/*
 * DaVinci timer subsystem
 *
 * Author: Kevin Hilman, MontaVista Software, Inc. <source@mvista.com>
 *
 * 2007 (c) MontaVista Software, Inc. This file is licensed under
 * the terms of the GNU General Public License version 2. This program
 * is licensed "as is" without any warranty of any kind, whether express
 * or implied.
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/interrupt.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/platform_device.h>

#include <mach/hardware.h>
#include <asm/mach/irq.h>
#include <asm/mach/time.h>
#include <mach/cputype.h>
#include <mach/time.h>
#include "clock.h"

static struct clock_event_device clockevent_davinci;
static unsigned int davinci_clock_tick_rate;

/*
 * This driver configures the 2 64-bit count-up timers as 4 independent
 * 32-bit count-up timers used as follows:
 */

enum {
        TID_CLOCKEVENT,
        TID_CLOCKSOURCE,
};

/* Timer register offsets */
#define PID12                   0x0
#define TIM12                   0x10
#define TIM34                   0x14
#define PRD12                   0x18
#define PRD34                   0x1c
#define TCR                     0x20
#define TGCR                    0x24
#define WDTCR                   0x28

/* Offsets of the 8 compare registers */
#define CMP12_0                 0x60
#define CMP12_1                 0x64
#define CMP12_2                 0x68
#define CMP12_3                 0x6c
#define CMP12_4                 0x70
#define CMP12_5                 0x74
#define CMP12_6                 0x78
#define CMP12_7                 0x7c

/* Timer register bitfields */
#define TCR_ENAMODE_DISABLE          0x0
#define TCR_ENAMODE_ONESHOT          0x1
#define TCR_ENAMODE_PERIODIC         0x2
#define TCR_ENAMODE_MASK             0x3

#define TGCR_TIMMODE_SHIFT           2
#define TGCR_TIMMODE_64BIT_GP        0x0
#define TGCR_TIMMODE_32BIT_UNCHAINED 0x1
#define TGCR_TIMMODE_64BIT_WDOG      0x2
#define TGCR_TIMMODE_32BIT_CHAINED   0x3

#define TGCR_TIM12RS_SHIFT           0
#define TGCR_TIM34RS_SHIFT           1
#define TGCR_RESET                   0x0
#define TGCR_UNRESET                 0x1
#define TGCR_RESET_MASK              0x3

#define WDTCR_WDEN_SHIFT             14
#define WDTCR_WDEN_DISABLE           0x0
#define WDTCR_WDEN_ENABLE            0x1
#define WDTCR_WDKEY_SHIFT            16
#define WDTCR_WDKEY_SEQ0             0xa5c6
#define WDTCR_WDKEY_SEQ1             0xda7e

struct timer_s {
        char *name;
        unsigned int id;
        unsigned long period;
        unsigned long opts;
        unsigned long flags;
        void __iomem *base;
        unsigned long tim_off;
        unsigned long prd_off;
        unsigned long enamode_shift;
        struct irqaction irqaction;
};
static struct timer_s timers[];

/* values for 'opts' field of struct timer_s */
#define TIMER_OPTS_DISABLED             0x01
#define TIMER_OPTS_ONESHOT              0x02
#define TIMER_OPTS_PERIODIC             0x04
#define TIMER_OPTS_STATE_MASK           0x07

#define TIMER_OPTS_USE_COMPARE          0x80000000
#define USING_COMPARE(t)                ((t)->opts & TIMER_OPTS_USE_COMPARE)

static char *id_to_name[] = {
        [T0_BOT]        = "timer0_0",
        [T0_TOP]        = "timer0_1",
        [T1_BOT]        = "timer1_0",
        [T1_TOP]        = "timer1_1",
};

static int timer32_config(struct timer_s *t)
{
        u32 tcr;
        struct davinci_soc_info *soc_info = &davinci_soc_info;

        if (USING_COMPARE(t)) {
                struct davinci_timer_instance *dtip =
                                soc_info->timer_info->timers;
                int event_timer = ID_TO_TIMER(timers[TID_CLOCKEVENT].id);

                /*
                 * Next interrupt should be the current time reg value plus
                 * the new period (using 32-bit unsigned addition/wrapping
                 * to 0 on overflow).  This assumes that the clocksource
                 * is setup to count to 2^32-1 before wrapping around to 0.
                 */
                __raw_writel(__raw_readl(t->base + t->tim_off) + t->period,
                        t->base + dtip[event_timer].cmp_off);
        } else {
                tcr = __raw_readl(t->base + TCR);

                /* disable timer */
                tcr &= ~(TCR_ENAMODE_MASK << t->enamode_shift);
                __raw_writel(tcr, t->base + TCR);

                /* reset counter to zero, set new period */
                __raw_writel(0, t->base + t->tim_off);
                __raw_writel(t->period, t->base + t->prd_off);

                /* Set enable mode */
                if (t->opts & TIMER_OPTS_ONESHOT)
                        tcr |= TCR_ENAMODE_ONESHOT << t->enamode_shift;
                else if (t->opts & TIMER_OPTS_PERIODIC)
                        tcr |= TCR_ENAMODE_PERIODIC << t->enamode_shift;

                __raw_writel(tcr, t->base + TCR);
        }
        return 0;
}

static inline u32 timer32_read(struct timer_s *t)
{
        return __raw_readl(t->base + t->tim_off);
}

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

        evt->event_handler(evt);
        return IRQ_HANDLED;
}

/* called when 32-bit counter wraps */
static irqreturn_t freerun_interrupt(int irq, void *dev_id)
{
        return IRQ_HANDLED;
}

static struct timer_s timers[] = {
        [TID_CLOCKEVENT] = {
                .name      = "clockevent",
                .opts      = TIMER_OPTS_DISABLED,
                .irqaction = {
                        .flags   = IRQF_DISABLED | IRQF_TIMER,
                        .handler = timer_interrupt,
                }
        },
        [TID_CLOCKSOURCE] = {
                .name       = "free-run counter",
                .period     = ~0,
                .opts       = TIMER_OPTS_PERIODIC,
                .irqaction = {
                        .flags   = IRQF_DISABLED | IRQF_TIMER,
                        .handler = freerun_interrupt,
                }
        },
};

static void __init timer_init(void)
{
        struct davinci_soc_info *soc_info = &davinci_soc_info;
        struct davinci_timer_instance *dtip = soc_info->timer_info->timers;
        void __iomem *base[2];
        int i;

        /* Global init of each 64-bit timer as a whole */
        for(i=0; i<2; i++) {
                u32 tgcr;

                base[i] = ioremap(dtip[i].base, SZ_4K);
                if (WARN_ON(!base[i]))
                        continue;

                /* Disabled, Internal clock source */
                __raw_writel(0, base[i] + TCR);

                /* reset both timers, no pre-scaler for timer34 */
                tgcr = 0;
                __raw_writel(tgcr, base[i] + TGCR);

                /* Set both timers to unchained 32-bit */
                tgcr = TGCR_TIMMODE_32BIT_UNCHAINED << TGCR_TIMMODE_SHIFT;
                __raw_writel(tgcr, base[i] + TGCR);

                /* Unreset timers */
                tgcr |= (TGCR_UNRESET << TGCR_TIM12RS_SHIFT) |
                        (TGCR_UNRESET << TGCR_TIM34RS_SHIFT);
                __raw_writel(tgcr, base[i] + TGCR);

                /* Init both counters to zero */
                __raw_writel(0, base[i] + TIM12);
                __raw_writel(0, base[i] + TIM34);
        }

        /* Init of each timer as a 32-bit timer */
        for (i=0; i< ARRAY_SIZE(timers); i++) {
                struct timer_s *t = &timers[i];
                int timer = ID_TO_TIMER(t->id);
                u32 irq;

                t->base = base[timer];
                if (!t->base)
                        continue;

                if (IS_TIMER_BOT(t->id)) {
                        t->enamode_shift = 6;
                        t->tim_off = TIM12;
                        t->prd_off = PRD12;
                        irq = dtip[timer].bottom_irq;
                } else {
                        t->enamode_shift = 22;
                        t->tim_off = TIM34;
                        t->prd_off = PRD34;
                        irq = dtip[timer].top_irq;
                }

                /* Register interrupt */
                t->irqaction.name = t->name;
                t->irqaction.dev_id = (void *)t;

                if (t->irqaction.handler != NULL) {
                        irq = USING_COMPARE(t) ? dtip[i].cmp_irq : irq;
                        setup_irq(irq, &t->irqaction);
                }
        }
}

/*
 * clocksource
 */
static cycle_t read_cycles(struct clocksource *cs)
{
        struct timer_s *t = &timers[TID_CLOCKSOURCE];

        return (cycles_t)timer32_read(t);
}

/*
 * Kernel assumes that sched_clock can be called early but may not have
 * things ready yet.
 */
static cycle_t read_dummy(struct clocksource *cs)
{
        return 0;
}


static struct clocksource clocksource_davinci = {
        .rating         = 300,
        .read           = read_dummy,
        .mask           = CLOCKSOURCE_MASK(32),
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

/*
 * Overwrite weak default sched_clock with something more precise
 */
unsigned long long notrace sched_clock(void)
{
        const cycle_t cyc = clocksource_davinci.read(&clocksource_davinci);

        return clocksource_cyc2ns(cyc, clocksource_davinci.mult,
                                clocksource_davinci.shift);
}

/*
 * clockevent
 */
static int davinci_set_next_event(unsigned long cycles,
                                  struct clock_event_device *evt)
{
        struct timer_s *t = &timers[TID_CLOCKEVENT];

        t->period = cycles;
        timer32_config(t);
        return 0;
}

static void davinci_set_mode(enum clock_event_mode mode,
                             struct clock_event_device *evt)
{
        struct timer_s *t = &timers[TID_CLOCKEVENT];

        switch (mode) {
        case CLOCK_EVT_MODE_PERIODIC:
                t->period = davinci_clock_tick_rate / (HZ);
                t->opts &= ~TIMER_OPTS_STATE_MASK;
                t->opts |= TIMER_OPTS_PERIODIC;
                timer32_config(t);
                break;
        case CLOCK_EVT_MODE_ONESHOT:
                t->opts &= ~TIMER_OPTS_STATE_MASK;
                t->opts |= TIMER_OPTS_ONESHOT;
                break;
        case CLOCK_EVT_MODE_UNUSED:
        case CLOCK_EVT_MODE_SHUTDOWN:
                t->opts &= ~TIMER_OPTS_STATE_MASK;
                t->opts |= TIMER_OPTS_DISABLED;
                break;
        case CLOCK_EVT_MODE_RESUME:
                break;
        }
}

static struct clock_event_device clockevent_davinci = {
        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
        .shift          = 32,
        .set_next_event = davinci_set_next_event,
        .set_mode       = davinci_set_mode,
};


static void __init davinci_timer_init(void)
{
        struct clk *timer_clk;
        struct davinci_soc_info *soc_info = &davinci_soc_info;
        unsigned int clockevent_id;
        unsigned int clocksource_id;
        static char err[] __initdata = KERN_ERR
                "%s: can't register clocksource!\n";
        int i;

        clockevent_id = soc_info->timer_info->clockevent_id;
        clocksource_id = soc_info->timer_info->clocksource_id;

        timers[TID_CLOCKEVENT].id = clockevent_id;
        timers[TID_CLOCKSOURCE].id = clocksource_id;

        /*
         * If using same timer for both clock events & clocksource,
         * a compare register must be used to generate an event interrupt.
         * This is equivalent to a oneshot timer only (not periodic).
         */
        if (clockevent_id == clocksource_id) {
                struct davinci_timer_instance *dtip =
                                soc_info->timer_info->timers;
                int event_timer = ID_TO_TIMER(clockevent_id);

                /* Only bottom timers can use compare regs */
                if (IS_TIMER_TOP(clockevent_id))
                        pr_warning("davinci_timer_init: Invalid use"
                                " of system timers.  Results unpredictable.\n");
                else if ((dtip[event_timer].cmp_off == 0)
                                || (dtip[event_timer].cmp_irq == 0))
                        pr_warning("davinci_timer_init:  Invalid timer instance"
                                " setup.  Results unpredictable.\n");
                else {
                        timers[TID_CLOCKEVENT].opts |= TIMER_OPTS_USE_COMPARE;
                        clockevent_davinci.features = CLOCK_EVT_FEAT_ONESHOT;
                }
        }

        timer_clk = clk_get(NULL, "timer0");
        BUG_ON(IS_ERR(timer_clk));
        clk_enable(timer_clk);

        /* init timer hw */
        timer_init();

        davinci_clock_tick_rate = clk_get_rate(timer_clk);

        /* setup clocksource */
        clocksource_davinci.read = read_cycles;
        clocksource_davinci.name = id_to_name[clocksource_id];
        if (clocksource_register_hz(&clocksource_davinci,
                                    davinci_clock_tick_rate))
                printk(err, clocksource_davinci.name);

        /* setup clockevent */
        clockevent_davinci.name = id_to_name[timers[TID_CLOCKEVENT].id];
        clockevent_davinci.mult = div_sc(davinci_clock_tick_rate, NSEC_PER_SEC,
                                         clockevent_davinci.shift);
        clockevent_davinci.max_delta_ns =
                clockevent_delta2ns(0xfffffffe, &clockevent_davinci);
        clockevent_davinci.min_delta_ns = 50000; /* 50 usec */

        clockevent_davinci.cpumask = cpumask_of(0);
        clockevents_register_device(&clockevent_davinci);

        for (i=0; i< ARRAY_SIZE(timers); i++)
                timer32_config(&timers[i]);
}

struct sys_timer davinci_timer = {
        .init   = davinci_timer_init,
};


/* reset board using watchdog timer */
void davinci_watchdog_reset(struct platform_device *pdev)
{
        u32 tgcr, wdtcr;
        void __iomem *base;
        struct clk *wd_clk;

        base = ioremap(pdev->resource[0].start, SZ_4K);
        if (WARN_ON(!base))
                return;

        wd_clk = clk_get(&pdev->dev, NULL);
        if (WARN_ON(IS_ERR(wd_clk)))
                return;
        clk_enable(wd_clk);

        /* disable, internal clock source */
        __raw_writel(0, base + TCR);

        /* reset timer, set mode to 64-bit watchdog, and unreset */
        tgcr = 0;
        __raw_writel(tgcr, base + TGCR);
        tgcr = TGCR_TIMMODE_64BIT_WDOG << TGCR_TIMMODE_SHIFT;
        tgcr |= (TGCR_UNRESET << TGCR_TIM12RS_SHIFT) |
                (TGCR_UNRESET << TGCR_TIM34RS_SHIFT);
        __raw_writel(tgcr, base + TGCR);

        /* clear counter and period regs */
        __raw_writel(0, base + TIM12);
        __raw_writel(0, base + TIM34);
        __raw_writel(0, base + PRD12);
        __raw_writel(0, base + PRD34);

        /* put watchdog in pre-active state */
        wdtcr = __raw_readl(base + WDTCR);
        wdtcr = (WDTCR_WDKEY_SEQ0 << WDTCR_WDKEY_SHIFT) |
                (WDTCR_WDEN_ENABLE << WDTCR_WDEN_SHIFT);
        __raw_writel(wdtcr, base + WDTCR);

        /* put watchdog in active state */
        wdtcr = (WDTCR_WDKEY_SEQ1 << WDTCR_WDKEY_SHIFT) |
                (WDTCR_WDEN_ENABLE << WDTCR_WDEN_SHIFT);
        __raw_writel(wdtcr, base + WDTCR);

        /* write an invalid value to the WDKEY field to trigger
         * a watchdog reset */
        wdtcr = 0x00004000;
        __raw_writel(wdtcr, base + WDTCR);
}