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_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);       \
  86         *val = get##wire(&priv->bit_data);                      \
  87         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);     \
  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_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);       \
  95         set##wire(&priv->bit_data, val);                        \
  96         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);     \
  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 void i2c_gpio_incomplete_transfer(struct i2c_gpio_private_data *priv,
 105                                         u32 pattern, u8 pattern_size)
 106 {
 107         struct i2c_algo_bit_data *bit_data = &priv->bit_data;
 108         int i;
 109
 110         i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 111
 112         /* START condition */
 113         setsda(bit_data, 0);
 114         udelay(bit_data->udelay);
 115
 116         /* Send pattern, request ACK, don't send STOP */
 117         for (i = pattern_size - 1; i >= 0; i--) {
 118                 setscl(bit_data, 0);
 119                 udelay(bit_data->udelay / 2);
 120                 setsda(bit_data, (pattern >> i) & 1);
 121                 udelay((bit_data->udelay + 1) / 2);
 122                 setscl(bit_data, 1);
 123                 udelay(bit_data->udelay);
 124         }
 125
 126         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 127 }
 128
 129 static int fops_incomplete_addr_phase_set(void *data, u64 addr)
 130 {
 131         struct i2c_gpio_private_data *priv = data;
 132         u32 pattern;
 133
 134         if (addr > 0x7f)
 135                 return -EINVAL;
 136
 137         /* ADDR (7 bit) + RD (1 bit) + Client ACK, keep SDA hi (1 bit) */
 138         pattern = (addr << 2) | 3;
 139
 140         i2c_gpio_incomplete_transfer(priv, pattern, 9);
 141
 142         return 0;
 143 }
 144 DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n");
 145
 146 static int fops_incomplete_write_byte_set(void *data, u64 addr)
 147 {
 148         struct i2c_gpio_private_data *priv = data;
 149         u32 pattern;
 150
 151         if (addr > 0x7f)
 152                 return -EINVAL;
 153
 154         /* ADDR (7 bit) + WR (1 bit) + Client ACK (1 bit) */
 155         pattern = (addr << 2) | 1;
 156         /* 0x00 (8 bit) + Client ACK, keep SDA hi (1 bit) */
 157         pattern = (pattern << 9) | 1;
 158
 159         i2c_gpio_incomplete_transfer(priv, pattern, 18);
 160
 161         return 0;
 162 }
 163 DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n");
 164
 165 static void i2c_gpio_fault_injector_init(struct platform_device *pdev)
 166 {
 167         struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
 168
 169         /*
 170          * If there will be a debugfs-dir per i2c adapter somewhen, put the
 171          * 'fault-injector' dir there. Until then, we have a global dir with
 172          * all adapters as subdirs.
 173          */
 174         if (!i2c_gpio_debug_dir) {
 175                 i2c_gpio_debug_dir = debugfs_create_dir("i2c-fault-injector", NULL);
 176                 if (!i2c_gpio_debug_dir)
 177                         return;
 178         }
 179
 180         priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir);
 181         if (!priv->debug_dir)
 182                 return;
 183
 184         debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl);
 185         debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda);
 186         debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir,
 187                                    priv, &fops_incomplete_addr_phase);
 188         debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->debug_dir,
 189                                    priv, &fops_incomplete_write_byte);
 190 }
 191
 192 static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)
 193 {
 194         struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
 195
 196         debugfs_remove_recursive(priv->debug_dir);
 197 }
 198 #else
 199 static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
 200 static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {}
 201 #endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
 202
 203 static void of_i2c_gpio_get_props(struct device_node *np,
 204                                   struct i2c_gpio_platform_data *pdata)
 205 {
 206         u32 reg;
 207
 208         of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
 209
 210         if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
 211                 pdata->timeout = msecs_to_jiffies(reg);
 212
 213         pdata->sda_is_open_drain =
 214                 of_property_read_bool(np, "i2c-gpio,sda-open-drain");
 215         pdata->scl_is_open_drain =
 216                 of_property_read_bool(np, "i2c-gpio,scl-open-drain");
 217         pdata->scl_is_output_only =
 218                 of_property_read_bool(np, "i2c-gpio,scl-output-only");
 219 }
 220
 221 static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
 222                                            const char *con_id,
 223                                            unsigned int index,
 224                                            enum gpiod_flags gflags)
 225 {
 226         struct gpio_desc *retdesc;
 227         int ret;
 228
 229         retdesc = devm_gpiod_get(dev, con_id, gflags);
 230         if (!IS_ERR(retdesc)) {
 231                 dev_dbg(dev, "got GPIO from name %s\n", con_id);
 232                 return retdesc;
 233         }
 234
 235         retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
 236         if (!IS_ERR(retdesc)) {
 237                 dev_dbg(dev, "got GPIO from index %u\n", index);
 238                 return retdesc;
 239         }
 240
 241         ret = PTR_ERR(retdesc);
 242
 243         /* FIXME: hack in the old code, is this really necessary? */
 244         if (ret == -EINVAL)
 245                 retdesc = ERR_PTR(-EPROBE_DEFER);
 246
 247         /* This happens if the GPIO driver is not yet probed, let's defer */
 248         if (ret == -ENOENT)
 249                 retdesc = ERR_PTR(-EPROBE_DEFER);
 250
 251         if (PTR_ERR(retdesc) != -EPROBE_DEFER)
 252                 dev_err(dev, "error trying to get descriptor: %d\n", ret);
 253
 254         return retdesc;
 255 }
 256
 257 static int i2c_gpio_probe(struct platform_device *pdev)
 258 {
 259         struct i2c_gpio_private_data *priv;
 260         struct i2c_gpio_platform_data *pdata;
 261         struct i2c_algo_bit_data *bit_data;
 262         struct i2c_adapter *adap;
 263         struct device *dev = &pdev->dev;
 264         struct device_node *np = dev->of_node;
 265         enum gpiod_flags gflags;
 266         int ret;
 267
 268         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 269         if (!priv)
 270                 return -ENOMEM;
 271
 272         adap = &priv->adap;
 273         bit_data = &priv->bit_data;
 274         pdata = &priv->pdata;
 275
 276         if (np) {
 277                 of_i2c_gpio_get_props(np, pdata);
 278         } else {
 279                 /*
 280                  * If all platform data settings are zero it is OK
 281                  * to not provide any platform data from the board.
 282                  */
 283                 if (dev_get_platdata(dev))
 284                         memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
 285         }
 286
 287         /*
 288          * First get the GPIO pins; if it fails, we'll defer the probe.
 289          * If the SDA line is marked from platform data or device tree as
 290          * "open drain" it means something outside of our control is making
 291          * this line being handled as open drain, and we should just handle
 292          * it as any other output. Else we enforce open drain as this is
 293          * required for an I2C bus.
 294          */
 295         if (pdata->sda_is_open_drain)
 296                 gflags = GPIOD_OUT_HIGH;
 297         else
 298                 gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 299         priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
 300         if (IS_ERR(priv->sda))
 301                 return PTR_ERR(priv->sda);
 302
 303         /*
 304          * If the SCL line is marked from platform data or device tree as
 305          * "open drain" it means something outside of our control is making
 306          * this line being handled as open drain, and we should just handle
 307          * it as any other output. Else we enforce open drain as this is
 308          * required for an I2C bus.
 309          */
 310         if (pdata->scl_is_open_drain)
 311                 gflags = GPIOD_OUT_HIGH;
 312         else
 313                 gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 314         priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
 315         if (IS_ERR(priv->scl))
 316                 return PTR_ERR(priv->scl);
 317
 318         if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl))
 319                 dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
 320
 321         bit_data->setsda = i2c_gpio_setsda_val;
 322         bit_data->setscl = i2c_gpio_setscl_val;
 323
 324         if (!pdata->scl_is_output_only)
 325                 bit_data->getscl = i2c_gpio_getscl;
 326         bit_data->getsda = i2c_gpio_getsda;
 327
 328         if (pdata->udelay)
 329                 bit_data->udelay = pdata->udelay;
 330         else if (pdata->scl_is_output_only)
 331                 bit_data->udelay = 50;                  /* 10 kHz */
 332         else
 333                 bit_data->udelay = 5;                   /* 100 kHz */
 334
 335         if (pdata->timeout)
 336                 bit_data->timeout = pdata->timeout;
 337         else
 338                 bit_data->timeout = HZ / 10;            /* 100 ms */
 339
 340         bit_data->data = priv;
 341
 342         adap->owner = THIS_MODULE;
 343         if (np)
 344                 strlcpy(adap->name, dev_name(dev), sizeof(adap->name));
 345         else
 346                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 347
 348         adap->algo_data = bit_data;
 349         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
 350         adap->dev.parent = dev;
 351         adap->dev.of_node = np;
 352
 353         adap->nr = pdev->id;
 354         ret = i2c_bit_add_numbered_bus(adap);
 355         if (ret)
 356                 return ret;
 357
 358         platform_set_drvdata(pdev, priv);
 359
 360         /*
 361          * FIXME: using global GPIO numbers is not helpful. If/when we
 362          * get accessors to get the actual name of the GPIO line,
 363          * from the descriptor, then provide that instead.
 364          */
 365         dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
 366                  desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
 367                  pdata->scl_is_output_only
 368                  ? ", no clock stretching" : "");
 369
 370         i2c_gpio_fault_injector_init(pdev);
 371
 372         return 0;
 373 }
 374
 375 static int i2c_gpio_remove(struct platform_device *pdev)
 376 {
 377         struct i2c_gpio_private_data *priv;
 378         struct i2c_adapter *adap;
 379
 380         i2c_gpio_fault_injector_exit(pdev);
 381
 382         priv = platform_get_drvdata(pdev);
 383         adap = &priv->adap;
 384
 385         i2c_del_adapter(adap);
 386
 387         return 0;
 388 }
 389
 390 #if defined(CONFIG_OF)
 391 static const struct of_device_id i2c_gpio_dt_ids[] = {
 392         { .compatible = "i2c-gpio", },
 393         { /* sentinel */ }
 394 };
 395
 396 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
 397 #endif
 398
 399 static struct platform_driver i2c_gpio_driver = {
 400         .driver         = {
 401                 .name   = "i2c-gpio",
 402                 .of_match_table = of_match_ptr(i2c_gpio_dt_ids),
 403         },
 404         .probe          = i2c_gpio_probe,
 405         .remove         = i2c_gpio_remove,
 406 };
 407
 408 static int __init i2c_gpio_init(void)
 409 {
 410         int ret;
 411
 412         ret = platform_driver_register(&i2c_gpio_driver);
 413         if (ret)
 414                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 415
 416         return ret;
 417 }
 418 subsys_initcall(i2c_gpio_init);
 419
 420 static void __exit i2c_gpio_exit(void)
 421 {
 422         platform_driver_unregister(&i2c_gpio_driver);
 423 }
 424 module_exit(i2c_gpio_exit);
 425
 426 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 427 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 428 MODULE_LICENSE("GPL");
 429 MODULE_ALIAS("platform:i2c-gpio");