/*
 * Copyright (c) 2007 Ben Dooks
 * Copyright (c) 2008 Simtec Electronics
 *     Ben Dooks <ben@simtec.co.uk>, <ben-linux@fluff.org>
 * Copyright (c) 2013 Tomasz Figa <tomasz.figa@gmail.com>
 *
 * PWM driver for Samsung SoCs
 *
 * 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.
 */

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/time.h>

/* For struct samsung_timer_variant and samsung_pwm_lock. */
#include <clocksource/samsung_pwm.h>

#define REG_TCFG0                       0x00
#define REG_TCFG1                       0x04
#define REG_TCON                        0x08

#define REG_TCNTB(chan)                 (0x0c + ((chan) * 0xc))
#define REG_TCMPB(chan)                 (0x10 + ((chan) * 0xc))

#define TCFG0_PRESCALER_MASK            0xff
#define TCFG0_PRESCALER1_SHIFT          8

#define TCFG1_MUX_MASK                  0xf
#define TCFG1_SHIFT(chan)               (4 * (chan))

/*
 * Each channel occupies 4 bits in TCON register, but there is a gap of 4
 * bits (one channel) after channel 0, so channels have different numbering
 * when accessing TCON register. See to_tcon_channel() function.
 *
 * In addition, the location of autoreload bit for channel 4 (TCON channel 5)
 * in its set of bits is 2 as opposed to 3 for other channels.
 */
#define TCON_START(chan)                BIT(4 * (chan) + 0)
#define TCON_MANUALUPDATE(chan)         BIT(4 * (chan) + 1)
#define TCON_INVERT(chan)               BIT(4 * (chan) + 2)
#define _TCON_AUTORELOAD(chan)          BIT(4 * (chan) + 3)
#define _TCON_AUTORELOAD4(chan)         BIT(4 * (chan) + 2)
#define TCON_AUTORELOAD(chan)           \
        ((chan < 5) ? _TCON_AUTORELOAD(chan) : _TCON_AUTORELOAD4(chan))

/**
 * struct samsung_pwm_channel - private data of PWM channel
 * @period_ns:  current period in nanoseconds programmed to the hardware
 * @duty_ns:    current duty time in nanoseconds programmed to the hardware
 * @tin_ns:     time of one timer tick in nanoseconds with current timer rate
 */
struct samsung_pwm_channel {
        u32 period_ns;
        u32 duty_ns;
        u32 tin_ns;
};

/**
 * struct samsung_pwm_chip - private data of PWM chip
 * @chip:               generic PWM chip
 * @variant:            local copy of hardware variant data
 * @inverter_mask:      inverter status for all channels - one bit per channel
 * @base:               base address of mapped PWM registers
 * @base_clk:           base clock used to drive the timers
 * @tclk0:              external clock 0 (can be ERR_PTR if not present)
 * @tclk1:              external clock 1 (can be ERR_PTR if not present)
 */
struct samsung_pwm_chip {
        struct pwm_chip chip;
        struct samsung_pwm_variant variant;
        u8 inverter_mask;

        void __iomem *base;
        struct clk *base_clk;
        struct clk *tclk0;
        struct clk *tclk1;
};

#ifndef CONFIG_CLKSRC_SAMSUNG_PWM
/*
 * PWM block is shared between pwm-samsung and samsung_pwm_timer drivers
 * and some registers need access synchronization. If both drivers are
 * compiled in, the spinlock is defined in the clocksource driver,
 * otherwise following definition is used.
 *
 * Currently we do not need any more complex synchronization method
 * because all the supported SoCs contain only one instance of the PWM
 * IP. Should this change, both drivers will need to be modified to
 * properly synchronize accesses to particular instances.
 */
static DEFINE_SPINLOCK(samsung_pwm_lock);
#endif

static inline
struct samsung_pwm_chip *to_samsung_pwm_chip(struct pwm_chip *chip)
{
        return container_of(chip, struct samsung_pwm_chip, chip);
}

static inline unsigned int to_tcon_channel(unsigned int channel)
{
        /* TCON register has a gap of 4 bits (1 channel) after channel 0 */
        return (channel == 0) ? 0 : (channel + 1);
}

static void pwm_samsung_set_divisor(struct samsung_pwm_chip *pwm,
                                    unsigned int channel, u8 divisor)
{
        u8 shift = TCFG1_SHIFT(channel);
        unsigned long flags;
        u32 reg;
        u8 bits;

        bits = (fls(divisor) - 1) - pwm->variant.div_base;

        spin_lock_irqsave(&samsung_pwm_lock, flags);

        reg = readl(pwm->base + REG_TCFG1);
        reg &= ~(TCFG1_MUX_MASK << shift);
        reg |= bits << shift;
        writel(reg, pwm->base + REG_TCFG1);

        spin_unlock_irqrestore(&samsung_pwm_lock, flags);
}

static int pwm_samsung_is_tdiv(struct samsung_pwm_chip *chip, unsigned int chan)
{
        struct samsung_pwm_variant *variant = &chip->variant;
        u32 reg;

        reg = readl(chip->base + REG_TCFG1);
        reg >>= TCFG1_SHIFT(chan);
        reg &= TCFG1_MUX_MASK;

        return (BIT(reg) & variant->tclk_mask) == 0;
}

static unsigned long pwm_samsung_get_tin_rate(struct samsung_pwm_chip *chip,
                                              unsigned int chan)
{
        unsigned long rate;
        u32 reg;

        rate = clk_get_rate(chip->base_clk);

        reg = readl(chip->base + REG_TCFG0);
        if (chan >= 2)
                reg >>= TCFG0_PRESCALER1_SHIFT;
        reg &= TCFG0_PRESCALER_MASK;

        return rate / (reg + 1);
}

static unsigned long pwm_samsung_calc_tin(struct samsung_pwm_chip *chip,
                                          unsigned int chan, unsigned long freq)
{
        struct samsung_pwm_variant *variant = &chip->variant;
        unsigned long rate;
        struct clk *clk;
        u8 div;

        if (!pwm_samsung_is_tdiv(chip, chan)) {
                clk = (chan < 2) ? chip->tclk0 : chip->tclk1;
                if (!IS_ERR(clk)) {
                        rate = clk_get_rate(clk);
                        if (rate)
                                return rate;
                }

                dev_warn(chip->chip.dev,
                        "tclk of PWM %d is inoperational, using tdiv\n", chan);
        }

        rate = pwm_samsung_get_tin_rate(chip, chan);
        dev_dbg(chip->chip.dev, "tin parent at %lu\n", rate);

        /*
         * Compare minimum PWM frequency that can be achieved with possible
         * divider settings and choose the lowest divisor that can generate
         * frequencies lower than requested.
         */
        if (variant->bits < 32) {
                /* Only for s3c24xx */
                for (div = variant->div_base; div < 4; ++div)
                        if ((rate >> (variant->bits + div)) < freq)
                                break;
        } else {
                /*
                 * Other variants have enough counter bits to generate any
                 * requested rate, so no need to check higher divisors.
                 */
                div = variant->div_base;
        }

        pwm_samsung_set_divisor(chip, chan, BIT(div));

        return rate >> div;
}

static int pwm_samsung_request(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
        struct samsung_pwm_channel *our_chan;

        if (!(our_chip->variant.output_mask & BIT(pwm->hwpwm))) {
                dev_warn(chip->dev,
                        "tried to request PWM channel %d without output\n",
                        pwm->hwpwm);
                return -EINVAL;
        }

        our_chan = devm_kzalloc(chip->dev, sizeof(*our_chan), GFP_KERNEL);
        if (!our_chan)
                return -ENOMEM;

        pwm_set_chip_data(pwm, our_chan);

        return 0;
}

static void pwm_samsung_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
        devm_kfree(chip->dev, pwm_get_chip_data(pwm));
        pwm_set_chip_data(pwm, NULL);
}

static int pwm_samsung_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
        unsigned int tcon_chan = to_tcon_channel(pwm->hwpwm);
        unsigned long flags;
        u32 tcon;

        spin_lock_irqsave(&samsung_pwm_lock, flags);

        tcon = readl(our_chip->base + REG_TCON);

        tcon &= ~TCON_START(tcon_chan);
        tcon |= TCON_MANUALUPDATE(tcon_chan);
        writel(tcon, our_chip->base + REG_TCON);

        tcon &= ~TCON_MANUALUPDATE(tcon_chan);
        tcon |= TCON_START(tcon_chan) | TCON_AUTORELOAD(tcon_chan);
        writel(tcon, our_chip->base + REG_TCON);

        spin_unlock_irqrestore(&samsung_pwm_lock, flags);

        return 0;
}

static void pwm_samsung_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
        unsigned int tcon_chan = to_tcon_channel(pwm->hwpwm);
        unsigned long flags;
        u32 tcon;

        spin_lock_irqsave(&samsung_pwm_lock, flags);

        tcon = readl(our_chip->base + REG_TCON);
        tcon &= ~TCON_AUTORELOAD(tcon_chan);
        writel(tcon, our_chip->base + REG_TCON);

        spin_unlock_irqrestore(&samsung_pwm_lock, flags);
}

static void pwm_samsung_manual_update(struct samsung_pwm_chip *chip,
                                      struct pwm_device *pwm)
{
        unsigned int tcon_chan = to_tcon_channel(pwm->hwpwm);
        u32 tcon;
        unsigned long flags;

        spin_lock_irqsave(&samsung_pwm_lock, flags);

        tcon = readl(chip->base + REG_TCON);
        tcon |= TCON_MANUALUPDATE(tcon_chan);
        writel(tcon, chip->base + REG_TCON);

        tcon &= ~TCON_MANUALUPDATE(tcon_chan);
        writel(tcon, chip->base + REG_TCON);

        spin_unlock_irqrestore(&samsung_pwm_lock, flags);
}

static int pwm_samsung_config(struct pwm_chip *chip, struct pwm_device *pwm,
                              int duty_ns, int period_ns)
{
        struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
        struct samsung_pwm_channel *chan = pwm_get_chip_data(pwm);
        u32 tin_ns = chan->tin_ns, tcnt, tcmp, oldtcmp;

        /*
         * We currently avoid using 64bit arithmetic by using the
         * fact that anything faster than 1Hz is easily representable
         * by 32bits.
         */
        if (period_ns > NSEC_PER_SEC)
                return -ERANGE;

        if (period_ns == chan->period_ns && duty_ns == chan->duty_ns)
                return 0;

        tcnt = readl(our_chip->base + REG_TCNTB(pwm->hwpwm));
        oldtcmp = readl(our_chip->base + REG_TCMPB(pwm->hwpwm));

        /* We need tick count for calculation, not last tick. */
        ++tcnt;

        /* Check to see if we are changing the clock rate of the PWM. */
        if (chan->period_ns != period_ns) {
                unsigned long tin_rate;
                u32 period;

                period = NSEC_PER_SEC / period_ns;

                dev_dbg(our_chip->chip.dev, "duty_ns=%d, period_ns=%d (%u)\n",
                                                duty_ns, period_ns, period);

                tin_rate = pwm_samsung_calc_tin(our_chip, pwm->hwpwm, period);

                dev_dbg(our_chip->chip.dev, "tin_rate=%lu\n", tin_rate);

                tin_ns = NSEC_PER_SEC / tin_rate;
                tcnt = period_ns / tin_ns;
        }

        /* Period is too short. */
        if (tcnt <= 1)
                return -ERANGE;

        /* Note that counters count down. */
        tcmp = duty_ns / tin_ns;

        /* 0% duty is not available */
        if (!tcmp)
                ++tcmp;

        tcmp = tcnt - tcmp;

        /* Decrement to get tick numbers, instead of tick counts. */
        --tcnt;
        /* -1UL will give 100% duty. */
        --tcmp;

        dev_dbg(our_chip->chip.dev,
                                "tin_ns=%u, tcmp=%u/%u\n", tin_ns, tcmp, tcnt);

        /* Update PWM registers. */
        writel(tcnt, our_chip->base + REG_TCNTB(pwm->hwpwm));
        writel(tcmp, our_chip->base + REG_TCMPB(pwm->hwpwm));

        /*
         * In case the PWM is currently at 100% duty cycle, force a manual
         * update to prevent the signal staying high if the PWM is disabled
         * shortly afer this update (before it autoreloaded the new values).
         */
        if (oldtcmp == (u32) -1) {
                dev_dbg(our_chip->chip.dev, "Forcing manual update");
                pwm_samsung_manual_update(our_chip, pwm);
        }

        chan->period_ns = period_ns;
        chan->tin_ns = tin_ns;
        chan->duty_ns = duty_ns;

        return 0;
}

static void pwm_samsung_set_invert(struct samsung_pwm_chip *chip,
                                   unsigned int channel, bool invert)
{
        unsigned int tcon_chan = to_tcon_channel(channel);
        unsigned long flags;
        u32 tcon;

        spin_lock_irqsave(&samsung_pwm_lock, flags);

        tcon = readl(chip->base + REG_TCON);

        if (invert) {
                chip->inverter_mask |= BIT(channel);
                tcon |= TCON_INVERT(tcon_chan);
        } else {
                chip->inverter_mask &= ~BIT(channel);
                tcon &= ~TCON_INVERT(tcon_chan);
        }

        writel(tcon, chip->base + REG_TCON);

        spin_unlock_irqrestore(&samsung_pwm_lock, flags);
}

static int pwm_samsung_set_polarity(struct pwm_chip *chip,
                                    struct pwm_device *pwm,
                                    enum pwm_polarity polarity)
{
        struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
        bool invert = (polarity == PWM_POLARITY_NORMAL);

        /* Inverted means normal in the hardware. */
        pwm_samsung_set_invert(our_chip, pwm->hwpwm, invert);

        return 0;
}

static const struct pwm_ops pwm_samsung_ops = {
        .request        = pwm_samsung_request,
        .free           = pwm_samsung_free,
        .enable         = pwm_samsung_enable,
        .disable        = pwm_samsung_disable,
        .config         = pwm_samsung_config,
        .set_polarity   = pwm_samsung_set_polarity,
        .owner          = THIS_MODULE,
};

#ifdef CONFIG_OF
static const struct samsung_pwm_variant s3c24xx_variant = {
        .bits           = 16,
        .div_base       = 1,
        .has_tint_cstat = false,
        .tclk_mask      = BIT(4),
};

static const struct samsung_pwm_variant s3c64xx_variant = {
        .bits           = 32,
        .div_base       = 0,
        .has_tint_cstat = true,
        .tclk_mask      = BIT(7) | BIT(6) | BIT(5),
};

static const struct samsung_pwm_variant s5p64x0_variant = {
        .bits           = 32,
        .div_base       = 0,
        .has_tint_cstat = true,
        .tclk_mask      = 0,
};

static const struct samsung_pwm_variant s5pc100_variant = {
        .bits           = 32,
        .div_base       = 0,
        .has_tint_cstat = true,
        .tclk_mask      = BIT(5),
};

static const struct of_device_id samsung_pwm_matches[] = {
        { .compatible = "samsung,s3c2410-pwm", .data = &s3c24xx_variant },
        { .compatible = "samsung,s3c6400-pwm", .data = &s3c64xx_variant },
        { .compatible = "samsung,s5p6440-pwm", .data = &s5p64x0_variant },
        { .compatible = "samsung,s5pc100-pwm", .data = &s5pc100_variant },
        { .compatible = "samsung,exynos4210-pwm", .data = &s5p64x0_variant },
        {},
};
MODULE_DEVICE_TABLE(of, samsung_pwm_matches);

static int pwm_samsung_parse_dt(struct samsung_pwm_chip *chip)
{
        struct device_node *np = chip->chip.dev->of_node;
        const struct of_device_id *match;
        struct property *prop;
        const __be32 *cur;
        u32 val;

        match = of_match_node(samsung_pwm_matches, np);
        if (!match)
                return -ENODEV;

        memcpy(&chip->variant, match->data, sizeof(chip->variant));

        of_property_for_each_u32(np, "samsung,pwm-outputs", prop, cur, val) {
                if (val >= SAMSUNG_PWM_NUM) {
                        dev_err(chip->chip.dev,
                                "%s: invalid channel index in samsung,pwm-outputs property\n",
                                                                __func__);
                        continue;
                }
                chip->variant.output_mask |= BIT(val);
        }

        return 0;
}
#else
static int pwm_samsung_parse_dt(struct samsung_pwm_chip *chip)
{
        return -ENODEV;
}
#endif

static int pwm_samsung_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct samsung_pwm_chip *chip;
        struct resource *res;
        unsigned int chan;
        int ret;

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

        chip->chip.dev = &pdev->dev;
        chip->chip.ops = &pwm_samsung_ops;
        chip->chip.base = -1;
        chip->chip.npwm = SAMSUNG_PWM_NUM;
        chip->inverter_mask = BIT(SAMSUNG_PWM_NUM) - 1;

        if (IS_ENABLED(CONFIG_OF) && pdev->dev.of_node) {
                ret = pwm_samsung_parse_dt(chip);
                if (ret)
                        return ret;

                chip->chip.of_xlate = of_pwm_xlate_with_flags;
                chip->chip.of_pwm_n_cells = 3;
        } else {
                if (!pdev->dev.platform_data) {
                        dev_err(&pdev->dev, "no platform data specified\n");
                        return -EINVAL;
                }

                memcpy(&chip->variant, pdev->dev.platform_data,
                                                        sizeof(chip->variant));
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        chip->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(chip->base))
                return PTR_ERR(chip->base);

        chip->base_clk = devm_clk_get(&pdev->dev, "timers");
        if (IS_ERR(chip->base_clk)) {
                dev_err(dev, "failed to get timer base clk\n");
                return PTR_ERR(chip->base_clk);
        }

        ret = clk_prepare_enable(chip->base_clk);
        if (ret < 0) {
                dev_err(dev, "failed to enable base clock\n");
                return ret;
        }

        for (chan = 0; chan < SAMSUNG_PWM_NUM; ++chan)
                if (chip->variant.output_mask & BIT(chan))
                        pwm_samsung_set_invert(chip, chan, true);

        /* Following clocks are optional. */
        chip->tclk0 = devm_clk_get(&pdev->dev, "pwm-tclk0");
        chip->tclk1 = devm_clk_get(&pdev->dev, "pwm-tclk1");

        platform_set_drvdata(pdev, chip);

        ret = pwmchip_add(&chip->chip);
        if (ret < 0) {
                dev_err(dev, "failed to register PWM chip\n");
                clk_disable_unprepare(chip->base_clk);
                return ret;
        }

        dev_dbg(dev, "base_clk at %lu, tclk0 at %lu, tclk1 at %lu\n",
                clk_get_rate(chip->base_clk),
                !IS_ERR(chip->tclk0) ? clk_get_rate(chip->tclk0) : 0,
                !IS_ERR(chip->tclk1) ? clk_get_rate(chip->tclk1) : 0);

        return 0;
}

static int pwm_samsung_remove(struct platform_device *pdev)
{
        struct samsung_pwm_chip *chip = platform_get_drvdata(pdev);
        int ret;

        ret = pwmchip_remove(&chip->chip);
        if (ret < 0)
                return ret;

        clk_disable_unprepare(chip->base_clk);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int pwm_samsung_suspend(struct device *dev)
{
        struct samsung_pwm_chip *chip = dev_get_drvdata(dev);
        unsigned int i;

        /*
         * No one preserves these values during suspend so reset them.
         * Otherwise driver leaves PWM unconfigured if same values are
         * passed to pwm_config() next time.
         */
        for (i = 0; i < SAMSUNG_PWM_NUM; ++i) {
                struct pwm_device *pwm = &chip->chip.pwms[i];
                struct samsung_pwm_channel *chan = pwm_get_chip_data(pwm);

                if (!chan)
                        continue;

                chan->period_ns = 0;
                chan->duty_ns = 0;
        }

        return 0;
}

static int pwm_samsung_resume(struct device *dev)
{
        struct samsung_pwm_chip *chip = dev_get_drvdata(dev);
        unsigned int chan;

        /*
         * Inverter setting must be preserved across suspend/resume
         * as nobody really seems to configure it more than once.
         */
        for (chan = 0; chan < SAMSUNG_PWM_NUM; ++chan) {
                if (chip->variant.output_mask & BIT(chan))
                        pwm_samsung_set_invert(chip, chan,
                                        chip->inverter_mask & BIT(chan));
        }

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(pwm_samsung_pm_ops, pwm_samsung_suspend,
                         pwm_samsung_resume);

static struct platform_driver pwm_samsung_driver = {
        .driver         = {
                .name   = "samsung-pwm",
                .pm     = &pwm_samsung_pm_ops,
                .of_match_table = of_match_ptr(samsung_pwm_matches),
        },
        .probe          = pwm_samsung_probe,
        .remove         = pwm_samsung_remove,
};
module_platform_driver(pwm_samsung_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Tomasz Figa <tomasz.figa@gmail.com>");
MODULE_ALIAS("platform:samsung-pwm");