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/debugfs.h>
  11 #include <linux/delay.h>
  12 #include <linux/i2c.h>
  13 #include <linux/i2c-algo-bit.h>
  14 #include <linux/platform_data/i2c-gpio.h>
  15 #include <linux/init.h>
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/gpio/consumer.h>
  20 #include <linux/of.h>
  21
  22 struct i2c_gpio_private_data {
  23         struct gpio_desc *sda;
  24         struct gpio_desc *scl;
  25         struct i2c_adapter adap;
  26         struct i2c_algo_bit_data bit_data;
  27         struct i2c_gpio_platform_data pdata;
  28 #ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
  29         struct dentry *debug_dir;
  30 #endif
  31 };
  32
  33 /*
  34  * Toggle SDA by changing the output value of the pin. This is only
  35  * valid for pins configured as open drain (i.e. setting the value
  36  * high effectively turns off the output driver.)
  37  */
  38 static void i2c_gpio_setsda_val(void *data, int state)
  39 {
  40         struct i2c_gpio_private_data *priv = data;
  41
  42         gpiod_set_value_cansleep(priv->sda, state);
  43 }
  44
  45 /*
  46  * Toggle SCL by changing the output value of the pin. This is used
  47  * for pins that are configured as open drain and for output-only
  48  * pins. The latter case will break the i2c protocol, but it will
  49  * often work in practice.
  50  */
  51 static void i2c_gpio_setscl_val(void *data, int state)
  52 {
  53         struct i2c_gpio_private_data *priv = data;
  54
  55         gpiod_set_value_cansleep(priv->scl, state);
  56 }
  57
  58 static int i2c_gpio_getsda(void *data)
  59 {
  60         struct i2c_gpio_private_data *priv = data;
  61
  62         return gpiod_get_value_cansleep(priv->sda);
  63 }
  64
  65 static int i2c_gpio_getscl(void *data)
  66 {
  67         struct i2c_gpio_private_data *priv = data;
  68
  69         return gpiod_get_value_cansleep(priv->scl);
  70 }
  71
  72 #ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
  73 static struct dentry *i2c_gpio_debug_dir;
  74
  75 #define setsda(bd, val) ((bd)->setsda((bd)->data, val))
  76 #define setscl(bd, val) ((bd)->setscl((bd)->data, val))
  77 #define getsda(bd)      ((bd)->getsda((bd)->data))
  78 #define getscl(bd)      ((bd)->getscl((bd)->data))
  79
  80 #define WIRE_ATTRIBUTE(wire) \
  81 static int fops_##wire##_get(void *data, u64 *val)      \
  82 {                                                       \
  83         struct i2c_gpio_private_data *priv = data;      \
  84                                                         \
  85         i2c_lock_adapter(&priv->adap);                  \
  86         *val = get##wire(&priv->bit_data);              \
  87         i2c_unlock_adapter(&priv->adap);                \
  88         return 0;                                       \
  89 }                                                       \
  90 static int fops_##wire##_set(void *data, u64 val)       \
  91 {                                                       \
  92         struct i2c_gpio_private_data *priv = data;      \
  93                                                         \
  94         i2c_lock_adapter(&priv->adap);                  \
  95         set##wire(&priv->bit_data, val);                \
  96         i2c_unlock_adapter(&priv->adap);                \
  97         return 0;                                       \
  98 }                                                       \
  99 DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n")
 100
 101 WIRE_ATTRIBUTE(scl);
 102 WIRE_ATTRIBUTE(sda);
 103
 104 static int fops_incomplete_transfer_set(void *data, u64 addr)
 105 {
 106         struct i2c_gpio_private_data *priv = data;
 107         struct i2c_algo_bit_data *bit_data = &priv->bit_data;
 108         int i, pattern;
 109
 110         if (addr > 0x7f)
 111                 return -EINVAL;
 112
 113         /* ADDR (7 bit) + RD (1 bit) + SDA hi (1 bit) */
 114         pattern = (addr << 2) | 3;
 115
 116         i2c_lock_adapter(&priv->adap);
 117
 118         /* START condition */
 119         setsda(bit_data, 0);
 120         udelay(bit_data->udelay);
 121
 122         /* Send ADDR+RD, request ACK, don't send STOP */
 123         for (i = 8; i >= 0; i--) {
 124                 setscl(bit_data, 0);
 125                 udelay(bit_data->udelay / 2);
 126                 setsda(bit_data, (pattern >> i) & 1);
 127                 udelay((bit_data->udelay + 1) / 2);
 128                 setscl(bit_data, 1);
 129                 udelay(bit_data->udelay);
 130         }
 131
 132         i2c_unlock_adapter(&priv->adap);
 133
 134         return 0;
 135 }
 136 DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_transfer, NULL, fops_incomplete_transfer_set, "%llu\n");
 137
 138 static void i2c_gpio_fault_injector_init(struct platform_device *pdev)
 139 {
 140         struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
 141
 142         /*
 143          * If there will be a debugfs-dir per i2c adapter somewhen, put the
 144          * 'fault-injector' dir there. Until then, we have a global dir with
 145          * all adapters as subdirs.
 146          */
 147         if (!i2c_gpio_debug_dir) {
 148                 i2c_gpio_debug_dir = debugfs_create_dir("i2c-fault-injector", NULL);
 149                 if (!i2c_gpio_debug_dir)
 150                         return;
 151         }
 152
 153         priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir);
 154         if (!priv->debug_dir)
 155                 return;
 156
 157         debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl);
 158         debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda);
 159         debugfs_create_file_unsafe("incomplete_transfer", 0200, priv->debug_dir,
 160                                    priv, &fops_incomplete_transfer);
 161 }
 162
 163 static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)
 164 {
 165         struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
 166
 167         debugfs_remove_recursive(priv->debug_dir);
 168 }
 169 #else
 170 static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
 171 static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {}
 172 #endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
 173
 174 static void of_i2c_gpio_get_props(struct device_node *np,
 175                                   struct i2c_gpio_platform_data *pdata)
 176 {
 177         u32 reg;
 178
 179         of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
 180
 181         if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
 182                 pdata->timeout = msecs_to_jiffies(reg);
 183
 184         pdata->sda_is_open_drain =
 185                 of_property_read_bool(np, "i2c-gpio,sda-open-drain");
 186         pdata->scl_is_open_drain =
 187                 of_property_read_bool(np, "i2c-gpio,scl-open-drain");
 188         pdata->scl_is_output_only =
 189                 of_property_read_bool(np, "i2c-gpio,scl-output-only");
 190 }
 191
 192 static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
 193                                            const char *con_id,
 194                                            unsigned int index,
 195                                            enum gpiod_flags gflags)
 196 {
 197         struct gpio_desc *retdesc;
 198         int ret;
 199
 200         retdesc = devm_gpiod_get(dev, con_id, gflags);
 201         if (!IS_ERR(retdesc)) {
 202                 dev_dbg(dev, "got GPIO from name %s\n", con_id);
 203                 return retdesc;
 204         }
 205
 206         retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
 207         if (!IS_ERR(retdesc)) {
 208                 dev_dbg(dev, "got GPIO from index %u\n", index);
 209                 return retdesc;
 210         }
 211
 212         ret = PTR_ERR(retdesc);
 213
 214         /* FIXME: hack in the old code, is this really necessary? */
 215         if (ret == -EINVAL)
 216                 retdesc = ERR_PTR(-EPROBE_DEFER);
 217
 218         /* This happens if the GPIO driver is not yet probed, let's defer */
 219         if (ret == -ENOENT)
 220                 retdesc = ERR_PTR(-EPROBE_DEFER);
 221
 222         if (ret != -EPROBE_DEFER)
 223                 dev_err(dev, "error trying to get descriptor: %d\n", ret);
 224
 225         return retdesc;
 226 }
 227
 228 static int i2c_gpio_probe(struct platform_device *pdev)
 229 {
 230         struct i2c_gpio_private_data *priv;
 231         struct i2c_gpio_platform_data *pdata;
 232         struct i2c_algo_bit_data *bit_data;
 233         struct i2c_adapter *adap;
 234         struct device *dev = &pdev->dev;
 235         struct device_node *np = dev->of_node;
 236         enum gpiod_flags gflags;
 237         int ret;
 238
 239         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 240         if (!priv)
 241                 return -ENOMEM;
 242
 243         adap = &priv->adap;
 244         bit_data = &priv->bit_data;
 245         pdata = &priv->pdata;
 246
 247         if (np) {
 248                 of_i2c_gpio_get_props(np, pdata);
 249         } else {
 250                 /*
 251                  * If all platform data settings are zero it is OK
 252                  * to not provide any platform data from the board.
 253                  */
 254                 if (dev_get_platdata(dev))
 255                         memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
 256         }
 257
 258         /*
 259          * First get the GPIO pins; if it fails, we'll defer the probe.
 260          * If the SDA line is marked from platform data or device tree as
 261          * "open drain" it means something outside of our control is making
 262          * this line being handled as open drain, and we should just handle
 263          * it as any other output. Else we enforce open drain as this is
 264          * required for an I2C bus.
 265          */
 266         if (pdata->sda_is_open_drain)
 267                 gflags = GPIOD_OUT_HIGH;
 268         else
 269                 gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 270         priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
 271         if (IS_ERR(priv->sda))
 272                 return PTR_ERR(priv->sda);
 273
 274         /*
 275          * If the SCL line is marked from platform data or device tree as
 276          * "open drain" it means something outside of our control is making
 277          * this line being handled as open drain, and we should just handle
 278          * it as any other output. Else we enforce open drain as this is
 279          * required for an I2C bus.
 280          */
 281         if (pdata->scl_is_open_drain)
 282                 gflags = GPIOD_OUT_LOW;
 283         else
 284                 gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
 285         priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
 286         if (IS_ERR(priv->scl))
 287                 return PTR_ERR(priv->scl);
 288
 289         if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl))
 290                 dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
 291
 292         bit_data->setsda = i2c_gpio_setsda_val;
 293         bit_data->setscl = i2c_gpio_setscl_val;
 294
 295         if (!pdata->scl_is_output_only)
 296                 bit_data->getscl = i2c_gpio_getscl;
 297         bit_data->getsda = i2c_gpio_getsda;
 298
 299         if (pdata->udelay)
 300                 bit_data->udelay = pdata->udelay;
 301         else if (pdata->scl_is_output_only)
 302                 bit_data->udelay = 50;                  /* 10 kHz */
 303         else
 304                 bit_data->udelay = 5;                   /* 100 kHz */
 305
 306         if (pdata->timeout)
 307                 bit_data->timeout = pdata->timeout;
 308         else
 309                 bit_data->timeout = HZ / 10;            /* 100 ms */
 310
 311         bit_data->data = priv;
 312
 313         adap->owner = THIS_MODULE;
 314         if (np)
 315                 strlcpy(adap->name, dev_name(dev), sizeof(adap->name));
 316         else
 317                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 318
 319         adap->algo_data = bit_data;
 320         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
 321         adap->dev.parent = dev;
 322         adap->dev.of_node = np;
 323
 324         adap->nr = pdev->id;
 325         ret = i2c_bit_add_numbered_bus(adap);
 326         if (ret)
 327                 return ret;
 328
 329         platform_set_drvdata(pdev, priv);
 330
 331         /*
 332          * FIXME: using global GPIO numbers is not helpful. If/when we
 333          * get accessors to get the actual name of the GPIO line,
 334          * from the descriptor, then provide that instead.
 335          */
 336         dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
 337                  desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
 338                  pdata->scl_is_output_only
 339                  ? ", no clock stretching" : "");
 340
 341         i2c_gpio_fault_injector_init(pdev);
 342
 343         return 0;
 344 }
 345
 346 static int i2c_gpio_remove(struct platform_device *pdev)
 347 {
 348         struct i2c_gpio_private_data *priv;
 349         struct i2c_adapter *adap;
 350
 351         i2c_gpio_fault_injector_exit(pdev);
 352
 353         priv = platform_get_drvdata(pdev);
 354         adap = &priv->adap;
 355
 356         i2c_del_adapter(adap);
 357
 358         return 0;
 359 }
 360
 361 #if defined(CONFIG_OF)
 362 static const struct of_device_id i2c_gpio_dt_ids[] = {
 363         { .compatible = "i2c-gpio", },
 364         { /* sentinel */ }
 365 };
 366
 367 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
 368 #endif
 369
 370 static struct platform_driver i2c_gpio_driver = {
 371         .driver         = {
 372                 .name   = "i2c-gpio",
 373                 .of_match_table = of_match_ptr(i2c_gpio_dt_ids),
 374         },
 375         .probe          = i2c_gpio_probe,
 376         .remove         = i2c_gpio_remove,
 377 };
 378
 379 static int __init i2c_gpio_init(void)
 380 {
 381         int ret;
 382
 383         ret = platform_driver_register(&i2c_gpio_driver);
 384         if (ret)
 385                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 386
 387         return ret;
 388 }
 389 subsys_initcall(i2c_gpio_init);
 390
 391 static void __exit i2c_gpio_exit(void)
 392 {
 393         platform_driver_unregister(&i2c_gpio_driver);
 394 }
 395 module_exit(i2c_gpio_exit);
 396
 397 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 398 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 399 MODULE_LICENSE("GPL");
 400 MODULE_ALIAS("platform:i2c-gpio");