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");