/*
   * Bitbanging I2C bus driver using the GPIO API
   *
   * Copyright (C) 2007 Atmel Corporation
   *
   * 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/i2c.h>
  #include <linux/i2c-algo-bit.h>
  #include <linux/i2c-gpio.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/platform_device.h>
  #include <linux/gpio.h>
  #include <linux/of.h>
  #include <linux/of_gpio.h>
  
  struct i2c_gpio_private_data {
  	struct i2c_adapter adap;
  	struct i2c_algo_bit_data bit_data;
  	struct i2c_gpio_platform_data pdata;
  };
  
  /* Toggle SDA by changing the direction of the pin */
  static void i2c_gpio_setsda_dir(void *data, int state)
  {
  	struct i2c_gpio_platform_data *pdata = data;
  
  	if (state)
  		gpio_direction_input(pdata->sda_pin);
  	else
  		gpio_direction_output(pdata->sda_pin, 0);
  }
  
  /*
   * Toggle SDA by changing the output value of the pin. This is only
   * valid for pins configured as open drain (i.e. setting the value
   * high effectively turns off the output driver.)
   */
  static void i2c_gpio_setsda_val(void *data, int state)
  {
  	struct i2c_gpio_platform_data *pdata = data;
  
  	gpio_set_value(pdata->sda_pin, state);
  }
  
  /* Toggle SCL by changing the direction of the pin. */
  static void i2c_gpio_setscl_dir(void *data, int state)
  {
  	struct i2c_gpio_platform_data *pdata = data;
  
  	if (state)
  		gpio_direction_input(pdata->scl_pin);
  	else
  		gpio_direction_output(pdata->scl_pin, 0);
  }
  
  /*
   * Toggle SCL by changing the output value of the pin. This is used
   * for pins that are configured as open drain and for output-only
   * pins. The latter case will break the i2c protocol, but it will
   * often work in practice.
   */
  static void i2c_gpio_setscl_val(void *data, int state)
  {
  	struct i2c_gpio_platform_data *pdata = data;
  
  	gpio_set_value(pdata->scl_pin, state);
  }
  
  static int i2c_gpio_getsda(void *data)
  {
  	struct i2c_gpio_platform_data *pdata = data;
  
  	return gpio_get_value(pdata->sda_pin);
  }
  
  static int i2c_gpio_getscl(void *data)
  {
  	struct i2c_gpio_platform_data *pdata = data;
  
  	return gpio_get_value(pdata->scl_pin);
  }
  
  static int of_i2c_gpio_get_pins(struct device_node *np,
  				unsigned int *sda_pin, unsigned int *scl_pin)
  {
  	if (of_gpio_count(np) < 2)
  		return -ENODEV;
  
  	*sda_pin = of_get_gpio(np, 0);
  	*scl_pin = of_get_gpio(np, 1);
  
  	if (!gpio_is_valid(*sda_pin) || !gpio_is_valid(*scl_pin)) {
  		pr_err("%s: invalid GPIO pins, sda=%d/scl=%d
  ",
  		       np->full_name, *sda_pin, *scl_pin);
  		return -ENODEV;
  	}
  
  	return 0;
  }
  
  static void of_i2c_gpio_get_props(struct device_node *np,
  				  struct i2c_gpio_platform_data *pdata)
  {
  	u32 reg;
  
  	of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
  
  	if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
  		pdata->timeout = msecs_to_jiffies(reg);
  
  	pdata->sda_is_open_drain =
  		of_property_read_bool(np, "i2c-gpio,sda-open-drain");
  	pdata->scl_is_open_drain =
  		of_property_read_bool(np, "i2c-gpio,scl-open-drain");
  	pdata->scl_is_output_only =
  		of_property_read_bool(np, "i2c-gpio,scl-output-only");
  }
  
  static int i2c_gpio_probe(struct platform_device *pdev)
  {
  	struct i2c_gpio_private_data *priv;
  	struct i2c_gpio_platform_data *pdata;
  	struct i2c_algo_bit_data *bit_data;
  	struct i2c_adapter *adap;
  	unsigned int sda_pin, scl_pin;
  	int ret;
  
  	/* First get the GPIO pins; if it fails, we'll defer the probe. */
  	if (pdev->dev.of_node) {
  		ret = of_i2c_gpio_get_pins(pdev->dev.of_node,
  					   &sda_pin, &scl_pin);
  		if (ret)
  			return ret;
  	} else {
  		if (!dev_get_platdata(&pdev->dev))
  			return -ENXIO;
  		pdata = dev_get_platdata(&pdev->dev);
  		sda_pin = pdata->sda_pin;
  		scl_pin = pdata->scl_pin;
  	}
  
  	ret = gpio_request(sda_pin, "sda");
  	if (ret) {
  		if (ret == -EINVAL)
  			ret = -EPROBE_DEFER;	/* Try again later */
  		goto err_request_sda;
  	}
  	ret = gpio_request(scl_pin, "scl");
  	if (ret) {
  		if (ret == -EINVAL)
  			ret = -EPROBE_DEFER;	/* Try again later */
  		goto err_request_scl;
  	}
  
  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv) {
  		ret = -ENOMEM;
  		goto err_add_bus;
  	}
  	adap = &priv->adap;
  	bit_data = &priv->bit_data;
  	pdata = &priv->pdata;
  
  	if (pdev->dev.of_node) {
  		pdata->sda_pin = sda_pin;
  		pdata->scl_pin = scl_pin;
  		of_i2c_gpio_get_props(pdev->dev.of_node, pdata);
  	} else {
  		memcpy(pdata, dev_get_platdata(&pdev->dev), sizeof(*pdata));
  	}
  
  	if (pdata->sda_is_open_drain) {
  		gpio_direction_output(pdata->sda_pin, 1);
  		bit_data->setsda = i2c_gpio_setsda_val;
  	} else {
  		gpio_direction_input(pdata->sda_pin);
  		bit_data->setsda = i2c_gpio_setsda_dir;
  	}
  
  	if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
  		gpio_direction_output(pdata->scl_pin, 1);
  		bit_data->setscl = i2c_gpio_setscl_val;
  	} else {
  		gpio_direction_input(pdata->scl_pin);
  		bit_data->setscl = i2c_gpio_setscl_dir;
  	}
  
  	if (!pdata->scl_is_output_only)
  		bit_data->getscl = i2c_gpio_getscl;
  	bit_data->getsda = i2c_gpio_getsda;
  
  	if (pdata->udelay)
  		bit_data->udelay = pdata->udelay;
  	else if (pdata->scl_is_output_only)
  		bit_data->udelay = 50;			/* 10 kHz */
  	else
  		bit_data->udelay = 5;			/* 100 kHz */
  
  	if (pdata->timeout)
  		bit_data->timeout = pdata->timeout;
  	else
  		bit_data->timeout = HZ / 10;		/* 100 ms */
  
  	bit_data->data = pdata;
  
  	adap->owner = THIS_MODULE;
  	if (pdev->dev.of_node)
  		strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
  	else
  		snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
  
  	adap->algo_data = bit_data;
  	adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
  	adap->dev.parent = &pdev->dev;
  	adap->dev.of_node = pdev->dev.of_node;
  
  	adap->nr = pdev->id;
  	ret = i2c_bit_add_numbered_bus(adap);
  	if (ret)
  		goto err_add_bus;
  
  	platform_set_drvdata(pdev, priv);
  
  	dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)
  ",
  		 pdata->sda_pin, pdata->scl_pin,
  		 pdata->scl_is_output_only
  		 ? ", no clock stretching" : "");
  
  	return 0;
  
  err_add_bus:
  	gpio_free(scl_pin);
  err_request_scl:
  	gpio_free(sda_pin);
  err_request_sda:
  	return ret;
  }
  
  static int i2c_gpio_remove(struct platform_device *pdev)
  {
  	struct i2c_gpio_private_data *priv;
  	struct i2c_gpio_platform_data *pdata;
  	struct i2c_adapter *adap;
  
  	priv = platform_get_drvdata(pdev);
  	adap = &priv->adap;
  	pdata = &priv->pdata;
  
  	i2c_del_adapter(adap);
  	gpio_free(pdata->scl_pin);
  	gpio_free(pdata->sda_pin);
  
  	return 0;
  }
  
  #if defined(CONFIG_OF)
  static const struct of_device_id i2c_gpio_dt_ids[] = {
  	{ .compatible = "i2c-gpio", },
  	{ /* sentinel */ }
  };
  
  MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
  #endif
  
  static struct platform_driver i2c_gpio_driver = {
  	.driver		= {
  		.name	= "i2c-gpio",
  		.owner	= THIS_MODULE,
  		.of_match_table	= of_match_ptr(i2c_gpio_dt_ids),
  	},
  	.probe		= i2c_gpio_probe,
  	.remove		= i2c_gpio_remove,
  };
  
  static int __init i2c_gpio_init(void)
  {
  	int ret;
  
  	ret = platform_driver_register(&i2c_gpio_driver);
  	if (ret)
  		printk(KERN_ERR "i2c-gpio: probe failed: %d
  ", ret);
  
  	return ret;
  }
  subsys_initcall(i2c_gpio_init);
  
  static void __exit i2c_gpio_exit(void)
  {
  	platform_driver_unregister(&i2c_gpio_driver);
  }
  module_exit(i2c_gpio_exit);
  
  MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
  MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:i2c-gpio");