// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2014 Zhang, Keguang <keguang.zhang@gmail.com>
 */

#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/sizes.h>
#include <asm/time.h>

#include <loongson1.h>
#include <platform.h>

#ifdef CONFIG_CEVT_CSRC_LS1X

#if defined(CONFIG_TIMER_USE_PWM1)
#define LS1X_TIMER_BASE LS1X_PWM1_BASE
#define LS1X_TIMER_IRQ  LS1X_PWM1_IRQ

#elif defined(CONFIG_TIMER_USE_PWM2)
#define LS1X_TIMER_BASE LS1X_PWM2_BASE
#define LS1X_TIMER_IRQ  LS1X_PWM2_IRQ

#elif defined(CONFIG_TIMER_USE_PWM3)
#define LS1X_TIMER_BASE LS1X_PWM3_BASE
#define LS1X_TIMER_IRQ  LS1X_PWM3_IRQ

#else
#define LS1X_TIMER_BASE LS1X_PWM0_BASE
#define LS1X_TIMER_IRQ  LS1X_PWM0_IRQ
#endif

DEFINE_RAW_SPINLOCK(ls1x_timer_lock);

static void __iomem *timer_reg_base;
static uint32_t ls1x_jiffies_per_tick;

static inline void ls1x_pwmtimer_set_period(uint32_t period)
{
        __raw_writel(period, timer_reg_base + PWM_HRC);
        __raw_writel(period, timer_reg_base + PWM_LRC);
}

static inline void ls1x_pwmtimer_restart(void)
{
        __raw_writel(0x0, timer_reg_base + PWM_CNT);
        __raw_writel(INT_EN | CNT_EN, timer_reg_base + PWM_CTRL);
}

void __init ls1x_pwmtimer_init(void)
{
        timer_reg_base = ioremap(LS1X_TIMER_BASE, SZ_16);
        if (!timer_reg_base)
                panic("Failed to remap timer registers");

        ls1x_jiffies_per_tick = DIV_ROUND_CLOSEST(mips_hpt_frequency, HZ);

        ls1x_pwmtimer_set_period(ls1x_jiffies_per_tick);
        ls1x_pwmtimer_restart();
}

static u64 ls1x_clocksource_read(struct clocksource *cs)
{
        unsigned long flags;
        int count;
        u32 jifs;
        static int old_count;
        static u32 old_jifs;

        raw_spin_lock_irqsave(&ls1x_timer_lock, flags);
        /*
         * Although our caller may have the read side of xtime_lock,
         * this is now a seqlock, and we are cheating in this routine
         * by having side effects on state that we cannot undo if
         * there is a collision on the seqlock and our caller has to
         * retry.  (Namely, old_jifs and old_count.)  So we must treat
         * jiffies as volatile despite the lock.  We read jiffies
         * before latching the timer count to guarantee that although
         * the jiffies value might be older than the count (that is,
         * the counter may underflow between the last point where
         * jiffies was incremented and the point where we latch the
         * count), it cannot be newer.
         */
        jifs = jiffies;
        /* read the count */
        count = __raw_readl(timer_reg_base + PWM_CNT);

        /*
         * It's possible for count to appear to go the wrong way for this
         * reason:
         *
         *  The timer counter underflows, but we haven't handled the resulting
         *  interrupt and incremented jiffies yet.
         *
         * Previous attempts to handle these cases intelligently were buggy, so
         * we just do the simple thing now.
         */
        if (count < old_count && jifs == old_jifs)
                count = old_count;

        old_count = count;
        old_jifs = jifs;

        raw_spin_unlock_irqrestore(&ls1x_timer_lock, flags);

        return (u64) (jifs * ls1x_jiffies_per_tick) + count;
}

static struct clocksource ls1x_clocksource = {
        .name           = "ls1x-pwmtimer",
        .read           = ls1x_clocksource_read,
        .mask           = CLOCKSOURCE_MASK(24),
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

static irqreturn_t ls1x_clockevent_isr(int irq, void *devid)
{
        struct clock_event_device *cd = devid;

        ls1x_pwmtimer_restart();
        cd->event_handler(cd);

        return IRQ_HANDLED;
}

static int ls1x_clockevent_set_state_periodic(struct clock_event_device *cd)
{
        raw_spin_lock(&ls1x_timer_lock);
        ls1x_pwmtimer_set_period(ls1x_jiffies_per_tick);
        ls1x_pwmtimer_restart();
        __raw_writel(INT_EN | CNT_EN, timer_reg_base + PWM_CTRL);
        raw_spin_unlock(&ls1x_timer_lock);

        return 0;
}

static int ls1x_clockevent_tick_resume(struct clock_event_device *cd)
{
        raw_spin_lock(&ls1x_timer_lock);
        __raw_writel(INT_EN | CNT_EN, timer_reg_base + PWM_CTRL);
        raw_spin_unlock(&ls1x_timer_lock);

        return 0;
}

static int ls1x_clockevent_set_state_shutdown(struct clock_event_device *cd)
{
        raw_spin_lock(&ls1x_timer_lock);
        __raw_writel(__raw_readl(timer_reg_base + PWM_CTRL) & ~CNT_EN,
                     timer_reg_base + PWM_CTRL);
        raw_spin_unlock(&ls1x_timer_lock);

        return 0;
}

static int ls1x_clockevent_set_next(unsigned long evt,
                                    struct clock_event_device *cd)
{
        raw_spin_lock(&ls1x_timer_lock);
        ls1x_pwmtimer_set_period(evt);
        ls1x_pwmtimer_restart();
        raw_spin_unlock(&ls1x_timer_lock);

        return 0;
}

static struct clock_event_device ls1x_clockevent = {
        .name                   = "ls1x-pwmtimer",
        .features               = CLOCK_EVT_FEAT_PERIODIC,
        .rating                 = 300,
        .irq                    = LS1X_TIMER_IRQ,
        .set_next_event         = ls1x_clockevent_set_next,
        .set_state_shutdown     = ls1x_clockevent_set_state_shutdown,
        .set_state_periodic     = ls1x_clockevent_set_state_periodic,
        .set_state_oneshot      = ls1x_clockevent_set_state_shutdown,
        .tick_resume            = ls1x_clockevent_tick_resume,
};

static void __init ls1x_time_init(void)
{
        struct clock_event_device *cd = &ls1x_clockevent;
        int ret;

        if (!mips_hpt_frequency)
                panic("Invalid timer clock rate");

        ls1x_pwmtimer_init();

        clockevent_set_clock(cd, mips_hpt_frequency);
        cd->max_delta_ns = clockevent_delta2ns(0xffffff, cd);
        cd->max_delta_ticks = 0xffffff;
        cd->min_delta_ns = clockevent_delta2ns(0x000300, cd);
        cd->min_delta_ticks = 0x000300;
        cd->cpumask = cpumask_of(smp_processor_id());
        clockevents_register_device(cd);

        ls1x_clocksource.rating = 200 + mips_hpt_frequency / 10000000;
        ret = clocksource_register_hz(&ls1x_clocksource, mips_hpt_frequency);
        if (ret)
                panic(KERN_ERR "Failed to register clocksource: %d\n", ret);

        if (request_irq(LS1X_TIMER_IRQ, ls1x_clockevent_isr,
                        IRQF_PERCPU | IRQF_TIMER, "ls1x-pwmtimer",
                        &ls1x_clockevent))
                pr_err("Failed to register ls1x-pwmtimer interrupt\n");
}
#endif /* CONFIG_CEVT_CSRC_LS1X */

void __init plat_time_init(void)
{
        struct clk *clk = NULL;

        /* initialize LS1X clocks */
        ls1x_clk_init();

#ifdef CONFIG_CEVT_CSRC_LS1X
        /* setup LS1X PWM timer */
        clk = clk_get(NULL, "ls1x-pwmtimer");
        if (IS_ERR(clk))
                panic("unable to get timer clock, err=%ld", PTR_ERR(clk));

        mips_hpt_frequency = clk_get_rate(clk);
        ls1x_time_init();
#else
        /* setup mips r4k timer */
        clk = clk_get(NULL, "cpu_clk");
        if (IS_ERR(clk))
                panic("unable to get cpu clock, err=%ld", PTR_ERR(clk));

        mips_hpt_frequency = clk_get_rate(clk) / 2;
#endif /* CONFIG_CEVT_CSRC_LS1X */
}