldfish_timer *timerdrv = ced_to_gf(evt);
        void __iomem *base = timerdrv->base;
        u64 now;

        now = goldfish_timer_read(&timerdrv->cs);

        now += delta;

        gf_iowrite32(upper_32_bits(now), base + TIMER_ALARM_HIGH);
        gf_iowrite32(lower_32_bits(now), base + TIMER_ALARM_LOW);

        return 0;
}

static irqreturn_t goldfish_timer_irq(int irq, void *dev_id)
{
        struct goldfish_timer *timerdrv = dev_id;
        struct clock_event_device *evt = &timerdrv->ced;
        void __iomem *base = timerdrv->base;

        gf_iowrite32(1, base + TIMER_CLEAR_INTERRUPT);

        evt->event_handler(evt);

        return IRQ_HANDLED;
}

int __init goldfish_timer_init(int irq, void __iomem *base)
{
        struct goldfish_timer *timerdrv;
        int ret;

        timerdrv = kzalloc_obj(*timerdrv);
        if (!timerdrv)
                return -ENOMEM;

        timerdrv->base = base;

        timerdrv->ced = (struct clock_event_device){
                .name                   = "goldfish_timer",
                .features               = CLOCK_EVT_FEAT_ONESHOT,
                .set_state_shutdown     = goldfish_timer_shutdown,
                .set_state_oneshot      = goldfish_timer_set_oneshot,
                .set_next_event         = goldfish_timer_next_event,
        };

        timerdrv->res = (struct resource){
                .name  = "goldfish_timer",
                .start = (unsigned long)base,
                .end   = (unsigned long)base + 0xfff,
        };

        ret = request_resource(&iomem_resource, &timerdrv->res);
        if (ret) {
                pr_err("Cannot allocate '%s' resource\n", timerdrv->res.name);
                return ret;
        }

        timerdrv->cs = (struct clocksource){
                .name           = "goldfish_timer",
                .rating         = 400,
                .read           = goldfish_timer_read,
                .mask           = CLOCKSOURCE_MASK(64),
                .flags          = 0,
                .max_idle_ns    = LONG_MAX,
        };

        clocksource_register_hz(&timerdrv->cs, NSEC_PER_SEC);

        ret = request_irq(irq, goldfish_timer_irq, IRQF_TIMER,
                          "goldfish_timer", timerdrv);
        if (ret) {
                pr_err("Couldn't register goldfish-timer interrupt\n");
                return ret;
        }

        clockevents_config_and_register(&timerdrv->ced, NSEC_PER_SEC,
                                        1, 0xffffffff);

        return 0;
}