[linux-block.git] / drivers / i2c / busses / i2c-gpio.c

/*
 * 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 direction of the pin */
static void i2c_gpio_setsda_dir(void *data, int state)
{
	struct i2c_gpio_private_data *priv = data;

	/*
	 * This is a way of saying "do not drive
	 * me actively high" which means emulating open drain.
	 * The right way to do this is for gpiolib to
	 * handle this, by the function below.
	 */
	if (state)
		gpiod_direction_input(priv->sda);
	else
		gpiod_direction_output(priv->sda, 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_private_data *priv = data;

	gpiod_set_value(priv->sda, state);
}

/* Toggle SCL by changing the direction of the pin. */
static void i2c_gpio_setscl_dir(void *data, int state)
{
	struct i2c_gpio_private_data *priv = data;

	if (state)
		gpiod_direction_input(priv->scl);
	else
		gpiod_direction_output(priv->scl, 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_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 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;
	int ret;

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

	/* First get the GPIO pins; if it fails, we'll defer the probe. */
	priv->sda = devm_gpiod_get_index(&pdev->dev, NULL, 0, GPIOD_OUT_HIGH);
	if (IS_ERR(priv->sda)) {
		ret = PTR_ERR(priv->sda);
		/* FIXME: hack in the old code, is this really necessary? */
		if (ret == -EINVAL)
			ret = -EPROBE_DEFER;
		return ret;
	}
	priv->scl = devm_gpiod_get_index(&pdev->dev, NULL, 1, GPIOD_OUT_LOW);
	if (IS_ERR(priv->scl)) {
		ret = PTR_ERR(priv->scl);
		/* FIXME: hack in the old code, is this really necessary? */
		if (ret == -EINVAL)
			ret = -EPROBE_DEFER;
		return ret;
	}

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

	if (pdev->dev.of_node) {
		of_i2c_gpio_get_props(pdev->dev.of_node, 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(&pdev->dev))
			memcpy(pdata, dev_get_platdata(&pdev->dev),
			       sizeof(*pdata));
	}

	/*
	 * FIXME: this is a hack emulating the open drain emulation
	 * that gpiolib can already do for us. Make all clients properly
	 * flag their lines as open drain and get rid of this property
	 * and the special callback.
	 */
	if (pdata->sda_is_open_drain) {
		gpiod_direction_output(priv->sda, 1);
		bit_data->setsda = i2c_gpio_setsda_val;
	} else {
		gpiod_direction_input(priv->sda);
		bit_data->setsda = i2c_gpio_setsda_dir;
	}

	if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
		gpiod_direction_output(priv->scl, 1);
		bit_data->setscl = i2c_gpio_setscl_val;
	} else {
		gpiod_direction_input(priv->scl);
		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 = priv;

	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)
		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(&pdev->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");
Commit	Line	Data
	1	/*
	2	* Bitbanging I2C bus driver using the GPIO API
	3	*
	4	* Copyright (C) 2007 Atmel Corporation
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License version 2 as
	8	* published by the Free Software Foundation.
	9	*/
	10	#include <linux/i2c.h>
	11	#include <linux/i2c-algo-bit.h>
	12	#include <linux/i2c-gpio.h>
	13	#include <linux/init.h>
	14	#include <linux/module.h>
	15	#include <linux/slab.h>
	16	#include <linux/platform_device.h>
	17	#include <linux/gpio/consumer.h>
	18	#include <linux/of.h>
	19
	20	struct i2c_gpio_private_data {
	21	struct gpio_desc *sda;
	22	struct gpio_desc *scl;
	23	struct i2c_adapter adap;
	24	struct i2c_algo_bit_data bit_data;
	25	struct i2c_gpio_platform_data pdata;
	26	};
	27
	28	/* Toggle SDA by changing the direction of the pin */
	29	static void i2c_gpio_setsda_dir(void *data, int state)
	30	{
	31	struct i2c_gpio_private_data *priv = data;
	32
	33	/*
	34	* This is a way of saying "do not drive
	35	* me actively high" which means emulating open drain.
	36	* The right way to do this is for gpiolib to
	37	* handle this, by the function below.
	38	*/
	39	if (state)
	40	gpiod_direction_input(priv->sda);
	41	else
	42	gpiod_direction_output(priv->sda, 0);
	43	}
	44
	45	/*
	46	* Toggle SDA by changing the output value of the pin. This is only
	47	* valid for pins configured as open drain (i.e. setting the value
	48	* high effectively turns off the output driver.)
	49	*/
	50	static void i2c_gpio_setsda_val(void *data, int state)
	51	{
	52	struct i2c_gpio_private_data *priv = data;
	53
	54	gpiod_set_value(priv->sda, state);
	55	}
	56
	57	/* Toggle SCL by changing the direction of the pin. */
	58	static void i2c_gpio_setscl_dir(void *data, int state)
	59	{
	60	struct i2c_gpio_private_data *priv = data;
	61
	62	if (state)
	63	gpiod_direction_input(priv->scl);
	64	else
	65	gpiod_direction_output(priv->scl, 0);
	66	}
	67
	68	/*
	69	* Toggle SCL by changing the output value of the pin. This is used
	70	* for pins that are configured as open drain and for output-only
	71	* pins. The latter case will break the i2c protocol, but it will
	72	* often work in practice.
	73	*/
	74	static void i2c_gpio_setscl_val(void *data, int state)
	75	{
	76	struct i2c_gpio_private_data *priv = data;
	77
	78	gpiod_set_value(priv->scl, state);
	79	}
	80
	81	static int i2c_gpio_getsda(void *data)
	82	{
	83	struct i2c_gpio_private_data *priv = data;
	84
	85	return gpiod_get_value(priv->sda);
	86	}
	87
	88	static int i2c_gpio_getscl(void *data)
	89	{
	90	struct i2c_gpio_private_data *priv = data;
	91
	92	return gpiod_get_value(priv->scl);
	93	}
	94
	95	static void of_i2c_gpio_get_props(struct device_node *np,
	96	struct i2c_gpio_platform_data *pdata)
	97	{
	98	u32 reg;
	99
	100	of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
	101
	102	if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
	103	pdata->timeout = msecs_to_jiffies(reg);
	104
	105	pdata->sda_is_open_drain =
	106	of_property_read_bool(np, "i2c-gpio,sda-open-drain");
	107	pdata->scl_is_open_drain =
	108	of_property_read_bool(np, "i2c-gpio,scl-open-drain");
	109	pdata->scl_is_output_only =
	110	of_property_read_bool(np, "i2c-gpio,scl-output-only");
	111	}
	112
	113	static int i2c_gpio_probe(struct platform_device *pdev)
	114	{
	115	struct i2c_gpio_private_data *priv;
	116	struct i2c_gpio_platform_data *pdata;
	117	struct i2c_algo_bit_data *bit_data;
	118	struct i2c_adapter *adap;
	119	int ret;
	120
	121	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
	122	if (!priv)
	123	return -ENOMEM;
	124
	125	/* First get the GPIO pins; if it fails, we'll defer the probe. */
	126	priv->sda = devm_gpiod_get_index(&pdev->dev, NULL, 0, GPIOD_OUT_HIGH);
	127	if (IS_ERR(priv->sda)) {
	128	ret = PTR_ERR(priv->sda);
	129	/* FIXME: hack in the old code, is this really necessary? */
	130	if (ret == -EINVAL)
	131	ret = -EPROBE_DEFER;
	132	return ret;
	133	}
	134	priv->scl = devm_gpiod_get_index(&pdev->dev, NULL, 1, GPIOD_OUT_LOW);
	135	if (IS_ERR(priv->scl)) {
	136	ret = PTR_ERR(priv->scl);
	137	/* FIXME: hack in the old code, is this really necessary? */
	138	if (ret == -EINVAL)
	139	ret = -EPROBE_DEFER;
	140	return ret;
	141	}
	142
	143	adap = &priv->adap;
	144	bit_data = &priv->bit_data;
	145	pdata = &priv->pdata;
	146
	147	if (pdev->dev.of_node) {
	148	of_i2c_gpio_get_props(pdev->dev.of_node, pdata);
	149	} else {
	150	/*
	151	* If all platform data settings are zero it is OK
	152	* to not provide any platform data from the board.
	153	*/
	154	if (dev_get_platdata(&pdev->dev))
	155	memcpy(pdata, dev_get_platdata(&pdev->dev),
	156	sizeof(*pdata));
	157	}
	158
	159	/*
	160	* FIXME: this is a hack emulating the open drain emulation
	161	* that gpiolib can already do for us. Make all clients properly
	162	* flag their lines as open drain and get rid of this property
	163	* and the special callback.
	164	*/
	165	if (pdata->sda_is_open_drain) {
	166	gpiod_direction_output(priv->sda, 1);
	167	bit_data->setsda = i2c_gpio_setsda_val;
	168	} else {
	169	gpiod_direction_input(priv->sda);
	170	bit_data->setsda = i2c_gpio_setsda_dir;
	171	}
	172
	173	if (pdata->scl_is_open_drain \|\| pdata->scl_is_output_only) {
	174	gpiod_direction_output(priv->scl, 1);
	175	bit_data->setscl = i2c_gpio_setscl_val;
	176	} else {
	177	gpiod_direction_input(priv->scl);
	178	bit_data->setscl = i2c_gpio_setscl_dir;
	179	}
	180
	181	if (!pdata->scl_is_output_only)
	182	bit_data->getscl = i2c_gpio_getscl;
	183	bit_data->getsda = i2c_gpio_getsda;
	184
	185	if (pdata->udelay)
	186	bit_data->udelay = pdata->udelay;
	187	else if (pdata->scl_is_output_only)
	188	bit_data->udelay = 50; /* 10 kHz */
	189	else
	190	bit_data->udelay = 5; /* 100 kHz */
	191
	192	if (pdata->timeout)
	193	bit_data->timeout = pdata->timeout;
	194	else
	195	bit_data->timeout = HZ / 10; /* 100 ms */
	196
	197	bit_data->data = priv;
	198
	199	adap->owner = THIS_MODULE;
	200	if (pdev->dev.of_node)
	201	strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
	202	else
	203	snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
	204
	205	adap->algo_data = bit_data;
	206	adap->class = I2C_CLASS_HWMON \| I2C_CLASS_SPD;
	207	adap->dev.parent = &pdev->dev;
	208	adap->dev.of_node = pdev->dev.of_node;
	209
	210	adap->nr = pdev->id;
	211	ret = i2c_bit_add_numbered_bus(adap);
	212	if (ret)
	213	return ret;
	214
	215	platform_set_drvdata(pdev, priv);
	216
	217	/*
	218	* FIXME: using global GPIO numbers is not helpful. If/when we
	219	* get accessors to get the actual name of the GPIO line,
	220	* from the descriptor, then provide that instead.
	221	*/
	222	dev_info(&pdev->dev, "using lines %u (SDA) and %u (SCL%s)\n",
	223	desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
	224	pdata->scl_is_output_only
	225	? ", no clock stretching" : "");
	226
	227	return 0;
	228	}
	229
	230	static int i2c_gpio_remove(struct platform_device *pdev)
	231	{
	232	struct i2c_gpio_private_data *priv;
	233	struct i2c_adapter *adap;
	234
	235	priv = platform_get_drvdata(pdev);
	236	adap = &priv->adap;
	237
	238	i2c_del_adapter(adap);
	239
	240	return 0;
	241	}
	242
	243	#if defined(CONFIG_OF)
	244	static const struct of_device_id i2c_gpio_dt_ids[] = {
	245	{ .compatible = "i2c-gpio", },
	246	{ /* sentinel */ }
	247	};
	248
	249	MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
	250	#endif
	251
	252	static struct platform_driver i2c_gpio_driver = {
	253	.driver = {
	254	.name = "i2c-gpio",
	255	.of_match_table = of_match_ptr(i2c_gpio_dt_ids),
	256	},
	257	.probe = i2c_gpio_probe,
	258	.remove = i2c_gpio_remove,
	259	};
	260
	261	static int __init i2c_gpio_init(void)
	262	{
	263	int ret;
	264
	265	ret = platform_driver_register(&i2c_gpio_driver);
	266	if (ret)
	267	printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
	268
	269	return ret;
	270	}
	271	subsys_initcall(i2c_gpio_init);
	272
	273	static void __exit i2c_gpio_exit(void)
	274	{
	275	platform_driver_unregister(&i2c_gpio_driver);
	276	}
	277	module_exit(i2c_gpio_exit);
	278
	279	MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
	280	MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
	281	MODULE_LICENSE("GPL");
	282	MODULE_ALIAS("platform:i2c-gpio");