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_gpio.h>
  19 #include <linux/of_i2c.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_probe(struct device_node *np,
  89                              struct i2c_gpio_platform_data *pdata)
  90 {
  91         u32 reg;
  92
  93         if (of_gpio_count(np) < 2)
  94                 return -ENODEV;
  95
  96         pdata->sda_pin = of_get_gpio(np, 0);
  97         pdata->scl_pin = of_get_gpio(np, 1);
  98
  99         if (!gpio_is_valid(pdata->sda_pin) || !gpio_is_valid(pdata->scl_pin)) {
 100                 pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
 101                        np->full_name, pdata->sda_pin, pdata->scl_pin);
 102                 return -ENODEV;
 103         }
 104
 105         of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
 106
 107         if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
 108                 pdata->timeout = msecs_to_jiffies(reg);
 109
 110         pdata->sda_is_open_drain =
 111                 of_property_read_bool(np, "i2c-gpio,sda-open-drain");
 112         pdata->scl_is_open_drain =
 113                 of_property_read_bool(np, "i2c-gpio,scl-open-drain");
 114         pdata->scl_is_output_only =
 115                 of_property_read_bool(np, "i2c-gpio,scl-output-only");
 116
 117         return 0;
 118 }
 119
 120 static int i2c_gpio_probe(struct platform_device *pdev)
 121 {
 122         struct i2c_gpio_private_data *priv;
 123         struct i2c_gpio_platform_data *pdata;
 124         struct i2c_algo_bit_data *bit_data;
 125         struct i2c_adapter *adap;
 126         int ret;
 127
 128         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 129         if (!priv)
 130                 return -ENOMEM;
 131         adap = &priv->adap;
 132         bit_data = &priv->bit_data;
 133         pdata = &priv->pdata;
 134
 135         if (pdev->dev.of_node) {
 136                 ret = of_i2c_gpio_probe(pdev->dev.of_node, pdata);
 137                 if (ret)
 138                         return ret;
 139         } else {
 140                 if (!pdev->dev.platform_data)
 141                         return -ENXIO;
 142                 memcpy(pdata, pdev->dev.platform_data, sizeof(*pdata));
 143         }
 144
 145         ret = gpio_request(pdata->sda_pin, "sda");
 146         if (ret)
 147                 goto err_request_sda;
 148         ret = gpio_request(pdata->scl_pin, "scl");
 149         if (ret)
 150                 goto err_request_scl;
 151
 152         if (pdata->sda_is_open_drain) {
 153                 gpio_direction_output(pdata->sda_pin, 1);
 154                 bit_data->setsda = i2c_gpio_setsda_val;
 155         } else {
 156                 gpio_direction_input(pdata->sda_pin);
 157                 bit_data->setsda = i2c_gpio_setsda_dir;
 158         }
 159
 160         if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
 161                 gpio_direction_output(pdata->scl_pin, 1);
 162                 bit_data->setscl = i2c_gpio_setscl_val;
 163         } else {
 164                 gpio_direction_input(pdata->scl_pin);
 165                 bit_data->setscl = i2c_gpio_setscl_dir;
 166         }
 167
 168         if (!pdata->scl_is_output_only)
 169                 bit_data->getscl = i2c_gpio_getscl;
 170         bit_data->getsda = i2c_gpio_getsda;
 171
 172         if (pdata->udelay)
 173                 bit_data->udelay = pdata->udelay;
 174         else if (pdata->scl_is_output_only)
 175                 bit_data->udelay = 50;                  /* 10 kHz */
 176         else
 177                 bit_data->udelay = 5;                   /* 100 kHz */
 178
 179         if (pdata->timeout)
 180                 bit_data->timeout = pdata->timeout;
 181         else
 182                 bit_data->timeout = HZ / 10;            /* 100 ms */
 183
 184         bit_data->data = pdata;
 185
 186         adap->owner = THIS_MODULE;
 187         if (pdev->dev.of_node)
 188                 strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
 189         else
 190                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 191
 192         adap->algo_data = bit_data;
 193         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
 194         adap->dev.parent = &pdev->dev;
 195         adap->dev.of_node = pdev->dev.of_node;
 196
 197         adap->nr = pdev->id;
 198         ret = i2c_bit_add_numbered_bus(adap);
 199         if (ret)
 200                 goto err_add_bus;
 201
 202         of_i2c_register_devices(adap);
 203
 204         platform_set_drvdata(pdev, priv);
 205
 206         dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
 207                  pdata->sda_pin, pdata->scl_pin,
 208                  pdata->scl_is_output_only
 209                  ? ", no clock stretching" : "");
 210
 211         return 0;
 212
 213 err_add_bus:
 214         gpio_free(pdata->scl_pin);
 215 err_request_scl:
 216         gpio_free(pdata->sda_pin);
 217 err_request_sda:
 218         return ret;
 219 }
 220
 221 static int i2c_gpio_remove(struct platform_device *pdev)
 222 {
 223         struct i2c_gpio_private_data *priv;
 224         struct i2c_gpio_platform_data *pdata;
 225         struct i2c_adapter *adap;
 226
 227         priv = platform_get_drvdata(pdev);
 228         adap = &priv->adap;
 229         pdata = &priv->pdata;
 230
 231         i2c_del_adapter(adap);
 232         gpio_free(pdata->scl_pin);
 233         gpio_free(pdata->sda_pin);
 234
 235         return 0;
 236 }
 237
 238 #if defined(CONFIG_OF)
 239 static const struct of_device_id i2c_gpio_dt_ids[] = {
 240         { .compatible = "i2c-gpio", },
 241         { /* sentinel */ }
 242 };
 243
 244 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
 245 #endif
 246
 247 static struct platform_driver i2c_gpio_driver = {
 248         .driver         = {
 249                 .name   = "i2c-gpio",
 250                 .owner  = THIS_MODULE,
 251                 .of_match_table = of_match_ptr(i2c_gpio_dt_ids),
 252         },
 253         .probe          = i2c_gpio_probe,
 254         .remove         = i2c_gpio_remove,
 255 };
 256
 257 static int __init i2c_gpio_init(void)
 258 {
 259         int ret;
 260
 261         ret = platform_driver_register(&i2c_gpio_driver);
 262         if (ret)
 263                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 264
 265         return ret;
 266 }
 267 subsys_initcall(i2c_gpio_init);
 268
 269 static void __exit i2c_gpio_exit(void)
 270 {
 271         platform_driver_unregister(&i2c_gpio_driver);
 272 }
 273 module_exit(i2c_gpio_exit);
 274
 275 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 276 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 277 MODULE_LICENSE("GPL");
 278 MODULE_ALIAS("platform:i2c-gpio");