drivers/i2c/busses/i2c-gpio.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Bitbanging I2C bus driver using the GPIO API
   4  *
   5  * Copyright (C) 2007 Atmel Corporation
   6  */
   7 #include <linux/completion.h>
   8 #include <linux/debugfs.h>
   9 #include <linux/delay.h>
  10 #include <linux/gpio/consumer.h>
  11 #include <linux/i2c-algo-bit.h>
  12 #include <linux/i2c.h>
  13 #include <linux/init.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/module.h>
  16 #include <linux/of.h>
  17 #include <linux/platform_data/i2c-gpio.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/slab.h>
  20
  21 struct i2c_gpio_private_data {
  22         struct gpio_desc *sda;
  23         struct gpio_desc *scl;
  24         struct i2c_adapter adap;
  25         struct i2c_algo_bit_data bit_data;
  26         struct i2c_gpio_platform_data pdata;
  27 #ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
  28         struct dentry *debug_dir;
  29         /* these must be protected by bus lock */
  30         struct completion scl_irq_completion;
  31         u64 scl_irq_data;
  32 #endif
  33 };
  34
  35 /*
  36  * Toggle SDA by changing the output value of the pin. This is only
  37  * valid for pins configured as open drain (i.e. setting the value
  38  * high effectively turns off the output driver.)
  39  */
  40 static void i2c_gpio_setsda_val(void *data, int state)
  41 {
  42         struct i2c_gpio_private_data *priv = data;
  43
  44         gpiod_set_value_cansleep(priv->sda, state);
  45 }
  46
  47 /*
  48  * Toggle SCL by changing the output value of the pin. This is used
  49  * for pins that are configured as open drain and for output-only
  50  * pins. The latter case will break the i2c protocol, but it will
  51  * often work in practice.
  52  */
  53 static void i2c_gpio_setscl_val(void *data, int state)
  54 {
  55         struct i2c_gpio_private_data *priv = data;
  56
  57         gpiod_set_value_cansleep(priv->scl, state);
  58 }
  59
  60 static int i2c_gpio_getsda(void *data)
  61 {
  62         struct i2c_gpio_private_data *priv = data;
  63
  64         return gpiod_get_value_cansleep(priv->sda);
  65 }
  66
  67 static int i2c_gpio_getscl(void *data)
  68 {
  69         struct i2c_gpio_private_data *priv = data;
  70
  71         return gpiod_get_value_cansleep(priv->scl);
  72 }
  73
  74 #ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
  75 static struct dentry *i2c_gpio_debug_dir;
  76
  77 #define setsda(bd, val) ((bd)->setsda((bd)->data, val))
  78 #define setscl(bd, val) ((bd)->setscl((bd)->data, val))
  79 #define getsda(bd)      ((bd)->getsda((bd)->data))
  80 #define getscl(bd)      ((bd)->getscl((bd)->data))
  81
  82 #define WIRE_ATTRIBUTE(wire) \
  83 static int fops_##wire##_get(void *data, u64 *val)              \
  84 {                                                               \
  85         struct i2c_gpio_private_data *priv = data;              \
  86                                                                 \
  87         i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);       \
  88         *val = get##wire(&priv->bit_data);                      \
  89         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);     \
  90         return 0;                                               \
  91 }                                                               \
  92 static int fops_##wire##_set(void *data, u64 val)               \
  93 {                                                               \
  94         struct i2c_gpio_private_data *priv = data;              \
  95                                                                 \
  96         i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);       \
  97         set##wire(&priv->bit_data, val);                        \
  98         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);     \
  99         return 0;                                               \
 100 }                                                               \
 101 DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n")
 102
 103 WIRE_ATTRIBUTE(scl);
 104 WIRE_ATTRIBUTE(sda);
 105
 106 static void i2c_gpio_incomplete_transfer(struct i2c_gpio_private_data *priv,
 107                                         u32 pattern, u8 pattern_size)
 108 {
 109         struct i2c_algo_bit_data *bit_data = &priv->bit_data;
 110         int i;
 111
 112         i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 113
 114         /* START condition */
 115         setsda(bit_data, 0);
 116         udelay(bit_data->udelay);
 117
 118         /* Send pattern, request ACK, don't send STOP */
 119         for (i = pattern_size - 1; i >= 0; i--) {
 120                 setscl(bit_data, 0);
 121                 udelay(bit_data->udelay / 2);
 122                 setsda(bit_data, (pattern >> i) & 1);
 123                 udelay((bit_data->udelay + 1) / 2);
 124                 setscl(bit_data, 1);
 125                 udelay(bit_data->udelay);
 126         }
 127
 128         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 129 }
 130
 131 static int fops_incomplete_addr_phase_set(void *data, u64 addr)
 132 {
 133         struct i2c_gpio_private_data *priv = data;
 134         u32 pattern;
 135
 136         if (addr > 0x7f)
 137                 return -EINVAL;
 138
 139         /* ADDR (7 bit) + RD (1 bit) + Client ACK, keep SDA hi (1 bit) */
 140         pattern = (addr << 2) | 3;
 141
 142         i2c_gpio_incomplete_transfer(priv, pattern, 9);
 143
 144         return 0;
 145 }
 146 DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n");
 147
 148 static int fops_incomplete_write_byte_set(void *data, u64 addr)
 149 {
 150         struct i2c_gpio_private_data *priv = data;
 151         u32 pattern;
 152
 153         if (addr > 0x7f)
 154                 return -EINVAL;
 155
 156         /* ADDR (7 bit) + WR (1 bit) + Client ACK (1 bit) */
 157         pattern = (addr << 2) | 1;
 158         /* 0x00 (8 bit) + Client ACK, keep SDA hi (1 bit) */
 159         pattern = (pattern << 9) | 1;
 160
 161         i2c_gpio_incomplete_transfer(priv, pattern, 18);
 162
 163         return 0;
 164 }
 165 DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n");
 166
 167 static int i2c_gpio_fi_act_on_scl_irq(struct i2c_gpio_private_data *priv,
 168                                        irqreturn_t handler(int, void*))
 169 {
 170         int ret, irq = gpiod_to_irq(priv->scl);
 171
 172         if (irq < 0)
 173                 return irq;
 174
 175         i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 176
 177         ret = gpiod_direction_input(priv->scl);
 178         if (ret)
 179                 goto unlock;
 180
 181         reinit_completion(&priv->scl_irq_completion);
 182
 183         ret = request_irq(irq, handler, IRQF_TRIGGER_FALLING,
 184                           "i2c_gpio_fault_injector_scl_irq", priv);
 185         if (ret)
 186                 goto output;
 187
 188         wait_for_completion_interruptible(&priv->scl_irq_completion);
 189
 190         free_irq(irq, priv);
 191  output:
 192         ret = gpiod_direction_output(priv->scl, 1) ?: ret;
 193  unlock:
 194         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 195
 196         return ret;
 197 }
 198
 199 static irqreturn_t lose_arbitration_irq(int irq, void *dev_id)
 200 {
 201         struct i2c_gpio_private_data *priv = dev_id;
 202
 203         setsda(&priv->bit_data, 0);
 204         udelay(priv->scl_irq_data);
 205         setsda(&priv->bit_data, 1);
 206
 207         complete(&priv->scl_irq_completion);
 208
 209         return IRQ_HANDLED;
 210 }
 211
 212 static int fops_lose_arbitration_set(void *data, u64 duration)
 213 {
 214         struct i2c_gpio_private_data *priv = data;
 215
 216         if (duration > 100 * 1000)
 217                 return -EINVAL;
 218
 219         priv->scl_irq_data = duration;
 220         /*
 221          * Interrupt on falling SCL. This ensures that the master under test has
 222          * really started the transfer. Interrupt on falling SDA did only
 223          * exercise 'bus busy' detection on some HW but not 'arbitration lost'.
 224          * Note that the interrupt latency may cause the first bits to be
 225          * transmitted correctly.
 226          */
 227         return i2c_gpio_fi_act_on_scl_irq(priv, lose_arbitration_irq);
 228 }
 229 DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n");
 230
 231 static irqreturn_t inject_panic_irq(int irq, void *dev_id)
 232 {
 233         struct i2c_gpio_private_data *priv = dev_id;
 234
 235         udelay(priv->scl_irq_data);
 236         panic("I2C fault injector induced panic");
 237
 238         return IRQ_HANDLED;
 239 }
 240
 241 static int fops_inject_panic_set(void *data, u64 duration)
 242 {
 243         struct i2c_gpio_private_data *priv = data;
 244
 245         if (duration > 100 * 1000)
 246                 return -EINVAL;
 247
 248         priv->scl_irq_data = duration;
 249         /*
 250          * Interrupt on falling SCL. This ensures that the master under test has
 251          * really started the transfer.
 252          */
 253         return i2c_gpio_fi_act_on_scl_irq(priv, inject_panic_irq);
 254 }
 255 DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n");
 256
 257 static void i2c_gpio_fault_injector_init(struct platform_device *pdev)
 258 {
 259         struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
 260
 261         /*
 262          * If there will be a debugfs-dir per i2c adapter somewhen, put the
 263          * 'fault-injector' dir there. Until then, we have a global dir with
 264          * all adapters as subdirs.
 265          */
 266         if (!i2c_gpio_debug_dir) {
 267                 i2c_gpio_debug_dir = debugfs_create_dir("i2c-fault-injector", NULL);
 268                 if (!i2c_gpio_debug_dir)
 269                         return;
 270         }
 271
 272         priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir);
 273         if (!priv->debug_dir)
 274                 return;
 275
 276         init_completion(&priv->scl_irq_completion);
 277
 278         debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir,
 279                                    priv, &fops_incomplete_addr_phase);
 280         debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->debug_dir,
 281                                    priv, &fops_incomplete_write_byte);
 282         if (priv->bit_data.getscl) {
 283                 debugfs_create_file_unsafe("inject_panic", 0200, priv->debug_dir,
 284                                            priv, &fops_inject_panic);
 285                 debugfs_create_file_unsafe("lose_arbitration", 0200, priv->debug_dir,
 286                                            priv, &fops_lose_arbitration);
 287         }
 288         debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl);
 289         debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda);
 290 }
 291
 292 static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)
 293 {
 294         struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
 295
 296         debugfs_remove_recursive(priv->debug_dir);
 297 }
 298 #else
 299 static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
 300 static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {}
 301 #endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
 302
 303 static void of_i2c_gpio_get_props(struct device_node *np,
 304                                   struct i2c_gpio_platform_data *pdata)
 305 {
 306         u32 reg;
 307
 308         of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
 309
 310         if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
 311                 pdata->timeout = msecs_to_jiffies(reg);
 312
 313         pdata->sda_is_open_drain =
 314                 of_property_read_bool(np, "i2c-gpio,sda-open-drain");
 315         pdata->scl_is_open_drain =
 316                 of_property_read_bool(np, "i2c-gpio,scl-open-drain");
 317         pdata->scl_is_output_only =
 318                 of_property_read_bool(np, "i2c-gpio,scl-output-only");
 319 }
 320
 321 static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
 322                                            const char *con_id,
 323                                            unsigned int index,
 324                                            enum gpiod_flags gflags)
 325 {
 326         struct gpio_desc *retdesc;
 327         int ret;
 328
 329         retdesc = devm_gpiod_get(dev, con_id, gflags);
 330         if (!IS_ERR(retdesc)) {
 331                 dev_dbg(dev, "got GPIO from name %s\n", con_id);
 332                 return retdesc;
 333         }
 334
 335         retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
 336         if (!IS_ERR(retdesc)) {
 337                 dev_dbg(dev, "got GPIO from index %u\n", index);
 338                 return retdesc;
 339         }
 340
 341         ret = PTR_ERR(retdesc);
 342
 343         /* FIXME: hack in the old code, is this really necessary? */
 344         if (ret == -EINVAL)
 345                 retdesc = ERR_PTR(-EPROBE_DEFER);
 346
 347         /* This happens if the GPIO driver is not yet probed, let's defer */
 348         if (ret == -ENOENT)
 349                 retdesc = ERR_PTR(-EPROBE_DEFER);
 350
 351         if (PTR_ERR(retdesc) != -EPROBE_DEFER)
 352                 dev_err(dev, "error trying to get descriptor: %d\n", ret);
 353
 354         return retdesc;
 355 }
 356
 357 static int i2c_gpio_probe(struct platform_device *pdev)
 358 {
 359         struct i2c_gpio_private_data *priv;
 360         struct i2c_gpio_platform_data *pdata;
 361         struct i2c_algo_bit_data *bit_data;
 362         struct i2c_adapter *adap;
 363         struct device *dev = &pdev->dev;
 364         struct device_node *np = dev->of_node;
 365         enum gpiod_flags gflags;
 366         int ret;
 367
 368         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 369         if (!priv)
 370                 return -ENOMEM;
 371
 372         adap = &priv->adap;
 373         bit_data = &priv->bit_data;
 374         pdata = &priv->pdata;
 375
 376         if (np) {
 377                 of_i2c_gpio_get_props(np, pdata);
 378         } else {
 379                 /*
 380                  * If all platform data settings are zero it is OK
 381                  * to not provide any platform data from the board.
 382                  */
 383                 if (dev_get_platdata(dev))
 384                         memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
 385         }
 386
 387         /*
 388          * First get the GPIO pins; if it fails, we'll defer the probe.
 389          * If the SCL/SDA lines are marked "open drain" by platform data or
 390          * device tree then this means that something outside of our control is
 391          * marking these lines to be handled as open drain, and we should just
 392          * handle them as we handle any other output. Else we enforce open
 393          * drain as this is required for an I2C bus.
 394          */
 395         if (pdata->sda_is_open_drain)
 396                 gflags = GPIOD_OUT_HIGH;
 397         else
 398                 gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 399         priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
 400         if (IS_ERR(priv->sda))
 401                 return PTR_ERR(priv->sda);
 402
 403         if (pdata->scl_is_open_drain)
 404                 gflags = GPIOD_OUT_HIGH;
 405         else
 406                 gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 407         priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
 408         if (IS_ERR(priv->scl))
 409                 return PTR_ERR(priv->scl);
 410
 411         if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl))
 412                 dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
 413         else
 414                 bit_data->can_do_atomic = true;
 415
 416         bit_data->setsda = i2c_gpio_setsda_val;
 417         bit_data->setscl = i2c_gpio_setscl_val;
 418
 419         if (!pdata->scl_is_output_only)
 420                 bit_data->getscl = i2c_gpio_getscl;
 421         bit_data->getsda = i2c_gpio_getsda;
 422
 423         if (pdata->udelay)
 424                 bit_data->udelay = pdata->udelay;
 425         else if (pdata->scl_is_output_only)
 426                 bit_data->udelay = 50;                  /* 10 kHz */
 427         else
 428                 bit_data->udelay = 5;                   /* 100 kHz */
 429
 430         if (pdata->timeout)
 431                 bit_data->timeout = pdata->timeout;
 432         else
 433                 bit_data->timeout = HZ / 10;            /* 100 ms */
 434
 435         bit_data->data = priv;
 436
 437         adap->owner = THIS_MODULE;
 438         if (np)
 439                 strlcpy(adap->name, dev_name(dev), sizeof(adap->name));
 440         else
 441                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 442
 443         adap->algo_data = bit_data;
 444         adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
 445         adap->dev.parent = dev;
 446         adap->dev.of_node = np;
 447
 448         adap->nr = pdev->id;
 449         ret = i2c_bit_add_numbered_bus(adap);
 450         if (ret)
 451                 return ret;
 452
 453         platform_set_drvdata(pdev, priv);
 454
 455         /*
 456          * FIXME: using global GPIO numbers is not helpful. If/when we
 457          * get accessors to get the actual name of the GPIO line,
 458          * from the descriptor, then provide that instead.
 459          */
 460         dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
 461                  desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
 462                  pdata->scl_is_output_only
 463                  ? ", no clock stretching" : "");
 464
 465         i2c_gpio_fault_injector_init(pdev);
 466
 467         return 0;
 468 }
 469
 470 static int i2c_gpio_remove(struct platform_device *pdev)
 471 {
 472         struct i2c_gpio_private_data *priv;
 473         struct i2c_adapter *adap;
 474
 475         i2c_gpio_fault_injector_exit(pdev);
 476
 477         priv = platform_get_drvdata(pdev);
 478         adap = &priv->adap;
 479
 480         i2c_del_adapter(adap);
 481
 482         return 0;
 483 }
 484
 485 #if defined(CONFIG_OF)
 486 static const struct of_device_id i2c_gpio_dt_ids[] = {
 487         { .compatible = "i2c-gpio", },
 488         { /* sentinel */ }
 489 };
 490
 491 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
 492 #endif
 493
 494 static struct platform_driver i2c_gpio_driver = {
 495         .driver         = {
 496                 .name   = "i2c-gpio",
 497                 .of_match_table = of_match_ptr(i2c_gpio_dt_ids),
 498         },
 499         .probe          = i2c_gpio_probe,
 500         .remove         = i2c_gpio_remove,
 501 };
 502
 503 static int __init i2c_gpio_init(void)
 504 {
 505         int ret;
 506
 507         ret = platform_driver_register(&i2c_gpio_driver);
 508         if (ret)
 509                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 510
 511         return ret;
 512 }
 513 subsys_initcall(i2c_gpio_init);
 514
 515 static void __exit i2c_gpio_exit(void)
 516 {
 517         platform_driver_unregister(&i2c_gpio_driver);
 518 }
 519 module_exit(i2c_gpio_exit);
 520
 521 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 522 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 523 MODULE_LICENSE("GPL");
 524 MODULE_ALIAS("platform:i2c-gpio");