// SPDX-License-Identifier: GPL-2.0-only
/*
 * Emma Mobile Timer Support - STI
 *
 *  Copyright (C) 2012 Magnus Damm
 */

#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/delay.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/slab.h>
#include <linux/module.h>

enum { USER_CLOCKSOURCE, USER_CLOCKEVENT, USER_NR };

struct em_sti_priv {
        void __iomem *base;
        struct clk *clk;
        struct platform_device *pdev;
        unsigned int active[USER_NR];
        unsigned long rate;
        raw_spinlock_t lock;
        struct clock_event_device ced;
        struct clocksource cs;
};

#define STI_CONTROL 0x00
#define STI_COMPA_H 0x10
#define STI_COMPA_L 0x14
#define STI_COMPB_H 0x18
#define STI_COMPB_L 0x1c
#define STI_COUNT_H 0x20
#define STI_COUNT_L 0x24
#define STI_COUNT_RAW_H 0x28
#define STI_COUNT_RAW_L 0x2c
#define STI_SET_H 0x30
#define STI_SET_L 0x34
#define STI_INTSTATUS 0x40
#define STI_INTRAWSTATUS 0x44
#define STI_INTENSET 0x48
#define STI_INTENCLR 0x4c
#define STI_INTFFCLR 0x50

static inline unsigned long em_sti_read(struct em_sti_priv *p, int offs)
{
        return ioread32(p->base + offs);
}

static inline void em_sti_write(struct em_sti_priv *p, int offs,
                                unsigned long value)
{
        iowrite32(value, p->base + offs);
}

static int em_sti_enable(struct em_sti_priv *p)
{
        int ret;

        /* enable clock */
        ret = clk_enable(p->clk);
        if (ret) {
                dev_err(&p->pdev->dev, "cannot enable clock\n");
                return ret;
        }

        /* reset the counter */
        em_sti_write(p, STI_SET_H, 0x40000000);
        em_sti_write(p, STI_SET_L, 0x00000000);

        /* mask and clear pending interrupts */
        em_sti_write(p, STI_INTENCLR, 3);
        em_sti_write(p, STI_INTFFCLR, 3);

        /* enable updates of counter registers */
        em_sti_write(p, STI_CONTROL, 1);

        return 0;
}

static void em_sti_disable(struct em_sti_priv *p)
{
        /* mask interrupts */
        em_sti_write(p, STI_INTENCLR, 3);

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

static u64 em_sti_count(struct em_sti_priv *p)
{
        u64 ticks;
        unsigned long flags;

        /* the STI hardware buffers the 48-bit count, but to
         * break it out into two 32-bit access the registers
         * must be accessed in a certain order.
         * Always read STI_COUNT_H before STI_COUNT_L.
         */
        raw_spin_lock_irqsave(&p->lock, flags);
        ticks = (u64)(em_sti_read(p, STI_COUNT_H) & 0xffff) << 32;
        ticks |= em_sti_read(p, STI_COUNT_L);
        raw_spin_unlock_irqrestore(&p->lock, flags);

        return ticks;
}

static u64 em_sti_set_next(struct em_sti_priv *p, u64 next)
{
        unsigned long flags;

        raw_spin_lock_irqsave(&p->lock, flags);

        /* mask compare A interrupt */
        em_sti_write(p, STI_INTENCLR, 1);

        /* update compare A value */
        em_sti_write(p, STI_COMPA_H, next >> 32);
        em_sti_write(p, STI_COMPA_L, next & 0xffffffff);

        /* clear compare A interrupt source */
        em_sti_write(p, STI_INTFFCLR, 1);

        /* unmask compare A interrupt */
        em_sti_write(p, STI_INTENSET, 1);

        raw_spin_unlock_irqrestore(&p->lock, flags);

        return next;
}

static irqreturn_t em_sti_interrupt(int irq, void *dev_id)
{
        struct em_sti_priv *p = dev_id;

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

static int em_sti_start(struct em_sti_priv *p, unsigned int user)
{
        unsigned long flags;
        int used_before;
        int ret = 0;

        raw_spin_lock_irqsave(&p->lock, flags);
        used_before = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];
        if (!used_before)
                ret = em_sti_enable(p);

        if (!ret)
                p->active[user] = 1;
        raw_spin_unlock_irqrestore(&p->lock, flags);

        return ret;
}

static void em_sti_stop(struct em_sti_priv *p, unsigned int user)
{
        unsigned long flags;
        int used_before, used_after;

        raw_spin_lock_irqsave(&p->lock, flags);
        used_before = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];
        p->active[user] = 0;
        used_after = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];

        if (used_before && !used_after)
                em_sti_disable(p);
        raw_spin_unlock_irqrestore(&p->lock, flags);
}

static struct em_sti_priv *cs_to_em_sti(struct clocksource *cs)
{
        return container_of(cs, struct em_sti_priv, cs);
}

static u64 em_sti_clocksource_read(struct clocksource *cs)
{
        return em_sti_count(cs_to_em_sti(cs));
}

static int em_sti_clocksource_enable(struct clocksource *cs)
{
        struct em_sti_priv *p = cs_to_em_sti(cs);

        return em_sti_start(p, USER_CLOCKSOURCE);
}

static void em_sti_clocksource_disable(struct clocksource *cs)
{
        em_sti_stop(cs_to_em_sti(cs), USER_CLOCKSOURCE);
}

static void em_sti_clocksource_resume(struct clocksource *cs)
{
        em_sti_clocksource_enable(cs);
}

static int em_sti_register_clocksource(struct em_sti_priv *p)
{
        struct clocksource *cs = &p->cs;

        cs->name = dev_name(&p->pdev->dev);
        cs->rating = 200;
        cs->read = em_sti_clocksource_read;
        cs->enable = em_sti_clocksource_enable;
        cs->disable = em_sti_clocksource_disable;
        cs->suspend = em_sti_clocksource_disable;
        cs->resume = em_sti_clocksource_resume;
        cs->mask = CLOCKSOURCE_MASK(48);
        cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;

        dev_info(&p->pdev->dev, "used as clock source\n");

        clocksource_register_hz(cs, p->rate);
        return 0;
}

static struct em_sti_priv *ced_to_em_sti(struct clock_event_device *ced)
{
        return container_of(ced, struct em_sti_priv, ced);
}

static int em_sti_clock_event_shutdown(struct clock_event_device *ced)
{
        struct em_sti_priv *p = ced_to_em_sti(ced);
        em_sti_stop(p, USER_CLOCKEVENT);
        return 0;
}

static int em_sti_clock_event_set_oneshot(struct clock_event_device *ced)
{
        struct em_sti_priv *p = ced_to_em_sti(ced);

        dev_info(&p->pdev->dev, "used for oneshot clock events\n");
        em_sti_start(p, USER_CLOCKEVENT);
        return 0;
}

static int em_sti_clock_event_next(unsigned long delta,
                                   struct clock_event_device *ced)
{
        struct em_sti_priv *p = ced_to_em_sti(ced);
        u64 next;
        int safe;

        next = em_sti_set_next(p, em_sti_count(p) + delta);
        safe = em_sti_count(p) < (next - 1);

        return !safe;
}

static void em_sti_register_clockevent(struct em_sti_priv *p)
{
        struct clock_event_device *ced = &p->ced;

        ced->name = dev_name(&p->pdev->dev);
        ced->features = CLOCK_EVT_FEAT_ONESHOT;
        ced->rating = 200;
        ced->cpumask = cpu_possible_mask;
        ced->set_next_event = em_sti_clock_event_next;
        ced->set_state_shutdown = em_sti_clock_event_shutdown;
        ced->set_state_oneshot = em_sti_clock_event_set_oneshot;

        dev_info(&p->pdev->dev, "used for clock events\n");

        clockevents_config_and_register(ced, p->rate, 2, 0xffffffff);
}

static int em_sti_probe(struct platform_device *pdev)
{
        struct em_sti_priv *p;
        int irq, ret;

        p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
        if (p == NULL)
                return -ENOMEM;

        p->pdev = pdev;
        platform_set_drvdata(pdev, p);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        /* map memory, let base point to the STI instance */
        p->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(p->base))
                return PTR_ERR(p->base);

        ret = devm_request_irq(&pdev->dev, irq, em_sti_interrupt,
                               IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
                               dev_name(&pdev->dev), p);
        if (ret) {
                dev_err(&pdev->dev, "failed to request low IRQ\n");
                return ret;
        }

        /* get hold of clock */
        p->clk = devm_clk_get(&pdev->dev, "sclk");
        if (IS_ERR(p->clk)) {
                dev_err(&pdev->dev, "cannot get clock\n");
                return PTR_ERR(p->clk);
        }

        ret = clk_prepare(p->clk);
        if (ret < 0) {
                dev_err(&pdev->dev, "cannot prepare clock\n");
                return ret;
        }

        ret = clk_enable(p->clk);
        if (ret < 0) {
                dev_err(&p->pdev->dev, "cannot enable clock\n");
                clk_unprepare(p->clk);
                return ret;
        }
        p->rate = clk_get_rate(p->clk);
        clk_disable(p->clk);

        raw_spin_lock_init(&p->lock);
        em_sti_register_clockevent(p);
        em_sti_register_clocksource(p);
        return 0;
}

static const struct of_device_id em_sti_dt_ids[] = {
        { .compatible = "renesas,em-sti", },
        {},
};
MODULE_DEVICE_TABLE(of, em_sti_dt_ids);

static struct platform_driver em_sti_device_driver = {
        .probe          = em_sti_probe,
        .driver         = {
                .name   = "em_sti",
                .of_match_table = em_sti_dt_ids,
                .suppress_bind_attrs = true,
        }
};

static int __init em_sti_init(void)
{
        return platform_driver_register(&em_sti_device_driver);
}

static void __exit em_sti_exit(void)
{
        platform_driver_unregister(&em_sti_device_driver);
}

subsys_initcall(em_sti_init);
module_exit(em_sti_exit);

MODULE_AUTHOR("Magnus Damm");
MODULE_DESCRIPTION("Renesas Emma Mobile STI Timer Driver");