/* drivers/pwm/pwm-samsung.c
 *
 * Copyright (c) 2007 Ben Dooks
 * Copyright (c) 2008 Simtec Electronics
 *	Ben Dooks <ben@simtec.co.uk>, <ben-linux@fluff.org>
 *
 * S3C series PWM device core
 *
 * 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.
*/

#define pr_fmt(fmt) "pwm-samsung: " fmt

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/pwm.h>

#include <mach/map.h>

#include <plat/regs-timer.h>

struct s3c_chip {
	struct platform_device	*pdev;

	struct clk		*clk_div;
	struct clk		*clk;
	const char		*label;

	unsigned int		 period_ns;
	unsigned int		 duty_ns;

	unsigned char		 tcon_base;
	unsigned char		 pwm_id;
	struct pwm_chip		 chip;
};

#define to_s3c_chip(chip)	container_of(chip, struct s3c_chip, chip)

#define pwm_dbg(_pwm, msg...) dev_dbg(&(_pwm)->pdev->dev, msg)

static struct clk *clk_scaler[2];

static inline int pwm_is_tdiv(struct s3c_chip *chip)
{
	return clk_get_parent(chip->clk) == chip->clk_div;
}

#define pwm_tcon_start(pwm) (1 << (pwm->tcon_base + 0))
#define pwm_tcon_invert(pwm) (1 << (pwm->tcon_base + 2))
#define pwm_tcon_autoreload(pwm) (1 << (pwm->tcon_base + 3))
#define pwm_tcon_manulupdate(pwm) (1 << (pwm->tcon_base + 1))

static int s3c_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct s3c_chip *s3c = to_s3c_chip(chip);
	unsigned long flags;
	unsigned long tcon;

	local_irq_save(flags);

	tcon = __raw_readl(S3C2410_TCON);
	tcon |= pwm_tcon_start(s3c);
	__raw_writel(tcon, S3C2410_TCON);

	local_irq_restore(flags);

	return 0;
}

static void s3c_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct s3c_chip *s3c = to_s3c_chip(chip);
	unsigned long flags;
	unsigned long tcon;

	local_irq_save(flags);

	tcon = __raw_readl(S3C2410_TCON);
	tcon &= ~pwm_tcon_start(s3c);
	__raw_writel(tcon, S3C2410_TCON);

	local_irq_restore(flags);
}

static unsigned long pwm_calc_tin(struct s3c_chip *s3c, unsigned long freq)
{
	unsigned long tin_parent_rate;
	unsigned int div;

	tin_parent_rate = clk_get_rate(clk_get_parent(s3c->clk_div));
	pwm_dbg(s3c, "tin parent at %lu\n", tin_parent_rate);

	for (div = 2; div <= 16; div *= 2) {
		if ((tin_parent_rate / (div << 16)) < freq)
			return tin_parent_rate / div;
	}

	return tin_parent_rate / 16;
}

#define NS_IN_HZ (1000000000UL)

static int s3c_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
		int duty_ns, int period_ns)
{
	struct s3c_chip *s3c = to_s3c_chip(chip);
	unsigned long tin_rate;
	unsigned long tin_ns;
	unsigned long period;
	unsigned long flags;
	unsigned long tcon;
	unsigned long tcnt;
	long tcmp;

	/* We currently avoid using 64bit arithmetic by using the
	 * fact that anything faster than 1Hz is easily representable
	 * by 32bits. */

	if (period_ns > NS_IN_HZ || duty_ns > NS_IN_HZ)
		return -ERANGE;

	if (period_ns == s3c->period_ns &&
	    duty_ns == s3c->duty_ns)
		return 0;

	/* The TCMP and TCNT can be read without a lock, they're not
	 * shared between the timers. */

	tcmp = __raw_readl(S3C2410_TCMPB(s3c->pwm_id));
	tcnt = __raw_readl(S3C2410_TCNTB(s3c->pwm_id));

	period = NS_IN_HZ / period_ns;

	pwm_dbg(s3c, "duty_ns=%d, period_ns=%d (%lu)\n",
		duty_ns, period_ns, period);

	/* Check to see if we are changing the clock rate of the PWM */

	if (s3c->period_ns != period_ns) {
		if (pwm_is_tdiv(s3c)) {
			tin_rate = pwm_calc_tin(s3c, period);
			clk_set_rate(s3c->clk_div, tin_rate);
		} else
			tin_rate = clk_get_rate(s3c->clk);

		s3c->period_ns = period_ns;

		pwm_dbg(s3c, "tin_rate=%lu\n", tin_rate);

		tin_ns = NS_IN_HZ / tin_rate;
		tcnt = period_ns / tin_ns;
	} else
		tin_ns = NS_IN_HZ / clk_get_rate(s3c->clk);

	/* Note, counters count down */

	tcmp = duty_ns / tin_ns;
	tcmp = tcnt - tcmp;
	/* the pwm hw only checks the compare register after a decrement,
	   so the pin never toggles if tcmp = tcnt */
	if (tcmp == tcnt)
		tcmp--;

	pwm_dbg(s3c, "tin_ns=%lu, tcmp=%ld/%lu\n", tin_ns, tcmp, tcnt);

	if (tcmp < 0)
		tcmp = 0;

	/* Update the PWM register block. */

	local_irq_save(flags);

	__raw_writel(tcmp, S3C2410_TCMPB(s3c->pwm_id));
	__raw_writel(tcnt, S3C2410_TCNTB(s3c->pwm_id));

	tcon = __raw_readl(S3C2410_TCON);
	tcon |= pwm_tcon_manulupdate(s3c);
	tcon |= pwm_tcon_autoreload(s3c);
	__raw_writel(tcon, S3C2410_TCON);

	tcon &= ~pwm_tcon_manulupdate(s3c);
	__raw_writel(tcon, S3C2410_TCON);

	local_irq_restore(flags);

	return 0;
}

static struct pwm_ops s3c_pwm_ops = {
	.enable = s3c_pwm_enable,
	.disable = s3c_pwm_disable,
	.config = s3c_pwm_config,
	.owner = THIS_MODULE,
};

static int s3c_pwm_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct s3c_chip *s3c;
	unsigned long flags;
	unsigned long tcon;
	unsigned int id = pdev->id;
	int ret;

	if (id == 4) {
		dev_err(dev, "TIMER4 is currently not supported\n");
		return -ENXIO;
	}

	s3c = devm_kzalloc(&pdev->dev, sizeof(*s3c), GFP_KERNEL);
	if (s3c == NULL) {
		dev_err(dev, "failed to allocate pwm_device\n");
		return -ENOMEM;
	}

	/* calculate base of control bits in TCON */
	s3c->tcon_base = id == 0 ? 0 : (id * 4) + 4;
	s3c->chip.dev = &pdev->dev;
	s3c->chip.ops = &s3c_pwm_ops;
	s3c->chip.base = -1;
	s3c->chip.npwm = 1;

	s3c->clk = devm_clk_get(dev, "pwm-tin");
	if (IS_ERR(s3c->clk)) {
		dev_err(dev, "failed to get pwm tin clk\n");
		return PTR_ERR(s3c->clk);
	}

	s3c->clk_div = devm_clk_get(dev, "pwm-tdiv");
	if (IS_ERR(s3c->clk_div)) {
		dev_err(dev, "failed to get pwm tdiv clk\n");
		return PTR_ERR(s3c->clk_div);
	}

	clk_enable(s3c->clk);
	clk_enable(s3c->clk_div);

	local_irq_save(flags);

	tcon = __raw_readl(S3C2410_TCON);
	tcon |= pwm_tcon_invert(s3c);
	__raw_writel(tcon, S3C2410_TCON);

	local_irq_restore(flags);

	ret = pwmchip_add(&s3c->chip);
	if (ret < 0) {
		dev_err(dev, "failed to register pwm\n");
		goto err_clk_tdiv;
	}

	pwm_dbg(s3c, "config bits %02x\n",
		(__raw_readl(S3C2410_TCON) >> s3c->tcon_base) & 0x0f);

	dev_info(dev, "tin at %lu, tdiv at %lu, tin=%sclk, base %d\n",
		 clk_get_rate(s3c->clk),
		 clk_get_rate(s3c->clk_div),
		 pwm_is_tdiv(s3c) ? "div" : "ext", s3c->tcon_base);

	platform_set_drvdata(pdev, s3c);
	return 0;

 err_clk_tdiv:
	clk_disable(s3c->clk_div);
	clk_disable(s3c->clk);
	return ret;
}

static int s3c_pwm_remove(struct platform_device *pdev)
{
	struct s3c_chip *s3c = platform_get_drvdata(pdev);
	int err;

	err = pwmchip_remove(&s3c->chip);
	if (err < 0)
		return err;

	clk_disable(s3c->clk_div);
	clk_disable(s3c->clk);

	return 0;
}

#ifdef CONFIG_PM
static int s3c_pwm_suspend(struct platform_device *pdev, pm_message_t state)
{
	struct s3c_chip *s3c = platform_get_drvdata(pdev);

	/* No one preserve these values during suspend so reset them
	 * Otherwise driver leaves PWM unconfigured if same values
	 * passed to pwm_config
	 */
	s3c->period_ns = 0;
	s3c->duty_ns = 0;

	return 0;
}

static int s3c_pwm_resume(struct platform_device *pdev)
{
	struct s3c_chip *s3c = platform_get_drvdata(pdev);
	unsigned long tcon;

	/* Restore invertion */
	tcon = __raw_readl(S3C2410_TCON);
	tcon |= pwm_tcon_invert(s3c);
	__raw_writel(tcon, S3C2410_TCON);

	return 0;
}

#else
#define s3c_pwm_suspend NULL
#define s3c_pwm_resume NULL
#endif

static struct platform_driver s3c_pwm_driver = {
	.driver		= {
		.name	= "s3c24xx-pwm",
		.owner	= THIS_MODULE,
	},
	.probe		= s3c_pwm_probe,
	.remove		= s3c_pwm_remove,
	.suspend	= s3c_pwm_suspend,
	.resume		= s3c_pwm_resume,
};

static int __init pwm_init(void)
{
	int ret;

	clk_scaler[0] = clk_get(NULL, "pwm-scaler0");
	clk_scaler[1] = clk_get(NULL, "pwm-scaler1");

	if (IS_ERR(clk_scaler[0]) || IS_ERR(clk_scaler[1])) {
		pr_err("failed to get scaler clocks\n");
		return -EINVAL;
	}

	ret = platform_driver_register(&s3c_pwm_driver);
	if (ret)
		pr_err("failed to add pwm driver\n");

	return ret;
}

arch_initcall(pwm_init);