/*
   * MEN 16Z127 GPIO driver
   *
   * Copyright (C) 2016 MEN Mikroelektronik GmbH (www.men.de)
   *
   * 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; version 2 of the License.
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/io.h>
  #include <linux/err.h>
  #include <linux/mcb.h>
  #include <linux/bitops.h>
  #include <linux/gpio/driver.h>
  
  #define MEN_Z127_CTRL	0x00
  #define MEN_Z127_PSR	0x04
  #define MEN_Z127_IRQR	0x08
  #define MEN_Z127_GPIODR	0x0c
  #define MEN_Z127_IER1	0x10
  #define MEN_Z127_IER2	0x14
  #define MEN_Z127_DBER	0x18
  #define MEN_Z127_ODER	0x1C
  #define GPIO_TO_DBCNT_REG(gpio)	((gpio * 4) + 0x80)
  
  #define MEN_Z127_DB_MIN_US	50
  /* 16 bit compare register. Each bit represents 50us */
  #define MEN_Z127_DB_MAX_US	(0xffff * MEN_Z127_DB_MIN_US)
  #define MEN_Z127_DB_IN_RANGE(db)	((db >= MEN_Z127_DB_MIN_US) && \
  					 (db <= MEN_Z127_DB_MAX_US))
  
  struct men_z127_gpio {
  	struct gpio_chip gc;
  	void __iomem *reg_base;

  	struct resource *mem;

  };
  
  static int men_z127_debounce(struct gpio_chip *gc, unsigned gpio,
  			     unsigned debounce)
  {
  	struct men_z127_gpio *priv = gpiochip_get_data(gc);

  	struct device *dev = gc->parent;

  	unsigned int rnd;
  	u32 db_en, db_cnt;
  
  	if (!MEN_Z127_DB_IN_RANGE(debounce)) {
  		dev_err(dev, "debounce value %u out of range", debounce);
  		return -EINVAL;
  	}
  
  	if (debounce > 0) {
  		/* round up or down depending on MSB-1 */
  		rnd = fls(debounce) - 1;
  
  		if (rnd && (debounce & BIT(rnd - 1)))
  			debounce = round_up(debounce, MEN_Z127_DB_MIN_US);
  		else
  			debounce = round_down(debounce, MEN_Z127_DB_MIN_US);
  
  		if (debounce > MEN_Z127_DB_MAX_US)
  			debounce = MEN_Z127_DB_MAX_US;
  
  		/* 50us per register unit */
  		debounce /= 50;
  	}

  	spin_lock(&gc->bgpio_lock);

  
  	db_en = readl(priv->reg_base + MEN_Z127_DBER);
  
  	if (debounce == 0) {
  		db_en &= ~BIT(gpio);
  		db_cnt = 0;
  	} else {
  		db_en |= BIT(gpio);
  		db_cnt = debounce;
  	}
  
  	writel(db_en, priv->reg_base + MEN_Z127_DBER);
  	writel(db_cnt, priv->reg_base + GPIO_TO_DBCNT_REG(gpio));

  	spin_unlock(&gc->bgpio_lock);

  
  	return 0;
  }

  static int men_z127_set_single_ended(struct gpio_chip *gc,
  				     unsigned offset,
  				     enum single_ended_mode mode)

  {
  	struct men_z127_gpio *priv = gpiochip_get_data(gc);
  	u32 od_en;

  	if (mode != LINE_MODE_OPEN_DRAIN &&
  	    mode != LINE_MODE_PUSH_PULL)
  		return -ENOTSUPP;

  	spin_lock(&gc->bgpio_lock);

  	od_en = readl(priv->reg_base + MEN_Z127_ODER);

  	if (mode == LINE_MODE_OPEN_DRAIN)
  		od_en |= BIT(offset);

  	else

  		/* Implicitly LINE_MODE_PUSH_PULL */
  		od_en &= ~BIT(offset);

  
  	writel(od_en, priv->reg_base + MEN_Z127_ODER);

  	spin_unlock(&gc->bgpio_lock);

  
  	return 0;
  }
  
  static int men_z127_probe(struct mcb_device *mdev,
  			  const struct mcb_device_id *id)
  {
  	struct men_z127_gpio *men_z127_gpio;
  	struct device *dev = &mdev->dev;
  	int ret;
  
  	men_z127_gpio = devm_kzalloc(dev, sizeof(struct men_z127_gpio),
  				     GFP_KERNEL);
  	if (!men_z127_gpio)
  		return -ENOMEM;
  
  	men_z127_gpio->mem = mcb_request_mem(mdev, dev_name(dev));
  	if (IS_ERR(men_z127_gpio->mem)) {
  		dev_err(dev, "failed to request device memory");
  		return PTR_ERR(men_z127_gpio->mem);
  	}
  
  	men_z127_gpio->reg_base = ioremap(men_z127_gpio->mem->start,
  					  resource_size(men_z127_gpio->mem));
  	if (men_z127_gpio->reg_base == NULL) {
  		ret = -ENXIO;
  		goto err_release;
  	}

  	mcb_set_drvdata(mdev, men_z127_gpio);
  
  	ret = bgpio_init(&men_z127_gpio->gc, &mdev->dev, 4,
  			 men_z127_gpio->reg_base + MEN_Z127_PSR,
  			 men_z127_gpio->reg_base + MEN_Z127_CTRL,
  			 NULL,
  			 men_z127_gpio->reg_base + MEN_Z127_GPIODR,
  			 NULL, 0);
  	if (ret)
  		goto err_unmap;
  
  	men_z127_gpio->gc.set_debounce = men_z127_debounce;

  	men_z127_gpio->gc.set_single_ended = men_z127_set_single_ended;

  
  	ret = gpiochip_add_data(&men_z127_gpio->gc, men_z127_gpio);
  	if (ret) {
  		dev_err(dev, "failed to register MEN 16Z127 GPIO controller");
  		goto err_unmap;
  	}
  
  	dev_info(dev, "MEN 16Z127 GPIO driver registered");
  
  	return 0;
  
  err_unmap:
  	iounmap(men_z127_gpio->reg_base);
  err_release:
  	mcb_release_mem(men_z127_gpio->mem);
  	return ret;
  }
  
  static void men_z127_remove(struct mcb_device *mdev)
  {
  	struct men_z127_gpio *men_z127_gpio = mcb_get_drvdata(mdev);
  
  	gpiochip_remove(&men_z127_gpio->gc);
  	iounmap(men_z127_gpio->reg_base);
  	mcb_release_mem(men_z127_gpio->mem);
  }
  
  static const struct mcb_device_id men_z127_ids[] = {
  	{ .device = 0x7f },
  	{ }
  };
  MODULE_DEVICE_TABLE(mcb, men_z127_ids);
  
  static struct mcb_driver men_z127_driver = {
  	.driver = {
  		.name = "z127-gpio",

  	},
  	.probe = men_z127_probe,
  	.remove = men_z127_remove,
  	.id_table = men_z127_ids,
  };
  module_mcb_driver(men_z127_driver);
  
  MODULE_AUTHOR("Andreas Werner <andreas.werner@men.de>");
  MODULE_DESCRIPTION("MEN 16z127 GPIO Controller");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS("mcb:16z127");