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Linux/drivers/i2c/busses/i2c-gpio.c

  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.h>
 18 #include <linux/of.h>
 19 #include <linux/of_gpio.h>
 20 
 21 struct i2c_gpio_private_data {
 22         struct i2c_adapter adap;
 23         struct i2c_algo_bit_data bit_data;
 24         struct i2c_gpio_platform_data pdata;
 25 };
 26 
 27 /* Toggle SDA by changing the direction of the pin */
 28 static void i2c_gpio_setsda_dir(void *data, int state)
 29 {
 30         struct i2c_gpio_platform_data *pdata = data;
 31 
 32         if (state)
 33                 gpio_direction_input(pdata->sda_pin);
 34         else
 35                 gpio_direction_output(pdata->sda_pin, 0);
 36 }
 37 
 38 /*
 39  * Toggle SDA by changing the output value of the pin. This is only
 40  * valid for pins configured as open drain (i.e. setting the value
 41  * high effectively turns off the output driver.)
 42  */
 43 static void i2c_gpio_setsda_val(void *data, int state)
 44 {
 45         struct i2c_gpio_platform_data *pdata = data;
 46 
 47         gpio_set_value(pdata->sda_pin, state);
 48 }
 49 
 50 /* Toggle SCL by changing the direction of the pin. */
 51 static void i2c_gpio_setscl_dir(void *data, int state)
 52 {
 53         struct i2c_gpio_platform_data *pdata = data;
 54 
 55         if (state)
 56                 gpio_direction_input(pdata->scl_pin);
 57         else
 58                 gpio_direction_output(pdata->scl_pin, 0);
 59 }
 60 
 61 /*
 62  * Toggle SCL by changing the output value of the pin. This is used
 63  * for pins that are configured as open drain and for output-only
 64  * pins. The latter case will break the i2c protocol, but it will
 65  * often work in practice.
 66  */
 67 static void i2c_gpio_setscl_val(void *data, int state)
 68 {
 69         struct i2c_gpio_platform_data *pdata = data;
 70 
 71         gpio_set_value(pdata->scl_pin, state);
 72 }
 73 
 74 static int i2c_gpio_getsda(void *data)
 75 {
 76         struct i2c_gpio_platform_data *pdata = data;
 77 
 78         return gpio_get_value(pdata->sda_pin);
 79 }
 80 
 81 static int i2c_gpio_getscl(void *data)
 82 {
 83         struct i2c_gpio_platform_data *pdata = data;
 84 
 85         return gpio_get_value(pdata->scl_pin);
 86 }
 87 
 88 static int of_i2c_gpio_get_pins(struct device_node *np,
 89                                 unsigned int *sda_pin, unsigned int *scl_pin)
 90 {
 91         if (of_gpio_count(np) < 2)
 92                 return -ENODEV;
 93 
 94         *sda_pin = of_get_gpio(np, 0);
 95         *scl_pin = of_get_gpio(np, 1);
 96 
 97         if (!gpio_is_valid(*sda_pin) || !gpio_is_valid(*scl_pin)) {
 98                 pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
 99                        np->full_name, *sda_pin, *scl_pin);
100                 return -ENODEV;
101         }
102 
103         return 0;
104 }
105 
106 static void of_i2c_gpio_get_props(struct device_node *np,
107                                   struct i2c_gpio_platform_data *pdata)
108 {
109         u32 reg;
110 
111         of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
112 
113         if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
114                 pdata->timeout = msecs_to_jiffies(reg);
115 
116         pdata->sda_is_open_drain =
117                 of_property_read_bool(np, "i2c-gpio,sda-open-drain");
118         pdata->scl_is_open_drain =
119                 of_property_read_bool(np, "i2c-gpio,scl-open-drain");
120         pdata->scl_is_output_only =
121                 of_property_read_bool(np, "i2c-gpio,scl-output-only");
122 }
123 
124 static int i2c_gpio_probe(struct platform_device *pdev)
125 {
126         struct i2c_gpio_private_data *priv;
127         struct i2c_gpio_platform_data *pdata;
128         struct i2c_algo_bit_data *bit_data;
129         struct i2c_adapter *adap;
130         unsigned int sda_pin, scl_pin;
131         int ret;
132 
133         /* First get the GPIO pins; if it fails, we'll defer the probe. */
134         if (pdev->dev.of_node) {
135                 ret = of_i2c_gpio_get_pins(pdev->dev.of_node,
136                                            &sda_pin, &scl_pin);
137                 if (ret)
138                         return ret;
139         } else {
140                 if (!dev_get_platdata(&pdev->dev))
141                         return -ENXIO;
142                 pdata = dev_get_platdata(&pdev->dev);
143                 sda_pin = pdata->sda_pin;
144                 scl_pin = pdata->scl_pin;
145         }
146 
147         ret = gpio_request(sda_pin, "sda");
148         if (ret) {
149                 if (ret == -EINVAL)
150                         ret = -EPROBE_DEFER;    /* Try again later */
151                 goto err_request_sda;
152         }
153         ret = gpio_request(scl_pin, "scl");
154         if (ret) {
155                 if (ret == -EINVAL)
156                         ret = -EPROBE_DEFER;    /* Try again later */
157                 goto err_request_scl;
158         }
159 
160         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
161         if (!priv) {
162                 ret = -ENOMEM;
163                 goto err_add_bus;
164         }
165         adap = &priv->adap;
166         bit_data = &priv->bit_data;
167         pdata = &priv->pdata;
168 
169         if (pdev->dev.of_node) {
170                 pdata->sda_pin = sda_pin;
171                 pdata->scl_pin = scl_pin;
172                 of_i2c_gpio_get_props(pdev->dev.of_node, pdata);
173         } else {
174                 memcpy(pdata, dev_get_platdata(&pdev->dev), sizeof(*pdata));
175         }
176 
177         if (pdata->sda_is_open_drain) {
178                 gpio_direction_output(pdata->sda_pin, 1);
179                 bit_data->setsda = i2c_gpio_setsda_val;
180         } else {
181                 gpio_direction_input(pdata->sda_pin);
182                 bit_data->setsda = i2c_gpio_setsda_dir;
183         }
184 
185         if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
186                 gpio_direction_output(pdata->scl_pin, 1);
187                 bit_data->setscl = i2c_gpio_setscl_val;
188         } else {
189                 gpio_direction_input(pdata->scl_pin);
190                 bit_data->setscl = i2c_gpio_setscl_dir;
191         }
192 
193         if (!pdata->scl_is_output_only)
194                 bit_data->getscl = i2c_gpio_getscl;
195         bit_data->getsda = i2c_gpio_getsda;
196 
197         if (pdata->udelay)
198                 bit_data->udelay = pdata->udelay;
199         else if (pdata->scl_is_output_only)
200                 bit_data->udelay = 50;                  /* 10 kHz */
201         else
202                 bit_data->udelay = 5;                   /* 100 kHz */
203 
204         if (pdata->timeout)
205                 bit_data->timeout = pdata->timeout;
206         else
207                 bit_data->timeout = HZ / 10;            /* 100 ms */
208 
209         bit_data->data = pdata;
210 
211         adap->owner = THIS_MODULE;
212         if (pdev->dev.of_node)
213                 strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
214         else
215                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
216 
217         adap->algo_data = bit_data;
218         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
219         adap->dev.parent = &pdev->dev;
220         adap->dev.of_node = pdev->dev.of_node;
221 
222         adap->nr = pdev->id;
223         ret = i2c_bit_add_numbered_bus(adap);
224         if (ret)
225                 goto err_add_bus;
226 
227         platform_set_drvdata(pdev, priv);
228 
229         dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
230                  pdata->sda_pin, pdata->scl_pin,
231                  pdata->scl_is_output_only
232                  ? ", no clock stretching" : "");
233 
234         return 0;
235 
236 err_add_bus:
237         gpio_free(scl_pin);
238 err_request_scl:
239         gpio_free(sda_pin);
240 err_request_sda:
241         return ret;
242 }
243 
244 static int i2c_gpio_remove(struct platform_device *pdev)
245 {
246         struct i2c_gpio_private_data *priv;
247         struct i2c_gpio_platform_data *pdata;
248         struct i2c_adapter *adap;
249 
250         priv = platform_get_drvdata(pdev);
251         adap = &priv->adap;
252         pdata = &priv->pdata;
253 
254         i2c_del_adapter(adap);
255         gpio_free(pdata->scl_pin);
256         gpio_free(pdata->sda_pin);
257 
258         return 0;
259 }
260 
261 #if defined(CONFIG_OF)
262 static const struct of_device_id i2c_gpio_dt_ids[] = {
263         { .compatible = "i2c-gpio", },
264         { /* sentinel */ }
265 };
266 
267 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
268 #endif
269 
270 static struct platform_driver i2c_gpio_driver = {
271         .driver         = {
272                 .name   = "i2c-gpio",
273                 .owner  = THIS_MODULE,
274                 .of_match_table = of_match_ptr(i2c_gpio_dt_ids),
275         },
276         .probe          = i2c_gpio_probe,
277         .remove         = i2c_gpio_remove,
278 };
279 
280 static int __init i2c_gpio_init(void)
281 {
282         int ret;
283 
284         ret = platform_driver_register(&i2c_gpio_driver);
285         if (ret)
286                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
287 
288         return ret;
289 }
290 subsys_initcall(i2c_gpio_init);
291 
292 static void __exit i2c_gpio_exit(void)
293 {
294         platform_driver_unregister(&i2c_gpio_driver);
295 }
296 module_exit(i2c_gpio_exit);
297 
298 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
299 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
300 MODULE_LICENSE("GPL");
301 MODULE_ALIAS("platform:i2c-gpio");
302 

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