/*
 * R-Mobile TPU PWM driver
 *
 * Copyright (C) 2012 Renesas Solutions Corp.
 *
 * 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
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; 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/err.h>
#include <linux/io.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#define TPU_CHANNEL_MAX         4

#define TPU_TSTR                0x00    /* Timer start register (shared) */

#define TPU_TCRn                0x00    /* Timer control register */
#define TPU_TCR_CCLR_NONE       (0 << 5)
#define TPU_TCR_CCLR_TGRA       (1 << 5)
#define TPU_TCR_CCLR_TGRB       (2 << 5)
#define TPU_TCR_CCLR_TGRC       (5 << 5)
#define TPU_TCR_CCLR_TGRD       (6 << 5)
#define TPU_TCR_CKEG_RISING     (0 << 3)
#define TPU_TCR_CKEG_FALLING    (1 << 3)
#define TPU_TCR_CKEG_BOTH       (2 << 3)
#define TPU_TMDRn               0x04    /* Timer mode register */
#define TPU_TMDR_BFWT           (1 << 6)
#define TPU_TMDR_BFB            (1 << 5)
#define TPU_TMDR_BFA            (1 << 4)
#define TPU_TMDR_MD_NORMAL      (0 << 0)
#define TPU_TMDR_MD_PWM         (2 << 0)
#define TPU_TIORn               0x08    /* Timer I/O control register */
#define TPU_TIOR_IOA_0          (0 << 0)
#define TPU_TIOR_IOA_0_CLR      (1 << 0)
#define TPU_TIOR_IOA_0_SET      (2 << 0)
#define TPU_TIOR_IOA_0_TOGGLE   (3 << 0)
#define TPU_TIOR_IOA_1          (4 << 0)
#define TPU_TIOR_IOA_1_CLR      (5 << 0)
#define TPU_TIOR_IOA_1_SET      (6 << 0)
#define TPU_TIOR_IOA_1_TOGGLE   (7 << 0)
#define TPU_TIERn               0x0c    /* Timer interrupt enable register */
#define TPU_TSRn                0x10    /* Timer status register */
#define TPU_TCNTn               0x14    /* Timer counter */
#define TPU_TGRAn               0x18    /* Timer general register A */
#define TPU_TGRBn               0x1c    /* Timer general register B */
#define TPU_TGRCn               0x20    /* Timer general register C */
#define TPU_TGRDn               0x24    /* Timer general register D */

#define TPU_CHANNEL_OFFSET      0x10
#define TPU_CHANNEL_SIZE        0x40

enum tpu_pin_state {
        TPU_PIN_INACTIVE,               /* Pin is driven inactive */
        TPU_PIN_PWM,                    /* Pin is driven by PWM */
        TPU_PIN_ACTIVE,                 /* Pin is driven active */
};

struct tpu_device;

struct tpu_pwm_device {
        bool timer_on;                  /* Whether the timer is running */

        struct tpu_device *tpu;
        unsigned int channel;           /* Channel number in the TPU */

        enum pwm_polarity polarity;
        unsigned int prescaler;
        u16 period;
        u16 duty;
};

struct tpu_device {
        struct platform_device *pdev;
        struct pwm_chip chip;
        spinlock_t lock;

        void __iomem *base;
        struct clk *clk;
};

#define to_tpu_device(c)        container_of(c, struct tpu_device, chip)

static void tpu_pwm_write(struct tpu_pwm_device *pwm, int reg_nr, u16 value)
{
        void __iomem *base = pwm->tpu->base + TPU_CHANNEL_OFFSET
                           + pwm->channel * TPU_CHANNEL_SIZE;

        iowrite16(value, base + reg_nr);
}

static void tpu_pwm_set_pin(struct tpu_pwm_device *pwm,
                            enum tpu_pin_state state)
{
        static const char * const states[] = { "inactive", "PWM", "active" };

        dev_dbg(&pwm->tpu->pdev->dev, "%u: configuring pin as %s\n",
                pwm->channel, states[state]);

        switch (state) {
        case TPU_PIN_INACTIVE:
                tpu_pwm_write(pwm, TPU_TIORn,
                              pwm->polarity == PWM_POLARITY_INVERSED ?
                              TPU_TIOR_IOA_1 : TPU_TIOR_IOA_0);
                break;
        case TPU_PIN_PWM:
                tpu_pwm_write(pwm, TPU_TIORn,
                              pwm->polarity == PWM_POLARITY_INVERSED ?
                              TPU_TIOR_IOA_0_SET : TPU_TIOR_IOA_1_CLR);
                break;
        case TPU_PIN_ACTIVE:
                tpu_pwm_write(pwm, TPU_TIORn,
                              pwm->polarity == PWM_POLARITY_INVERSED ?
                              TPU_TIOR_IOA_0 : TPU_TIOR_IOA_1);
                break;
        }
}

static void tpu_pwm_start_stop(struct tpu_pwm_device *pwm, int start)
{
        unsigned long flags;
        u16 value;

        spin_lock_irqsave(&pwm->tpu->lock, flags);
        value = ioread16(pwm->tpu->base + TPU_TSTR);

        if (start)
                value |= 1 << pwm->channel;
        else
                value &= ~(1 << pwm->channel);

        iowrite16(value, pwm->tpu->base + TPU_TSTR);
        spin_unlock_irqrestore(&pwm->tpu->lock, flags);
}

static int tpu_pwm_timer_start(struct tpu_pwm_device *pwm)
{
        int ret;

        if (!pwm->timer_on) {
                /* Wake up device and enable clock. */
                pm_runtime_get_sync(&pwm->tpu->pdev->dev);
                ret = clk_prepare_enable(pwm->tpu->clk);
                if (ret) {
                        dev_err(&pwm->tpu->pdev->dev, "cannot enable clock\n");
                        return ret;
                }
                pwm->timer_on = true;
        }

        /*
         * Make sure the channel is stopped, as we need to reconfigure it
         * completely. First drive the pin to the inactive state to avoid
         * glitches.
         */
        tpu_pwm_set_pin(pwm, TPU_PIN_INACTIVE);
        tpu_pwm_start_stop(pwm, false);

        /*
         * - Clear TCNT on TGRB match
         * - Count on rising edge
         * - Set prescaler
         * - Output 0 until TGRA, output 1 until TGRB (active low polarity)
         * - Output 1 until TGRA, output 0 until TGRB (active high polarity
         * - PWM mode
         */
        tpu_pwm_write(pwm, TPU_TCRn, TPU_TCR_CCLR_TGRB | TPU_TCR_CKEG_RISING |
                      pwm->prescaler);
        tpu_pwm_write(pwm, TPU_TMDRn, TPU_TMDR_MD_PWM);
        tpu_pwm_set_pin(pwm, TPU_PIN_PWM);
        tpu_pwm_write(pwm, TPU_TGRAn, pwm->duty);
        tpu_pwm_write(pwm, TPU_TGRBn, pwm->period);

        dev_dbg(&pwm->tpu->pdev->dev, "%u: TGRA 0x%04x TGRB 0x%04x\n",
                pwm->channel, pwm->duty, pwm->period);

        /* Start the channel. */
        tpu_pwm_start_stop(pwm, true);

        return 0;
}

static void tpu_pwm_timer_stop(struct tpu_pwm_device *pwm)
{
        if (!pwm->timer_on)
                return;

        /* Disable channel. */
        tpu_pwm_start_stop(pwm, false);

        /* Stop clock and mark device as idle. */
        clk_disable_unprepare(pwm->tpu->clk);
        pm_runtime_put(&pwm->tpu->pdev->dev);

        pwm->timer_on = false;
}

/* -----------------------------------------------------------------------------
 * PWM API
 */

static int tpu_pwm_request(struct pwm_chip *chip, struct pwm_device *_pwm)
{
        struct tpu_device *tpu = to_tpu_device(chip);
        struct tpu_pwm_device *pwm;

        if (_pwm->hwpwm >= TPU_CHANNEL_MAX)
                return -EINVAL;

        pwm = kzalloc(sizeof(*pwm), GFP_KERNEL);
        if (pwm == NULL)
                return -ENOMEM;

        pwm->tpu = tpu;
        pwm->channel = _pwm->hwpwm;
        pwm->polarity = PWM_POLARITY_NORMAL;
        pwm->prescaler = 0;
        pwm->period = 0;
        pwm->duty = 0;

        pwm->timer_on = false;

        pwm_set_chip_data(_pwm, pwm);

        return 0;
}

static void tpu_pwm_free(struct pwm_chip *chip, struct pwm_device *_pwm)
{
        struct tpu_pwm_device *pwm = pwm_get_chip_data(_pwm);

        tpu_pwm_timer_stop(pwm);
        kfree(pwm);
}

static int tpu_pwm_config(struct pwm_chip *chip, struct pwm_device *_pwm,
                          int duty_ns, int period_ns)
{
        static const unsigned int prescalers[] = { 1, 4, 16, 64 };
        struct tpu_pwm_device *pwm = pwm_get_chip_data(_pwm);
        struct tpu_device *tpu = to_tpu_device(chip);
        unsigned int prescaler;
        bool duty_only = false;
        u32 clk_rate;
        u32 period;
        u32 duty;
        int ret;

        /*
         * Pick a prescaler to avoid overflowing the counter.
         * TODO: Pick the highest acceptable prescaler.
         */
        clk_rate = clk_get_rate(tpu->clk);

        for (prescaler = 0; prescaler < ARRAY_SIZE(prescalers); ++prescaler) {
                period = clk_rate / prescalers[prescaler]
                       / (NSEC_PER_SEC / period_ns);
                if (period <= 0xffff)
                        break;
        }

        if (prescaler == ARRAY_SIZE(prescalers) || period == 0) {
                dev_err(&tpu->pdev->dev, "clock rate mismatch\n");
                return -ENOTSUPP;
        }

        if (duty_ns) {
                duty = clk_rate / prescalers[prescaler]
                     / (NSEC_PER_SEC / duty_ns);
                if (duty > period)
                        return -EINVAL;
        } else {
                duty = 0;
        }

        dev_dbg(&tpu->pdev->dev,
                "rate %u, prescaler %u, period %u, duty %u\n",
                clk_rate, prescalers[prescaler], period, duty);

        if (pwm->prescaler == prescaler && pwm->period == period)
                duty_only = true;

        pwm->prescaler = prescaler;
        pwm->period = period;
        pwm->duty = duty;

        /* If the channel is disabled we're done. */
        if (!pwm_is_enabled(_pwm))
                return 0;

        if (duty_only && pwm->timer_on) {
                /*
                 * If only the duty cycle changed and the timer is already
                 * running, there's no need to reconfigure it completely, Just
                 * modify the duty cycle.
                 */
                tpu_pwm_write(pwm, TPU_TGRAn, pwm->duty);
                dev_dbg(&tpu->pdev->dev, "%u: TGRA 0x%04x\n", pwm->channel,
                        pwm->duty);
        } else {
                /* Otherwise perform a full reconfiguration. */
                ret = tpu_pwm_timer_start(pwm);
                if (ret < 0)
                        return ret;
        }

        if (duty == 0 || duty == period) {
                /*
                 * To avoid running the timer when not strictly required, handle
                 * 0% and 100% duty cycles as fixed levels and stop the timer.
                 */
                tpu_pwm_set_pin(pwm, duty ? TPU_PIN_ACTIVE : TPU_PIN_INACTIVE);
                tpu_pwm_timer_stop(pwm);
        }

        return 0;
}

static int tpu_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *_pwm,
                                enum pwm_polarity polarity)
{
        struct tpu_pwm_device *pwm = pwm_get_chip_data(_pwm);

        pwm->polarity = polarity;

        return 0;
}

static int tpu_pwm_enable(struct pwm_chip *chip, struct pwm_device *_pwm)
{
        struct tpu_pwm_device *pwm = pwm_get_chip_data(_pwm);
        int ret;

        ret = tpu_pwm_timer_start(pwm);
        if (ret < 0)
                return ret;

        /*
         * To avoid running the timer when not strictly required, handle 0% and
         * 100% duty cycles as fixed levels and stop the timer.
         */
        if (pwm->duty == 0 || pwm->duty == pwm->period) {
                tpu_pwm_set_pin(pwm, pwm->duty ?
                                TPU_PIN_ACTIVE : TPU_PIN_INACTIVE);
                tpu_pwm_timer_stop(pwm);
        }

        return 0;
}

static void tpu_pwm_disable(struct pwm_chip *chip, struct pwm_device *_pwm)
{
        struct tpu_pwm_device *pwm = pwm_get_chip_data(_pwm);

        /* The timer must be running to modify the pin output configuration. */
        tpu_pwm_timer_start(pwm);
        tpu_pwm_set_pin(pwm, TPU_PIN_INACTIVE);
        tpu_pwm_timer_stop(pwm);
}

static const struct pwm_ops tpu_pwm_ops = {
        .request = tpu_pwm_request,
        .free = tpu_pwm_free,
        .config = tpu_pwm_config,
        .set_polarity = tpu_pwm_set_polarity,
        .enable = tpu_pwm_enable,
        .disable = tpu_pwm_disable,
        .owner = THIS_MODULE,
};

/* -----------------------------------------------------------------------------
 * Probe and remove
 */

static int tpu_probe(struct platform_device *pdev)
{
        struct tpu_device *tpu;
        struct resource *res;
        int ret;

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

        spin_lock_init(&tpu->lock);
        tpu->pdev = pdev;

        /* Map memory, get clock and pin control. */
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        tpu->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(tpu->base))
                return PTR_ERR(tpu->base);

        tpu->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(tpu->clk)) {
                dev_err(&pdev->dev, "cannot get clock\n");
                return PTR_ERR(tpu->clk);
        }

        /* Initialize and register the device. */
        platform_set_drvdata(pdev, tpu);

        tpu->chip.dev = &pdev->dev;
        tpu->chip.ops = &tpu_pwm_ops;
        tpu->chip.of_xlate = of_pwm_xlate_with_flags;
        tpu->chip.of_pwm_n_cells = 3;
        tpu->chip.base = -1;
        tpu->chip.npwm = TPU_CHANNEL_MAX;

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

        dev_info(&pdev->dev, "TPU PWM %d registered\n", tpu->pdev->id);

        pm_runtime_enable(&pdev->dev);

        return 0;
}

static int tpu_remove(struct platform_device *pdev)
{
        struct tpu_device *tpu = platform_get_drvdata(pdev);
        int ret;

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

        pm_runtime_disable(&pdev->dev);

        return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id tpu_of_table[] = {
        { .compatible = "renesas,tpu-r8a73a4", },
        { .compatible = "renesas,tpu-r8a7740", },
        { .compatible = "renesas,tpu-r8a7790", },
        { .compatible = "renesas,tpu-sh7372", },
        { .compatible = "renesas,tpu", },
        { },
};

MODULE_DEVICE_TABLE(of, tpu_of_table);
#endif

static struct platform_driver tpu_driver = {
        .probe          = tpu_probe,
        .remove         = tpu_remove,
        .driver         = {
                .name   = "renesas-tpu-pwm",
                .of_match_table = of_match_ptr(tpu_of_table),
        }
};

module_platform_driver(tpu_driver);

MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
MODULE_DESCRIPTION("Renesas TPU PWM Driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:renesas-tpu-pwm");