/*
 * SuperH Timer Support - TMU
 *
 *  Copyright (C) 2009 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.
 */

#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/sh_timer.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

enum sh_tmu_model {
        SH_TMU,
        SH_TMU_SH3,
};

struct sh_tmu_device;

struct sh_tmu_channel {
        struct sh_tmu_device *tmu;
        unsigned int index;

        void __iomem *base;
        int irq;

        unsigned long rate;
        unsigned long periodic;
        struct clock_event_device ced;
        struct clocksource cs;
        bool cs_enabled;
        unsigned int enable_count;
};

struct sh_tmu_device {
        struct platform_device *pdev;

        void __iomem *mapbase;
        struct clk *clk;

        enum sh_tmu_model model;

        raw_spinlock_t lock; /* Protect the shared start/stop register */

        struct sh_tmu_channel *channels;
        unsigned int num_channels;

        bool has_clockevent;
        bool has_clocksource;
};

#define TSTR -1 /* shared register */
#define TCOR  0 /* channel register */
#define TCNT 1 /* channel register */
#define TCR 2 /* channel register */

#define TCR_UNF                 (1 << 8)
#define TCR_UNIE                (1 << 5)
#define TCR_TPSC_CLK4           (0 << 0)
#define TCR_TPSC_CLK16          (1 << 0)
#define TCR_TPSC_CLK64          (2 << 0)
#define TCR_TPSC_CLK256         (3 << 0)
#define TCR_TPSC_CLK1024        (4 << 0)
#define TCR_TPSC_MASK           (7 << 0)

static inline unsigned long sh_tmu_read(struct sh_tmu_channel *ch, int reg_nr)
{
        unsigned long offs;

        if (reg_nr == TSTR) {
                switch (ch->tmu->model) {
                case SH_TMU_SH3:
                        return ioread8(ch->tmu->mapbase + 2);
                case SH_TMU:
                        return ioread8(ch->tmu->mapbase + 4);
                }
        }

        offs = reg_nr << 2;

        if (reg_nr == TCR)
                return ioread16(ch->base + offs);
        else
                return ioread32(ch->base + offs);
}

static inline void sh_tmu_write(struct sh_tmu_channel *ch, int reg_nr,
                                unsigned long value)
{
        unsigned long offs;

        if (reg_nr == TSTR) {
                switch (ch->tmu->model) {
                case SH_TMU_SH3:
                        return iowrite8(value, ch->tmu->mapbase + 2);
                case SH_TMU:
                        return iowrite8(value, ch->tmu->mapbase + 4);
                }
        }

        offs = reg_nr << 2;

        if (reg_nr == TCR)
                iowrite16(value, ch->base + offs);
        else
                iowrite32(value, ch->base + offs);
}

static void sh_tmu_start_stop_ch(struct sh_tmu_channel *ch, int start)
{
        unsigned long flags, value;

        /* start stop register shared by multiple timer channels */
        raw_spin_lock_irqsave(&ch->tmu->lock, flags);
        value = sh_tmu_read(ch, TSTR);

        if (start)
                value |= 1 << ch->index;
        else
                value &= ~(1 << ch->index);

        sh_tmu_write(ch, TSTR, value);
        raw_spin_unlock_irqrestore(&ch->tmu->lock, flags);
}

static int __sh_tmu_enable(struct sh_tmu_channel *ch)
{
        int ret;

        /* enable clock */
        ret = clk_enable(ch->tmu->clk);
        if (ret) {
                dev_err(&ch->tmu->pdev->dev, "ch%u: cannot enable clock\n",
                        ch->index);
                return ret;
        }

        /* make sure channel is disabled */
        sh_tmu_start_stop_ch(ch, 0);

        /* maximum timeout */
        sh_tmu_write(ch, TCOR, 0xffffffff);
        sh_tmu_write(ch, TCNT, 0xffffffff);

        /* configure channel to parent clock / 4, irq off */
        ch->rate = clk_get_rate(ch->tmu->clk) / 4;
        sh_tmu_write(ch, TCR, TCR_TPSC_CLK4);

        /* enable channel */
        sh_tmu_start_stop_ch(ch, 1);

        return 0;
}

static int sh_tmu_enable(struct sh_tmu_channel *ch)
{
        if (ch->enable_count++ > 0)
                return 0;

        pm_runtime_get_sync(&ch->tmu->pdev->dev);
        dev_pm_syscore_device(&ch->tmu->pdev->dev, true);

        return __sh_tmu_enable(ch);
}

static void __sh_tmu_disable(struct sh_tmu_channel *ch)
{
        /* disable channel */
        sh_tmu_start_stop_ch(ch, 0);

        /* disable interrupts in TMU block */
        sh_tmu_write(ch, TCR, TCR_TPSC_CLK4);

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

static void sh_tmu_disable(struct sh_tmu_channel *ch)
{
        if (WARN_ON(ch->enable_count == 0))
                return;

        if (--ch->enable_count > 0)
                return;

        __sh_tmu_disable(ch);

        dev_pm_syscore_device(&ch->tmu->pdev->dev, false);
        pm_runtime_put(&ch->tmu->pdev->dev);
}

static void sh_tmu_set_next(struct sh_tmu_channel *ch, unsigned long delta,
                            int periodic)
{
        /* stop timer */
        sh_tmu_start_stop_ch(ch, 0);

        /* acknowledge interrupt */
        sh_tmu_read(ch, TCR);

        /* enable interrupt */
        sh_tmu_write(ch, TCR, TCR_UNIE | TCR_TPSC_CLK4);

        /* reload delta value in case of periodic timer */
        if (periodic)
                sh_tmu_write(ch, TCOR, delta);
        else
                sh_tmu_write(ch, TCOR, 0xffffffff);

        sh_tmu_write(ch, TCNT, delta);

        /* start timer */
        sh_tmu_start_stop_ch(ch, 1);
}

static irqreturn_t sh_tmu_interrupt(int irq, void *dev_id)
{
        struct sh_tmu_channel *ch = dev_id;

        /* disable or acknowledge interrupt */
        if (clockevent_state_oneshot(&ch->ced))
                sh_tmu_write(ch, TCR, TCR_TPSC_CLK4);
        else
                sh_tmu_write(ch, TCR, TCR_UNIE | TCR_TPSC_CLK4);

        /* notify clockevent layer */
        ch->ced.event_handler(&ch->ced);
        return IRQ_HANDLED;
}

static struct sh_tmu_channel *cs_to_sh_tmu(struct clocksource *cs)
{
        return container_of(cs, struct sh_tmu_channel, cs);
}

static cycle_t sh_tmu_clocksource_read(struct clocksource *cs)
{
        struct sh_tmu_channel *ch = cs_to_sh_tmu(cs);

        return sh_tmu_read(ch, TCNT) ^ 0xffffffff;
}

static int sh_tmu_clocksource_enable(struct clocksource *cs)
{
        struct sh_tmu_channel *ch = cs_to_sh_tmu(cs);
        int ret;

        if (WARN_ON(ch->cs_enabled))
                return 0;

        ret = sh_tmu_enable(ch);
        if (!ret) {
                __clocksource_update_freq_hz(cs, ch->rate);
                ch->cs_enabled = true;
        }

        return ret;
}

static void sh_tmu_clocksource_disable(struct clocksource *cs)
{
        struct sh_tmu_channel *ch = cs_to_sh_tmu(cs);

        if (WARN_ON(!ch->cs_enabled))
                return;

        sh_tmu_disable(ch);
        ch->cs_enabled = false;
}

static void sh_tmu_clocksource_suspend(struct clocksource *cs)
{
        struct sh_tmu_channel *ch = cs_to_sh_tmu(cs);

        if (!ch->cs_enabled)
                return;

        if (--ch->enable_count == 0) {
                __sh_tmu_disable(ch);
                pm_genpd_syscore_poweroff(&ch->tmu->pdev->dev);
        }
}

static void sh_tmu_clocksource_resume(struct clocksource *cs)
{
        struct sh_tmu_channel *ch = cs_to_sh_tmu(cs);

        if (!ch->cs_enabled)
                return;

        if (ch->enable_count++ == 0) {
                pm_genpd_syscore_poweron(&ch->tmu->pdev->dev);
                __sh_tmu_enable(ch);
        }
}

static int sh_tmu_register_clocksource(struct sh_tmu_channel *ch,
                                       const char *name)
{
        struct clocksource *cs = &ch->cs;

        cs->name = name;
        cs->rating = 200;
        cs->read = sh_tmu_clocksource_read;
        cs->enable = sh_tmu_clocksource_enable;
        cs->disable = sh_tmu_clocksource_disable;
        cs->suspend = sh_tmu_clocksource_suspend;
        cs->resume = sh_tmu_clocksource_resume;
        cs->mask = CLOCKSOURCE_MASK(32);
        cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;

        dev_info(&ch->tmu->pdev->dev, "ch%u: used as clock source\n",
                 ch->index);

        /* Register with dummy 1 Hz value, gets updated in ->enable() */
        clocksource_register_hz(cs, 1);
        return 0;
}

static struct sh_tmu_channel *ced_to_sh_tmu(struct clock_event_device *ced)
{
        return container_of(ced, struct sh_tmu_channel, ced);
}

static void sh_tmu_clock_event_start(struct sh_tmu_channel *ch, int periodic)
{
        struct clock_event_device *ced = &ch->ced;

        sh_tmu_enable(ch);

        clockevents_config(ced, ch->rate);

        if (periodic) {
                ch->periodic = (ch->rate + HZ/2) / HZ;
                sh_tmu_set_next(ch, ch->periodic, 1);
        }
}

static int sh_tmu_clock_event_shutdown(struct clock_event_device *ced)
{
        struct sh_tmu_channel *ch = ced_to_sh_tmu(ced);

        if (clockevent_state_oneshot(ced) || clockevent_state_periodic(ced))
                sh_tmu_disable(ch);
        return 0;
}

static int sh_tmu_clock_event_set_state(struct clock_event_device *ced,
                                        int periodic)
{
        struct sh_tmu_channel *ch = ced_to_sh_tmu(ced);

        /* deal with old setting first */
        if (clockevent_state_oneshot(ced) || clockevent_state_periodic(ced))
                sh_tmu_disable(ch);

        dev_info(&ch->tmu->pdev->dev, "ch%u: used for %s clock events\n",
                 ch->index, periodic ? "periodic" : "oneshot");
        sh_tmu_clock_event_start(ch, periodic);
        return 0;
}

static int sh_tmu_clock_event_set_oneshot(struct clock_event_device *ced)
{
        return sh_tmu_clock_event_set_state(ced, 0);
}

static int sh_tmu_clock_event_set_periodic(struct clock_event_device *ced)
{
        return sh_tmu_clock_event_set_state(ced, 1);
}

static int sh_tmu_clock_event_next(unsigned long delta,
                                   struct clock_event_device *ced)
{
        struct sh_tmu_channel *ch = ced_to_sh_tmu(ced);

        BUG_ON(!clockevent_state_oneshot(ced));

        /* program new delta value */
        sh_tmu_set_next(ch, delta, 0);
        return 0;
}

static void sh_tmu_clock_event_suspend(struct clock_event_device *ced)
{
        pm_genpd_syscore_poweroff(&ced_to_sh_tmu(ced)->tmu->pdev->dev);
}

static void sh_tmu_clock_event_resume(struct clock_event_device *ced)
{
        pm_genpd_syscore_poweron(&ced_to_sh_tmu(ced)->tmu->pdev->dev);
}

static void sh_tmu_register_clockevent(struct sh_tmu_channel *ch,
                                       const char *name)
{
        struct clock_event_device *ced = &ch->ced;
        int ret;

        ced->name = name;
        ced->features = CLOCK_EVT_FEAT_PERIODIC;
        ced->features |= CLOCK_EVT_FEAT_ONESHOT;
        ced->rating = 200;
        ced->cpumask = cpu_possible_mask;
        ced->set_next_event = sh_tmu_clock_event_next;
        ced->set_state_shutdown = sh_tmu_clock_event_shutdown;
        ced->set_state_periodic = sh_tmu_clock_event_set_periodic;
        ced->set_state_oneshot = sh_tmu_clock_event_set_oneshot;
        ced->suspend = sh_tmu_clock_event_suspend;
        ced->resume = sh_tmu_clock_event_resume;

        dev_info(&ch->tmu->pdev->dev, "ch%u: used for clock events\n",
                 ch->index);

        clockevents_config_and_register(ced, 1, 0x300, 0xffffffff);

        ret = request_irq(ch->irq, sh_tmu_interrupt,
                          IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
                          dev_name(&ch->tmu->pdev->dev), ch);
        if (ret) {
                dev_err(&ch->tmu->pdev->dev, "ch%u: failed to request irq %d\n",
                        ch->index, ch->irq);
                return;
        }
}

static int sh_tmu_register(struct sh_tmu_channel *ch, const char *name,
                           bool clockevent, bool clocksource)
{
        if (clockevent) {
                ch->tmu->has_clockevent = true;
                sh_tmu_register_clockevent(ch, name);
        } else if (clocksource) {
                ch->tmu->has_clocksource = true;
                sh_tmu_register_clocksource(ch, name);
        }

        return 0;
}

static int sh_tmu_channel_setup(struct sh_tmu_channel *ch, unsigned int index,
                                bool clockevent, bool clocksource,
                                struct sh_tmu_device *tmu)
{
        /* Skip unused channels. */
        if (!clockevent && !clocksource)
                return 0;

        ch->tmu = tmu;
        ch->index = index;

        if (tmu->model == SH_TMU_SH3)
                ch->base = tmu->mapbase + 4 + ch->index * 12;
        else
                ch->base = tmu->mapbase + 8 + ch->index * 12;

        ch->irq = platform_get_irq(tmu->pdev, index);
        if (ch->irq < 0) {
                dev_err(&tmu->pdev->dev, "ch%u: failed to get irq\n",
                        ch->index);
                return ch->irq;
        }

        ch->cs_enabled = false;
        ch->enable_count = 0;

        return sh_tmu_register(ch, dev_name(&tmu->pdev->dev),
                               clockevent, clocksource);
}

static int sh_tmu_map_memory(struct sh_tmu_device *tmu)
{
        struct resource *res;

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

        tmu->mapbase = ioremap_nocache(res->start, resource_size(res));
        if (tmu->mapbase == NULL)
                return -ENXIO;

        return 0;
}

static int sh_tmu_parse_dt(struct sh_tmu_device *tmu)
{
        struct device_node *np = tmu->pdev->dev.of_node;

        tmu->model = SH_TMU;
        tmu->num_channels = 3;

        of_property_read_u32(np, "#renesas,channels", &tmu->num_channels);

        if (tmu->num_channels != 2 && tmu->num_channels != 3) {
                dev_err(&tmu->pdev->dev, "invalid number of channels %u\n",
                        tmu->num_channels);
                return -EINVAL;
        }

        return 0;
}

static int sh_tmu_setup(struct sh_tmu_device *tmu, struct platform_device *pdev)
{
        unsigned int i;
        int ret;

        tmu->pdev = pdev;

        raw_spin_lock_init(&tmu->lock);

        if (IS_ENABLED(CONFIG_OF) && pdev->dev.of_node) {
                ret = sh_tmu_parse_dt(tmu);
                if (ret < 0)
                        return ret;
        } else if (pdev->dev.platform_data) {
                const struct platform_device_id *id = pdev->id_entry;
                struct sh_timer_config *cfg = pdev->dev.platform_data;

                tmu->model = id->driver_data;
                tmu->num_channels = hweight8(cfg->channels_mask);
        } else {
                dev_err(&tmu->pdev->dev, "missing platform data\n");
                return -ENXIO;
        }

        /* Get hold of clock. */
        tmu->clk = clk_get(&tmu->pdev->dev, "fck");
        if (IS_ERR(tmu->clk)) {
                dev_err(&tmu->pdev->dev, "cannot get clock\n");
                return PTR_ERR(tmu->clk);
        }

        ret = clk_prepare(tmu->clk);
        if (ret < 0)
                goto err_clk_put;

        /* Map the memory resource. */
        ret = sh_tmu_map_memory(tmu);
        if (ret < 0) {
                dev_err(&tmu->pdev->dev, "failed to remap I/O memory\n");
                goto err_clk_unprepare;
        }

        /* Allocate and setup the channels. */
        tmu->channels = kzalloc(sizeof(*tmu->channels) * tmu->num_channels,
                                GFP_KERNEL);
        if (tmu->channels == NULL) {
                ret = -ENOMEM;
                goto err_unmap;
        }

        /*
         * Use the first channel as a clock event device and the second channel
         * as a clock source.
         */
        for (i = 0; i < tmu->num_channels; ++i) {
                ret = sh_tmu_channel_setup(&tmu->channels[i], i,
                                           i == 0, i == 1, tmu);
                if (ret < 0)
                        goto err_unmap;
        }

        platform_set_drvdata(pdev, tmu);

        return 0;

err_unmap:
        kfree(tmu->channels);
        iounmap(tmu->mapbase);
err_clk_unprepare:
        clk_unprepare(tmu->clk);
err_clk_put:
        clk_put(tmu->clk);
        return ret;
}

static int sh_tmu_probe(struct platform_device *pdev)
{
        struct sh_tmu_device *tmu = platform_get_drvdata(pdev);
        int ret;

        if (!is_early_platform_device(pdev)) {
                pm_runtime_set_active(&pdev->dev);
                pm_runtime_enable(&pdev->dev);
        }

        if (tmu) {
                dev_info(&pdev->dev, "kept as earlytimer\n");
                goto out;
        }

        tmu = kzalloc(sizeof(*tmu), GFP_KERNEL);
        if (tmu == NULL)
                return -ENOMEM;

        ret = sh_tmu_setup(tmu, pdev);
        if (ret) {
                kfree(tmu);
                pm_runtime_idle(&pdev->dev);
                return ret;
        }
        if (is_early_platform_device(pdev))
                return 0;

 out:
        if (tmu->has_clockevent || tmu->has_clocksource)
                pm_runtime_irq_safe(&pdev->dev);
        else
                pm_runtime_idle(&pdev->dev);

        return 0;
}

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

static const struct platform_device_id sh_tmu_id_table[] = {
        { "sh-tmu", SH_TMU },
        { "sh-tmu-sh3", SH_TMU_SH3 },
        { }
};
MODULE_DEVICE_TABLE(platform, sh_tmu_id_table);

static const struct of_device_id sh_tmu_of_table[] __maybe_unused = {
        { .compatible = "renesas,tmu" },
        { }
};
MODULE_DEVICE_TABLE(of, sh_tmu_of_table);

static struct platform_driver sh_tmu_device_driver = {
        .probe          = sh_tmu_probe,
        .remove         = sh_tmu_remove,
        .driver         = {
                .name   = "sh_tmu",
                .of_match_table = of_match_ptr(sh_tmu_of_table),
        },
        .id_table       = sh_tmu_id_table,
};

static int __init sh_tmu_init(void)
{
        return platform_driver_register(&sh_tmu_device_driver);
}

static void __exit sh_tmu_exit(void)
{
        platform_driver_unregister(&sh_tmu_device_driver);
}

early_platform_init("earlytimer", &sh_tmu_device_driver);
subsys_initcall(sh_tmu_init);
module_exit(sh_tmu_exit);

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