/*
 * Marvell Berlin PWM driver
 *
 * Copyright (C) 2015 Marvell Technology Group Ltd.
 *
 * Author: Antoine Tenart <antoine.tenart@free-electrons.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/clk.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>

#define BERLIN_PWM_EN                   0x0
#define  BERLIN_PWM_ENABLE              BIT(0)
#define BERLIN_PWM_CONTROL              0x4
/*
 * The prescaler claims to support 8 different moduli, configured using the
 * low three bits of PWM_CONTROL. (Sequentially, they are 1, 4, 8, 16, 64,
 * 256, 1024, and 4096.)  However, the moduli from 4 to 1024 appear to be
 * implemented by internally shifting TCNT left without adding additional
 * bits. So, the max TCNT that actually works for a modulus of 4 is 0x3fff;
 * for 8, 0x1fff; and so on. This means that those moduli are entirely
 * useless, as we could just do the shift ourselves. The 4096 modulus is
 * implemented with a real prescaler, so we do use that, but we treat it
 * as a flag instead of pretending the modulus is actually configurable.
 */
#define  BERLIN_PWM_PRESCALE_4096       0x7
#define  BERLIN_PWM_INVERT_POLARITY     BIT(3)
#define BERLIN_PWM_DUTY                 0x8
#define BERLIN_PWM_TCNT                 0xc
#define  BERLIN_PWM_MAX_TCNT            65535

#define BERLIN_PWM_NUMPWMS              4

struct berlin_pwm_channel {
        u32 enable;
        u32 ctrl;
        u32 duty;
        u32 tcnt;
};

struct berlin_pwm_chip {
        struct clk *clk;
        void __iomem *base;
        struct berlin_pwm_channel channel[BERLIN_PWM_NUMPWMS];
};

static inline struct berlin_pwm_chip *to_berlin_pwm_chip(struct pwm_chip *chip)
{
        return pwmchip_get_drvdata(chip);
}

static inline u32 berlin_pwm_readl(struct berlin_pwm_chip *bpc,
                                   unsigned int channel, unsigned long offset)
{
        return readl_relaxed(bpc->base + channel * 0x10 + offset);
}

static inline void berlin_pwm_writel(struct berlin_pwm_chip *bpc,
                                     unsigned int channel, u32 value,
                                     unsigned long offset)
{
        writel_relaxed(value, bpc->base + channel * 0x10 + offset);
}

static int berlin_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
                             u64 duty_ns, u64 period_ns)
{
        struct berlin_pwm_chip *bpc = to_berlin_pwm_chip(chip);
        bool prescale_4096 = false;
        u32 value, duty, period;
        u64 cycles;

        cycles = clk_get_rate(bpc->clk);
        cycles *= period_ns;
        do_div(cycles, NSEC_PER_SEC);

        if (cycles > BERLIN_PWM_MAX_TCNT) {
                prescale_4096 = true;
                cycles >>= 12; // Prescaled by 4096

                if (cycles > BERLIN_PWM_MAX_TCNT)
                        return -ERANGE;
        }

        period = cycles;
        cycles *= duty_ns;
        do_div(cycles, period_ns);
        duty = cycles;

        value = berlin_pwm_readl(bpc, pwm->hwpwm, BERLIN_PWM_CONTROL);
        if (prescale_4096)
                value |= BERLIN_PWM_PRESCALE_4096;
        else
                value &= ~BERLIN_PWM_PRESCALE_4096;
        berlin_pwm_writel(bpc, pwm->hwpwm, value, BERLIN_PWM_CONTROL);

        berlin_pwm_writel(bpc, pwm->hwpwm, duty, BERLIN_PWM_DUTY);
        berlin_pwm_writel(bpc, pwm->hwpwm, period, BERLIN_PWM_TCNT);

        return 0;
}

static int berlin_pwm_set_polarity(struct pwm_chip *chip,
                                   struct pwm_device *pwm,
                                   enum pwm_polarity polarity)
{
        struct berlin_pwm_chip *bpc = to_berlin_pwm_chip(chip);
        u32 value;

        value = berlin_pwm_readl(bpc, pwm->hwpwm, BERLIN_PWM_CONTROL);

        if (polarity == PWM_POLARITY_NORMAL)
                value &= ~BERLIN_PWM_INVERT_POLARITY;
        else
                value |= BERLIN_PWM_INVERT_POLARITY;

        berlin_pwm_writel(bpc, pwm->hwpwm, value, BERLIN_PWM_CONTROL);

        return 0;
}

static int berlin_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct berlin_pwm_chip *bpc = to_berlin_pwm_chip(chip);
        u32 value;

        value = berlin_pwm_readl(bpc, pwm->hwpwm, BERLIN_PWM_EN);
        value |= BERLIN_PWM_ENABLE;
        berlin_pwm_writel(bpc, pwm->hwpwm, value, BERLIN_PWM_EN);

        return 0;
}

static void berlin_pwm_disable(struct pwm_chip *chip,
                               struct pwm_device *pwm)
{
        struct berlin_pwm_chip *bpc = to_berlin_pwm_chip(chip);
        u32 value;

        value = berlin_pwm_readl(bpc, pwm->hwpwm, BERLIN_PWM_EN);
        value &= ~BERLIN_PWM_ENABLE;
        berlin_pwm_writel(bpc, pwm->hwpwm, value, BERLIN_PWM_EN);
}

static int berlin_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
                            const struct pwm_state *state)
{
        int err;
        bool enabled = pwm->state.enabled;

        if (state->polarity != pwm->state.polarity) {
                if (enabled) {
                        berlin_pwm_disable(chip, pwm);
                        enabled = false;
                }

                err = berlin_pwm_set_polarity(chip, pwm, state->polarity);
                if (err)
                        return err;
        }

        if (!state->enabled) {
                if (enabled)
                        berlin_pwm_disable(chip, pwm);
                return 0;
        }

        err = berlin_pwm_config(chip, pwm, state->duty_cycle, state->period);
        if (err)
                return err;

        if (!enabled)
                return berlin_pwm_enable(chip, pwm);

        return 0;
}

static const struct pwm_ops berlin_pwm_ops = {
        .apply = berlin_pwm_apply,
};

static const struct of_device_id berlin_pwm_match[] = {
        { .compatible = "marvell,berlin-pwm" },
        { },
};
MODULE_DEVICE_TABLE(of, berlin_pwm_match);

static int berlin_pwm_probe(struct platform_device *pdev)
{
        struct pwm_chip *chip;
        struct berlin_pwm_chip *bpc;
        int ret;

        chip = devm_pwmchip_alloc(&pdev->dev, BERLIN_PWM_NUMPWMS, sizeof(*bpc));
        if (IS_ERR(chip))
                return PTR_ERR(chip);
        bpc = to_berlin_pwm_chip(chip);

        bpc->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(bpc->base))
                return PTR_ERR(bpc->base);

        bpc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
        if (IS_ERR(bpc->clk))
                return PTR_ERR(bpc->clk);

        chip->ops = &berlin_pwm_ops;

        ret = devm_pwmchip_add(&pdev->dev, chip);
        if (ret < 0)
                return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");

        platform_set_drvdata(pdev, chip);

        return 0;
}

static int berlin_pwm_suspend(struct device *dev)
{
        struct pwm_chip *chip = dev_get_drvdata(dev);
        struct berlin_pwm_chip *bpc = to_berlin_pwm_chip(chip);
        unsigned int i;

        for (i = 0; i < chip->npwm; i++) {
                struct berlin_pwm_channel *channel = &bpc->channel[i];

                channel->enable = berlin_pwm_readl(bpc, i, BERLIN_PWM_EN);
                channel->ctrl = berlin_pwm_readl(bpc, i, BERLIN_PWM_CONTROL);
                channel->duty = berlin_pwm_readl(bpc, i, BERLIN_PWM_DUTY);
                channel->tcnt = berlin_pwm_readl(bpc, i, BERLIN_PWM_TCNT);
        }

        clk_disable_unprepare(bpc->clk);

        return 0;
}

static int berlin_pwm_resume(struct device *dev)
{
        struct pwm_chip *chip = dev_get_drvdata(dev);
        struct berlin_pwm_chip *bpc = to_berlin_pwm_chip(chip);
        unsigned int i;
        int ret;

        ret = clk_prepare_enable(bpc->clk);
        if (ret)
                return ret;

        for (i = 0; i < chip->npwm; i++) {
                struct berlin_pwm_channel *channel = &bpc->channel[i];

                berlin_pwm_writel(bpc, i, channel->ctrl, BERLIN_PWM_CONTROL);
                berlin_pwm_writel(bpc, i, channel->duty, BERLIN_PWM_DUTY);
                berlin_pwm_writel(bpc, i, channel->tcnt, BERLIN_PWM_TCNT);
                berlin_pwm_writel(bpc, i, channel->enable, BERLIN_PWM_EN);
        }

        return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(berlin_pwm_pm_ops, berlin_pwm_suspend,
                                berlin_pwm_resume);

static struct platform_driver berlin_pwm_driver = {
        .probe = berlin_pwm_probe,
        .driver = {
                .name = "berlin-pwm",
                .of_match_table = berlin_pwm_match,
                .pm = pm_ptr(&berlin_pwm_pm_ops),
        },
};
module_platform_driver(berlin_pwm_driver);

MODULE_AUTHOR("Antoine Tenart <antoine.tenart@free-electrons.com>");
MODULE_DESCRIPTION("Marvell Berlin PWM driver");
MODULE_LICENSE("GPL v2");