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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 (*sda_pin == -EPROBE_DEFER || *scl_pin == -EPROBE_DEFER)
 98                 return -EPROBE_DEFER;
 99 
100         if (!gpio_is_valid(*sda_pin) || !gpio_is_valid(*scl_pin)) {
101                 pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
102                        np->full_name, *sda_pin, *scl_pin);
103                 return -ENODEV;
104         }
105 
106         return 0;
107 }
108 
109 static void of_i2c_gpio_get_props(struct device_node *np,
110                                   struct i2c_gpio_platform_data *pdata)
111 {
112         u32 reg;
113 
114         of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
115 
116         if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
117                 pdata->timeout = msecs_to_jiffies(reg);
118 
119         pdata->sda_is_open_drain =
120                 of_property_read_bool(np, "i2c-gpio,sda-open-drain");
121         pdata->scl_is_open_drain =
122                 of_property_read_bool(np, "i2c-gpio,scl-open-drain");
123         pdata->scl_is_output_only =
124                 of_property_read_bool(np, "i2c-gpio,scl-output-only");
125 }
126 
127 static int i2c_gpio_probe(struct platform_device *pdev)
128 {
129         struct i2c_gpio_private_data *priv;
130         struct i2c_gpio_platform_data *pdata;
131         struct i2c_algo_bit_data *bit_data;
132         struct i2c_adapter *adap;
133         unsigned int sda_pin, scl_pin;
134         int ret;
135 
136         /* First get the GPIO pins; if it fails, we'll defer the probe. */
137         if (pdev->dev.of_node) {
138                 ret = of_i2c_gpio_get_pins(pdev->dev.of_node,
139                                            &sda_pin, &scl_pin);
140                 if (ret)
141                         return ret;
142         } else {
143                 if (!dev_get_platdata(&pdev->dev))
144                         return -ENXIO;
145                 pdata = dev_get_platdata(&pdev->dev);
146                 sda_pin = pdata->sda_pin;
147                 scl_pin = pdata->scl_pin;
148         }
149 
150         ret = gpio_request(sda_pin, "sda");
151         if (ret) {
152                 if (ret == -EINVAL)
153                         ret = -EPROBE_DEFER;    /* Try again later */
154                 goto err_request_sda;
155         }
156         ret = gpio_request(scl_pin, "scl");
157         if (ret) {
158                 if (ret == -EINVAL)
159                         ret = -EPROBE_DEFER;    /* Try again later */
160                 goto err_request_scl;
161         }
162 
163         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
164         if (!priv) {
165                 ret = -ENOMEM;
166                 goto err_add_bus;
167         }
168         adap = &priv->adap;
169         bit_data = &priv->bit_data;
170         pdata = &priv->pdata;
171 
172         if (pdev->dev.of_node) {
173                 pdata->sda_pin = sda_pin;
174                 pdata->scl_pin = scl_pin;
175                 of_i2c_gpio_get_props(pdev->dev.of_node, pdata);
176         } else {
177                 memcpy(pdata, dev_get_platdata(&pdev->dev), sizeof(*pdata));
178         }
179 
180         if (pdata->sda_is_open_drain) {
181                 gpio_direction_output(pdata->sda_pin, 1);
182                 bit_data->setsda = i2c_gpio_setsda_val;
183         } else {
184                 gpio_direction_input(pdata->sda_pin);
185                 bit_data->setsda = i2c_gpio_setsda_dir;
186         }
187 
188         if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
189                 gpio_direction_output(pdata->scl_pin, 1);
190                 bit_data->setscl = i2c_gpio_setscl_val;
191         } else {
192                 gpio_direction_input(pdata->scl_pin);
193                 bit_data->setscl = i2c_gpio_setscl_dir;
194         }
195 
196         if (!pdata->scl_is_output_only)
197                 bit_data->getscl = i2c_gpio_getscl;
198         bit_data->getsda = i2c_gpio_getsda;
199 
200         if (pdata->udelay)
201                 bit_data->udelay = pdata->udelay;
202         else if (pdata->scl_is_output_only)
203                 bit_data->udelay = 50;                  /* 10 kHz */
204         else
205                 bit_data->udelay = 5;                   /* 100 kHz */
206 
207         if (pdata->timeout)
208                 bit_data->timeout = pdata->timeout;
209         else
210                 bit_data->timeout = HZ / 10;            /* 100 ms */
211 
212         bit_data->data = pdata;
213 
214         adap->owner = THIS_MODULE;
215         if (pdev->dev.of_node)
216                 strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
217         else
218                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
219 
220         adap->algo_data = bit_data;
221         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
222         adap->dev.parent = &pdev->dev;
223         adap->dev.of_node = pdev->dev.of_node;
224 
225         adap->nr = pdev->id;
226         ret = i2c_bit_add_numbered_bus(adap);
227         if (ret)
228                 goto err_add_bus;
229 
230         platform_set_drvdata(pdev, priv);
231 
232         dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
233                  pdata->sda_pin, pdata->scl_pin,
234                  pdata->scl_is_output_only
235                  ? ", no clock stretching" : "");
236 
237         return 0;
238 
239 err_add_bus:
240         gpio_free(scl_pin);
241 err_request_scl:
242         gpio_free(sda_pin);
243 err_request_sda:
244         return ret;
245 }
246 
247 static int i2c_gpio_remove(struct platform_device *pdev)
248 {
249         struct i2c_gpio_private_data *priv;
250         struct i2c_gpio_platform_data *pdata;
251         struct i2c_adapter *adap;
252 
253         priv = platform_get_drvdata(pdev);
254         adap = &priv->adap;
255         pdata = &priv->pdata;
256 
257         i2c_del_adapter(adap);
258         gpio_free(pdata->scl_pin);
259         gpio_free(pdata->sda_pin);
260 
261         return 0;
262 }
263 
264 #if defined(CONFIG_OF)
265 static const struct of_device_id i2c_gpio_dt_ids[] = {
266         { .compatible = "i2c-gpio", },
267         { /* sentinel */ }
268 };
269 
270 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
271 #endif
272 
273 static struct platform_driver i2c_gpio_driver = {
274         .driver         = {
275                 .name   = "i2c-gpio",
276                 .owner  = THIS_MODULE,
277                 .of_match_table = of_match_ptr(i2c_gpio_dt_ids),
278         },
279         .probe          = i2c_gpio_probe,
280         .remove         = i2c_gpio_remove,
281 };
282 
283 static int __init i2c_gpio_init(void)
284 {
285         int ret;
286 
287         ret = platform_driver_register(&i2c_gpio_driver);
288         if (ret)
289                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
290 
291         return ret;
292 }
293 subsys_initcall(i2c_gpio_init);
294 
295 static void __exit i2c_gpio_exit(void)
296 {
297         platform_driver_unregister(&i2c_gpio_driver);
298 }
299 module_exit(i2c_gpio_exit);
300 
301 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
302 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
303 MODULE_LICENSE("GPL");
304 MODULE_ALIAS("platform:i2c-gpio");
305 

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