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 = devm_gpio_request(&pdev->dev, sda_pin, "sda");
 151         if (ret) {
 152                 if (ret == -EINVAL)
 153                         ret = -EPROBE_DEFER;    /* Try again later */
 154                 return ret;
 155         }
 156         ret = devm_gpio_request(&pdev->dev, scl_pin, "scl");
 157         if (ret) {
 158                 if (ret == -EINVAL)
 159                         ret = -EPROBE_DEFER;    /* Try again later */
 160                 return ret;
 161         }
 162
 163         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 164         if (!priv)
 165                 return -ENOMEM;
 166         adap = &priv->adap;
 167         bit_data = &priv->bit_data;
 168         pdata = &priv->pdata;
 169
 170         if (pdev->dev.of_node) {
 171                 pdata->sda_pin = sda_pin;
 172                 pdata->scl_pin = scl_pin;
 173                 of_i2c_gpio_get_props(pdev->dev.of_node, pdata);
 174         } else {
 175                 memcpy(pdata, dev_get_platdata(&pdev->dev), sizeof(*pdata));
 176         }
 177
 178         if (pdata->sda_is_open_drain) {
 179                 gpio_direction_output(pdata->sda_pin, 1);
 180                 bit_data->setsda = i2c_gpio_setsda_val;
 181         } else {
 182                 gpio_direction_input(pdata->sda_pin);
 183                 bit_data->setsda = i2c_gpio_setsda_dir;
 184         }
 185
 186         if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
 187                 gpio_direction_output(pdata->scl_pin, 1);
 188                 bit_data->setscl = i2c_gpio_setscl_val;
 189         } else {
 190                 gpio_direction_input(pdata->scl_pin);
 191                 bit_data->setscl = i2c_gpio_setscl_dir;
 192         }
 193
 194         if (!pdata->scl_is_output_only)
 195                 bit_data->getscl = i2c_gpio_getscl;
 196         bit_data->getsda = i2c_gpio_getsda;
 197
 198         if (pdata->udelay)
 199                 bit_data->udelay = pdata->udelay;
 200         else if (pdata->scl_is_output_only)
 201                 bit_data->udelay = 50;                  /* 10 kHz */
 202         else
 203                 bit_data->udelay = 5;                   /* 100 kHz */
 204
 205         if (pdata->timeout)
 206                 bit_data->timeout = pdata->timeout;
 207         else
 208                 bit_data->timeout = HZ / 10;            /* 100 ms */
 209
 210         bit_data->data = pdata;
 211
 212         adap->owner = THIS_MODULE;
 213         if (pdev->dev.of_node)
 214                 strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
 215         else
 216                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 217
 218         adap->algo_data = bit_data;
 219         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
 220         adap->dev.parent = &pdev->dev;
 221         adap->dev.of_node = pdev->dev.of_node;
 222
 223         adap->nr = pdev->id;
 224         ret = i2c_bit_add_numbered_bus(adap);
 225         if (ret)
 226                 return ret;
 227
 228         platform_set_drvdata(pdev, priv);
 229
 230         dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
 231                  pdata->sda_pin, pdata->scl_pin,
 232                  pdata->scl_is_output_only
 233                  ? ", no clock stretching" : "");
 234
 235         return 0;
 236 }
 237
 238 static int i2c_gpio_remove(struct platform_device *pdev)
 239 {
 240         struct i2c_gpio_private_data *priv;
 241         struct i2c_adapter *adap;
 242
 243         priv = platform_get_drvdata(pdev);
 244         adap = &priv->adap;
 245
 246         i2c_del_adapter(adap);
 247
 248         return 0;
 249 }
 250
 251 #if defined(CONFIG_OF)
 252 static const struct of_device_id i2c_gpio_dt_ids[] = {
 253         { .compatible = "i2c-gpio", },
 254         { /* sentinel */ }
 255 };
 256
 257 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
 258 #endif
 259
 260 static struct platform_driver i2c_gpio_driver = {
 261         .driver         = {
 262                 .name   = "i2c-gpio",
 263                 .of_match_table = of_match_ptr(i2c_gpio_dt_ids),
 264         },
 265         .probe          = i2c_gpio_probe,
 266         .remove         = i2c_gpio_remove,
 267 };
 268
 269 static int __init i2c_gpio_init(void)
 270 {
 271         int ret;
 272
 273         ret = platform_driver_register(&i2c_gpio_driver);
 274         if (ret)
 275                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 276
 277         return ret;
 278 }
 279 subsys_initcall(i2c_gpio_init);
 280
 281 static void __exit i2c_gpio_exit(void)
 282 {
 283         platform_driver_unregister(&i2c_gpio_driver);
 284 }
 285 module_exit(i2c_gpio_exit);
 286
 287 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 288 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 289 MODULE_LICENSE("GPL");
 290 MODULE_ALIAS("platform:i2c-gpio");