drivers/i2c/busses/i2c-gpio.c - arm/linux - Git at Google

 /*
  * 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/consumer.h>
 #include <linux/of.h>

 struct i2c_gpio_private_data {
 	struct gpio_desc *sda;
 	struct gpio_desc *scl;
 	struct i2c_adapter adap;
 	struct i2c_algo_bit_data bit_data;
 	struct i2c_gpio_platform_data pdata;
 };

 /*
  * 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_private_data *priv = data;

 	gpiod_set_value(priv->sda, state);
 }

 /*
  * 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_private_data *priv = data;

 	gpiod_set_value(priv->scl, state);
 }

 static int i2c_gpio_getsda(void *data)
 {
 	struct i2c_gpio_private_data *priv = data;

 	return gpiod_get_value(priv->sda);
 }

 static int i2c_gpio_getscl(void *data)
 {
 	struct i2c_gpio_private_data *priv = data;

 	return gpiod_get_value(priv->scl);
 }

 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 struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
 					   const char *con_id,
 					   unsigned int index,
 					   enum gpiod_flags gflags)
 {
 	struct gpio_desc *retdesc;
 	int ret;

 	retdesc = devm_gpiod_get(dev, con_id, gflags);
 	if (!IS_ERR(retdesc)) {
 		dev_dbg(dev, "got GPIO from name %s\n", con_id);
 		return retdesc;
 	}

 	retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
 	if (!IS_ERR(retdesc)) {
 		dev_dbg(dev, "got GPIO from index %u\n", index);
 		return retdesc;
 	}

 	ret = PTR_ERR(retdesc);

 	/* FIXME: hack in the old code, is this really necessary? */
 	if (ret == -EINVAL)
 		retdesc = ERR_PTR(-EPROBE_DEFER);

 	/* This happens if the GPIO driver is not yet probed, let's defer */
 	if (ret == -ENOENT)
 		retdesc = ERR_PTR(-EPROBE_DEFER);

 	if (ret != -EPROBE_DEFER)
 		dev_err(dev, "error trying to get descriptor: %d\n", ret);

 	return retdesc;
 }

 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;
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
 	enum gpiod_flags gflags;
 	int ret;

 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

 	adap = &priv->adap;
 	bit_data = &priv->bit_data;
 	pdata = &priv->pdata;

 	if (np) {
 		of_i2c_gpio_get_props(np, pdata);
 	} else {
 		/*
 		 * If all platform data settings are zero it is OK
 		 * to not provide any platform data from the board.
 		 */
 		if (dev_get_platdata(dev))
 			memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
 	}

 	/*
 	 * First get the GPIO pins; if it fails, we'll defer the probe.
 	 * If the SDA line is marked from platform data or device tree as
 	 * "open drain" it means something outside of our control is making
 	 * this line being handled as open drain, and we should just handle
 	 * it as any other output. Else we enforce open drain as this is
 	 * required for an I2C bus.
 	 */
 	if (pdata->sda_is_open_drain)
 		gflags = GPIOD_OUT_HIGH;
 	else
 		gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 	priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
 	if (IS_ERR(priv->sda))
 		return PTR_ERR(priv->sda);

 	/*
 	 * If the SCL line is marked from platform data or device tree as
 	 * "open drain" it means something outside of our control is making
 	 * this line being handled as open drain, and we should just handle
 	 * it as any other output. Else we enforce open drain as this is
 	 * required for an I2C bus.
 	 */
 	if (pdata->scl_is_open_drain)
 		gflags = GPIOD_OUT_LOW;
 	else
 		gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
 	priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
 	if (IS_ERR(priv->scl))
 		return PTR_ERR(priv->scl);

 	bit_data->setsda = i2c_gpio_setsda_val;
 	bit_data->setscl = i2c_gpio_setscl_val;

 	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 = priv;

 	adap->owner = THIS_MODULE;
 	if (np)
 		strlcpy(adap->name, dev_name(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 = dev;
 	adap->dev.of_node = np;

 	adap->nr = pdev->id;
 	ret = i2c_bit_add_numbered_bus(adap);
 	if (ret)
 		return ret;

 	platform_set_drvdata(pdev, priv);

 	/*
 	 * FIXME: using global GPIO numbers is not helpful. If/when we
 	 * get accessors to get the actual name of the GPIO line,
 	 * from the descriptor, then provide that instead.
 	 */
 	dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
 		 desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
 		 pdata->scl_is_output_only
 		 ? ", no clock stretching" : "");

 	return 0;
 }

 static int i2c_gpio_remove(struct platform_device *pdev)
 {
 	struct i2c_gpio_private_data *priv;
 	struct i2c_adapter *adap;

 	priv = platform_get_drvdata(pdev);
 	adap = &priv->adap;

 	i2c_del_adapter(adap);

 	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",
 		.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\n", 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");
	/*
	* 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/consumer.h>
	#include <linux/of.h>

	struct i2c_gpio_private_data {
	struct gpio_desc *sda;
	struct gpio_desc *scl;
	struct i2c_adapter adap;
	struct i2c_algo_bit_data bit_data;
	struct i2c_gpio_platform_data pdata;
	};

	/*
	* 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_private_data *priv = data;

	gpiod_set_value(priv->sda, state);
	}

	/*
	* 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_private_data *priv = data;

	gpiod_set_value(priv->scl, state);
	}

	static int i2c_gpio_getsda(void *data)
	{
	struct i2c_gpio_private_data *priv = data;

	return gpiod_get_value(priv->sda);
	}

	static int i2c_gpio_getscl(void *data)
	{
	struct i2c_gpio_private_data *priv = data;

	return gpiod_get_value(priv->scl);
	}

	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 struct gpio_desc i2c_gpio_get_desc(struct device dev,
	const char *con_id,
	unsigned int index,
	enum gpiod_flags gflags)
	{
	struct gpio_desc *retdesc;
	int ret;

	retdesc = devm_gpiod_get(dev, con_id, gflags);
	if (!IS_ERR(retdesc)) {
	dev_dbg(dev, "got GPIO from name %s\n", con_id);
	return retdesc;
	}

	retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
	if (!IS_ERR(retdesc)) {
	dev_dbg(dev, "got GPIO from index %u\n", index);
	return retdesc;
	}

	ret = PTR_ERR(retdesc);

	/* FIXME: hack in the old code, is this really necessary? */
	if (ret == -EINVAL)
	retdesc = ERR_PTR(-EPROBE_DEFER);

	/* This happens if the GPIO driver is not yet probed, let's defer */
	if (ret == -ENOENT)
	retdesc = ERR_PTR(-EPROBE_DEFER);

	if (ret != -EPROBE_DEFER)
	dev_err(dev, "error trying to get descriptor: %d\n", ret);

	return retdesc;
	}

	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;
	struct device *dev = &pdev->dev;
	struct device_node *np = dev->of_node;
	enum gpiod_flags gflags;
	int ret;

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
	return -ENOMEM;

	adap = &priv->adap;
	bit_data = &priv->bit_data;
	pdata = &priv->pdata;

	if (np) {
	of_i2c_gpio_get_props(np, pdata);
	} else {
	/*
	* If all platform data settings are zero it is OK
	* to not provide any platform data from the board.
	*/
	if (dev_get_platdata(dev))
	memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
	}

	/*
	* First get the GPIO pins; if it fails, we'll defer the probe.
	* If the SDA line is marked from platform data or device tree as
	* "open drain" it means something outside of our control is making
	* this line being handled as open drain, and we should just handle
	* it as any other output. Else we enforce open drain as this is
	* required for an I2C bus.
	*/
	if (pdata->sda_is_open_drain)
	gflags = GPIOD_OUT_HIGH;
	else
	gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
	priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
	if (IS_ERR(priv->sda))
	return PTR_ERR(priv->sda);

	/*
	* If the SCL line is marked from platform data or device tree as
	* "open drain" it means something outside of our control is making
	* this line being handled as open drain, and we should just handle
	* it as any other output. Else we enforce open drain as this is
	* required for an I2C bus.
	*/
	if (pdata->scl_is_open_drain)
	gflags = GPIOD_OUT_LOW;
	else
	gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
	priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
	if (IS_ERR(priv->scl))
	return PTR_ERR(priv->scl);

	bit_data->setsda = i2c_gpio_setsda_val;
	bit_data->setscl = i2c_gpio_setscl_val;

	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 = priv;

	adap->owner = THIS_MODULE;
	if (np)
	strlcpy(adap->name, dev_name(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 = dev;
	adap->dev.of_node = np;

	adap->nr = pdev->id;
	ret = i2c_bit_add_numbered_bus(adap);
	if (ret)
	return ret;

	platform_set_drvdata(pdev, priv);

	/*
	* FIXME: using global GPIO numbers is not helpful. If/when we
	* get accessors to get the actual name of the GPIO line,
	* from the descriptor, then provide that instead.
	*/
	dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
	desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
	pdata->scl_is_output_only
	? ", no clock stretching" : "");

	return 0;
	}

	static int i2c_gpio_remove(struct platform_device *pdev)
	{
	struct i2c_gpio_private_data *priv;
	struct i2c_adapter *adap;

	priv = platform_get_drvdata(pdev);
	adap = &priv->adap;

	i2c_del_adapter(adap);

	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",
	.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\n", 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");