/*
   * CBUS I2C driver for Nokia Internet Tablets.
   *
   * Copyright (C) 2004-2010 Nokia Corporation
   *
   * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and
   * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.
   *
   * This file is subject to the terms and conditions of the GNU General
   * Public License. See the file "COPYING" in the main directory of this
   * archive for more details.
   *
   * 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/io.h>
  #include <linux/i2c.h>
  #include <linux/gpio.h>
  #include <linux/slab.h>
  #include <linux/delay.h>
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/of_gpio.h>
  #include <linux/interrupt.h>
  #include <linux/platform_device.h>
  #include <linux/platform_data/i2c-cbus-gpio.h>
  
  /*
   * Bit counts are derived from Nokia implementation. These should be checked
   * if other CBUS implementations appear.
   */
  #define CBUS_ADDR_BITS	3
  #define CBUS_REG_BITS	5
  
  struct cbus_host {
  	spinlock_t	lock;		/* host lock */
  	struct device	*dev;
  	int		clk_gpio;
  	int		dat_gpio;
  	int		sel_gpio;
  };
  
  /**
   * cbus_send_bit - sends one bit over the bus
   * @host: the host we're using
   * @bit: one bit of information to send
   */
  static void cbus_send_bit(struct cbus_host *host, unsigned bit)
  {
  	gpio_set_value(host->dat_gpio, bit ? 1 : 0);
  	gpio_set_value(host->clk_gpio, 1);
  	gpio_set_value(host->clk_gpio, 0);
  }
  
  /**
   * cbus_send_data - sends @len amount of data over the bus
   * @host: the host we're using
   * @data: the data to send
   * @len: size of the transfer
   */
  static void cbus_send_data(struct cbus_host *host, unsigned data, unsigned len)
  {
  	int i;
  
  	for (i = len; i > 0; i--)
  		cbus_send_bit(host, data & (1 << (i - 1)));
  }
  
  /**
   * cbus_receive_bit - receives one bit from the bus
   * @host: the host we're using
   */
  static int cbus_receive_bit(struct cbus_host *host)
  {
  	int ret;
  
  	gpio_set_value(host->clk_gpio, 1);
  	ret = gpio_get_value(host->dat_gpio);
  	gpio_set_value(host->clk_gpio, 0);
  	return ret;
  }
  
  /**
   * cbus_receive_word - receives 16-bit word from the bus
   * @host: the host we're using
   */
  static int cbus_receive_word(struct cbus_host *host)
  {
  	int ret = 0;
  	int i;
  
  	for (i = 16; i > 0; i--) {
  		int bit = cbus_receive_bit(host);
  
  		if (bit < 0)
  			return bit;
  
  		if (bit)
  			ret |= 1 << (i - 1);
  	}
  	return ret;
  }
  
  /**
   * cbus_transfer - transfers data over the bus
   * @host: the host we're using
   * @rw: read/write flag
   * @dev: device address
   * @reg: register address
   * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0
   */
  static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,
  			 unsigned reg, unsigned data)
  {
  	unsigned long flags;
  	int ret;
  
  	/* We don't want interrupts disturbing our transfer */
  	spin_lock_irqsave(&host->lock, flags);
  
  	/* Reset state and start of transfer, SEL stays down during transfer */
  	gpio_set_value(host->sel_gpio, 0);
  
  	/* Set the DAT pin to output */
  	gpio_direction_output(host->dat_gpio, 1);
  
  	/* Send the device address */
  	cbus_send_data(host, dev, CBUS_ADDR_BITS);
  
  	/* Send the rw flag */
  	cbus_send_bit(host, rw == I2C_SMBUS_READ);
  
  	/* Send the register address */
  	cbus_send_data(host, reg, CBUS_REG_BITS);
  
  	if (rw == I2C_SMBUS_WRITE) {
  		cbus_send_data(host, data, 16);
  		ret = 0;
  	} else {
  		ret = gpio_direction_input(host->dat_gpio);
  		if (ret) {
  			dev_dbg(host->dev, "failed setting direction
  ");
  			goto out;
  		}
  		gpio_set_value(host->clk_gpio, 1);
  
  		ret = cbus_receive_word(host);
  		if (ret < 0) {
  			dev_dbg(host->dev, "failed receiving data
  ");
  			goto out;
  		}
  	}
  
  	/* Indicate end of transfer, SEL goes up until next transfer */
  	gpio_set_value(host->sel_gpio, 1);
  	gpio_set_value(host->clk_gpio, 1);
  	gpio_set_value(host->clk_gpio, 0);
  
  out:
  	spin_unlock_irqrestore(&host->lock, flags);
  
  	return ret;
  }
  
  static int cbus_i2c_smbus_xfer(struct i2c_adapter	*adapter,
  			       u16			addr,
  			       unsigned short		flags,
  			       char			read_write,
  			       u8			command,
  			       int			size,
  			       union i2c_smbus_data	*data)
  {
  	struct cbus_host *chost = i2c_get_adapdata(adapter);
  	int ret;
  
  	if (size != I2C_SMBUS_WORD_DATA)
  		return -EINVAL;
  
  	ret = cbus_transfer(chost, read_write == I2C_SMBUS_READ, addr,
  			    command, data->word);
  	if (ret < 0)
  		return ret;
  
  	if (read_write == I2C_SMBUS_READ)
  		data->word = ret;
  
  	return 0;
  }
  
  static u32 cbus_i2c_func(struct i2c_adapter *adapter)
  {
  	return I2C_FUNC_SMBUS_READ_WORD_DATA | I2C_FUNC_SMBUS_WRITE_WORD_DATA;
  }
  
  static const struct i2c_algorithm cbus_i2c_algo = {
  	.smbus_xfer	= cbus_i2c_smbus_xfer,
  	.functionality	= cbus_i2c_func,
  };
  
  static int cbus_i2c_remove(struct platform_device *pdev)
  {
  	struct i2c_adapter *adapter = platform_get_drvdata(pdev);
  
  	i2c_del_adapter(adapter);
  
  	return 0;
  }
  
  static int cbus_i2c_probe(struct platform_device *pdev)
  {
  	struct i2c_adapter *adapter;
  	struct cbus_host *chost;
  	int ret;
  
  	adapter = devm_kzalloc(&pdev->dev, sizeof(struct i2c_adapter),
  			       GFP_KERNEL);
  	if (!adapter)
  		return -ENOMEM;
  
  	chost = devm_kzalloc(&pdev->dev, sizeof(*chost), GFP_KERNEL);
  	if (!chost)
  		return -ENOMEM;
  
  	if (pdev->dev.of_node) {
  		struct device_node *dnode = pdev->dev.of_node;
  		if (of_gpio_count(dnode) != 3)
  			return -ENODEV;
  		chost->clk_gpio = of_get_gpio(dnode, 0);
  		chost->dat_gpio = of_get_gpio(dnode, 1);
  		chost->sel_gpio = of_get_gpio(dnode, 2);
  	} else if (dev_get_platdata(&pdev->dev)) {
  		struct i2c_cbus_platform_data *pdata =
  			dev_get_platdata(&pdev->dev);
  		chost->clk_gpio = pdata->clk_gpio;
  		chost->dat_gpio = pdata->dat_gpio;
  		chost->sel_gpio = pdata->sel_gpio;
  	} else {
  		return -ENODEV;
  	}
  
  	adapter->owner		= THIS_MODULE;
  	adapter->class		= I2C_CLASS_HWMON;
  	adapter->dev.parent	= &pdev->dev;
  	adapter->dev.of_node	= pdev->dev.of_node;
  	adapter->nr		= pdev->id;
  	adapter->timeout	= HZ;
  	adapter->algo		= &cbus_i2c_algo;
  	strlcpy(adapter->name, "CBUS I2C adapter", sizeof(adapter->name));
  
  	spin_lock_init(&chost->lock);
  	chost->dev = &pdev->dev;
  
  	ret = devm_gpio_request_one(&pdev->dev, chost->clk_gpio,
  				    GPIOF_OUT_INIT_LOW, "CBUS clk");
  	if (ret)
  		return ret;
  
  	ret = devm_gpio_request_one(&pdev->dev, chost->dat_gpio, GPIOF_IN,
  				    "CBUS data");
  	if (ret)
  		return ret;
  
  	ret = devm_gpio_request_one(&pdev->dev, chost->sel_gpio,
  				    GPIOF_OUT_INIT_HIGH, "CBUS sel");
  	if (ret)
  		return ret;
  
  	i2c_set_adapdata(adapter, chost);
  	platform_set_drvdata(pdev, adapter);
  
  	return i2c_add_numbered_adapter(adapter);
  }
  
  #if defined(CONFIG_OF)
  static const struct of_device_id i2c_cbus_dt_ids[] = {
  	{ .compatible = "i2c-cbus-gpio", },
  	{ }
  };
  MODULE_DEVICE_TABLE(of, i2c_cbus_dt_ids);
  #endif
  
  static struct platform_driver cbus_i2c_driver = {
  	.probe	= cbus_i2c_probe,
  	.remove	= cbus_i2c_remove,
  	.driver	= {
  		.name	= "i2c-cbus-gpio",
  		.of_match_table = of_match_ptr(i2c_cbus_dt_ids),
  	},
  };
  module_platform_driver(cbus_i2c_driver);
  
  MODULE_ALIAS("platform:i2c-cbus-gpio");
  MODULE_DESCRIPTION("CBUS I2C driver");
  MODULE_AUTHOR("Juha Yrjölä");
  MODULE_AUTHOR("David Weinehall");
  MODULE_AUTHOR("Mikko Ylinen");
  MODULE_AUTHOR("Felipe Balbi");
  MODULE_AUTHOR("Aaro Koskinen <aaro.koskinen@iki.fi>");
  MODULE_LICENSE("GPL");