/*
 * drivers/pwm/pwm-tegra.c
 *
 * Tegra pulse-width-modulation controller driver
 *
 * Copyright (c) 2010-2020, NVIDIA CORPORATION. All rights reserved.
 *
 * 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.
 */

#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	BIT(31)
#define PWM_DUTY_WIDTH	8
#define PWM_DUTY_SHIFT	16
#define PWM_SCALE_WIDTH	13
#define PWM_SCALE_SHIFT	0

#define CLK_1MHZ	1000000UL

struct tegra_pwm_soc {
	unsigned int num_channels;
	unsigned long max_clk_limit;
};

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

	struct clk *clk;
	struct reset_control *rst;

	unsigned long clk_rate;

	void __iomem *regs;

	const struct tegra_pwm_soc *soc;
	unsigned long		max_clk_limit;
	int (*clk_enable)(struct clk *clk);
	void (*clk_disable)(struct clk *clk);
};

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;
	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;

	/*
	 * Its okay to ignore the fraction part since we will be trying to set
	 * slightly lower value to rate than the actual required rate
	 */
	rate = NSEC_PER_SEC/period_ns;

	/*
	 *  Period in nano second has to be <= highest allowed period
	 *  based on the max clock rate of the pwm controller.
	 *
	 *  higher limit = max clock limit >> PWM_DUTY_WIDTH
	 */
	if (rate > (pc->max_clk_limit >> PWM_DUTY_WIDTH))
		return -EINVAL;

	/*
	 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
	 * cycles at the PWM clock rate will take period_ns nanoseconds.
	 */
	if (pc->soc->num_channels == 1) {
		/*
		 * Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches with the
		 * hieghest applicable rate that the controller can provide. Any further
		 * lower value can be derived by setting PFM bits[0:12]
		 * Higher mark is taken since BPMP has round-up mechanism implemented.
		 */
		rate = rate << PWM_DUTY_WIDTH;

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

		rate = clk_get_rate(pc->clk) >> PWM_DUTY_WIDTH;
	} else {
		/*
		 * This is the case for SoCs who support multiple channels:
		 *
		 * clk_set_rate() can not be called again in config because T210
		 * or any prior chip supports one pwm-controller and multiple channels.
		 * Hence in this case cached clock rate will be considered which was
		 * stored during probe.
		 */
		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 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 = pc->clk_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))
		pc->clk_disable(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 = pc->clk_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);

	pc->clk_disable(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;
	bool no_clk_sleeping_in_ops;
	struct clk *parent_clk;
	struct clk *parent_slow;
	u32 pval;
	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;

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

	platform_set_drvdata(pdev, pwm);

	no_clk_sleeping_in_ops = of_property_read_bool(pdev->dev.of_node,
						       "nvidia,no-clk-sleeping-in-ops");
	dev_info(&pdev->dev, "PWM clk can%s sleep in ops\n",
			no_clk_sleeping_in_ops ? "not" : "");

	ret = of_property_read_u32(pdev->dev.of_node,
				   "pwm-minimum-frequency-hz", &pval);
	if (!ret)
		pwm->max_clk_limit = pval * 256 * (1 << PWM_SCALE_WIDTH);
	else
		pwm->max_clk_limit = pwm->soc->max_clk_limit;

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

	parent_clk = devm_clk_get(&pdev->dev, "parent");
	if (!IS_ERR(parent_clk)) {
		struct device *dev = &pdev->dev;

		/*
		 * Set PWM frequency to lower so that it can switch
		 * to parent with higher clock rate.
		 */
		ret = clk_set_rate(pwm->clk, CLK_1MHZ);
		if (ret < 0) {
			dev_err(dev, "Failed to set 1M clock rate: %d\n", ret);
			return ret;
		}

		ret = clk_set_parent(pwm->clk, parent_clk);
		if (ret < 0) {
			dev_err(dev, "Failed to set parent clk: %d\n", ret);
			return ret;
		}

		/* Set clock to maximum clock limit */
		ret = clk_set_rate(pwm->clk, pwm->max_clk_limit);
		if (ret < 0) {
			dev_err(dev, "Failed to set max clk rate: %d\n", ret);
			return ret;
		}
	}

	/* Read PWM clock rate from source */
	pwm->clk_rate = clk_get_rate(pwm->clk);

	/* Limit the maximum clock rate */
	if (pwm->max_clk_limit &&
	    (pwm->clk_rate > pwm->max_clk_limit)) {
		ret = clk_set_rate(pwm->clk, pwm->max_clk_limit);
		if (ret < 0) {
			dev_err(&pdev->dev, "Failed to set max clk rate: %d\n",
				ret);
			return ret;
		}
		pwm->clk_rate = clk_get_rate(pwm->clk);
	}

	if (pwm->clk_rate <= pwm->max_clk_limit)
		goto parent_done;
	/*
	 * If clk_rate is still higher than the max_clk_limit then
	 * switch to slow parent if exist
	 */
	parent_slow = devm_clk_get(&pdev->dev, "slow-parent");
	if (IS_ERR(parent_slow)) {
		dev_warn(&pdev->dev, "Source clock %lu is higher than required %lu\n",
			 pwm->clk_rate, pwm->max_clk_limit);
		goto parent_done;
	}

	ret = clk_set_parent(pwm->clk, parent_slow);
	if (ret < 0) {
		dev_err(&pdev->dev, "Failed to set slow-parent: %d\n", ret);
		return ret;
	}

	/* Set clock to maximum clock limit */
	ret = clk_set_rate(pwm->clk, pwm->max_clk_limit);
	if (ret < 0) {
		dev_err(&pdev->dev, "Failed to set max clk rate: %d\n", ret);
		return ret;
	}
	pwm->clk_rate = clk_get_rate(pwm->clk);

parent_done:
	if (no_clk_sleeping_in_ops) {
		ret = clk_prepare(pwm->clk);
		if (ret) {
			dev_err(&pdev->dev, "PWM clock prepare failed\n");
			return ret;
		}
		pwm->clk_enable = clk_enable;
		pwm->clk_disable = clk_disable;
	} else {
		pwm->clk_enable = clk_prepare_enable;
		pwm->clk_disable = clk_disable_unprepare;
	}

	pwm->rst = devm_reset_control_get(&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.base = -1;
	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);
	unsigned int i;
	int err;

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

	err = pc->clk_enable(pc->clk);
	if (err < 0)
		return err;

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

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

		pwm_writel(pc, i, 0);

		pc->clk_disable(pc->clk);
	}

	reset_control_assert(pc->rst);
	clk_disable_unprepare(pc->clk);

	return pwmchip_remove(&pc->chip);
}

#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_clk_limit = 48000000UL, /* 48 MHz */
};

static const struct tegra_pwm_soc tegra186_pwm_soc = {
	.num_channels = 1,
	.max_clk_limit = 102000000UL, /*102 MHz */
};

static const struct tegra_pwm_soc tegra194_pwm_soc = {
	.num_channels = 1,
	.max_clk_limit = 408000000UL, /*408 MHz */
};

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