/*
 * Copyright (C) 2012 Broadcom 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.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/init.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/clockchips.h>
#include <linux/types.h>
#include <linux/clk.h>

#include <linux/io.h>

#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>


#define KONA_GPTIMER_STCS_OFFSET                        0x00000000
#define KONA_GPTIMER_STCLO_OFFSET                       0x00000004
#define KONA_GPTIMER_STCHI_OFFSET                       0x00000008
#define KONA_GPTIMER_STCM0_OFFSET                       0x0000000C

#define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT             0
#define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT          4

struct kona_bcm_timers {
        int tmr_irq;
        void __iomem *tmr_regs;
};

static struct kona_bcm_timers timers;

static u32 arch_timer_rate;

/*
 * We use the peripheral timers for system tick, the cpu global timer for
 * profile tick
 */
static void kona_timer_disable_and_clear(void __iomem *base)
{
        uint32_t reg;

        /*
         * clear and disable interrupts
         * We are using compare/match register 0 for our system interrupts
         */
        reg = readl(base + KONA_GPTIMER_STCS_OFFSET);

        /* Clear compare (0) interrupt */
        reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
        /* disable compare */
        reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);

        writel(reg, base + KONA_GPTIMER_STCS_OFFSET);

}

static int
kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
{
        int loop_limit = 3;

        /*
         * Read 64-bit free running counter
         * 1. Read hi-word
         * 2. Read low-word
         * 3. Read hi-word again
         * 4.1
         *      if new hi-word is not equal to previously read hi-word, then
         *      start from #1
         * 4.2
         *      if new hi-word is equal to previously read hi-word then stop.
         */

        do {
                *msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET);
                *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET);
                if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET))
                        break;
        } while (--loop_limit);
        if (!loop_limit) {
                pr_err("bcm_kona_timer: getting counter failed.\n");
                pr_err(" Timer will be impacted\n");
                return -ETIMEDOUT;
        }

        return 0;
}

static int kona_timer_set_next_event(unsigned long clc,
                                  struct clock_event_device *unused)
{
        /*
         * timer (0) is disabled by the timer interrupt already
         * so, here we reload the next event value and re-enable
         * the timer.
         *
         * This way, we are potentially losing the time between
         * timer-interrupt->set_next_event. CPU local timers, when
         * they come in should get rid of skew.
         */

        uint32_t lsw, msw;
        uint32_t reg;
        int ret;

        ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
        if (ret)
                return ret;

        /* Load the "next" event tick value */
        writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);

        /* Enable compare */
        reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
        reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
        writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);

        return 0;
}

static int kona_timer_shutdown(struct clock_event_device *evt)
{
        kona_timer_disable_and_clear(timers.tmr_regs);
        return 0;
}

static struct clock_event_device kona_clockevent_timer = {
        .name = "timer 1",
        .features = CLOCK_EVT_FEAT_ONESHOT,
        .set_next_event = kona_timer_set_next_event,
        .set_state_shutdown = kona_timer_shutdown,
        .tick_resume = kona_timer_shutdown,
};

static void __init kona_timer_clockevents_init(void)
{
        kona_clockevent_timer.cpumask = cpumask_of(0);
        clockevents_config_and_register(&kona_clockevent_timer,
                arch_timer_rate, 6, 0xffffffff);
}

static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
{
        struct clock_event_device *evt = &kona_clockevent_timer;

        kona_timer_disable_and_clear(timers.tmr_regs);
        evt->event_handler(evt);
        return IRQ_HANDLED;
}

static struct irqaction kona_timer_irq = {
        .name = "Kona Timer Tick",
        .flags = IRQF_TIMER,
        .handler = kona_timer_interrupt,
};

static int __init kona_timer_init(struct device_node *node)
{
        u32 freq;
        struct clk *external_clk;

        external_clk = of_clk_get_by_name(node, NULL);

        if (!IS_ERR(external_clk)) {
                arch_timer_rate = clk_get_rate(external_clk);
                clk_prepare_enable(external_clk);
        } else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
                arch_timer_rate = freq;
        } else {
                pr_err("Kona Timer v1 unable to determine clock-frequency\n");
                return -EINVAL;
        }

        /* Setup IRQ numbers */
        timers.tmr_irq = irq_of_parse_and_map(node, 0);

        /* Setup IO addresses */
        timers.tmr_regs = of_iomap(node, 0);

        kona_timer_disable_and_clear(timers.tmr_regs);

        kona_timer_clockevents_init();
        setup_irq(timers.tmr_irq, &kona_timer_irq);
        kona_timer_set_next_event((arch_timer_rate / HZ), NULL);

        return 0;
}

TIMER_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
/*
 * bcm,kona-timer is deprecated by brcm,kona-timer
 * being kept here for driver compatibility
 */
TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);