text: /*
   * linux/arch/unicore32/kernel/pwm.c
   *
   * Code specific to PKUnity SoC and UniCore ISA
   *
   *	Maintained by GUAN Xue-tao <gxt@mprc.pku.edu.cn>
   *	Copyright (C) 2001-2010 Guan Xuetao
   *
   * 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/module.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 <asm/div64.h>
  #include <mach/hardware.h>
  
  struct puv3_pwm_chip {
  	struct pwm_chip chip;
  	void __iomem *base;
  	struct clk *clk;
  };
  
  static inline struct puv3_pwm_chip *to_puv3(struct pwm_chip *chip)
  {
  	return container_of(chip, struct puv3_pwm_chip, chip);
  }
  
  /*
   * period_ns = 10^9 * (PRESCALE + 1) * (PV + 1) / PWM_CLK_RATE
   * duty_ns   = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
   */
  static int puv3_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  			   int duty_ns, int period_ns)
  {
  	unsigned long period_cycles, prescale, pv, dc;
  	struct puv3_pwm_chip *puv3 = to_puv3(chip);
  	unsigned long long c;
  
  	c = clk_get_rate(puv3->clk);
  	c = c * period_ns;
  	do_div(c, 1000000000);
  	period_cycles = c;
  
  	if (period_cycles < 1)
  		period_cycles = 1;
  
  	prescale = (period_cycles - 1) / 1024;
  	pv = period_cycles / (prescale + 1) - 1;
  
  	if (prescale > 63)
  		return -EINVAL;
  
  	if (duty_ns == period_ns)
  		dc = OST_PWMDCCR_FDCYCLE;
  	else
  		dc = (pv + 1) * duty_ns / period_ns;
  
  	/*
  	 * NOTE: the clock to PWM has to be enabled first
  	 * before writing to the registers
  	 */
  	clk_prepare_enable(puv3->clk);
  
  	writel(prescale, puv3->base + OST_PWM_PWCR);
  	writel(pv - dc, puv3->base + OST_PWM_DCCR);
  	writel(pv, puv3->base + OST_PWM_PCR);
  
  	clk_disable_unprepare(puv3->clk);
  
  	return 0;
  }
  
  static int puv3_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  {
  	struct puv3_pwm_chip *puv3 = to_puv3(chip);
  
  	return clk_prepare_enable(puv3->clk);
  }
  
  static void puv3_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
  {
  	struct puv3_pwm_chip *puv3 = to_puv3(chip);
  
  	clk_disable_unprepare(puv3->clk);
  }
  
  static const struct pwm_ops puv3_pwm_ops = {
  	.config = puv3_pwm_config,
  	.enable = puv3_pwm_enable,
  	.disable = puv3_pwm_disable,
  	.owner = THIS_MODULE,
  };
  
  static int pwm_probe(struct platform_device *pdev)
  {
  	struct puv3_pwm_chip *puv3;
  	struct resource *r;
  	int ret;
  
  	puv3 = devm_kzalloc(&pdev->dev, sizeof(*puv3), GFP_KERNEL);
  	if (puv3 == NULL) {
  		dev_err(&pdev->dev, "failed to allocate memory\n");
  		return -ENOMEM;
  	}
  
  	puv3->clk = devm_clk_get(&pdev->dev, "OST_CLK");
  	if (IS_ERR(puv3->clk))
  		return PTR_ERR(puv3->clk);
  
  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (r == NULL) {
  		dev_err(&pdev->dev, "no memory resource defined\n");
  		return -ENODEV;
  	}
  
  	puv3->base = devm_ioremap_resource(&pdev->dev, r);
  	if (IS_ERR(puv3->base))
  		return PTR_ERR(puv3->base);
  
  	puv3->chip.dev = &pdev->dev;
  	puv3->chip.ops = &puv3_pwm_ops;
  	puv3->chip.base = -1;
  	puv3->chip.npwm = 1;
  
  	ret = pwmchip_add(&puv3->chip);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
  		return ret;
  	}
  
  	platform_set_drvdata(pdev, puv3);
  	return 0;
  }
  
  static int pwm_remove(struct platform_device *pdev)
  {
  	struct puv3_pwm_chip *puv3 = platform_get_drvdata(pdev);
  
  	return pwmchip_remove(&puv3->chip);
  }
  
  static struct platform_driver puv3_pwm_driver = {
  	.driver = {
  		.name = "PKUnity-v3-PWM",
  	},
  	.probe = pwm_probe,
  	.remove = pwm_remove,
  };
  module_platform_driver(puv3_pwm_driver);
  
  MODULE_LICENSE("GPL v2");
  