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
  18 #include <asm/gpio.h>
  19
  20 /* Toggle SDA by changing the direction of the pin */
  21 static void i2c_gpio_setsda_dir(void *data, int state)
  22 {
  23         struct i2c_gpio_platform_data *pdata = data;
  24
  25         if (state)
  26                 gpio_direction_input(pdata->sda_pin);
  27         else
  28                 gpio_direction_output(pdata->sda_pin, 0);
  29 }
  30
  31 /*
  32  * Toggle SDA by changing the output value of the pin. This is only
  33  * valid for pins configured as open drain (i.e. setting the value
  34  * high effectively turns off the output driver.)
  35  */
  36 static void i2c_gpio_setsda_val(void *data, int state)
  37 {
  38         struct i2c_gpio_platform_data *pdata = data;
  39
  40         gpio_set_value(pdata->sda_pin, state);
  41 }
  42
  43 /* Toggle SCL by changing the direction of the pin. */
  44 static void i2c_gpio_setscl_dir(void *data, int state)
  45 {
  46         struct i2c_gpio_platform_data *pdata = data;
  47
  48         if (state)
  49                 gpio_direction_input(pdata->scl_pin);
  50         else
  51                 gpio_direction_output(pdata->scl_pin, 0);
  52 }
  53
  54 /*
  55  * Toggle SCL by changing the output value of the pin. This is used
  56  * for pins that are configured as open drain and for output-only
  57  * pins. The latter case will break the i2c protocol, but it will
  58  * often work in practice.
  59  */
  60 static void i2c_gpio_setscl_val(void *data, int state)
  61 {
  62         struct i2c_gpio_platform_data *pdata = data;
  63
  64         gpio_set_value(pdata->scl_pin, state);
  65 }
  66
  67 static int i2c_gpio_getsda(void *data)
  68 {
  69         struct i2c_gpio_platform_data *pdata = data;
  70
  71         return gpio_get_value(pdata->sda_pin);
  72 }
  73
  74 static int i2c_gpio_getscl(void *data)
  75 {
  76         struct i2c_gpio_platform_data *pdata = data;
  77
  78         return gpio_get_value(pdata->scl_pin);
  79 }
  80
  81 static int __devinit i2c_gpio_probe(struct platform_device *pdev)
  82 {
  83         struct i2c_gpio_platform_data *pdata;
  84         struct i2c_algo_bit_data *bit_data;
  85         struct i2c_adapter *adap;
  86         int ret;
  87
  88         pdata = pdev->dev.platform_data;
  89         if (!pdata)
  90                 return -ENXIO;
  91
  92         ret = -ENOMEM;
  93         adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
  94         if (!adap)
  95                 goto err_alloc_adap;
  96         bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
  97         if (!bit_data)
  98                 goto err_alloc_bit_data;
  99
 100         ret = gpio_request(pdata->sda_pin, "sda");
 101         if (ret)
 102                 goto err_request_sda;
 103         ret = gpio_request(pdata->scl_pin, "scl");
 104         if (ret)
 105                 goto err_request_scl;
 106
 107         if (pdata->sda_is_open_drain) {
 108                 gpio_direction_output(pdata->sda_pin, 1);
 109                 bit_data->setsda = i2c_gpio_setsda_val;
 110         } else {
 111                 gpio_direction_input(pdata->sda_pin);
 112                 bit_data->setsda = i2c_gpio_setsda_dir;
 113         }
 114
 115         if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
 116                 gpio_direction_output(pdata->scl_pin, 1);
 117                 bit_data->setscl = i2c_gpio_setscl_val;
 118         } else {
 119                 gpio_direction_input(pdata->scl_pin);
 120                 bit_data->setscl = i2c_gpio_setscl_dir;
 121         }
 122
 123         if (!pdata->scl_is_output_only)
 124                 bit_data->getscl = i2c_gpio_getscl;
 125         bit_data->getsda = i2c_gpio_getsda;
 126
 127         if (pdata->udelay)
 128                 bit_data->udelay = pdata->udelay;
 129         else if (pdata->scl_is_output_only)
 130                 bit_data->udelay = 50;                  /* 10 kHz */
 131         else
 132                 bit_data->udelay = 5;                   /* 100 kHz */
 133
 134         if (pdata->timeout)
 135                 bit_data->timeout = pdata->timeout;
 136         else
 137                 bit_data->timeout = HZ / 10;            /* 100 ms */
 138
 139         bit_data->data = pdata;
 140
 141         adap->owner = THIS_MODULE;
 142         snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 143         adap->algo_data = bit_data;
 144         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
 145         adap->dev.parent = &pdev->dev;
 146
 147         /*
 148          * If "dev->id" is negative we consider it as zero.
 149          * The reason to do so is to avoid sysfs names that only make
 150          * sense when there are multiple adapters.
 151          */
 152         adap->nr = (pdev->id != -1) ? pdev->id : 0;
 153         ret = i2c_bit_add_numbered_bus(adap);
 154         if (ret)
 155                 goto err_add_bus;
 156
 157         platform_set_drvdata(pdev, adap);
 158
 159         dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
 160                  pdata->sda_pin, pdata->scl_pin,
 161                  pdata->scl_is_output_only
 162                  ? ", no clock stretching" : "");
 163
 164         return 0;
 165
 166 err_add_bus:
 167         gpio_free(pdata->scl_pin);
 168 err_request_scl:
 169         gpio_free(pdata->sda_pin);
 170 err_request_sda:
 171         kfree(bit_data);
 172 err_alloc_bit_data:
 173         kfree(adap);
 174 err_alloc_adap:
 175         return ret;
 176 }
 177
 178 static int __devexit i2c_gpio_remove(struct platform_device *pdev)
 179 {
 180         struct i2c_gpio_platform_data *pdata;
 181         struct i2c_adapter *adap;
 182
 183         adap = platform_get_drvdata(pdev);
 184         pdata = pdev->dev.platform_data;
 185
 186         i2c_del_adapter(adap);
 187         gpio_free(pdata->scl_pin);
 188         gpio_free(pdata->sda_pin);
 189         kfree(adap->algo_data);
 190         kfree(adap);
 191
 192         return 0;
 193 }
 194
 195 static struct platform_driver i2c_gpio_driver = {
 196         .driver         = {
 197                 .name   = "i2c-gpio",
 198                 .owner  = THIS_MODULE,
 199         },
 200         .probe          = i2c_gpio_probe,
 201         .remove         = __devexit_p(i2c_gpio_remove),
 202 };
 203
 204 static int __init i2c_gpio_init(void)
 205 {
 206         int ret;
 207
 208         ret = platform_driver_register(&i2c_gpio_driver);
 209         if (ret)
 210                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 211
 212         return ret;
 213 }
 214 subsys_initcall(i2c_gpio_init);
 215
 216 static void __exit i2c_gpio_exit(void)
 217 {
 218         platform_driver_unregister(&i2c_gpio_driver);
 219 }
 220 module_exit(i2c_gpio_exit);
 221
 222 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 223 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 224 MODULE_LICENSE("GPL");
 225 MODULE_ALIAS("platform:i2c-gpio");