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/platform_device.h>
16
17#include <asm/gpio.h>
18
19/* Toggle SDA by changing the direction of the pin */
20static void i2c_gpio_setsda_dir(void *data, int state)
21{
22	struct i2c_gpio_platform_data *pdata = data;
23
24	if (state)
25		gpio_direction_input(pdata->sda_pin);
26	else
27		gpio_direction_output(pdata->sda_pin, 0);
28}
29
30/*
31 * Toggle SDA by changing the output value of the pin. This is only
32 * valid for pins configured as open drain (i.e. setting the value
33 * high effectively turns off the output driver.)
34 */
35static void i2c_gpio_setsda_val(void *data, int state)
36{
37	struct i2c_gpio_platform_data *pdata = data;
38
39	gpio_set_value(pdata->sda_pin, state);
40}
41
42/* Toggle SCL by changing the direction of the pin. */
43static void i2c_gpio_setscl_dir(void *data, int state)
44{
45	struct i2c_gpio_platform_data *pdata = data;
46
47	if (state)
48		gpio_direction_input(pdata->scl_pin);
49	else
50		gpio_direction_output(pdata->scl_pin, 0);
51}
52
53/*
54 * Toggle SCL by changing the output value of the pin. This is used
55 * for pins that are configured as open drain and for output-only
56 * pins. The latter case will break the i2c protocol, but it will
57 * often work in practice.
58 */
59static void i2c_gpio_setscl_val(void *data, int state)
60{
61	struct i2c_gpio_platform_data *pdata = data;
62
63	gpio_set_value(pdata->scl_pin, state);
64}
65
66static int i2c_gpio_getsda(void *data)
67{
68	struct i2c_gpio_platform_data *pdata = data;
69
70	return gpio_get_value(pdata->sda_pin);
71}
72
73static int i2c_gpio_getscl(void *data)
74{
75	struct i2c_gpio_platform_data *pdata = data;
76
77	return gpio_get_value(pdata->scl_pin);
78}
79
80static int __devinit i2c_gpio_probe(struct platform_device *pdev)
81{
82	struct i2c_gpio_platform_data *pdata;
83	struct i2c_algo_bit_data *bit_data;
84	struct i2c_adapter *adap;
85	int ret;
86
87	pdata = pdev->dev.platform_data;
88	if (!pdata)
89		return -ENXIO;
90
91	ret = -ENOMEM;
92	adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
93	if (!adap)
94		goto err_alloc_adap;
95	bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
96	if (!bit_data)
97		goto err_alloc_bit_data;
98
99	ret = gpio_request(pdata->sda_pin, "sda");
100	if (ret)
101		goto err_request_sda;
102	ret = gpio_request(pdata->scl_pin, "scl");
103	if (ret)
104		goto err_request_scl;
105
106	if (pdata->sda_is_open_drain) {
107		gpio_direction_output(pdata->sda_pin, 1);
108		bit_data->setsda = i2c_gpio_setsda_val;
109	} else {
110		gpio_direction_input(pdata->sda_pin);
111		bit_data->setsda = i2c_gpio_setsda_dir;
112	}
113
114	if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
115		gpio_direction_output(pdata->scl_pin, 1);
116		bit_data->setscl = i2c_gpio_setscl_val;
117	} else {
118		gpio_direction_input(pdata->scl_pin);
119		bit_data->setscl = i2c_gpio_setscl_dir;
120	}
121
122	if (!pdata->scl_is_output_only)
123		bit_data->getscl = i2c_gpio_getscl;
124	bit_data->getsda = i2c_gpio_getsda;
125
126	if (pdata->udelay)
127		bit_data->udelay = pdata->udelay;
128	else if (pdata->scl_is_output_only)
129		bit_data->udelay = 50;			/* 10 kHz */
130	else
131		bit_data->udelay = 5;			/* 100 kHz */
132
133	if (pdata->timeout)
134		bit_data->timeout = pdata->timeout;
135	else
136		bit_data->timeout = HZ / 10;		/* 100 ms */
137
138	bit_data->data = pdata;
139
140	adap->owner = THIS_MODULE;
141	snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
142	adap->algo_data = bit_data;
143	//adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
144	adap->class = I2C_CLASS_HWMON;
145	adap->dev.parent = &pdev->dev;
146
147	/*
148	 * If "dev->id" is negative we consider it as zero.
149	 * The reason to do so is to avoid sysfs names that only make
150	 * sense when there are multiple adapters.
151	 */
152	adap->nr = (pdev->id != -1) ? pdev->id : 0;
153	ret = i2c_bit_add_numbered_bus(adap);
154	if (ret)
155		goto err_add_bus;
156
157	platform_set_drvdata(pdev, adap);
158
159	dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
160		 pdata->sda_pin, pdata->scl_pin,
161		 pdata->scl_is_output_only
162		 ? ", no clock stretching" : "");
163
164	return 0;
165
166err_add_bus:
167	gpio_free(pdata->scl_pin);
168err_request_scl:
169	gpio_free(pdata->sda_pin);
170err_request_sda:
171	kfree(bit_data);
172err_alloc_bit_data:
173	kfree(adap);
174err_alloc_adap:
175	return ret;
176}
177
178static int __devexit i2c_gpio_remove(struct platform_device *pdev)
179{
180	struct i2c_gpio_platform_data *pdata;
181	struct i2c_adapter *adap;
182
183	adap = platform_get_drvdata(pdev);
184	pdata = pdev->dev.platform_data;
185
186	i2c_del_adapter(adap);
187	gpio_free(pdata->scl_pin);
188	gpio_free(pdata->sda_pin);
189	kfree(adap->algo_data);
190	kfree(adap);
191
192	return 0;
193}
194
195static struct platform_driver i2c_gpio_driver = {
196	.driver		= {
197		.name	= "i2c-gpio",
198		.owner	= THIS_MODULE,
199	},
200	.probe		= i2c_gpio_probe,
201	.remove		= __devexit_p(i2c_gpio_remove),
202};
203
204static int __init i2c_gpio_init(void)
205{
206	int ret;
207
208	ret = platform_driver_register(&i2c_gpio_driver);
209	if (ret)
210		printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
211
212	return ret;
213}
214module_init(i2c_gpio_init);
215
216static void __exit i2c_gpio_exit(void)
217{
218	platform_driver_unregister(&i2c_gpio_driver);
219}
220module_exit(i2c_gpio_exit);
221
222MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>");
223MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
224MODULE_LICENSE("GPL");
225MODULE_ALIAS("platform:i2c-gpio");
226