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/platform_device.h>
  16
  17 #include <asm/gpio.h>
  18
  19 /* Toggle SDA by changing the direction of the pin */
  20 static void i2c_gpio_setsda_dir(void *data, int state)
  21 {
  22         struct i2c_gpio_platform_data *pdata = data;
  23
  24         if (state)
  25                 gpio_direction_input(pdata->sda_pin);
  26         else
  27                 gpio_direction_output(pdata->sda_pin, 0);
  28 }
  29
  30 /*
  31  * Toggle SDA by changing the output value of the pin. This is only
  32  * valid for pins configured as open drain (i.e. setting the value
  33  * high effectively turns off the output driver.)
  34  */
  35 static void i2c_gpio_setsda_val(void *data, int state)
  36 {
  37         struct i2c_gpio_platform_data *pdata = data;
  38
  39         gpio_set_value(pdata->sda_pin, state);
  40 }
  41
  42 /* Toggle SCL by changing the direction of the pin. */
  43 static void i2c_gpio_setscl_dir(void *data, int state)
  44 {
  45         struct i2c_gpio_platform_data *pdata = data;
  46
  47         if (state)
  48                 gpio_direction_input(pdata->scl_pin);
  49         else
  50                 gpio_direction_output(pdata->scl_pin, 0);
  51 }
  52
  53 /*
  54  * Toggle SCL by changing the output value of the pin. This is used
  55  * for pins that are configured as open drain and for output-only
  56  * pins. The latter case will break the i2c protocol, but it will
  57  * often work in practice.
  58  */
  59 static void i2c_gpio_setscl_val(void *data, int state)
  60 {
  61         struct i2c_gpio_platform_data *pdata = data;
  62
  63         gpio_set_value(pdata->scl_pin, state);
  64 }
  65
  66 static int i2c_gpio_getsda(void *data)
  67 {
  68         struct i2c_gpio_platform_data *pdata = data;
  69
  70         return gpio_get_value(pdata->sda_pin);
  71 }
  72
  73 static int i2c_gpio_getscl(void *data)
  74 {
  75         struct i2c_gpio_platform_data *pdata = data;
  76
  77         return gpio_get_value(pdata->scl_pin);
  78 }
  79
  80 static int __init i2c_gpio_probe(struct platform_device *pdev)
  81 {
  82         struct i2c_gpio_platform_data *pdata;
  83         struct i2c_algo_bit_data *bit_data;
  84         struct i2c_adapter *adap;
  85         int ret;
  86
  87         pdata = pdev->dev.platform_data;
  88         if (!pdata)
  89                 return -ENXIO;
  90
  91         ret = -ENOMEM;
  92         adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
  93         if (!adap)
  94                 goto err_alloc_adap;
  95         bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
  96         if (!bit_data)
  97                 goto err_alloc_bit_data;
  98
  99         ret = gpio_request(pdata->sda_pin, "sda");
 100         if (ret)
 101                 goto err_request_sda;
 102         ret = gpio_request(pdata->scl_pin, "scl");
 103         if (ret)
 104                 goto err_request_scl;
 105
 106         if (pdata->sda_is_open_drain) {
 107                 gpio_direction_output(pdata->sda_pin, 1);
 108                 bit_data->setsda = i2c_gpio_setsda_val;
 109         } else {
 110                 gpio_direction_input(pdata->sda_pin);
 111                 bit_data->setsda = i2c_gpio_setsda_dir;
 112         }
 113
 114         if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
 115                 gpio_direction_output(pdata->scl_pin, 1);
 116                 bit_data->setscl = i2c_gpio_setscl_val;
 117         } else {
 118                 gpio_direction_input(pdata->scl_pin);
 119                 bit_data->setscl = i2c_gpio_setscl_dir;
 120         }
 121
 122         if (!pdata->scl_is_output_only)
 123                 bit_data->getscl = i2c_gpio_getscl;
 124         bit_data->getsda = i2c_gpio_getsda;
 125
 126         if (pdata->udelay)
 127                 bit_data->udelay = pdata->udelay;
 128         else if (pdata->scl_is_output_only)
 129                 bit_data->udelay = 50;                  /* 10 kHz */
 130         else
 131                 bit_data->udelay = 5;                   /* 100 kHz */
 132
 133         if (pdata->timeout)
 134                 bit_data->timeout = pdata->timeout;
 135         else
 136                 bit_data->timeout = HZ / 10;            /* 100 ms */
 137
 138         bit_data->data = pdata;
 139
 140         adap->owner = THIS_MODULE;
 141         snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 142         adap->algo_data = bit_data;
 143         adap->dev.parent = &pdev->dev;
 144
 145         /*
 146          * If "dev->id" is negative we consider it as zero.
 147          * The reason to do so is to avoid sysfs names that only make
 148          * sense when there are multiple adapters.
 149          */
 150         adap->nr = (pdev->id != -1) ? pdev->id : 0;
 151         ret = i2c_bit_add_numbered_bus(adap);
 152         if (ret)
 153                 goto err_add_bus;
 154
 155         platform_set_drvdata(pdev, adap);
 156
 157         dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
 158                  pdata->sda_pin, pdata->scl_pin,
 159                  pdata->scl_is_output_only
 160                  ? ", no clock stretching" : "");
 161
 162         return 0;
 163
 164 err_add_bus:
 165         gpio_free(pdata->scl_pin);
 166 err_request_scl:
 167         gpio_free(pdata->sda_pin);
 168 err_request_sda:
 169         kfree(bit_data);
 170 err_alloc_bit_data:
 171         kfree(adap);
 172 err_alloc_adap:
 173         return ret;
 174 }
 175
 176 static int __exit i2c_gpio_remove(struct platform_device *pdev)
 177 {
 178         struct i2c_gpio_platform_data *pdata;
 179         struct i2c_adapter *adap;
 180
 181         adap = platform_get_drvdata(pdev);
 182         pdata = pdev->dev.platform_data;
 183
 184         i2c_del_adapter(adap);
 185         gpio_free(pdata->scl_pin);
 186         gpio_free(pdata->sda_pin);
 187         kfree(adap->algo_data);
 188         kfree(adap);
 189
 190         return 0;
 191 }
 192
 193 static struct platform_driver i2c_gpio_driver = {
 194         .driver         = {
 195                 .name   = "i2c-gpio",
 196                 .owner  = THIS_MODULE,
 197         },
 198         .remove         = __exit_p(i2c_gpio_remove),
 199 };
 200
 201 static int __init i2c_gpio_init(void)
 202 {
 203         int ret;
 204
 205         ret = platform_driver_probe(&i2c_gpio_driver, i2c_gpio_probe);
 206         if (ret)
 207                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 208
 209         return ret;
 210 }
 211 module_init(i2c_gpio_init);
 212
 213 static void __exit i2c_gpio_exit(void)
 214 {
 215         platform_driver_unregister(&i2c_gpio_driver);
 216 }
 217 module_exit(i2c_gpio_exit);
 218
 219 MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>");
 220 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 221 MODULE_LICENSE("GPL");