/*
   * Kontron PLD GPIO driver
   *
   * Copyright (c) 2010-2013 Kontron Europe GmbH
   * Author: Michael Brunner <michael.brunner@kontron.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License 2 as published
   * by the Free Software Foundation.
   *
   * 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/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/bitops.h>
  #include <linux/errno.h>
  #include <linux/platform_device.h>
  #include <linux/gpio.h>
  #include <linux/mfd/kempld.h>
  
  #define KEMPLD_GPIO_MAX_NUM		16
  #define KEMPLD_GPIO_MASK(x)		(BIT((x) % 8))
  #define KEMPLD_GPIO_DIR_NUM(x)		(0x40 + (x) / 8)
  #define KEMPLD_GPIO_LVL_NUM(x)		(0x42 + (x) / 8)
  #define KEMPLD_GPIO_EVT_LVL_EDGE	0x46
  #define KEMPLD_GPIO_IEN			0x4A
  
  struct kempld_gpio_data {
  	struct gpio_chip		chip;
  	struct kempld_device_data	*pld;
  };
  
  /*
   * Set or clear GPIO bit
   * kempld_get_mutex must be called prior to calling this function.
   */
  static void kempld_gpio_bitop(struct kempld_device_data *pld,
  			      u8 reg, u8 bit, u8 val)
  {
  	u8 status;
  
  	status = kempld_read8(pld, reg);
  	if (val)
  		status |= KEMPLD_GPIO_MASK(bit);
  	else
  		status &= ~KEMPLD_GPIO_MASK(bit);
  	kempld_write8(pld, reg, status);
  }
  
  static int kempld_gpio_get_bit(struct kempld_device_data *pld, u8 reg, u8 bit)
  {
  	u8 status;
  
  	kempld_get_mutex(pld);
  	status = kempld_read8(pld, reg);
  	kempld_release_mutex(pld);
  
  	return !!(status & KEMPLD_GPIO_MASK(bit));
  }
  
  static int kempld_gpio_get(struct gpio_chip *chip, unsigned offset)
  {
  	struct kempld_gpio_data *gpio
  		= container_of(chip, struct kempld_gpio_data, chip);
  	struct kempld_device_data *pld = gpio->pld;
  
  	return kempld_gpio_get_bit(pld, KEMPLD_GPIO_LVL_NUM(offset), offset);
  }
  
  static void kempld_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
  {
  	struct kempld_gpio_data *gpio
  		= container_of(chip, struct kempld_gpio_data, chip);
  	struct kempld_device_data *pld = gpio->pld;
  
  	kempld_get_mutex(pld);
  	kempld_gpio_bitop(pld, KEMPLD_GPIO_LVL_NUM(offset), offset, value);
  	kempld_release_mutex(pld);
  }
  
  static int kempld_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
  {
  	struct kempld_gpio_data *gpio
  		= container_of(chip, struct kempld_gpio_data, chip);
  	struct kempld_device_data *pld = gpio->pld;
  
  	kempld_get_mutex(pld);
  	kempld_gpio_bitop(pld, KEMPLD_GPIO_DIR_NUM(offset), offset, 0);
  	kempld_release_mutex(pld);
  
  	return 0;
  }
  
  static int kempld_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
  					int value)
  {
  	struct kempld_gpio_data *gpio
  		= container_of(chip, struct kempld_gpio_data, chip);
  	struct kempld_device_data *pld = gpio->pld;
  
  	kempld_get_mutex(pld);
  	kempld_gpio_bitop(pld, KEMPLD_GPIO_LVL_NUM(offset), offset, value);
  	kempld_gpio_bitop(pld, KEMPLD_GPIO_DIR_NUM(offset), offset, 1);
  	kempld_release_mutex(pld);
  
  	return 0;
  }
  
  static int kempld_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
  {
  	struct kempld_gpio_data *gpio
  		= container_of(chip, struct kempld_gpio_data, chip);
  	struct kempld_device_data *pld = gpio->pld;
  
  	return !kempld_gpio_get_bit(pld, KEMPLD_GPIO_DIR_NUM(offset), offset);
  }
  
  static int kempld_gpio_pincount(struct kempld_device_data *pld)
  {
  	u16 evt, evt_back;
  
  	kempld_get_mutex(pld);
  
  	/* Backup event register as it might be already initialized */
  	evt_back = kempld_read16(pld, KEMPLD_GPIO_EVT_LVL_EDGE);
  	/* Clear event register */
  	kempld_write16(pld, KEMPLD_GPIO_EVT_LVL_EDGE, 0x0000);
  	/* Read back event register */
  	evt = kempld_read16(pld, KEMPLD_GPIO_EVT_LVL_EDGE);
  	/* Restore event register */
  	kempld_write16(pld, KEMPLD_GPIO_EVT_LVL_EDGE, evt_back);
  
  	kempld_release_mutex(pld);
  
  	return evt ? __ffs(evt) : 16;
  }
  
  static int kempld_gpio_probe(struct platform_device *pdev)
  {
  	struct device *dev = &pdev->dev;
  	struct kempld_device_data *pld = dev_get_drvdata(dev->parent);
  	struct kempld_platform_data *pdata = dev_get_platdata(pld->dev);
  	struct kempld_gpio_data *gpio;
  	struct gpio_chip *chip;
  	int ret;
  
  	if (pld->info.spec_major < 2) {
  		dev_err(dev,
  			"Driver only supports GPIO devices compatible to PLD spec. rev. 2.0 or higher
  ");
  		return -ENODEV;
  	}
  
  	gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
  	if (!gpio)
  		return -ENOMEM;
  
  	gpio->pld = pld;
  
  	platform_set_drvdata(pdev, gpio);
  
  	chip = &gpio->chip;
  	chip->label = "gpio-kempld";
  	chip->owner = THIS_MODULE;
  	chip->dev = dev;
  	chip->can_sleep = true;
  	if (pdata && pdata->gpio_base)
  		chip->base = pdata->gpio_base;
  	else
  		chip->base = -1;
  	chip->direction_input = kempld_gpio_direction_input;
  	chip->direction_output = kempld_gpio_direction_output;
  	chip->get_direction = kempld_gpio_get_direction;
  	chip->get = kempld_gpio_get;
  	chip->set = kempld_gpio_set;
  	chip->ngpio = kempld_gpio_pincount(pld);
  	if (chip->ngpio == 0) {
  		dev_err(dev, "No GPIO pins detected
  ");
  		return -ENODEV;
  	}
  
  	ret = gpiochip_add(chip);
  	if (ret) {
  		dev_err(dev, "Could not register GPIO chip
  ");
  		return ret;
  	}
  
  	dev_info(dev, "GPIO functionality initialized with %d pins
  ",
  		 chip->ngpio);
  
  	return 0;
  }
  
  static int kempld_gpio_remove(struct platform_device *pdev)
  {
  	struct kempld_gpio_data *gpio = platform_get_drvdata(pdev);
  
  	gpiochip_remove(&gpio->chip);
  	return 0;
  }
  
  static struct platform_driver kempld_gpio_driver = {
  	.driver = {
  		.name = "kempld-gpio",
  	},
  	.probe		= kempld_gpio_probe,
  	.remove		= kempld_gpio_remove,
  };
  
  module_platform_driver(kempld_gpio_driver);
  
  MODULE_DESCRIPTION("KEM PLD GPIO Driver");
  MODULE_AUTHOR("Michael Brunner <michael.brunner@kontron.com>");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:kempld-gpio");