/*
 * PWM device driver for ST SoCs.
 * Author: Ajit Pal Singh <ajitpal.singh@st.com>
 *
 * Copyright (C) 2013-2014 STMicroelectronics (R&D) Limited
 *
 * 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/math64.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/regmap.h>
#include <linux/slab.h>
#include <linux/time.h>

#define STI_DS_REG(ch)  (4 * (ch))      /* Channel's Duty Cycle register */
#define STI_PWMCR       0x50            /* Control/Config register */
#define STI_INTEN       0x54            /* Interrupt Enable/Disable register */
#define PWM_PRESCALE_LOW_MASK           0x0f
#define PWM_PRESCALE_HIGH_MASK          0xf0

/* Regfield IDs */
enum {
        PWMCLK_PRESCALE_LOW,
        PWMCLK_PRESCALE_HIGH,
        PWM_EN,
        PWM_INT_EN,

        /* Keep last */
        MAX_REGFIELDS
};

struct sti_pwm_compat_data {
        const struct reg_field *reg_fields;
        unsigned int num_chan;
        unsigned int max_pwm_cnt;
        unsigned int max_prescale;
};

struct sti_pwm_chip {
        struct device *dev;
        struct clk *clk;
        unsigned long clk_rate;
        struct regmap *regmap;
        struct sti_pwm_compat_data *cdata;
        struct regmap_field *prescale_low;
        struct regmap_field *prescale_high;
        struct regmap_field *pwm_en;
        struct regmap_field *pwm_int_en;
        struct pwm_chip chip;
        struct pwm_device *cur;
        unsigned int en_count;
        struct mutex sti_pwm_lock; /* To sync between enable/disable calls */
        void __iomem *mmio;
};

static const struct reg_field sti_pwm_regfields[MAX_REGFIELDS] = {
        [PWMCLK_PRESCALE_LOW]   = REG_FIELD(STI_PWMCR, 0, 3),
        [PWMCLK_PRESCALE_HIGH]  = REG_FIELD(STI_PWMCR, 11, 14),
        [PWM_EN]                = REG_FIELD(STI_PWMCR, 9, 9),
        [PWM_INT_EN]            = REG_FIELD(STI_INTEN, 0, 0),
};

static inline struct sti_pwm_chip *to_sti_pwmchip(struct pwm_chip *chip)
{
        return container_of(chip, struct sti_pwm_chip, chip);
}

/*
 * Calculate the prescaler value corresponding to the period.
 */
static int sti_pwm_get_prescale(struct sti_pwm_chip *pc, unsigned long period,
                                unsigned int *prescale)
{
        struct sti_pwm_compat_data *cdata = pc->cdata;
        unsigned long val;
        unsigned int ps;

        /*
         * prescale = ((period_ns * clk_rate) / (10^9 * (max_pwm_count + 1)) - 1
         */
        val = NSEC_PER_SEC / pc->clk_rate;
        val *= cdata->max_pwm_cnt + 1;

        if (period % val) {
                return -EINVAL;
        } else {
                ps  = period / val - 1;
                if (ps > cdata->max_prescale)
                        return -EINVAL;
        }
        *prescale = ps;

        return 0;
}

/* Calculate the number of PWM devices configured with a period. */
static unsigned int sti_pwm_count_configured(struct pwm_chip *chip)
{
        struct pwm_device *pwm;
        unsigned int ncfg = 0;
        unsigned int i;

        for (i = 0; i < chip->npwm; i++) {
                pwm = &chip->pwms[i];
                if (test_bit(PWMF_REQUESTED, &pwm->flags)) {
                        if (pwm_get_period(pwm))
                                ncfg++;
                }
        }

        return ncfg;
}

/*
 * For STiH4xx PWM IP, the PWM period is fixed to 256 local clock cycles.
 * The only way to change the period (apart from changing the PWM input clock)
 * is to change the PWM clock prescaler.
 * The prescaler is of 8 bits, so 256 prescaler values and hence
 * 256 possible period values are supported (for a particular clock rate).
 * The requested period will be applied only if it matches one of these
 * 256 values.
 */
static int sti_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
                         int duty_ns, int period_ns)
{
        struct sti_pwm_chip *pc = to_sti_pwmchip(chip);
        struct sti_pwm_compat_data *cdata = pc->cdata;
        struct pwm_device *cur = pc->cur;
        struct device *dev = pc->dev;
        unsigned int prescale = 0, pwmvalx;
        int ret;
        unsigned int ncfg;
        bool period_same = false;

        ncfg = sti_pwm_count_configured(chip);
        if (ncfg)
                period_same = (period_ns == pwm_get_period(cur));

        /* Allow configuration changes if one of the
         * following conditions satisfy.
         * 1. No channels have been configured.
         * 2. Only one channel has been configured and the new request
         *    is for the same channel.
         * 3. Only one channel has been configured and the new request is
         *    for a new channel and period of the new channel is same as
         *    the current configured period.
         * 4. More than one channels are configured and period of the new
         *    requestis the same as the current period.
         */
        if (!ncfg ||
            ((ncfg == 1) && (pwm->hwpwm == cur->hwpwm)) ||
            ((ncfg == 1) && (pwm->hwpwm != cur->hwpwm) && period_same) ||
            ((ncfg > 1) && period_same)) {
                /* Enable clock before writing to PWM registers. */
                ret = clk_enable(pc->clk);
                if (ret)
                        return ret;

                if (!period_same) {
                        ret = sti_pwm_get_prescale(pc, period_ns, &prescale);
                        if (ret)
                                goto clk_dis;

                        ret =
                        regmap_field_write(pc->prescale_low,
                                           prescale & PWM_PRESCALE_LOW_MASK);
                        if (ret)
                                goto clk_dis;

                        ret =
                        regmap_field_write(pc->prescale_high,
                                (prescale & PWM_PRESCALE_HIGH_MASK) >> 4);
                        if (ret)
                                goto clk_dis;
                }

                /*
                 * When PWMVal == 0, PWM pulse = 1 local clock cycle.
                 * When PWMVal == max_pwm_count,
                 * PWM pulse = (max_pwm_count + 1) local cycles,
                 * that is continuous pulse: signal never goes low.
                 */
                pwmvalx = cdata->max_pwm_cnt * duty_ns / period_ns;

                ret = regmap_write(pc->regmap, STI_DS_REG(pwm->hwpwm), pwmvalx);
                if (ret)
                        goto clk_dis;

                ret = regmap_field_write(pc->pwm_int_en, 0);

                pc->cur = pwm;

                dev_dbg(dev, "prescale:%u, period:%i, duty:%i, pwmvalx:%u\n",
                        prescale, period_ns, duty_ns, pwmvalx);
        } else {
                return -EINVAL;
        }

clk_dis:
        clk_disable(pc->clk);
        return ret;
}

static int sti_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct sti_pwm_chip *pc = to_sti_pwmchip(chip);
        struct device *dev = pc->dev;
        int ret = 0;

        /*
         * Since we have a common enable for all PWM channels,
         * do not enable if already enabled.
         */
        mutex_lock(&pc->sti_pwm_lock);
        if (!pc->en_count) {
                ret = clk_enable(pc->clk);
                if (ret)
                        goto out;

                ret = regmap_field_write(pc->pwm_en, 1);
                if (ret) {
                        dev_err(dev, "failed to enable PWM device:%d\n",
                                pwm->hwpwm);
                        goto out;
                }
        }
        pc->en_count++;
out:
        mutex_unlock(&pc->sti_pwm_lock);
        return ret;
}

static void sti_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct sti_pwm_chip *pc = to_sti_pwmchip(chip);

        mutex_lock(&pc->sti_pwm_lock);
        if (--pc->en_count) {
                mutex_unlock(&pc->sti_pwm_lock);
                return;
        }
        regmap_field_write(pc->pwm_en, 0);

        clk_disable(pc->clk);
        mutex_unlock(&pc->sti_pwm_lock);
}

static const struct pwm_ops sti_pwm_ops = {
        .config = sti_pwm_config,
        .enable = sti_pwm_enable,
        .disable = sti_pwm_disable,
        .owner = THIS_MODULE,
};

static int sti_pwm_probe_dt(struct sti_pwm_chip *pc)
{
        struct device *dev = pc->dev;
        const struct reg_field *reg_fields;
        struct device_node *np = dev->of_node;
        struct sti_pwm_compat_data *cdata = pc->cdata;
        u32 num_chan;

        of_property_read_u32(np, "st,pwm-num-chan", &num_chan);
        if (num_chan)
                cdata->num_chan = num_chan;

        reg_fields = cdata->reg_fields;

        pc->prescale_low = devm_regmap_field_alloc(dev, pc->regmap,
                                        reg_fields[PWMCLK_PRESCALE_LOW]);
        if (IS_ERR(pc->prescale_low))
                return PTR_ERR(pc->prescale_low);

        pc->prescale_high = devm_regmap_field_alloc(dev, pc->regmap,
                                        reg_fields[PWMCLK_PRESCALE_HIGH]);
        if (IS_ERR(pc->prescale_high))
                return PTR_ERR(pc->prescale_high);

        pc->pwm_en = devm_regmap_field_alloc(dev, pc->regmap,
                                             reg_fields[PWM_EN]);
        if (IS_ERR(pc->pwm_en))
                return PTR_ERR(pc->pwm_en);

        pc->pwm_int_en = devm_regmap_field_alloc(dev, pc->regmap,
                                                 reg_fields[PWM_INT_EN]);
        if (IS_ERR(pc->pwm_int_en))
                return PTR_ERR(pc->pwm_int_en);

        return 0;
}

static const struct regmap_config sti_pwm_regmap_config = {
        .reg_bits = 32,
        .val_bits = 32,
        .reg_stride = 4,
};

static int sti_pwm_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct sti_pwm_compat_data *cdata;
        struct sti_pwm_chip *pc;
        struct resource *res;
        int ret;

        pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
        if (!pc)
                return -ENOMEM;

        cdata = devm_kzalloc(dev, sizeof(*cdata), GFP_KERNEL);
        if (!cdata)
                return -ENOMEM;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

        pc->mmio = devm_ioremap_resource(dev, res);
        if (IS_ERR(pc->mmio))
                return PTR_ERR(pc->mmio);

        pc->regmap = devm_regmap_init_mmio(dev, pc->mmio,
                                           &sti_pwm_regmap_config);
        if (IS_ERR(pc->regmap))
                return PTR_ERR(pc->regmap);

        /*
         * Setup PWM data with default values: some values could be replaced
         * with specific ones provided from Device Tree.
         */
        cdata->reg_fields   = &sti_pwm_regfields[0];
        cdata->max_prescale = 0xff;
        cdata->max_pwm_cnt  = 255;
        cdata->num_chan     = 1;

        pc->cdata = cdata;
        pc->dev = dev;
        pc->en_count = 0;
        mutex_init(&pc->sti_pwm_lock);

        ret = sti_pwm_probe_dt(pc);
        if (ret)
                return ret;

        pc->clk = of_clk_get_by_name(dev->of_node, "pwm");
        if (IS_ERR(pc->clk)) {
                dev_err(dev, "failed to get PWM clock\n");
                return PTR_ERR(pc->clk);
        }

        pc->clk_rate = clk_get_rate(pc->clk);
        if (!pc->clk_rate) {
                dev_err(dev, "failed to get clock rate\n");
                return -EINVAL;
        }

        ret = clk_prepare(pc->clk);
        if (ret) {
                dev_err(dev, "failed to prepare clock\n");
                return ret;
        }

        pc->chip.dev = dev;
        pc->chip.ops = &sti_pwm_ops;
        pc->chip.base = -1;
        pc->chip.npwm = pc->cdata->num_chan;
        pc->chip.can_sleep = true;

        ret = pwmchip_add(&pc->chip);
        if (ret < 0) {
                clk_unprepare(pc->clk);
                return ret;
        }

        platform_set_drvdata(pdev, pc);

        return 0;
}

static int sti_pwm_remove(struct platform_device *pdev)
{
        struct sti_pwm_chip *pc = platform_get_drvdata(pdev);
        unsigned int i;

        for (i = 0; i < pc->cdata->num_chan; i++)
                pwm_disable(&pc->chip.pwms[i]);

        clk_unprepare(pc->clk);

        return pwmchip_remove(&pc->chip);
}

static const struct of_device_id sti_pwm_of_match[] = {
        { .compatible = "st,sti-pwm", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, sti_pwm_of_match);

static struct platform_driver sti_pwm_driver = {
        .driver = {
                .name = "sti-pwm",
                .of_match_table = sti_pwm_of_match,
        },
        .probe = sti_pwm_probe,
        .remove = sti_pwm_remove,
};
module_platform_driver(sti_pwm_driver);

MODULE_AUTHOR("Ajit Pal Singh <ajitpal.singh@st.com>");
MODULE_DESCRIPTION("STMicroelectronics ST PWM driver");
MODULE_LICENSE("GPL");