/*
 * Freescale FlexTimer Module (FTM) timer driver.
 *
 * Copyright 2014 Freescale Semiconductor, Inc.
 *
 * 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, or (at your option) any later version.
 */

#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/sched_clock.h>
#include <linux/slab.h>

#define FTM_SC          0x00
#define FTM_SC_CLK_SHIFT        3
#define FTM_SC_CLK_MASK (0x3 << FTM_SC_CLK_SHIFT)
#define FTM_SC_CLK(c)   ((c) << FTM_SC_CLK_SHIFT)
#define FTM_SC_PS_MASK  0x7
#define FTM_SC_TOIE     BIT(6)
#define FTM_SC_TOF      BIT(7)

#define FTM_CNT         0x04
#define FTM_MOD         0x08
#define FTM_CNTIN       0x4C

#define FTM_PS_MAX      7

struct ftm_clock_device {
        void __iomem *clksrc_base;
        void __iomem *clkevt_base;
        unsigned long periodic_cyc;
        unsigned long ps;
        bool big_endian;
};

static struct ftm_clock_device *priv;

static inline u32 ftm_readl(void __iomem *addr)
{
        if (priv->big_endian)
                return ioread32be(addr);
        else
                return ioread32(addr);
}

static inline void ftm_writel(u32 val, void __iomem *addr)
{
        if (priv->big_endian)
                iowrite32be(val, addr);
        else
                iowrite32(val, addr);
}

static inline void ftm_counter_enable(void __iomem *base)
{
        u32 val;

        /* select and enable counter clock source */
        val = ftm_readl(base + FTM_SC);
        val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
        val |= priv->ps | FTM_SC_CLK(1);
        ftm_writel(val, base + FTM_SC);
}

static inline void ftm_counter_disable(void __iomem *base)
{
        u32 val;

        /* disable counter clock source */
        val = ftm_readl(base + FTM_SC);
        val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
        ftm_writel(val, base + FTM_SC);
}

static inline void ftm_irq_acknowledge(void __iomem *base)
{
        u32 val;

        val = ftm_readl(base + FTM_SC);
        val &= ~FTM_SC_TOF;
        ftm_writel(val, base + FTM_SC);
}

static inline void ftm_irq_enable(void __iomem *base)
{
        u32 val;

        val = ftm_readl(base + FTM_SC);
        val |= FTM_SC_TOIE;
        ftm_writel(val, base + FTM_SC);
}

static inline void ftm_irq_disable(void __iomem *base)
{
        u32 val;

        val = ftm_readl(base + FTM_SC);
        val &= ~FTM_SC_TOIE;
        ftm_writel(val, base + FTM_SC);
}

static inline void ftm_reset_counter(void __iomem *base)
{
        /*
         * The CNT register contains the FTM counter value.
         * Reset clears the CNT register. Writing any value to COUNT
         * updates the counter with its initial value, CNTIN.
         */
        ftm_writel(0x00, base + FTM_CNT);
}

static u64 notrace ftm_read_sched_clock(void)
{
        return ftm_readl(priv->clksrc_base + FTM_CNT);
}

static int ftm_set_next_event(unsigned long delta,
                                struct clock_event_device *unused)
{
        /*
         * The CNNIN and MOD are all double buffer registers, writing
         * to the MOD register latches the value into a buffer. The MOD
         * register is updated with the value of its write buffer with
         * the following scenario:
         * a, the counter source clock is diabled.
         */
        ftm_counter_disable(priv->clkevt_base);

        /* Force the value of CNTIN to be loaded into the FTM counter */
        ftm_reset_counter(priv->clkevt_base);

        /*
         * The counter increments until the value of MOD is reached,
         * at which point the counter is reloaded with the value of CNTIN.
         * The TOF (the overflow flag) bit is set when the FTM counter
         * changes from MOD to CNTIN. So we should using the delta - 1.
         */
        ftm_writel(delta - 1, priv->clkevt_base + FTM_MOD);

        ftm_counter_enable(priv->clkevt_base);

        ftm_irq_enable(priv->clkevt_base);

        return 0;
}

static int ftm_set_oneshot(struct clock_event_device *evt)
{
        ftm_counter_disable(priv->clkevt_base);
        return 0;
}

static int ftm_set_periodic(struct clock_event_device *evt)
{
        ftm_set_next_event(priv->periodic_cyc, evt);
        return 0;
}

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

        ftm_irq_acknowledge(priv->clkevt_base);

        if (likely(clockevent_state_oneshot(evt))) {
                ftm_irq_disable(priv->clkevt_base);
                ftm_counter_disable(priv->clkevt_base);
        }

        evt->event_handler(evt);

        return IRQ_HANDLED;
}

static struct clock_event_device ftm_clockevent = {
        .name                   = "Freescale ftm timer",
        .features               = CLOCK_EVT_FEAT_PERIODIC |
                                  CLOCK_EVT_FEAT_ONESHOT,
        .set_state_periodic     = ftm_set_periodic,
        .set_state_oneshot      = ftm_set_oneshot,
        .set_next_event         = ftm_set_next_event,
        .rating                 = 300,
};

static struct irqaction ftm_timer_irq = {
        .name           = "Freescale ftm timer",
        .flags          = IRQF_TIMER | IRQF_IRQPOLL,
        .handler        = ftm_evt_interrupt,
        .dev_id         = &ftm_clockevent,
};

static int __init ftm_clockevent_init(unsigned long freq, int irq)
{
        int err;

        ftm_writel(0x00, priv->clkevt_base + FTM_CNTIN);
        ftm_writel(~0u, priv->clkevt_base + FTM_MOD);

        ftm_reset_counter(priv->clkevt_base);

        err = setup_irq(irq, &ftm_timer_irq);
        if (err) {
                pr_err("ftm: setup irq failed: %d\n", err);
                return err;
        }

        ftm_clockevent.cpumask = cpumask_of(0);
        ftm_clockevent.irq = irq;

        clockevents_config_and_register(&ftm_clockevent,
                                        freq / (1 << priv->ps),
                                        1, 0xffff);

        ftm_counter_enable(priv->clkevt_base);

        return 0;
}

static int __init ftm_clocksource_init(unsigned long freq)
{
        int err;

        ftm_writel(0x00, priv->clksrc_base + FTM_CNTIN);
        ftm_writel(~0u, priv->clksrc_base + FTM_MOD);

        ftm_reset_counter(priv->clksrc_base);

        sched_clock_register(ftm_read_sched_clock, 16, freq / (1 << priv->ps));
        err = clocksource_mmio_init(priv->clksrc_base + FTM_CNT, "fsl-ftm",
                                    freq / (1 << priv->ps), 300, 16,
                                    clocksource_mmio_readl_up);
        if (err) {
                pr_err("ftm: init clock source mmio failed: %d\n", err);
                return err;
        }

        ftm_counter_enable(priv->clksrc_base);

        return 0;
}

static int __init __ftm_clk_init(struct device_node *np, char *cnt_name,
                                 char *ftm_name)
{
        struct clk *clk;
        int err;

        clk = of_clk_get_by_name(np, cnt_name);
        if (IS_ERR(clk)) {
                pr_err("ftm: Cannot get \"%s\": %ld\n", cnt_name, PTR_ERR(clk));
                return PTR_ERR(clk);
        }
        err = clk_prepare_enable(clk);
        if (err) {
                pr_err("ftm: clock failed to prepare+enable \"%s\": %d\n",
                        cnt_name, err);
                return err;
        }

        clk = of_clk_get_by_name(np, ftm_name);
        if (IS_ERR(clk)) {
                pr_err("ftm: Cannot get \"%s\": %ld\n", ftm_name, PTR_ERR(clk));
                return PTR_ERR(clk);
        }
        err = clk_prepare_enable(clk);
        if (err)
                pr_err("ftm: clock failed to prepare+enable \"%s\": %d\n",
                        ftm_name, err);

        return clk_get_rate(clk);
}

static unsigned long __init ftm_clk_init(struct device_node *np)
{
        unsigned long freq;

        freq = __ftm_clk_init(np, "ftm-evt-counter-en", "ftm-evt");
        if (freq <= 0)
                return 0;

        freq = __ftm_clk_init(np, "ftm-src-counter-en", "ftm-src");
        if (freq <= 0)
                return 0;

        return freq;
}

static int __init ftm_calc_closest_round_cyc(unsigned long freq)
{
        priv->ps = 0;

        /* The counter register is only using the lower 16 bits, and
         * if the 'freq' value is to big here, then the periodic_cyc
         * may exceed 0xFFFF.
         */
        do {
                priv->periodic_cyc = DIV_ROUND_CLOSEST(freq,
                                                HZ * (1 << priv->ps++));
        } while (priv->periodic_cyc > 0xFFFF);

        if (priv->ps > FTM_PS_MAX) {
                pr_err("ftm: the prescaler is %lu > %d\n",
                                priv->ps, FTM_PS_MAX);
                return -EINVAL;
        }

        return 0;
}

static int __init ftm_timer_init(struct device_node *np)
{
        unsigned long freq;
        int ret, irq;

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        ret = -ENXIO;
        priv->clkevt_base = of_iomap(np, 0);
        if (!priv->clkevt_base) {
                pr_err("ftm: unable to map event timer registers\n");
                goto err;
        }

        priv->clksrc_base = of_iomap(np, 1);
        if (!priv->clksrc_base) {
                pr_err("ftm: unable to map source timer registers\n");
                goto err;
        }

        ret = -EINVAL;
        irq = irq_of_parse_and_map(np, 0);
        if (irq <= 0) {
                pr_err("ftm: unable to get IRQ from DT, %d\n", irq);
                goto err;
        }

        priv->big_endian = of_property_read_bool(np, "big-endian");

        freq = ftm_clk_init(np);
        if (!freq)
                goto err;

        ret = ftm_calc_closest_round_cyc(freq);
        if (ret)
                goto err;

        ret = ftm_clocksource_init(freq);
        if (ret)
                goto err;

        ret = ftm_clockevent_init(freq, irq);
        if (ret)
                goto err;

        return 0;

err:
        kfree(priv);
        return ret;
}
CLOCKSOURCE_OF_DECLARE(flextimer, "fsl,ftm-timer", ftm_timer_init);