/*
   * PWM framework driver for Cirrus Logic EP93xx
   *
   * Copyright (c) 2009        Matthieu Crapet <mcrapet@gmail.com>
   * Copyright (c) 2009, 2013  H Hartley Sweeten <hsweeten@visionengravers.com>
   *
   * EP9301/02 have only one channel:
   *   platform device ep93xx-pwm.1 - PWMOUT1 (EGPIO14)
   *
   * EP9307 has only one channel:
   *   platform device ep93xx-pwm.0 - PWMOUT
   *
   * EP9312/15 have two channels:
   *   platform device ep93xx-pwm.0 - PWMOUT
   *   platform device ep93xx-pwm.1 - PWMOUT1 (EGPIO14)
   *
   * 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/module.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <linux/io.h>
  #include <linux/pwm.h>
  
  #include <asm/div64.h>
  
  #include <mach/platform.h>	/* for ep93xx_pwm_{acquire,release}_gpio() */
  
  #define EP93XX_PWMx_TERM_COUNT	0x00
  #define EP93XX_PWMx_DUTY_CYCLE	0x04
  #define EP93XX_PWMx_ENABLE	0x08
  #define EP93XX_PWMx_INVERT	0x0c
  
  struct ep93xx_pwm {
  	void __iomem *base;
  	struct clk *clk;
  	struct pwm_chip chip;
  };
  
  static inline struct ep93xx_pwm *to_ep93xx_pwm(struct pwm_chip *chip)
  {
  	return container_of(chip, struct ep93xx_pwm, chip);
  }
  
  static int ep93xx_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
  {
  	struct platform_device *pdev = to_platform_device(chip->dev);
  
  	return ep93xx_pwm_acquire_gpio(pdev);
  }
  
  static void ep93xx_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
  {
  	struct platform_device *pdev = to_platform_device(chip->dev);
  
  	ep93xx_pwm_release_gpio(pdev);
  }
  
  static int ep93xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  			     int duty_ns, int period_ns)
  {
  	struct ep93xx_pwm *ep93xx_pwm = to_ep93xx_pwm(chip);
  	void __iomem *base = ep93xx_pwm->base;
  	unsigned long long c;
  	unsigned long period_cycles;
  	unsigned long duty_cycles;
  	unsigned long term;
  	int ret = 0;
  
  	/*
  	 * The clock needs to be enabled to access the PWM registers.
  	 * Configuration can be changed at any time.
  	 */
  	if (!pwm_is_enabled(pwm)) {
  		ret = clk_enable(ep93xx_pwm->clk);
  		if (ret)
  			return ret;
  	}
  
  	c = clk_get_rate(ep93xx_pwm->clk);
  	c *= period_ns;
  	do_div(c, 1000000000);
  	period_cycles = c;
  
  	c = period_cycles;
  	c *= duty_ns;
  	do_div(c, period_ns);
  	duty_cycles = c;
  
  	if (period_cycles < 0x10000 && duty_cycles < 0x10000) {
  		term = readw(base + EP93XX_PWMx_TERM_COUNT);
  
  		/* Order is important if PWM is running */
  		if (period_cycles > term) {
  			writew(period_cycles, base + EP93XX_PWMx_TERM_COUNT);
  			writew(duty_cycles, base + EP93XX_PWMx_DUTY_CYCLE);
  		} else {
  			writew(duty_cycles, base + EP93XX_PWMx_DUTY_CYCLE);
  			writew(period_cycles, base + EP93XX_PWMx_TERM_COUNT);
  		}
  	} else {
  		ret = -EINVAL;
  	}
  
  	if (!pwm_is_enabled(pwm))
  		clk_disable(ep93xx_pwm->clk);
  
  	return ret;
  }
  
  static int ep93xx_pwm_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
  			       enum pwm_polarity polarity)
  {
  	struct ep93xx_pwm *ep93xx_pwm = to_ep93xx_pwm(chip);
  	int ret;
  
  	/*
  	 * The clock needs to be enabled to access the PWM registers.
  	 * Polarity can only be changed when the PWM is disabled.
  	 */
  	ret = clk_enable(ep93xx_pwm->clk);
  	if (ret)
  		return ret;
  
  	if (polarity == PWM_POLARITY_INVERSED)
  		writew(0x1, ep93xx_pwm->base + EP93XX_PWMx_INVERT);
  	else
  		writew(0x0, ep93xx_pwm->base + EP93XX_PWMx_INVERT);
  
  	clk_disable(ep93xx_pwm->clk);
  
  	return 0;
  }
  
  static int ep93xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  {
  	struct ep93xx_pwm *ep93xx_pwm = to_ep93xx_pwm(chip);
  	int ret;
  
  	ret = clk_enable(ep93xx_pwm->clk);
  	if (ret)
  		return ret;
  
  	writew(0x1, ep93xx_pwm->base + EP93XX_PWMx_ENABLE);
  
  	return 0;
  }
  
  static void ep93xx_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
  {
  	struct ep93xx_pwm *ep93xx_pwm = to_ep93xx_pwm(chip);
  
  	writew(0x0, ep93xx_pwm->base + EP93XX_PWMx_ENABLE);
  	clk_disable(ep93xx_pwm->clk);
  }
  
  static const struct pwm_ops ep93xx_pwm_ops = {
  	.request = ep93xx_pwm_request,
  	.free = ep93xx_pwm_free,
  	.config = ep93xx_pwm_config,
  	.set_polarity = ep93xx_pwm_polarity,
  	.enable = ep93xx_pwm_enable,
  	.disable = ep93xx_pwm_disable,
  	.owner = THIS_MODULE,
  };
  
  static int ep93xx_pwm_probe(struct platform_device *pdev)
  {
  	struct ep93xx_pwm *ep93xx_pwm;
  	struct resource *res;
  	int ret;
  
  	ep93xx_pwm = devm_kzalloc(&pdev->dev, sizeof(*ep93xx_pwm), GFP_KERNEL);
  	if (!ep93xx_pwm)
  		return -ENOMEM;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	ep93xx_pwm->base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(ep93xx_pwm->base))
  		return PTR_ERR(ep93xx_pwm->base);
  
  	ep93xx_pwm->clk = devm_clk_get(&pdev->dev, "pwm_clk");
  	if (IS_ERR(ep93xx_pwm->clk))
  		return PTR_ERR(ep93xx_pwm->clk);
  
  	ep93xx_pwm->chip.dev = &pdev->dev;
  	ep93xx_pwm->chip.ops = &ep93xx_pwm_ops;
  	ep93xx_pwm->chip.base = -1;
  	ep93xx_pwm->chip.npwm = 1;
  
  	ret = pwmchip_add(&ep93xx_pwm->chip);
  	if (ret < 0)
  		return ret;
  
  	platform_set_drvdata(pdev, ep93xx_pwm);
  	return 0;
  }
  
  static int ep93xx_pwm_remove(struct platform_device *pdev)
  {
  	struct ep93xx_pwm *ep93xx_pwm = platform_get_drvdata(pdev);
  
  	return pwmchip_remove(&ep93xx_pwm->chip);
  }
  
  static struct platform_driver ep93xx_pwm_driver = {
  	.driver = {
  		.name = "ep93xx-pwm",
  	},
  	.probe = ep93xx_pwm_probe,
  	.remove = ep93xx_pwm_remove,
  };
  module_platform_driver(ep93xx_pwm_driver);
  
  MODULE_DESCRIPTION("Cirrus Logic EP93xx PWM driver");
  MODULE_AUTHOR("Matthieu Crapet <mcrapet@gmail.com>");
  MODULE_AUTHOR("H Hartley Sweeten <hsweeten@visionengravers.com>");
  MODULE_ALIAS("platform:ep93xx-pwm");
  MODULE_LICENSE("GPL");