xref: /openbmc/linux/drivers/i2c/busses/i2c-gpio.c (revision 9ac8d3fb)
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 */
20 static 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  */
35 static 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. */
43 static 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  */
59 static 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 
66 static 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 
73 static 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 
80 static 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->dev.parent = &pdev->dev;
145 
146 	/*
147 	 * If "dev->id" is negative we consider it as zero.
148 	 * The reason to do so is to avoid sysfs names that only make
149 	 * sense when there are multiple adapters.
150 	 */
151 	adap->nr = (pdev->id != -1) ? pdev->id : 0;
152 	ret = i2c_bit_add_numbered_bus(adap);
153 	if (ret)
154 		goto err_add_bus;
155 
156 	platform_set_drvdata(pdev, adap);
157 
158 	dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
159 		 pdata->sda_pin, pdata->scl_pin,
160 		 pdata->scl_is_output_only
161 		 ? ", no clock stretching" : "");
162 
163 	return 0;
164 
165 err_add_bus:
166 	gpio_free(pdata->scl_pin);
167 err_request_scl:
168 	gpio_free(pdata->sda_pin);
169 err_request_sda:
170 	kfree(bit_data);
171 err_alloc_bit_data:
172 	kfree(adap);
173 err_alloc_adap:
174 	return ret;
175 }
176 
177 static int __devexit i2c_gpio_remove(struct platform_device *pdev)
178 {
179 	struct i2c_gpio_platform_data *pdata;
180 	struct i2c_adapter *adap;
181 
182 	adap = platform_get_drvdata(pdev);
183 	pdata = pdev->dev.platform_data;
184 
185 	i2c_del_adapter(adap);
186 	gpio_free(pdata->scl_pin);
187 	gpio_free(pdata->sda_pin);
188 	kfree(adap->algo_data);
189 	kfree(adap);
190 
191 	return 0;
192 }
193 
194 static struct platform_driver i2c_gpio_driver = {
195 	.driver		= {
196 		.name	= "i2c-gpio",
197 		.owner	= THIS_MODULE,
198 	},
199 	.probe		= i2c_gpio_probe,
200 	.remove		= __devexit_p(i2c_gpio_remove),
201 };
202 
203 static int __init i2c_gpio_init(void)
204 {
205 	int ret;
206 
207 	ret = platform_driver_register(&i2c_gpio_driver);
208 	if (ret)
209 		printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
210 
211 	return ret;
212 }
213 module_init(i2c_gpio_init);
214 
215 static void __exit i2c_gpio_exit(void)
216 {
217 	platform_driver_unregister(&i2c_gpio_driver);
218 }
219 module_exit(i2c_gpio_exit);
220 
221 MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>");
222 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
223 MODULE_LICENSE("GPL");
224 MODULE_ALIAS("platform:i2c-gpio");
225