#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/errno.h>
#include <linux/hpet.h>
#include <linux/init.h>
#include <linux/sysdev.h>
#include <linux/pm.h>

#include <asm/hpet.h>
#include <asm/io.h>

extern struct clock_event_device *global_clock_event;

#define HPET_MASK       CLOCKSOURCE_MASK(32)
#define HPET_SHIFT      22

/* FSEC = 10^-15 NSEC = 10^-9 */
#define FSEC_PER_NSEC   1000000

/*
 * HPET address is set in acpi/boot.c, when an ACPI entry exists
 */
unsigned long hpet_address;
static void __iomem * hpet_virt_address;

static inline unsigned long hpet_readl(unsigned long a)
{
        return readl(hpet_virt_address + a);
}

static inline void hpet_writel(unsigned long d, unsigned long a)
{
        writel(d, hpet_virt_address + a);
}

/*
 * HPET command line enable / disable
 */
static int boot_hpet_disable;

static int __init hpet_setup(char* str)
{
        if (str) {
                if (!strncmp("disable", str, 7))
                        boot_hpet_disable = 1;
        }
        return 1;
}
__setup("hpet=", hpet_setup);

static inline int is_hpet_capable(void)
{
        return (!boot_hpet_disable && hpet_address);
}

/*
 * HPET timer interrupt enable / disable
 */
static int hpet_legacy_int_enabled;

/**
 * is_hpet_enabled - check whether the hpet timer interrupt is enabled
 */
int is_hpet_enabled(void)
{
        return is_hpet_capable() && hpet_legacy_int_enabled;
}

/*
 * When the hpet driver (/dev/hpet) is enabled, we need to reserve
 * timer 0 and timer 1 in case of RTC emulation.
 */
#ifdef CONFIG_HPET
static void hpet_reserve_platform_timers(unsigned long id)
{
        struct hpet __iomem *hpet = hpet_virt_address;
        struct hpet_timer __iomem *timer = &hpet->hpet_timers[2];
        unsigned int nrtimers, i;
        struct hpet_data hd;

        nrtimers = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT) + 1;

        memset(&hd, 0, sizeof (hd));
        hd.hd_phys_address = hpet_address;
        hd.hd_address = hpet_virt_address;
        hd.hd_nirqs = nrtimers;
        hd.hd_flags = HPET_DATA_PLATFORM;
        hpet_reserve_timer(&hd, 0);

#ifdef CONFIG_HPET_EMULATE_RTC
        hpet_reserve_timer(&hd, 1);
#endif

        hd.hd_irq[0] = HPET_LEGACY_8254;
        hd.hd_irq[1] = HPET_LEGACY_RTC;

        for (i = 2; i < nrtimers; timer++, i++)
                hd.hd_irq[i] = (timer->hpet_config & Tn_INT_ROUTE_CNF_MASK) >>
                        Tn_INT_ROUTE_CNF_SHIFT;

        hpet_alloc(&hd);

}
#else
static void hpet_reserve_platform_timers(unsigned long id) { }
#endif

/*
 * Common hpet info
 */
static unsigned long hpet_period;

static void hpet_set_mode(enum clock_event_mode mode,
                          struct clock_event_device *evt);
static int hpet_next_event(unsigned long delta,
                           struct clock_event_device *evt);

/*
 * The hpet clock event device
 */
static struct clock_event_device hpet_clockevent = {
        .name           = "hpet",
        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
        .set_mode       = hpet_set_mode,
        .set_next_event = hpet_next_event,
        .shift          = 32,
        .irq            = 0,
};

static void hpet_start_counter(void)
{
        unsigned long cfg = hpet_readl(HPET_CFG);

        cfg &= ~HPET_CFG_ENABLE;
        hpet_writel(cfg, HPET_CFG);
        hpet_writel(0, HPET_COUNTER);
        hpet_writel(0, HPET_COUNTER + 4);
        cfg |= HPET_CFG_ENABLE;
        hpet_writel(cfg, HPET_CFG);
}

static void hpet_enable_int(void)
{
        unsigned long cfg = hpet_readl(HPET_CFG);

        cfg |= HPET_CFG_LEGACY;
        hpet_writel(cfg, HPET_CFG);
        hpet_legacy_int_enabled = 1;
}

static void hpet_set_mode(enum clock_event_mode mode,
                          struct clock_event_device *evt)
{
        unsigned long cfg, cmp, now;
        uint64_t delta;

        switch(mode) {
        case CLOCK_EVT_MODE_PERIODIC:
                delta = ((uint64_t)(NSEC_PER_SEC/HZ)) * hpet_clockevent.mult;
                delta >>= hpet_clockevent.shift;
                now = hpet_readl(HPET_COUNTER);
                cmp = now + (unsigned long) delta;
                cfg = hpet_readl(HPET_T0_CFG);
                cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
                       HPET_TN_SETVAL | HPET_TN_32BIT;
                hpet_writel(cfg, HPET_T0_CFG);
                /*
                 * The first write after writing TN_SETVAL to the
                 * config register sets the counter value, the second
                 * write sets the period.
                 */
                hpet_writel(cmp, HPET_T0_CMP);
                udelay(1);
                hpet_writel((unsigned long) delta, HPET_T0_CMP);
                break;

        case CLOCK_EVT_MODE_ONESHOT:
                cfg = hpet_readl(HPET_T0_CFG);
                cfg &= ~HPET_TN_PERIODIC;
                cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
                hpet_writel(cfg, HPET_T0_CFG);
                break;

        case CLOCK_EVT_MODE_UNUSED:
        case CLOCK_EVT_MODE_SHUTDOWN:
                cfg = hpet_readl(HPET_T0_CFG);
                cfg &= ~HPET_TN_ENABLE;
                hpet_writel(cfg, HPET_T0_CFG);
                break;
        }
}

static int hpet_next_event(unsigned long delta,
                           struct clock_event_device *evt)
{
        unsigned long cnt;

        cnt = hpet_readl(HPET_COUNTER);
        cnt += delta;
        hpet_writel(cnt, HPET_T0_CMP);

        return ((long)(hpet_readl(HPET_COUNTER) - cnt ) > 0) ? -ETIME : 0;
}

/*
 * Clock source related code
 */
static cycle_t read_hpet(void)
{
        return (cycle_t)hpet_readl(HPET_COUNTER);
}

static struct clocksource clocksource_hpet = {
        .name           = "hpet",
        .rating         = 250,
        .read           = read_hpet,
        .mask           = HPET_MASK,
        .shift          = HPET_SHIFT,
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

/*
 * Try to setup the HPET timer
 */
int __init hpet_enable(void)
{
        unsigned long id;
        uint64_t hpet_freq;
        u64 tmp, start, now;
        cycle_t t1;

        if (!is_hpet_capable())
                return 0;

        hpet_virt_address = ioremap_nocache(hpet_address, HPET_MMAP_SIZE);

        /*
         * Read the period and check for a sane value:
         */
        hpet_period = hpet_readl(HPET_PERIOD);
        if (hpet_period < HPET_MIN_PERIOD || hpet_period > HPET_MAX_PERIOD)
                goto out_nohpet;

        /*
         * The period is a femto seconds value. We need to calculate the
         * scaled math multiplication factor for nanosecond to hpet tick
         * conversion.
         */
        hpet_freq = 1000000000000000ULL;
        do_div(hpet_freq, hpet_period);
        hpet_clockevent.mult = div_sc((unsigned long) hpet_freq,
                                      NSEC_PER_SEC, 32);
        /* Calculate the min / max delta */
        hpet_clockevent.max_delta_ns = clockevent_delta2ns(0x7FFFFFFF,
                                                           &hpet_clockevent);
        hpet_clockevent.min_delta_ns = clockevent_delta2ns(0x30,
                                                           &hpet_clockevent);

        /*
         * Read the HPET ID register to retrieve the IRQ routing
         * information and the number of channels
         */
        id = hpet_readl(HPET_ID);

#ifdef CONFIG_HPET_EMULATE_RTC
        /*
         * The legacy routing mode needs at least two channels, tick timer
         * and the rtc emulation channel.
         */
        if (!(id & HPET_ID_NUMBER))
                goto out_nohpet;
#endif

        /* Start the counter */
        hpet_start_counter();

        /* Verify whether hpet counter works */
        t1 = read_hpet();
        rdtscll(start);

        /*
         * We don't know the TSC frequency yet, but waiting for
         * 200000 TSC cycles is safe:
         * 4 GHz == 50us
         * 1 GHz == 200us
         */
        do {
                rep_nop();
                rdtscll(now);
        } while ((now - start) < 200000UL);

        if (t1 == read_hpet()) {
                printk(KERN_WARNING
                       "HPET counter not counting. HPET disabled\n");
                goto out_nohpet;
        }

        /* Initialize and register HPET clocksource
         *
         * hpet period is in femto seconds per cycle
         * so we need to convert this to ns/cyc units
         * aproximated by mult/2^shift
         *
         *  fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
         *  fsec/cyc * 1ns/1000000fsec * 2^shift = mult
         *  fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
         *  (fsec/cyc << shift)/1000000 = mult
         *  (hpet_period << shift)/FSEC_PER_NSEC = mult
         */
        tmp = (u64)hpet_period << HPET_SHIFT;
        do_div(tmp, FSEC_PER_NSEC);
        clocksource_hpet.mult = (u32)tmp;

        clocksource_register(&clocksource_hpet);


        if (id & HPET_ID_LEGSUP) {
                hpet_enable_int();
                hpet_reserve_platform_timers(id);
                /*
                 * Start hpet with the boot cpu mask and make it
                 * global after the IO_APIC has been initialized.
                 */
                hpet_clockevent.cpumask =cpumask_of_cpu(0);
                clockevents_register_device(&hpet_clockevent);
                global_clock_event = &hpet_clockevent;
                return 1;
        }
        return 0;

out_nohpet:
        iounmap(hpet_virt_address);
        hpet_virt_address = NULL;
        boot_hpet_disable = 1;
        return 0;
}


#ifdef CONFIG_HPET_EMULATE_RTC

/* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET
 * is enabled, we support RTC interrupt functionality in software.
 * RTC has 3 kinds of interrupts:
 * 1) Update Interrupt - generate an interrupt, every sec, when RTC clock
 *    is updated
 * 2) Alarm Interrupt - generate an interrupt at a specific time of day
 * 3) Periodic Interrupt - generate periodic interrupt, with frequencies
 *    2Hz-8192Hz (2Hz-64Hz for non-root user) (all freqs in powers of 2)
 * (1) and (2) above are implemented using polling at a frequency of
 * 64 Hz. The exact frequency is a tradeoff between accuracy and interrupt
 * overhead. (DEFAULT_RTC_INT_FREQ)
 * For (3), we use interrupts at 64Hz or user specified periodic
 * frequency, whichever is higher.
 */
#include <linux/mc146818rtc.h>
#include <linux/rtc.h>

#define DEFAULT_RTC_INT_FREQ    64
#define DEFAULT_RTC_SHIFT       6
#define RTC_NUM_INTS            1

static unsigned long hpet_rtc_flags;
static unsigned long hpet_prev_update_sec;
static struct rtc_time hpet_alarm_time;
static unsigned long hpet_pie_count;
static unsigned long hpet_t1_cmp;
static unsigned long hpet_default_delta;
static unsigned long hpet_pie_delta;
static unsigned long hpet_pie_limit;

/*
 * Timer 1 for RTC emulation. We use one shot mode, as periodic mode
 * is not supported by all HPET implementations for timer 1.
 *
 * hpet_rtc_timer_init() is called when the rtc is initialized.
 */
int hpet_rtc_timer_init(void)
{
        unsigned long cfg, cnt, delta, flags;

        if (!is_hpet_enabled())
                return 0;

        if (!hpet_default_delta) {
                uint64_t clc;

                clc = (uint64_t) hpet_clockevent.mult * NSEC_PER_SEC;
                clc >>= hpet_clockevent.shift + DEFAULT_RTC_SHIFT;
                hpet_default_delta = (unsigned long) clc;
        }

        if (!(hpet_rtc_flags & RTC_PIE) || hpet_pie_limit)
                delta = hpet_default_delta;
        else
                delta = hpet_pie_delta;

        local_irq_save(flags);

        cnt = delta + hpet_readl(HPET_COUNTER);
        hpet_writel(cnt, HPET_T1_CMP);
        hpet_t1_cmp = cnt;

        cfg = hpet_readl(HPET_T1_CFG);
        cfg &= ~HPET_TN_PERIODIC;
        cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
        hpet_writel(cfg, HPET_T1_CFG);

        local_irq_restore(flags);

        return 1;
}

/*
 * The functions below are called from rtc driver.
 * Return 0 if HPET is not being used.
 * Otherwise do the necessary changes and return 1.
 */
int hpet_mask_rtc_irq_bit(unsigned long bit_mask)
{
        if (!is_hpet_enabled())
                return 0;

        hpet_rtc_flags &= ~bit_mask;
        return 1;
}

int hpet_set_rtc_irq_bit(unsigned long bit_mask)
{
        unsigned long oldbits = hpet_rtc_flags;

        if (!is_hpet_enabled())
                return 0;

        hpet_rtc_flags |= bit_mask;

        if (!oldbits)
                hpet_rtc_timer_init();

        return 1;
}

int hpet_set_alarm_time(unsigned char hrs, unsigned char min,
                        unsigned char sec)
{
        if (!is_hpet_enabled())
                return 0;

        hpet_alarm_time.tm_hour = hrs;
        hpet_alarm_time.tm_min = min;
        hpet_alarm_time.tm_sec = sec;

        return 1;
}

int hpet_set_periodic_freq(unsigned long freq)
{
        uint64_t clc;

        if (!is_hpet_enabled())
                return 0;

        if (freq <= DEFAULT_RTC_INT_FREQ)
                hpet_pie_limit = DEFAULT_RTC_INT_FREQ / freq;
        else {
                clc = (uint64_t) hpet_clockevent.mult * NSEC_PER_SEC;
                do_div(clc, freq);
                clc >>= hpet_clockevent.shift;
                hpet_pie_delta = (unsigned long) clc;
        }
        return 1;
}

int hpet_rtc_dropped_irq(void)
{
        return is_hpet_enabled();
}

static void hpet_rtc_timer_reinit(void)
{
        unsigned long cfg, delta;
        int lost_ints = -1;

        if (unlikely(!hpet_rtc_flags)) {
                cfg = hpet_readl(HPET_T1_CFG);
                cfg &= ~HPET_TN_ENABLE;
                hpet_writel(cfg, HPET_T1_CFG);
                return;
        }

        if (!(hpet_rtc_flags & RTC_PIE) || hpet_pie_limit)
                delta = hpet_default_delta;
        else
                delta = hpet_pie_delta;

        /*
         * Increment the comparator value until we are ahead of the
         * current count.
         */
        do {
                hpet_t1_cmp += delta;
                hpet_writel(hpet_t1_cmp, HPET_T1_CMP);
                lost_ints++;
        } while ((long)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0);

        if (lost_ints) {
                if (hpet_rtc_flags & RTC_PIE)
                        hpet_pie_count += lost_ints;
                if (printk_ratelimit())
                        printk(KERN_WARNING "rtc: lost %d interrupts\n",
                                lost_ints);
        }
}

irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
{
        struct rtc_time curr_time;
        unsigned long rtc_int_flag = 0;

        hpet_rtc_timer_reinit();

        if (hpet_rtc_flags & (RTC_UIE | RTC_AIE))
                rtc_get_rtc_time(&curr_time);

        if (hpet_rtc_flags & RTC_UIE &&
            curr_time.tm_sec != hpet_prev_update_sec) {
                rtc_int_flag = RTC_UF;
                hpet_prev_update_sec = curr_time.tm_sec;
        }

        if (hpet_rtc_flags & RTC_PIE &&
            ++hpet_pie_count >= hpet_pie_limit) {
                rtc_int_flag |= RTC_PF;
                hpet_pie_count = 0;
        }

        if (hpet_rtc_flags & RTC_PIE &&
            (curr_time.tm_sec == hpet_alarm_time.tm_sec) &&
            (curr_time.tm_min == hpet_alarm_time.tm_min) &&
            (curr_time.tm_hour == hpet_alarm_time.tm_hour))
                        rtc_int_flag |= RTC_AF;

        if (rtc_int_flag) {
                rtc_int_flag |= (RTC_IRQF | (RTC_NUM_INTS << 8));
                rtc_interrupt(rtc_int_flag, dev_id);
        }
        return IRQ_HANDLED;
}
#endif


/*
 * Suspend/resume part
 */

#ifdef CONFIG_PM

static int hpet_suspend(struct sys_device *sys_device, pm_message_t state)
{
        unsigned long cfg = hpet_readl(HPET_CFG);

        cfg &= ~(HPET_CFG_ENABLE|HPET_CFG_LEGACY);
        hpet_writel(cfg, HPET_CFG);

        return 0;
}

static int hpet_resume(struct sys_device *sys_device)
{
        unsigned int id;

        hpet_start_counter();

        id = hpet_readl(HPET_ID);

        if (id & HPET_ID_LEGSUP)
                hpet_enable_int();

        return 0;
}

static struct sysdev_class hpet_class = {
        set_kset_name("hpet"),
        .suspend        = hpet_suspend,
        .resume         = hpet_resume,
};

static struct sys_device hpet_device = {
        .id             = 0,
        .cls            = &hpet_class,
};


static __init int hpet_register_sysfs(void)
{
        int err;

        if (!is_hpet_capable())
                return 0;

        err = sysdev_class_register(&hpet_class);

        if (!err) {
                err = sysdev_register(&hpet_device);
                if (err)
                        sysdev_class_unregister(&hpet_class);
        }

        return err;
}

device_initcall(hpet_register_sysfs);

#endif