LXR linux/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
  21struct 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 */
  28static 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 */
  43static 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. */
  51static 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 */
  67static 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
  74static 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
  81static 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
  88static 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
 109static 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
 127static 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
 238static 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)
 252static const struct of_device_id i2c_gpio_dt_ids[] = {
 253        { .compatible = "i2c-gpio", },
 254        { /* sentinel */ }
 255};
 256
 257MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
 258#endif
 259
 260static 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
 269static 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}
 279subsys_initcall(i2c_gpio_init);
 280
 281static void __exit i2c_gpio_exit(void)
 282{
 283        platform_driver_unregister(&i2c_gpio_driver);
 284}
 285module_exit(i2c_gpio_exit);
 286
 287MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 288MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 289MODULE_LICENSE("GPL");
 290MODULE_ALIAS("platform:i2c-gpio");
 291