/*
 * Copyright (C) 2014 Broadcom Corporation
 *
 * 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 version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; 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/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/types.h>

/*
 * The Kona PWM has some unusual characteristics.  Here are the main points.
 *
 * 1) There is no disable bit and the hardware docs advise programming a zero
 *    duty to achieve output equivalent to that of a normal disable operation.
 *
 * 2) Changes to prescale, duty, period, and polarity do not take effect until
 *    a subsequent rising edge of the trigger bit.
 *
 * 3) If the smooth bit and trigger bit are both low, the output is a constant
 *    high signal.  Otherwise, the earlier waveform continues to be output.
 *
 * 4) If the smooth bit is set on the rising edge of the trigger bit, output
 *    will transition to the new settings on a period boundary (which could be
 *    seconds away).  If the smooth bit is clear, new settings will be applied
 *    as soon as possible (the hardware always has a 400ns delay).
 *
 * 5) When the external clock that feeds the PWM is disabled, output is pegged
 *    high or low depending on its state at that exact instant.
 */

#define PWM_CONTROL_OFFSET                      0x00000000
#define PWM_CONTROL_SMOOTH_SHIFT(chan)          (24 + (chan))
#define PWM_CONTROL_TYPE_SHIFT(chan)            (16 + (chan))
#define PWM_CONTROL_POLARITY_SHIFT(chan)        (8 + (chan))
#define PWM_CONTROL_TRIGGER_SHIFT(chan)         (chan)

#define PRESCALE_OFFSET                         0x00000004
#define PRESCALE_SHIFT(chan)                    ((chan) << 2)
#define PRESCALE_MASK(chan)                     (0x7 << PRESCALE_SHIFT(chan))
#define PRESCALE_MIN                            0x00000000
#define PRESCALE_MAX                            0x00000007

#define PERIOD_COUNT_OFFSET(chan)               (0x00000008 + ((chan) << 3))
#define PERIOD_COUNT_MIN                        0x00000002
#define PERIOD_COUNT_MAX                        0x00ffffff

#define DUTY_CYCLE_HIGH_OFFSET(chan)            (0x0000000c + ((chan) << 3))
#define DUTY_CYCLE_HIGH_MIN                     0x00000000
#define DUTY_CYCLE_HIGH_MAX                     0x00ffffff

struct kona_pwmc {
        struct pwm_chip chip;
        void __iomem *base;
        struct clk *clk;
};

static inline struct kona_pwmc *to_kona_pwmc(struct pwm_chip *_chip)
{
        return container_of(_chip, struct kona_pwmc, chip);
}

/*
 * Clear trigger bit but set smooth bit to maintain old output.
 */
static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp,
        unsigned int chan)
{
        unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);

        value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
        value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
        writel(value, kp->base + PWM_CONTROL_OFFSET);

        /*
         * There must be a min 400ns delay between clearing trigger and setting
         * it. Failing to do this may result in no PWM signal.
         */
        ndelay(400);
}

static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
{
        unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);

        /* Set trigger bit and clear smooth bit to apply new settings */
        value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
        value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
        writel(value, kp->base + PWM_CONTROL_OFFSET);

        /* Trigger bit must be held high for at least 400 ns. */
        ndelay(400);
}

static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
                            int duty_ns, int period_ns)
{
        struct kona_pwmc *kp = to_kona_pwmc(chip);
        u64 val, div, rate;
        unsigned long prescale = PRESCALE_MIN, pc, dc;
        unsigned int value, chan = pwm->hwpwm;

        /*
         * Find period count, duty count and prescale to suit duty_ns and
         * period_ns. This is done according to formulas described below:
         *
         * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
         * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
         *
         * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
         * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
         */

        rate = clk_get_rate(kp->clk);

        while (1) {
                div = 1000000000;
                div *= 1 + prescale;
                val = rate * period_ns;
                pc = div64_u64(val, div);
                val = rate * duty_ns;
                dc = div64_u64(val, div);

                /* If duty_ns or period_ns are not achievable then return */
                if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN)
                        return -EINVAL;

                /* If pc and dc are in bounds, the calculation is done */
                if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
                        break;

                /* Otherwise, increase prescale and recalculate pc and dc */
                if (++prescale > PRESCALE_MAX)
                        return -EINVAL;
        }

        /*
         * Don't apply settings if disabled. The period and duty cycle are
         * always calculated above to ensure the new values are
         * validated immediately instead of on enable.
         */
        if (pwm_is_enabled(pwm)) {
                kona_pwmc_prepare_for_settings(kp, chan);

                value = readl(kp->base + PRESCALE_OFFSET);
                value &= ~PRESCALE_MASK(chan);
                value |= prescale << PRESCALE_SHIFT(chan);
                writel(value, kp->base + PRESCALE_OFFSET);

                writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan));

                writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));

                kona_pwmc_apply_settings(kp, chan);
        }

        return 0;
}

static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
                                  enum pwm_polarity polarity)
{
        struct kona_pwmc *kp = to_kona_pwmc(chip);
        unsigned int chan = pwm->hwpwm;
        unsigned int value;
        int ret;

        ret = clk_prepare_enable(kp->clk);
        if (ret < 0) {
                dev_err(chip->dev, "failed to enable clock: %d\n", ret);
                return ret;
        }

        kona_pwmc_prepare_for_settings(kp, chan);

        value = readl(kp->base + PWM_CONTROL_OFFSET);

        if (polarity == PWM_POLARITY_NORMAL)
                value |= 1 << PWM_CONTROL_POLARITY_SHIFT(chan);
        else
                value &= ~(1 << PWM_CONTROL_POLARITY_SHIFT(chan));

        writel(value, kp->base + PWM_CONTROL_OFFSET);

        kona_pwmc_apply_settings(kp, chan);

        clk_disable_unprepare(kp->clk);

        return 0;
}

static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct kona_pwmc *kp = to_kona_pwmc(chip);
        int ret;

        ret = clk_prepare_enable(kp->clk);
        if (ret < 0) {
                dev_err(chip->dev, "failed to enable clock: %d\n", ret);
                return ret;
        }

        ret = kona_pwmc_config(chip, pwm, pwm_get_duty_cycle(pwm),
                               pwm_get_period(pwm));
        if (ret < 0) {
                clk_disable_unprepare(kp->clk);
                return ret;
        }

        return 0;
}

static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct kona_pwmc *kp = to_kona_pwmc(chip);
        unsigned int chan = pwm->hwpwm;
        unsigned int value;

        kona_pwmc_prepare_for_settings(kp, chan);

        /* Simulate a disable by configuring for zero duty */
        writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
        writel(0, kp->base + PERIOD_COUNT_OFFSET(chan));

        /* Set prescale to 0 for this channel */
        value = readl(kp->base + PRESCALE_OFFSET);
        value &= ~PRESCALE_MASK(chan);
        writel(value, kp->base + PRESCALE_OFFSET);

        kona_pwmc_apply_settings(kp, chan);

        clk_disable_unprepare(kp->clk);
}

static const struct pwm_ops kona_pwm_ops = {
        .config = kona_pwmc_config,
        .set_polarity = kona_pwmc_set_polarity,
        .enable = kona_pwmc_enable,
        .disable = kona_pwmc_disable,
        .owner = THIS_MODULE,
};

static int kona_pwmc_probe(struct platform_device *pdev)
{
        struct kona_pwmc *kp;
        struct resource *res;
        unsigned int chan;
        unsigned int value = 0;
        int ret = 0;

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

        platform_set_drvdata(pdev, kp);

        kp->chip.dev = &pdev->dev;
        kp->chip.ops = &kona_pwm_ops;
        kp->chip.base = -1;
        kp->chip.npwm = 6;
        kp->chip.of_xlate = of_pwm_xlate_with_flags;
        kp->chip.of_pwm_n_cells = 3;

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

        kp->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(kp->clk)) {
                dev_err(&pdev->dev, "failed to get clock: %ld\n",
                        PTR_ERR(kp->clk));
                return PTR_ERR(kp->clk);
        }

        ret = clk_prepare_enable(kp->clk);
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to enable clock: %d\n", ret);
                return ret;
        }

        /* Set push/pull for all channels */
        for (chan = 0; chan < kp->chip.npwm; chan++)
                value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan));

        writel(value, kp->base + PWM_CONTROL_OFFSET);

        clk_disable_unprepare(kp->clk);

        ret = pwmchip_add_with_polarity(&kp->chip, PWM_POLARITY_INVERSED);
        if (ret < 0)
                dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);

        return ret;
}

static int kona_pwmc_remove(struct platform_device *pdev)
{
        struct kona_pwmc *kp = platform_get_drvdata(pdev);
        unsigned int chan;

        for (chan = 0; chan < kp->chip.npwm; chan++)
                if (pwm_is_enabled(&kp->chip.pwms[chan]))
                        clk_disable_unprepare(kp->clk);

        return pwmchip_remove(&kp->chip);
}

static const struct of_device_id bcm_kona_pwmc_dt[] = {
        { .compatible = "brcm,kona-pwm" },
        { },
};
MODULE_DEVICE_TABLE(of, bcm_kona_pwmc_dt);

static struct platform_driver kona_pwmc_driver = {
        .driver = {
                .name = "bcm-kona-pwm",
                .of_match_table = bcm_kona_pwmc_dt,
        },
        .probe = kona_pwmc_probe,
        .remove = kona_pwmc_remove,
};
module_platform_driver(kona_pwmc_driver);

MODULE_AUTHOR("Broadcom Corporation <bcm-kernel-feedback-list@broadcom.com>");
MODULE_AUTHOR("Tim Kryger <tkryger@broadcom.com>");
MODULE_DESCRIPTION("Broadcom Kona PWM driver");
MODULE_LICENSE("GPL v2");