/*
 * PWM driver for Rockchip SoCs
 *
 * Copyright (C) 2014 Beniamino Galvani <b.galvani@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 */

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

#define PWM_CNTR		0x00		/* Counter register */
#define PWM_HRC			0x04		/* High reference register */
#define PWM_LRC			0x08		/* Low reference register */
#define PWM_CTRL		0x0c		/* Control register */
#define PWM_CTRL_TIMER_EN	(1 << 0)
#define PWM_CTRL_OUTPUT_EN	(1 << 3)

#define PRESCALER		2

struct rockchip_pwm_chip {
	struct pwm_chip chip;
	struct clk *clk;
	void __iomem *base;
};

static inline struct rockchip_pwm_chip *to_rockchip_pwm_chip(struct pwm_chip *c)
{
	return container_of(c, struct rockchip_pwm_chip, chip);
}

static int rockchip_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
			       int duty_ns, int period_ns)
{
	struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
	unsigned long period, duty;
	u64 clk_rate, div;
	int ret;

	clk_rate = clk_get_rate(pc->clk);

	/*
	 * Since period and duty cycle registers have a width of 32
	 * bits, every possible input period can be obtained using the
	 * default prescaler value for all practical clock rate values.
	 */
	div = clk_rate * period_ns;
	do_div(div, PRESCALER * NSEC_PER_SEC);
	period = div;

	div = clk_rate * duty_ns;
	do_div(div, PRESCALER * NSEC_PER_SEC);
	duty = div;

	ret = clk_enable(pc->clk);
	if (ret)
		return ret;

	writel(period, pc->base + PWM_LRC);
	writel(duty, pc->base + PWM_HRC);
	writel(0, pc->base + PWM_CNTR);

	clk_disable(pc->clk);

	return 0;
}

static int rockchip_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
	int ret;
	u32 val;

	ret = clk_enable(pc->clk);
	if (ret)
		return ret;

	val = readl_relaxed(pc->base + PWM_CTRL);
	val |= PWM_CTRL_OUTPUT_EN | PWM_CTRL_TIMER_EN;
	writel_relaxed(val, pc->base + PWM_CTRL);

	return 0;
}

static void rockchip_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
	u32 val;

	val = readl_relaxed(pc->base + PWM_CTRL);
	val &= ~(PWM_CTRL_OUTPUT_EN | PWM_CTRL_TIMER_EN);
	writel_relaxed(val, pc->base + PWM_CTRL);

	clk_disable(pc->clk);
}

static const struct pwm_ops rockchip_pwm_ops = {
	.config = rockchip_pwm_config,
	.enable = rockchip_pwm_enable,
	.disable = rockchip_pwm_disable,
	.owner = THIS_MODULE,
};

static int rockchip_pwm_probe(struct platform_device *pdev)
{
	struct rockchip_pwm_chip *pc;
	struct resource *r;
	int ret;

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

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

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

	ret = clk_prepare(pc->clk);
	if (ret)
		return ret;

	platform_set_drvdata(pdev, pc);

	pc->chip.dev = &pdev->dev;
	pc->chip.ops = &rockchip_pwm_ops;
	pc->chip.base = -1;
	pc->chip.npwm = 1;

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

	return ret;
}

static int rockchip_pwm_remove(struct platform_device *pdev)
{
	struct rockchip_pwm_chip *pc = platform_get_drvdata(pdev);

	clk_unprepare(pc->clk);

	return pwmchip_remove(&pc->chip);
}

static const struct of_device_id rockchip_pwm_dt_ids[] = {
	{ .compatible = "rockchip,rk2928-pwm" },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, rockchip_pwm_dt_ids);

static struct platform_driver rockchip_pwm_driver = {
	.driver = {
		.name = "rockchip-pwm",
		.of_match_table = rockchip_pwm_dt_ids,
	},
	.probe = rockchip_pwm_probe,
	.remove = rockchip_pwm_remove,
};
module_platform_driver(rockchip_pwm_driver);

MODULE_AUTHOR("Beniamino Galvani <b.galvani@gmail.com>");
MODULE_DESCRIPTION("Rockchip SoC PWM driver");
MODULE_LICENSE("GPL v2");