// SPDX-License-Identifier: GPL-2.0
/*
 * Intel Keem Bay PWM driver
 *
 * Copyright (C) 2020 Intel Corporation
 * Authors: Lai Poey Seng <poey.seng.lai@intel.com>
 *          Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>
 *
 * Limitations:
 * - Upon disabling a channel, the currently running
 *   period will not be completed. However, upon
 *   reconfiguration of the duty cycle/period, the
 *   currently running period will be completed first.
 */

#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/regmap.h>

#define KMB_TOTAL_PWM_CHANNELS		6
#define KMB_PWM_COUNT_MAX		U16_MAX
#define KMB_PWM_EN_BIT			BIT(31)

/* Mask */
#define KMB_PWM_HIGH_MASK		GENMASK(31, 16)
#define KMB_PWM_LOW_MASK		GENMASK(15, 0)
#define KMB_PWM_LEADIN_MASK		GENMASK(30, 0)

/* PWM Register offset */
#define KMB_PWM_LEADIN_OFFSET(ch)	(0x00 + 4 * (ch))
#define KMB_PWM_HIGHLOW_OFFSET(ch)	(0x20 + 4 * (ch))

struct keembay_pwm {
	struct pwm_chip chip;
	struct device *dev;
	struct clk *clk;
	void __iomem *base;
};

static inline struct keembay_pwm *to_keembay_pwm_dev(struct pwm_chip *chip)
{
	return container_of(chip, struct keembay_pwm, chip);
}

static void keembay_clk_unprepare(void *data)
{
	clk_disable_unprepare(data);
}

static int keembay_clk_enable(struct device *dev, struct clk *clk)
{
	int ret;

	ret = clk_prepare_enable(clk);
	if (ret)
		return ret;

	return devm_add_action_or_reset(dev, keembay_clk_unprepare, clk);
}

/*
 * With gcc 10, CONFIG_CC_OPTIMIZE_FOR_SIZE and only "inline" instead of
 * "__always_inline" this fails to compile because the compiler doesn't notice
 * for all valid masks (e.g. KMB_PWM_LEADIN_MASK) that they are ok.
 */
static __always_inline void keembay_pwm_update_bits(struct keembay_pwm *priv, u32 mask,
					   u32 val, u32 offset)
{
	u32 buff = readl(priv->base + offset);

	buff = u32_replace_bits(buff, val, mask);
	writel(buff, priv->base + offset);
}

static void keembay_pwm_enable(struct keembay_pwm *priv, int ch)
{
	keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 1,
				KMB_PWM_LEADIN_OFFSET(ch));
}

static void keembay_pwm_disable(struct keembay_pwm *priv, int ch)
{
	keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 0,
				KMB_PWM_LEADIN_OFFSET(ch));
}

static int keembay_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
				 struct pwm_state *state)
{
	struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
	unsigned long long high, low;
	unsigned long clk_rate;
	u32 highlow;

	clk_rate = clk_get_rate(priv->clk);

	/* Read channel enabled status */
	highlow = readl(priv->base + KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));
	if (highlow & KMB_PWM_EN_BIT)
		state->enabled = true;
	else
		state->enabled = false;

	/* Read period and duty cycle */
	highlow = readl(priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));
	low = FIELD_GET(KMB_PWM_LOW_MASK, highlow) * NSEC_PER_SEC;
	high = FIELD_GET(KMB_PWM_HIGH_MASK, highlow) * NSEC_PER_SEC;
	state->duty_cycle = DIV_ROUND_UP_ULL(high, clk_rate);
	state->period = DIV_ROUND_UP_ULL(high + low, clk_rate);
	state->polarity = PWM_POLARITY_NORMAL;

	return 0;
}

static int keembay_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
			     const struct pwm_state *state)
{
	struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
	struct pwm_state current_state;
	unsigned long long div;
	unsigned long clk_rate;
	u32 pwm_count = 0;
	u16 high, low;

	if (state->polarity != PWM_POLARITY_NORMAL)
		return -EINVAL;

	/*
	 * Configure the pwm repeat count as infinite at (15:0) and leadin
	 * low time as 0 at (30:16), which is in terms of clock cycles.
	 */
	keembay_pwm_update_bits(priv, KMB_PWM_LEADIN_MASK, 0,
				KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));

	keembay_pwm_get_state(chip, pwm, &current_state);

	if (!state->enabled) {
		if (current_state.enabled)
			keembay_pwm_disable(priv, pwm->hwpwm);
		return 0;
	}

	/*
	 * The upper 16 bits and lower 16 bits of the KMB_PWM_HIGHLOW_OFFSET
	 * register contain the high time and low time of waveform accordingly.
	 * All the values are in terms of clock cycles.
	 */

	clk_rate = clk_get_rate(priv->clk);
	div = clk_rate * state->duty_cycle;
	div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC);
	if (div > KMB_PWM_COUNT_MAX)
		return -ERANGE;

	high = div;
	div = clk_rate * state->period;
	div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC);
	div = div - high;
	if (div > KMB_PWM_COUNT_MAX)
		return -ERANGE;

	low = div;

	pwm_count = FIELD_PREP(KMB_PWM_HIGH_MASK, high) |
		    FIELD_PREP(KMB_PWM_LOW_MASK, low);

	writel(pwm_count, priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));

	if (state->enabled && !current_state.enabled)
		keembay_pwm_enable(priv, pwm->hwpwm);

	return 0;
}

static const struct pwm_ops keembay_pwm_ops = {
	.apply = keembay_pwm_apply,
	.get_state = keembay_pwm_get_state,
};

static int keembay_pwm_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct keembay_pwm *priv;
	int ret;

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

	priv->clk = devm_clk_get(dev, NULL);
	if (IS_ERR(priv->clk))
		return dev_err_probe(dev, PTR_ERR(priv->clk), "Failed to get clock\n");

	priv->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->base))
		return PTR_ERR(priv->base);

	ret = keembay_clk_enable(dev, priv->clk);
	if (ret)
		return ret;

	priv->chip.dev = dev;
	priv->chip.ops = &keembay_pwm_ops;
	priv->chip.npwm = KMB_TOTAL_PWM_CHANNELS;

	ret = devm_pwmchip_add(dev, &priv->chip);
	if (ret)
		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");

	return 0;
}

static const struct of_device_id keembay_pwm_of_match[] = {
	{ .compatible = "intel,keembay-pwm" },
	{ }
};
MODULE_DEVICE_TABLE(of, keembay_pwm_of_match);

static struct platform_driver keembay_pwm_driver = {
	.probe	= keembay_pwm_probe,
	.driver	= {
		.name = "pwm-keembay",
		.of_match_table = keembay_pwm_of_match,
	},
};
module_platform_driver(keembay_pwm_driver);

MODULE_ALIAS("platform:pwm-keembay");
MODULE_DESCRIPTION("Intel Keem Bay PWM driver");
MODULE_LICENSE("GPL v2");