// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * drivers/pwm/pwm-tegra.c
 *
 * Tegra pulse-width-modulation controller driver
 *
 * Copyright (c) 2010-2020, NVIDIA Corporation.
 * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
 *
 * Overview of Tegra Pulse Width Modulator Register:
 * 1. 13-bit: Frequency division (SCALE)
 * 2. 8-bit : Pulse division (DUTY)
 * 3. 1-bit : Enable bit
 *
 * The PWM clock frequency is divided by 256 before subdividing it based
 * on the programmable frequency division value to generate the required
 * frequency for PWM output. The maximum output frequency that can be
 * achieved is (max rate of source clock) / 256.
 * e.g. if source clock rate is 408 MHz, maximum output frequency can be:
 * 408 MHz/256 = 1.6 MHz.
 * This 1.6 MHz frequency can further be divided using SCALE value in PWM.
 *
 * PWM pulse width: 8 bits are usable [23:16] for varying pulse width.
 * To achieve 100% duty cycle, program Bit [24] of this register to
 * 1’b1. In which case the other bits [23:16] are set to don't care.
 *
 * Limitations:
 * -    When PWM is disabled, the output is driven to inactive.
 * -    It does not allow the current PWM period to complete and
 *      stops abruptly.
 *
 * -    If the register is reconfigured while PWM is running,
 *      it does not complete the currently running period.
 *
 * -    If the user input duty is beyond acceptible limits,
 *      -EINVAL is returned.
 */

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

struct tegra_pwm_soc {
        unsigned int num_channels;

        /* Maximum IP frequency for given SoCs */
        unsigned long max_frequency;
};

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

        struct clk *clk;
        struct reset_control*rst;

        unsigned long clk_rate;
        unsigned long min_period_ns;

        void __iomem *regs;

        const struct tegra_pwm_soc *soc;
};

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->regs + (num << 4));
}

static inline void pwm_writel(struct tegra_pwm_chip *chip, unsigned int num,
                             unsigned long val)
{
        writel(val, chip->regs + (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 = duty_ns, hz;
        unsigned long rate, required_clk_rate;
        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 *= (1 << PWM_DUTY_WIDTH);
        c = DIV_ROUND_CLOSEST_ULL(c, period_ns);

        val = (u32)c << PWM_DUTY_SHIFT;

        /*
         *  min period = max clock limit >> PWM_DUTY_WIDTH
         */
        if (period_ns < pc->min_period_ns)
                return -EINVAL;

        /*
         * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
         * cycles at the PWM clock rate will take period_ns nanoseconds.
         *
         * num_channels: If single instance of PWM controller has multiple
         * channels (e.g. Tegra210 or older) then it is not possible to
         * configure separate clock rates to each of the channels, in such
         * case the value stored during probe will be referred.
         *
         * If every PWM controller instance has one channel respectively, i.e.
         * nums_channels == 1 then only the clock rate can be modified
         * dynamically (e.g. Tegra186 or Tegra194).
         */
        if (pc->soc->num_channels == 1) {
                /*
                 * Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches
                 * with the maximum possible rate that the controller can
                 * provide. Any further lower value can be derived by setting
                 * PFM bits[0:12].
                 *
                 * required_clk_rate is a reference rate for source clock and
                 * it is derived based on user requested period. By setting the
                 * source clock rate as required_clk_rate, PWM controller will
                 * be able to configure the requested period.
                 */
                required_clk_rate =
                        (NSEC_PER_SEC / period_ns) << PWM_DUTY_WIDTH;

                err = clk_set_rate(pc->clk, required_clk_rate);
                if (err < 0)
                        return -EINVAL;

                /* Store the new rate for further references */
                pc->clk_rate = clk_get_rate(pc->clk);
        }

        rate = pc->clk_rate >> PWM_DUTY_WIDTH;

        /* Consider precision in PWM_SCALE_WIDTH rate calculation */
        hz = DIV_ROUND_CLOSEST_ULL(100ULL * NSEC_PER_SEC, period_ns);
        rate = DIV_ROUND_CLOSEST_ULL(100ULL * rate, hz);

        /*
         * Since the actual PWM divider is the register's frequency divider
         * field plus 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;
        int ret;

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

        pwm->soc = of_device_get_match_data(&pdev->dev);
        pwm->dev = &pdev->dev;

        pwm->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(pwm->regs))
                return PTR_ERR(pwm->regs);

        platform_set_drvdata(pdev, pwm);

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

        /* Set maximum frequency of the IP */
        ret = clk_set_rate(pwm->clk, pwm->soc->max_frequency);
        if (ret < 0) {
                dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
                return ret;
        }

        /*
         * The requested and configured frequency may differ due to
         * clock register resolutions. Get the configured frequency
         * so that PWM period can be calculated more accurately.
         */
        pwm->clk_rate = clk_get_rate(pwm->clk);

        /* Set minimum limit of PWM period for the IP */
        pwm->min_period_ns =
            (NSEC_PER_SEC / (pwm->soc->max_frequency >> PWM_DUTY_WIDTH)) + 1;

        pwm->rst = devm_reset_control_get_exclusive(&pdev->dev, "pwm");
        if (IS_ERR(pwm->rst)) {
                ret = PTR_ERR(pwm->rst);
                dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
                return ret;
        }

        reset_control_deassert(pwm->rst);

        pwm->chip.dev = &pdev->dev;
        pwm->chip.ops = &tegra_pwm_ops;
        pwm->chip.npwm = pwm->soc->num_channels;

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

        return 0;
}

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

        pwmchip_remove(&pc->chip);

        reset_control_assert(pc->rst);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int tegra_pwm_suspend(struct device *dev)
{
        return pinctrl_pm_select_sleep_state(dev);
}

static int tegra_pwm_resume(struct device *dev)
{
        return pinctrl_pm_select_default_state(dev);
}
#endif

static const struct tegra_pwm_soc tegra20_pwm_soc = {
        .num_channels = 4,
        .max_frequency = 48000000UL,
};

static const struct tegra_pwm_soc tegra186_pwm_soc = {
        .num_channels = 1,
        .max_frequency = 102000000UL,
};

static const struct tegra_pwm_soc tegra194_pwm_soc = {
        .num_channels = 1,
        .max_frequency = 408000000UL,
};

static const struct of_device_id tegra_pwm_of_match[] = {
        { .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
        { .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
        { .compatible = "nvidia,tegra194-pwm", .data = &tegra194_pwm_soc },
        { }
};
MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);

static const struct dev_pm_ops tegra_pwm_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(tegra_pwm_suspend, tegra_pwm_resume)
};

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

module_platform_driver(tegra_pwm_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sandipan Patra <spatra@nvidia.com>");
MODULE_DESCRIPTION("Tegra PWM controller driver");
MODULE_ALIAS("platform:tegra-pwm");