/*
   * Digital I/O driver for Technologic Systems I2C FPGA Core
   *
   * Copyright (C) 2015 Technologic Systems
   * Copyright (C) 2016 Savoir-Faire Linux
   *
   * 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.
   *
   * This program is distributed "as is" WITHOUT ANY WARRANTY of any
   * kind, whether expressed or implied; without even the implied warranty
   * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License version 2 for more details.
   */
  
  #include <linux/gpio/driver.h>
  #include <linux/i2c.h>
  #include <linux/of_device.h>
  #include <linux/module.h>
  #include <linux/regmap.h>
  
  #define DEFAULT_PIN_NUMBER	32
  /*
   * Register bits used by the GPIO device
   * Some boards, such as TS-7970 do not have a separate input bit
   */
  #define TS4900_GPIO_OE		0x01
  #define TS4900_GPIO_OUT		0x02
  #define TS4900_GPIO_IN		0x04
  #define TS7970_GPIO_IN		0x02
  
  struct ts4900_gpio_priv {
  	struct regmap *regmap;
  	struct gpio_chip gpio_chip;
  	unsigned int input_bit;
  };
  
  static int ts4900_gpio_get_direction(struct gpio_chip *chip,
  				     unsigned int offset)
  {
  	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
  	unsigned int reg;
  
  	regmap_read(priv->regmap, offset, &reg);

  	if (reg & TS4900_GPIO_OE)
  		return GPIO_LINE_DIRECTION_OUT;
  
  	return GPIO_LINE_DIRECTION_IN;

  }
  
  static int ts4900_gpio_direction_input(struct gpio_chip *chip,
  				       unsigned int offset)
  {
  	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
  
  	/*
  	 * This will clear the output enable bit, the other bits are
  	 * dontcare when this is cleared
  	 */
  	return regmap_write(priv->regmap, offset, 0);
  }
  
  static int ts4900_gpio_direction_output(struct gpio_chip *chip,
  					unsigned int offset, int value)
  {
  	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
  	int ret;
  
  	if (value)
  		ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE |
  							 TS4900_GPIO_OUT);
  	else
  		ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE);
  
  	return ret;
  }
  
  static int ts4900_gpio_get(struct gpio_chip *chip, unsigned int offset)
  {
  	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
  	unsigned int reg;
  
  	regmap_read(priv->regmap, offset, &reg);
  
  	return !!(reg & priv->input_bit);
  }
  
  static void ts4900_gpio_set(struct gpio_chip *chip, unsigned int offset,
  			    int value)
  {
  	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
  
  	if (value)
  		regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT,
  				   TS4900_GPIO_OUT);
  	else
  		regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT, 0);
  }
  
  static const struct regmap_config ts4900_regmap_config = {
  	.reg_bits = 16,
  	.val_bits = 8,
  };

  static const struct gpio_chip template_chip = {

  	.label			= "ts4900-gpio",
  	.owner			= THIS_MODULE,
  	.get_direction		= ts4900_gpio_get_direction,
  	.direction_input	= ts4900_gpio_direction_input,
  	.direction_output	= ts4900_gpio_direction_output,
  	.get			= ts4900_gpio_get,
  	.set			= ts4900_gpio_set,
  	.base			= -1,
  	.can_sleep		= true,
  };
  
  static const struct of_device_id ts4900_gpio_of_match_table[] = {
  	{
  		.compatible = "technologic,ts4900-gpio",
  		.data = (void *)TS4900_GPIO_IN,
  	}, {
  		.compatible = "technologic,ts7970-gpio",
  		.data = (void *)TS7970_GPIO_IN,
  	},
  	{ /* sentinel */ },
  };
  MODULE_DEVICE_TABLE(of, ts4900_gpio_of_match_table);
  
  static int ts4900_gpio_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)
  {

  	struct ts4900_gpio_priv *priv;
  	u32 ngpio;
  	int ret;

  	if (of_property_read_u32(client->dev.of_node, "ngpios", &ngpio))
  		ngpio = DEFAULT_PIN_NUMBER;
  
  	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	priv->gpio_chip = template_chip;
  	priv->gpio_chip.label = "ts4900-gpio";
  	priv->gpio_chip.ngpio = ngpio;
  	priv->gpio_chip.parent = &client->dev;

  	priv->input_bit = (uintptr_t)of_device_get_match_data(&client->dev);

  
  	priv->regmap = devm_regmap_init_i2c(client, &ts4900_regmap_config);
  	if (IS_ERR(priv->regmap)) {
  		ret = PTR_ERR(priv->regmap);
  		dev_err(&client->dev, "Failed to allocate register map: %d
  ",
  			ret);
  		return ret;
  	}
  
  	ret = devm_gpiochip_add_data(&client->dev, &priv->gpio_chip, priv);
  	if (ret < 0) {
  		dev_err(&client->dev, "Unable to register gpiochip
  ");
  		return ret;
  	}
  
  	i2c_set_clientdata(client, priv);
  
  	return 0;
  }
  
  static const struct i2c_device_id ts4900_gpio_id_table[] = {
  	{ "ts4900-gpio", },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(i2c, ts4900_gpio_id_table);
  
  static struct i2c_driver ts4900_gpio_driver = {
  	.driver = {
  		.name = "ts4900-gpio",
  		.of_match_table = ts4900_gpio_of_match_table,
  	},
  	.probe = ts4900_gpio_probe,
  	.id_table = ts4900_gpio_id_table,
  };
  module_i2c_driver(ts4900_gpio_driver);
  
  MODULE_AUTHOR("Technologic Systems");
  MODULE_DESCRIPTION("GPIO interface for Technologic Systems I2C-FPGA core");
  MODULE_LICENSE("GPL");