/*
 * SuperH Timer Support - CMT
 *
 *  Copyright (C) 2008 Magnus Damm
 *
 * 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; either version 2 of the License
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/irq.h>
#include <linux/err.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/sh_timer.h>

struct sh_cmt_priv {
        void __iomem *mapbase;
        struct clk *clk;
        unsigned long width; /* 16 or 32 bit version of hardware block */
        unsigned long overflow_bit;
        unsigned long clear_bits;
        struct irqaction irqaction;
        struct platform_device *pdev;

        unsigned long flags;
        unsigned long flags_suspend;
        unsigned long match_value;
        unsigned long next_match_value;
        unsigned long max_match_value;
        unsigned long rate;
        spinlock_t lock;
        struct clock_event_device ced;
        struct clocksource cs;
        unsigned long total_cycles;
};

static DEFINE_SPINLOCK(sh_cmt_lock);

#define CMSTR -1 /* shared register */
#define CMCSR 0 /* channel register */
#define CMCNT 1 /* channel register */
#define CMCOR 2 /* channel register */

static inline unsigned long sh_cmt_read(struct sh_cmt_priv *p, int reg_nr)
{
        struct sh_timer_config *cfg = p->pdev->dev.platform_data;
        void __iomem *base = p->mapbase;
        unsigned long offs;

        if (reg_nr == CMSTR) {
                offs = 0;
                base -= cfg->channel_offset;
        } else
                offs = reg_nr;

        if (p->width == 16)
                offs <<= 1;
        else {
                offs <<= 2;
                if ((reg_nr == CMCNT) || (reg_nr == CMCOR))
                        return ioread32(base + offs);
        }

        return ioread16(base + offs);
}

static inline void sh_cmt_write(struct sh_cmt_priv *p, int reg_nr,
                                unsigned long value)
{
        struct sh_timer_config *cfg = p->pdev->dev.platform_data;
        void __iomem *base = p->mapbase;
        unsigned long offs;

        if (reg_nr == CMSTR) {
                offs = 0;
                base -= cfg->channel_offset;
        } else
                offs = reg_nr;

        if (p->width == 16)
                offs <<= 1;
        else {
                offs <<= 2;
                if ((reg_nr == CMCNT) || (reg_nr == CMCOR)) {
                        iowrite32(value, base + offs);
                        return;
                }
        }

        iowrite16(value, base + offs);
}

static unsigned long sh_cmt_get_counter(struct sh_cmt_priv *p,
                                        int *has_wrapped)
{
        unsigned long v1, v2, v3;
        int o1, o2;

        o1 = sh_cmt_read(p, CMCSR) & p->overflow_bit;

        /* Make sure the timer value is stable. Stolen from acpi_pm.c */
        do {
                o2 = o1;
                v1 = sh_cmt_read(p, CMCNT);
                v2 = sh_cmt_read(p, CMCNT);
                v3 = sh_cmt_read(p, CMCNT);
                o1 = sh_cmt_read(p, CMCSR) & p->overflow_bit;
        } while (unlikely((o1 != o2) || (v1 > v2 && v1 < v3)
                          || (v2 > v3 && v2 < v1) || (v3 > v1 && v3 < v2)));

        *has_wrapped = o1;
        return v2;
}


static void sh_cmt_start_stop_ch(struct sh_cmt_priv *p, int start)
{
        struct sh_timer_config *cfg = p->pdev->dev.platform_data;
        unsigned long flags, value;

        /* start stop register shared by multiple timer channels */
        spin_lock_irqsave(&sh_cmt_lock, flags);
        value = sh_cmt_read(p, CMSTR);

        if (start)
                value |= 1 << cfg->timer_bit;
        else
                value &= ~(1 << cfg->timer_bit);

        sh_cmt_write(p, CMSTR, value);
        spin_unlock_irqrestore(&sh_cmt_lock, flags);
}

static int sh_cmt_enable(struct sh_cmt_priv *p, unsigned long *rate)
{
        struct sh_timer_config *cfg = p->pdev->dev.platform_data;
        int ret;

        /* enable clock */
        ret = clk_enable(p->clk);
        if (ret) {
                pr_err("sh_cmt: cannot enable clock \"%s\"\n", cfg->clk);
                return ret;
        }

        /* make sure channel is disabled */
        sh_cmt_start_stop_ch(p, 0);

        /* configure channel, periodic mode and maximum timeout */
        if (p->width == 16) {
                *rate = clk_get_rate(p->clk) / 512;
                sh_cmt_write(p, CMCSR, 0x43);
        } else {
                *rate = clk_get_rate(p->clk) / 8;
                sh_cmt_write(p, CMCSR, 0x01a4);
        }

        sh_cmt_write(p, CMCOR, 0xffffffff);
        sh_cmt_write(p, CMCNT, 0);

        /* enable channel */
        sh_cmt_start_stop_ch(p, 1);
        return 0;
}

static void sh_cmt_disable(struct sh_cmt_priv *p)
{
        /* disable channel */
        sh_cmt_start_stop_ch(p, 0);

        /* disable interrupts in CMT block */
        sh_cmt_write(p, CMCSR, 0);

        /* stop clock */
        clk_disable(p->clk);
}

/* private flags */
#define FLAG_CLOCKEVENT (1 << 0)
#define FLAG_CLOCKSOURCE (1 << 1)
#define FLAG_REPROGRAM (1 << 2)
#define FLAG_SKIPEVENT (1 << 3)
#define FLAG_IRQCONTEXT (1 << 4)

static void sh_cmt_clock_event_program_verify(struct sh_cmt_priv *p,
                                              int absolute)
{
        unsigned long new_match;
        unsigned long value = p->next_match_value;
        unsigned long delay = 0;
        unsigned long now = 0;
        int has_wrapped;

        now = sh_cmt_get_counter(p, &has_wrapped);
        p->flags |= FLAG_REPROGRAM; /* force reprogram */

        if (has_wrapped) {
                /* we're competing with the interrupt handler.
                 *  -> let the interrupt handler reprogram the timer.
                 *  -> interrupt number two handles the event.
                 */
                p->flags |= FLAG_SKIPEVENT;
                return;
        }

        if (absolute)
                now = 0;

        do {
                /* reprogram the timer hardware,
                 * but don't save the new match value yet.
                 */
                new_match = now + value + delay;
                if (new_match > p->max_match_value)
                        new_match = p->max_match_value;

                sh_cmt_write(p, CMCOR, new_match);

                now = sh_cmt_get_counter(p, &has_wrapped);
                if (has_wrapped && (new_match > p->match_value)) {
                        /* we are changing to a greater match value,
                         * so this wrap must be caused by the counter
                         * matching the old value.
                         * -> first interrupt reprograms the timer.
                         * -> interrupt number two handles the event.
                         */
                        p->flags |= FLAG_SKIPEVENT;
                        break;
                }

                if (has_wrapped) {
                        /* we are changing to a smaller match value,
                         * so the wrap must be caused by the counter
                         * matching the new value.
                         * -> save programmed match value.
                         * -> let isr handle the event.
                         */
                        p->match_value = new_match;
                        break;
                }

                /* be safe: verify hardware settings */
                if (now < new_match) {
                        /* timer value is below match value, all good.
                         * this makes sure we won't miss any match events.
                         * -> save programmed match value.
                         * -> let isr handle the event.
                         */
                        p->match_value = new_match;
                        break;
                }

                /* the counter has reached a value greater
                 * than our new match value. and since the
                 * has_wrapped flag isn't set we must have
                 * programmed a too close event.
                 * -> increase delay and retry.
                 */
                if (delay)
                        delay <<= 1;
                else
                        delay = 1;

                if (!delay)
                        pr_warning("sh_cmt: too long delay\n");

        } while (delay);
}

static void sh_cmt_set_next(struct sh_cmt_priv *p, unsigned long delta)
{
        unsigned long flags;

        if (delta > p->max_match_value)
                pr_warning("sh_cmt: delta out of range\n");

        spin_lock_irqsave(&p->lock, flags);
        p->next_match_value = delta;
        sh_cmt_clock_event_program_verify(p, 0);
        spin_unlock_irqrestore(&p->lock, flags);
}

static irqreturn_t sh_cmt_interrupt(int irq, void *dev_id)
{
        struct sh_cmt_priv *p = dev_id;

        /* clear flags */
        sh_cmt_write(p, CMCSR, sh_cmt_read(p, CMCSR) & p->clear_bits);

        /* update clock source counter to begin with if enabled
         * the wrap flag should be cleared by the timer specific
         * isr before we end up here.
         */
        if (p->flags & FLAG_CLOCKSOURCE)
                p->total_cycles += p->match_value;

        if (!(p->flags & FLAG_REPROGRAM))
                p->next_match_value = p->max_match_value;

        p->flags |= FLAG_IRQCONTEXT;

        if (p->flags & FLAG_CLOCKEVENT) {
                if (!(p->flags & FLAG_SKIPEVENT)) {
                        if (p->ced.mode == CLOCK_EVT_MODE_ONESHOT) {
                                p->next_match_value = p->max_match_value;
                                p->flags |= FLAG_REPROGRAM;
                        }

                        p->ced.event_handler(&p->ced);
                }
        }

        p->flags &= ~FLAG_SKIPEVENT;

        if (p->flags & FLAG_REPROGRAM) {
                p->flags &= ~FLAG_REPROGRAM;
                sh_cmt_clock_event_program_verify(p, 1);

                if (p->flags & FLAG_CLOCKEVENT)
                        if ((p->ced.mode == CLOCK_EVT_MODE_SHUTDOWN)
                            || (p->match_value == p->next_match_value))
                                p->flags &= ~FLAG_REPROGRAM;
        }

        p->flags &= ~FLAG_IRQCONTEXT;

        return IRQ_HANDLED;
}

static int sh_cmt_start(struct sh_cmt_priv *p, unsigned long flag)
{
        int ret = 0;
        unsigned long flags;

        spin_lock_irqsave(&p->lock, flags);

        if (!(p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
                ret = sh_cmt_enable(p, &p->rate);

        if (ret)
                goto out;
        p->flags |= flag;

        /* setup timeout if no clockevent */
        if ((flag == FLAG_CLOCKSOURCE) && (!(p->flags & FLAG_CLOCKEVENT)))
                sh_cmt_set_next(p, p->max_match_value);
 out:
        spin_unlock_irqrestore(&p->lock, flags);

        return ret;
}

static void sh_cmt_stop(struct sh_cmt_priv *p, unsigned long flag)
{
        unsigned long flags;
        unsigned long f;

        spin_lock_irqsave(&p->lock, flags);

        f = p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE);
        p->flags &= ~flag;

        if (f && !(p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
                sh_cmt_disable(p);

        /* adjust the timeout to maximum if only clocksource left */
        if ((flag == FLAG_CLOCKEVENT) && (p->flags & FLAG_CLOCKSOURCE))
                sh_cmt_set_next(p, p->max_match_value);

        spin_unlock_irqrestore(&p->lock, flags);
}

static struct sh_cmt_priv *cs_to_sh_cmt(struct clocksource *cs)
{
        return container_of(cs, struct sh_cmt_priv, cs);
}

static cycle_t sh_cmt_clocksource_read(struct clocksource *cs)
{
        struct sh_cmt_priv *p = cs_to_sh_cmt(cs);
        unsigned long flags, raw;
        unsigned long value;
        int has_wrapped;

        spin_lock_irqsave(&p->lock, flags);
        value = p->total_cycles;
        raw = sh_cmt_get_counter(p, &has_wrapped);

        if (unlikely(has_wrapped))
                raw += p->match_value;
        spin_unlock_irqrestore(&p->lock, flags);

        return value + raw;
}

static int sh_cmt_clocksource_enable(struct clocksource *cs)
{
        struct sh_cmt_priv *p = cs_to_sh_cmt(cs);
        int ret;

        p->total_cycles = 0;

        ret = sh_cmt_start(p, FLAG_CLOCKSOURCE);
        if (ret)
                return ret;

        /* TODO: calculate good shift from rate and counter bit width */
        cs->shift = 0;
        cs->mult = clocksource_hz2mult(p->rate, cs->shift);
        return 0;
}

static void sh_cmt_clocksource_disable(struct clocksource *cs)
{
        sh_cmt_stop(cs_to_sh_cmt(cs), FLAG_CLOCKSOURCE);
}

static int sh_cmt_register_clocksource(struct sh_cmt_priv *p,
                                       char *name, unsigned long rating)
{
        struct clocksource *cs = &p->cs;

        cs->name = name;
        cs->rating = rating;
        cs->read = sh_cmt_clocksource_read;
        cs->enable = sh_cmt_clocksource_enable;
        cs->disable = sh_cmt_clocksource_disable;
        cs->mask = CLOCKSOURCE_MASK(sizeof(unsigned long) * 8);
        cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;
        pr_info("sh_cmt: %s used as clock source\n", cs->name);
        clocksource_register(cs);
        return 0;
}

static struct sh_cmt_priv *ced_to_sh_cmt(struct clock_event_device *ced)
{
        return container_of(ced, struct sh_cmt_priv, ced);
}

static void sh_cmt_clock_event_start(struct sh_cmt_priv *p, int periodic)
{
        struct clock_event_device *ced = &p->ced;

        sh_cmt_start(p, FLAG_CLOCKEVENT);

        /* TODO: calculate good shift from rate and counter bit width */

        ced->shift = 32;
        ced->mult = div_sc(p->rate, NSEC_PER_SEC, ced->shift);
        ced->max_delta_ns = clockevent_delta2ns(p->max_match_value, ced);
        ced->min_delta_ns = clockevent_delta2ns(0x1f, ced);

        if (periodic)
                sh_cmt_set_next(p, (p->rate + HZ/2) / HZ);
        else
                sh_cmt_set_next(p, p->max_match_value);
}

static void sh_cmt_clock_event_mode(enum clock_event_mode mode,
                                    struct clock_event_device *ced)
{
        struct sh_cmt_priv *p = ced_to_sh_cmt(ced);

        /* deal with old setting first */
        switch (ced->mode) {
        case CLOCK_EVT_MODE_PERIODIC:
        case CLOCK_EVT_MODE_ONESHOT:
                sh_cmt_stop(p, FLAG_CLOCKEVENT);
                break;
        default:
                break;
        }

        switch (mode) {
        case CLOCK_EVT_MODE_PERIODIC:
                pr_info("sh_cmt: %s used for periodic clock events\n",
                        ced->name);
                sh_cmt_clock_event_start(p, 1);
                break;
        case CLOCK_EVT_MODE_ONESHOT:
                pr_info("sh_cmt: %s used for oneshot clock events\n",
                        ced->name);
                sh_cmt_clock_event_start(p, 0);
                break;
        case CLOCK_EVT_MODE_SHUTDOWN:
        case CLOCK_EVT_MODE_UNUSED:
                sh_cmt_stop(p, FLAG_CLOCKEVENT);
                break;
        default:
                break;
        }
}

static int sh_cmt_clock_event_next(unsigned long delta,
                                   struct clock_event_device *ced)
{
        struct sh_cmt_priv *p = ced_to_sh_cmt(ced);

        BUG_ON(ced->mode != CLOCK_EVT_MODE_ONESHOT);
        if (likely(p->flags & FLAG_IRQCONTEXT))
                p->next_match_value = delta;
        else
                sh_cmt_set_next(p, delta);

        return 0;
}

static void sh_cmt_register_clockevent(struct sh_cmt_priv *p,
                                       char *name, unsigned long rating)
{
        struct clock_event_device *ced = &p->ced;

        memset(ced, 0, sizeof(*ced));

        ced->name = name;
        ced->features = CLOCK_EVT_FEAT_PERIODIC;
        ced->features |= CLOCK_EVT_FEAT_ONESHOT;
        ced->rating = rating;
        ced->cpumask = cpumask_of(0);
        ced->set_next_event = sh_cmt_clock_event_next;
        ced->set_mode = sh_cmt_clock_event_mode;

        pr_info("sh_cmt: %s used for clock events\n", ced->name);
        clockevents_register_device(ced);
}

static int sh_cmt_register(struct sh_cmt_priv *p, char *name,
                           unsigned long clockevent_rating,
                           unsigned long clocksource_rating)
{
        if (p->width == (sizeof(p->max_match_value) * 8))
                p->max_match_value = ~0;
        else
                p->max_match_value = (1 << p->width) - 1;

        p->match_value = p->max_match_value;
        spin_lock_init(&p->lock);

        if (clockevent_rating)
                sh_cmt_register_clockevent(p, name, clockevent_rating);

        if (clocksource_rating)
                sh_cmt_register_clocksource(p, name, clocksource_rating);

        return 0;
}

static int sh_cmt_setup(struct sh_cmt_priv *p, struct platform_device *pdev)
{
        struct sh_timer_config *cfg = pdev->dev.platform_data;
        struct resource *res;
        int irq, ret;
        ret = -ENXIO;

        memset(p, 0, sizeof(*p));
        p->pdev = pdev;

        if (!cfg) {
                dev_err(&p->pdev->dev, "missing platform data\n");
                goto err0;
        }

        platform_set_drvdata(pdev, p);

        res = platform_get_resource(p->pdev, IORESOURCE_MEM, 0);
        if (!res) {
                dev_err(&p->pdev->dev, "failed to get I/O memory\n");
                goto err0;
        }

        irq = platform_get_irq(p->pdev, 0);
        if (irq < 0) {
                dev_err(&p->pdev->dev, "failed to get irq\n");
                goto err0;
        }

        /* map memory, let mapbase point to our channel */
        p->mapbase = ioremap_nocache(res->start, resource_size(res));
        if (p->mapbase == NULL) {
                pr_err("sh_cmt: failed to remap I/O memory\n");
                goto err0;
        }

        /* request irq using setup_irq() (too early for request_irq()) */
        p->irqaction.name = cfg->name;
        p->irqaction.handler = sh_cmt_interrupt;
        p->irqaction.dev_id = p;
        p->irqaction.flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL;
        ret = setup_irq(irq, &p->irqaction);
        if (ret) {
                pr_err("sh_cmt: failed to request irq %d\n", irq);
                goto err1;
        }

        /* get hold of clock */
        p->clk = clk_get(&p->pdev->dev, cfg->clk);
        if (IS_ERR(p->clk)) {
                pr_err("sh_cmt: cannot get clock \"%s\"\n", cfg->clk);
                ret = PTR_ERR(p->clk);
                goto err2;
        }

        if (resource_size(res) == 6) {
                p->width = 16;
                p->overflow_bit = 0x80;
                p->clear_bits = ~0x80;
        } else {
                p->width = 32;
                p->overflow_bit = 0x8000;
                p->clear_bits = ~0xc000;
        }

        return sh_cmt_register(p, cfg->name,
                               cfg->clockevent_rating,
                               cfg->clocksource_rating);
 err2:
        remove_irq(irq, &p->irqaction);
 err1:
        iounmap(p->mapbase);
 err0:
        return ret;
}

static int __devinit sh_cmt_probe(struct platform_device *pdev)
{
        struct sh_cmt_priv *p = platform_get_drvdata(pdev);
        struct sh_timer_config *cfg = pdev->dev.platform_data;
        int ret;

        if (p) {
                pr_info("sh_cmt: %s kept as earlytimer\n", cfg->name);
                return 0;
        }

        p = kmalloc(sizeof(*p), GFP_KERNEL);
        if (p == NULL) {
                dev_err(&pdev->dev, "failed to allocate driver data\n");
                return -ENOMEM;
        }

        ret = sh_cmt_setup(p, pdev);
        if (ret) {
                kfree(p);
                platform_set_drvdata(pdev, NULL);
        }
        return ret;
}

static int __devexit sh_cmt_remove(struct platform_device *pdev)
{
        return -EBUSY; /* cannot unregister clockevent and clocksource */
}

static int sh_cmt_suspend(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct sh_cmt_priv *p = platform_get_drvdata(pdev);

        /* save flag state and stop CMT channel */
        p->flags_suspend = p->flags;
        sh_cmt_stop(p, p->flags);
        return 0;
}

static int sh_cmt_resume(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct sh_cmt_priv *p = platform_get_drvdata(pdev);

        /* start CMT channel from saved state */
        sh_cmt_start(p, p->flags_suspend);
        return 0;
}

static struct dev_pm_ops sh_cmt_dev_pm_ops = {
        .suspend = sh_cmt_suspend,
        .resume = sh_cmt_resume,
};

static struct platform_driver sh_cmt_device_driver = {
        .probe          = sh_cmt_probe,
        .remove         = __devexit_p(sh_cmt_remove),
        .driver         = {
                .name   = "sh_cmt",
                .pm     = &sh_cmt_dev_pm_ops,
        }
};

static int __init sh_cmt_init(void)
{
        return platform_driver_register(&sh_cmt_device_driver);
}

static void __exit sh_cmt_exit(void)
{
        platform_driver_unregister(&sh_cmt_device_driver);
}

early_platform_init("earlytimer", &sh_cmt_device_driver);
module_init(sh_cmt_init);
module_exit(sh_cmt_exit);

MODULE_AUTHOR("Magnus Damm");
MODULE_DESCRIPTION("SuperH CMT Timer Driver");
MODULE_LICENSE("GPL v2");