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1c23af90 HS |
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 | 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 | 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 __init 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->dev.parent = &pdev->dev; | |
144 | ||
145 | ret = i2c_bit_add_bus(adap); | |
146 | if (ret) | |
147 | goto err_add_bus; | |
148 | ||
149 | platform_set_drvdata(pdev, adap); | |
150 | ||
151 | dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n", | |
152 | pdata->sda_pin, pdata->scl_pin, | |
153 | pdata->scl_is_output_only | |
154 | ? ", no clock stretching" : ""); | |
155 | ||
156 | return 0; | |
157 | ||
158 | err_add_bus: | |
159 | gpio_free(pdata->scl_pin); | |
160 | err_request_scl: | |
161 | gpio_free(pdata->sda_pin); | |
162 | err_request_sda: | |
163 | kfree(bit_data); | |
164 | err_alloc_bit_data: | |
165 | kfree(adap); | |
166 | err_alloc_adap: | |
167 | return ret; | |
168 | } | |
169 | ||
170 | static int __exit i2c_gpio_remove(struct platform_device *pdev) | |
171 | { | |
172 | struct i2c_gpio_platform_data *pdata; | |
173 | struct i2c_adapter *adap; | |
174 | ||
175 | adap = platform_get_drvdata(pdev); | |
176 | pdata = pdev->dev.platform_data; | |
177 | ||
178 | i2c_del_adapter(adap); | |
179 | gpio_free(pdata->scl_pin); | |
180 | gpio_free(pdata->sda_pin); | |
181 | kfree(adap->algo_data); | |
182 | kfree(adap); | |
183 | ||
184 | return 0; | |
185 | } | |
186 | ||
187 | static struct platform_driver i2c_gpio_driver = { | |
188 | .driver = { | |
189 | .name = "i2c-gpio", | |
190 | .owner = THIS_MODULE, | |
191 | }, | |
192 | .remove = __exit_p(i2c_gpio_remove), | |
193 | }; | |
194 | ||
195 | static int __init i2c_gpio_init(void) | |
196 | { | |
197 | int ret; | |
198 | ||
199 | ret = platform_driver_probe(&i2c_gpio_driver, i2c_gpio_probe); | |
200 | if (ret) | |
201 | printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret); | |
202 | ||
203 | return ret; | |
204 | } | |
205 | module_init(i2c_gpio_init); | |
206 | ||
207 | static void __exit i2c_gpio_exit(void) | |
208 | { | |
209 | platform_driver_unregister(&i2c_gpio_driver); | |
210 | } | |
211 | module_exit(i2c_gpio_exit); | |
212 | ||
213 | MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>"); | |
214 | MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver"); | |
215 | MODULE_LICENSE("GPL"); |