/*
 * drivers/pwm/pwm-tegra.c
 *
 * Tegra pulse-width-modulation controller driver
 *
 * Copyright (c) 2010, NVIDIA Corporation.
 * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
 *
 * 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.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/pwm.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#define PWM_ENABLE      (1 << 31)
#define PWM_DUTY_WIDTH  8
#define PWM_DUTY_SHIFT  16
#define PWM_SCALE_WIDTH 13
#define PWM_SCALE_SHIFT 0

#define NUM_PWM 4

struct tegra_pwm_chip {
        struct pwm_chip         chip;
        struct device           *dev;

        struct clk              *clk;

        void __iomem            *mmio_base;
};

static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
{
        return container_of(chip, struct tegra_pwm_chip, chip);
}

static inline u32 pwm_readl(struct tegra_pwm_chip *chip, unsigned int num)
{
        return readl(chip->mmio_base + (num << 4));
}

static inline void pwm_writel(struct tegra_pwm_chip *chip, unsigned int num,
                             unsigned long val)
{
        writel(val, chip->mmio_base + (num << 4));
}

static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
                            int duty_ns, int period_ns)
{
        struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
        unsigned long long c;
        unsigned long rate, hz;
        u32 val = 0;
        int err;

        /*
         * Convert from duty_ns / period_ns to a fixed number of duty ticks
         * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
         * nearest integer during division.
         */
        c = duty_ns * ((1 << PWM_DUTY_WIDTH) - 1) + period_ns / 2;
        do_div(c, period_ns);

        val = (u32)c << PWM_DUTY_SHIFT;

        /*
         * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
         * cycles at the PWM clock rate will take period_ns nanoseconds.
         */
        rate = clk_get_rate(pc->clk) >> PWM_DUTY_WIDTH;
        hz = NSEC_PER_SEC / period_ns;

        rate = (rate + (hz / 2)) / hz;

        /*
         * Since the actual PWM divider is the register's frequency divider
         * field minus 1, we need to decrement to get the correct value to
         * write to the register.
         */
        if (rate > 0)
                rate--;

        /*
         * Make sure that the rate will fit in the register's frequency
         * divider field.
         */
        if (rate >> PWM_SCALE_WIDTH)
                return -EINVAL;

        val |= rate << PWM_SCALE_SHIFT;

        /*
         * If the PWM channel is disabled, make sure to turn on the clock
         * before writing the register. Otherwise, keep it enabled.
         */
        if (!pwm_is_enabled(pwm)) {
                err = clk_prepare_enable(pc->clk);
                if (err < 0)
                        return err;
        } else
                val |= PWM_ENABLE;

        pwm_writel(pc, pwm->hwpwm, val);

        /*
         * If the PWM is not enabled, turn the clock off again to save power.
         */
        if (!pwm_is_enabled(pwm))
                clk_disable_unprepare(pc->clk);

        return 0;
}

static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
        int rc = 0;
        u32 val;

        rc = clk_prepare_enable(pc->clk);
        if (rc < 0)
                return rc;

        val = pwm_readl(pc, pwm->hwpwm);
        val |= PWM_ENABLE;
        pwm_writel(pc, pwm->hwpwm, val);

        return 0;
}

static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
        struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
        u32 val;

        val = pwm_readl(pc, pwm->hwpwm);
        val &= ~PWM_ENABLE;
        pwm_writel(pc, pwm->hwpwm, val);

        clk_disable_unprepare(pc->clk);
}

static const struct pwm_ops tegra_pwm_ops = {
        .config = tegra_pwm_config,
        .enable = tegra_pwm_enable,
        .disable = tegra_pwm_disable,
        .owner = THIS_MODULE,
};

static int tegra_pwm_probe(struct platform_device *pdev)
{
        struct tegra_pwm_chip *pwm;
        struct resource *r;
        int ret;

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

        pwm->dev = &pdev->dev;

        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        pwm->mmio_base = devm_ioremap_resource(&pdev->dev, r);
        if (IS_ERR(pwm->mmio_base))
                return PTR_ERR(pwm->mmio_base);

        platform_set_drvdata(pdev, pwm);

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

        pwm->chip.dev = &pdev->dev;
        pwm->chip.ops = &tegra_pwm_ops;
        pwm->chip.base = -1;
        pwm->chip.npwm = NUM_PWM;

        ret = pwmchip_add(&pwm->chip);
        if (ret < 0) {
                dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
                return ret;
        }

        return 0;
}

static int tegra_pwm_remove(struct platform_device *pdev)
{
        struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);
        int i;

        if (WARN_ON(!pc))
                return -ENODEV;

        for (i = 0; i < NUM_PWM; i++) {
                struct pwm_device *pwm = &pc->chip.pwms[i];

                if (!pwm_is_enabled(pwm))
                        if (clk_prepare_enable(pc->clk) < 0)
                                continue;

                pwm_writel(pc, i, 0);

                clk_disable_unprepare(pc->clk);
        }

        return pwmchip_remove(&pc->chip);
}

static const struct of_device_id tegra_pwm_of_match[] = {
        { .compatible = "nvidia,tegra20-pwm" },
        { .compatible = "nvidia,tegra30-pwm" },
        { }
};

MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);

static struct platform_driver tegra_pwm_driver = {
        .driver = {
                .name = "tegra-pwm",
                .of_match_table = tegra_pwm_of_match,
        },
        .probe = tegra_pwm_probe,
        .remove = tegra_pwm_remove,
};

module_platform_driver(tegra_pwm_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("NVIDIA Corporation");
MODULE_ALIAS("platform:tegra-pwm");