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/platform_data/i2c-gpio.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/property.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         /* these must be protected by bus lock */
  29         struct completion scl_irq_completion;
  30         u64 scl_irq_data;
  31 #endif
  32 };
  33
  34 /*
  35  * Toggle SDA by changing the output value of the pin. This is only
  36  * valid for pins configured as open drain (i.e. setting the value
  37  * high effectively turns off the output driver.)
  38  */
  39 static void i2c_gpio_setsda_val(void *data, int state)
  40 {
  41         struct i2c_gpio_private_data *priv = data;
  42
  43         gpiod_set_value_cansleep(priv->sda, state);
  44 }
  45
  46 /*
  47  * Toggle SCL by changing the output value of the pin. This is used
  48  * for pins that are configured as open drain and for output-only
  49  * pins. The latter case will break the i2c protocol, but it will
  50  * often work in practice.
  51  */
  52 static void i2c_gpio_setscl_val(void *data, int state)
  53 {
  54         struct i2c_gpio_private_data *priv = data;
  55
  56         gpiod_set_value_cansleep(priv->scl, state);
  57 }
  58
  59 static int i2c_gpio_getsda(void *data)
  60 {
  61         struct i2c_gpio_private_data *priv = data;
  62
  63         return gpiod_get_value_cansleep(priv->sda);
  64 }
  65
  66 static int i2c_gpio_getscl(void *data)
  67 {
  68         struct i2c_gpio_private_data *priv = data;
  69
  70         return gpiod_get_value_cansleep(priv->scl);
  71 }
  72
  73 #ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
  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 int i2c_gpio_fi_act_on_scl_irq(struct i2c_gpio_private_data *priv,
 166                                        irqreturn_t handler(int, void*))
 167 {
 168         int ret, irq = gpiod_to_irq(priv->scl);
 169
 170         if (irq < 0)
 171                 return irq;
 172
 173         i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 174
 175         ret = gpiod_direction_input(priv->scl);
 176         if (ret)
 177                 goto unlock;
 178
 179         reinit_completion(&priv->scl_irq_completion);
 180
 181         ret = request_irq(irq, handler, IRQF_TRIGGER_FALLING,
 182                           "i2c_gpio_fault_injector_scl_irq", priv);
 183         if (ret)
 184                 goto output;
 185
 186         wait_for_completion_interruptible(&priv->scl_irq_completion);
 187
 188         free_irq(irq, priv);
 189  output:
 190         ret = gpiod_direction_output(priv->scl, 1) ?: ret;
 191  unlock:
 192         i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
 193
 194         return ret;
 195 }
 196
 197 static irqreturn_t lose_arbitration_irq(int irq, void *dev_id)
 198 {
 199         struct i2c_gpio_private_data *priv = dev_id;
 200
 201         setsda(&priv->bit_data, 0);
 202         udelay(priv->scl_irq_data);
 203         setsda(&priv->bit_data, 1);
 204
 205         complete(&priv->scl_irq_completion);
 206
 207         return IRQ_HANDLED;
 208 }
 209
 210 static int fops_lose_arbitration_set(void *data, u64 duration)
 211 {
 212         struct i2c_gpio_private_data *priv = data;
 213
 214         if (duration > 100 * 1000)
 215                 return -EINVAL;
 216
 217         priv->scl_irq_data = duration;
 218         /*
 219          * Interrupt on falling SCL. This ensures that the controller under test
 220          * has really started the transfer. Interrupt on falling SDA did only
 221          * exercise 'bus busy' detection on some HW but not 'arbitration lost'.
 222          * Note that the interrupt latency may cause the first bits to be
 223          * transmitted correctly.
 224          */
 225         return i2c_gpio_fi_act_on_scl_irq(priv, lose_arbitration_irq);
 226 }
 227 DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n");
 228
 229 static irqreturn_t inject_panic_irq(int irq, void *dev_id)
 230 {
 231         struct i2c_gpio_private_data *priv = dev_id;
 232
 233         udelay(priv->scl_irq_data);
 234         panic("I2C fault injector induced panic");
 235
 236         return IRQ_HANDLED;
 237 }
 238
 239 static int fops_inject_panic_set(void *data, u64 duration)
 240 {
 241         struct i2c_gpio_private_data *priv = data;
 242
 243         if (duration > 100 * 1000)
 244                 return -EINVAL;
 245
 246         priv->scl_irq_data = duration;
 247         /*
 248          * Interrupt on falling SCL. This ensures that the controller under test
 249          * has really started the transfer.
 250          */
 251         return i2c_gpio_fi_act_on_scl_irq(priv, inject_panic_irq);
 252 }
 253 DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n");
 254
 255 static void i2c_gpio_fault_injector_init(struct platform_device *pdev)
 256 {
 257         struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
 258
 259         init_completion(&priv->scl_irq_completion);
 260
 261         debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->adap.debugfs,
 262                                    priv, &fops_incomplete_addr_phase);
 263         debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->adap.debugfs,
 264                                    priv, &fops_incomplete_write_byte);
 265         if (priv->bit_data.getscl) {
 266                 debugfs_create_file_unsafe("inject_panic", 0200, priv->adap.debugfs,
 267                                            priv, &fops_inject_panic);
 268                 debugfs_create_file_unsafe("lose_arbitration", 0200, priv->adap.debugfs,
 269                                            priv, &fops_lose_arbitration);
 270         }
 271         debugfs_create_file_unsafe("scl", 0600, priv->adap.debugfs, priv, &fops_scl);
 272         debugfs_create_file_unsafe("sda", 0600, priv->adap.debugfs, priv, &fops_sda);
 273 }
 274 #else
 275 static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
 276 #endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
 277
 278 /* Get i2c-gpio properties from DT or ACPI table */
 279 static void i2c_gpio_get_properties(struct device *dev,
 280                                     struct i2c_gpio_platform_data *pdata)
 281 {
 282         u32 reg;
 283
 284         device_property_read_u32(dev, "i2c-gpio,delay-us", &pdata->udelay);
 285
 286         if (!device_property_read_u32(dev, "i2c-gpio,timeout-ms", &reg))
 287                 pdata->timeout = msecs_to_jiffies(reg);
 288
 289         pdata->sda_is_open_drain =
 290                 device_property_read_bool(dev, "i2c-gpio,sda-open-drain");
 291         pdata->scl_is_open_drain =
 292                 device_property_read_bool(dev, "i2c-gpio,scl-open-drain");
 293         pdata->scl_is_output_only =
 294                 device_property_read_bool(dev, "i2c-gpio,scl-output-only");
 295         pdata->sda_is_output_only =
 296                 device_property_read_bool(dev, "i2c-gpio,sda-output-only");
 297         pdata->sda_has_no_pullup =
 298                 device_property_read_bool(dev, "i2c-gpio,sda-has-no-pullup");
 299         pdata->scl_has_no_pullup =
 300                 device_property_read_bool(dev, "i2c-gpio,scl-has-no-pullup");
 301 }
 302
 303 static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
 304                                            const char *con_id,
 305                                            unsigned int index,
 306                                            enum gpiod_flags gflags)
 307 {
 308         struct gpio_desc *retdesc;
 309         int ret;
 310
 311         retdesc = devm_gpiod_get(dev, con_id, gflags);
 312         if (!IS_ERR(retdesc)) {
 313                 dev_dbg(dev, "got GPIO from name %s\n", con_id);
 314                 return retdesc;
 315         }
 316
 317         retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
 318         if (!IS_ERR(retdesc)) {
 319                 dev_dbg(dev, "got GPIO from index %u\n", index);
 320                 return retdesc;
 321         }
 322
 323         ret = PTR_ERR(retdesc);
 324
 325         /* FIXME: hack in the old code, is this really necessary? */
 326         if (ret == -EINVAL)
 327                 retdesc = ERR_PTR(-EPROBE_DEFER);
 328
 329         /* This happens if the GPIO driver is not yet probed, let's defer */
 330         if (ret == -ENOENT)
 331                 retdesc = ERR_PTR(-EPROBE_DEFER);
 332
 333         if (PTR_ERR(retdesc) != -EPROBE_DEFER)
 334                 dev_err(dev, "error trying to get descriptor: %d\n", ret);
 335
 336         return retdesc;
 337 }
 338
 339 static int i2c_gpio_probe(struct platform_device *pdev)
 340 {
 341         struct i2c_gpio_private_data *priv;
 342         struct i2c_gpio_platform_data *pdata;
 343         struct i2c_algo_bit_data *bit_data;
 344         struct i2c_adapter *adap;
 345         struct device *dev = &pdev->dev;
 346         struct fwnode_handle *fwnode = dev_fwnode(dev);
 347         enum gpiod_flags gflags;
 348         int ret;
 349
 350         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 351         if (!priv)
 352                 return -ENOMEM;
 353
 354         adap = &priv->adap;
 355         bit_data = &priv->bit_data;
 356         pdata = &priv->pdata;
 357
 358         if (fwnode) {
 359                 i2c_gpio_get_properties(dev, pdata);
 360         } else {
 361                 /*
 362                  * If all platform data settings are zero it is OK
 363                  * to not provide any platform data from the board.
 364                  */
 365                 if (dev_get_platdata(dev))
 366                         memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
 367         }
 368
 369         /*
 370          * First get the GPIO pins; if it fails, we'll defer the probe.
 371          * If the SCL/SDA lines are marked "open drain" by platform data or
 372          * device tree then this means that something outside of our control is
 373          * marking these lines to be handled as open drain, and we should just
 374          * handle them as we handle any other output. Else we enforce open
 375          * drain as this is required for an I2C bus.
 376          */
 377         if (pdata->sda_is_open_drain || pdata->sda_has_no_pullup)
 378                 gflags = GPIOD_OUT_HIGH;
 379         else
 380                 gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 381         priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
 382         if (IS_ERR(priv->sda))
 383                 return PTR_ERR(priv->sda);
 384
 385         if (pdata->scl_is_open_drain || pdata->scl_has_no_pullup)
 386                 gflags = GPIOD_OUT_HIGH;
 387         else
 388                 gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
 389         priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
 390         if (IS_ERR(priv->scl))
 391                 return PTR_ERR(priv->scl);
 392
 393         if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl))
 394                 dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
 395         else
 396                 bit_data->can_do_atomic = true;
 397
 398         bit_data->setsda = i2c_gpio_setsda_val;
 399         bit_data->setscl = i2c_gpio_setscl_val;
 400
 401         if (!pdata->scl_is_output_only)
 402                 bit_data->getscl = i2c_gpio_getscl;
 403         if (!pdata->sda_is_output_only)
 404                 bit_data->getsda = i2c_gpio_getsda;
 405
 406         if (pdata->udelay)
 407                 bit_data->udelay = pdata->udelay;
 408         else if (pdata->scl_is_output_only)
 409                 bit_data->udelay = 50;                  /* 10 kHz */
 410         else
 411                 bit_data->udelay = 5;                   /* 100 kHz */
 412
 413         if (pdata->timeout)
 414                 bit_data->timeout = pdata->timeout;
 415         else
 416                 bit_data->timeout = HZ / 10;            /* 100 ms */
 417
 418         bit_data->data = priv;
 419
 420         adap->owner = THIS_MODULE;
 421         if (fwnode)
 422                 strscpy(adap->name, dev_name(dev), sizeof(adap->name));
 423         else
 424                 snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
 425
 426         adap->algo_data = bit_data;
 427         adap->class = I2C_CLASS_HWMON;
 428         adap->dev.parent = dev;
 429         device_set_node(&adap->dev, fwnode);
 430
 431         adap->nr = pdev->id;
 432         ret = i2c_bit_add_numbered_bus(adap);
 433         if (ret)
 434                 return ret;
 435
 436         platform_set_drvdata(pdev, priv);
 437
 438         /*
 439          * FIXME: using global GPIO numbers is not helpful. If/when we
 440          * get accessors to get the actual name of the GPIO line,
 441          * from the descriptor, then provide that instead.
 442          */
 443         dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
 444                  desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
 445                  pdata->scl_is_output_only
 446                  ? ", no clock stretching" : "");
 447
 448         i2c_gpio_fault_injector_init(pdev);
 449
 450         return 0;
 451 }
 452
 453 static void i2c_gpio_remove(struct platform_device *pdev)
 454 {
 455         struct i2c_gpio_private_data *priv;
 456         struct i2c_adapter *adap;
 457
 458         priv = platform_get_drvdata(pdev);
 459         adap = &priv->adap;
 460
 461         i2c_del_adapter(adap);
 462 }
 463
 464 static const struct of_device_id i2c_gpio_dt_ids[] = {
 465         { .compatible = "i2c-gpio", },
 466         { /* sentinel */ }
 467 };
 468
 469 MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
 470
 471 static const struct acpi_device_id i2c_gpio_acpi_match[] = {
 472         { "LOON0005" }, /* LoongArch */
 473         { }
 474 };
 475 MODULE_DEVICE_TABLE(acpi, i2c_gpio_acpi_match);
 476
 477 static struct platform_driver i2c_gpio_driver = {
 478         .driver         = {
 479                 .name   = "i2c-gpio",
 480                 .of_match_table = i2c_gpio_dt_ids,
 481                 .acpi_match_table = i2c_gpio_acpi_match,
 482         },
 483         .probe          = i2c_gpio_probe,
 484         .remove         = i2c_gpio_remove,
 485 };
 486
 487 static int __init i2c_gpio_init(void)
 488 {
 489         int ret;
 490
 491         ret = platform_driver_register(&i2c_gpio_driver);
 492         if (ret)
 493                 printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
 494
 495         return ret;
 496 }
 497 subsys_initcall(i2c_gpio_init);
 498
 499 static void __exit i2c_gpio_exit(void)
 500 {
 501         platform_driver_unregister(&i2c_gpio_driver);
 502 }
 503 module_exit(i2c_gpio_exit);
 504
 505 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 506 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
 507 MODULE_LICENSE("GPL v2");
 508 MODULE_ALIAS("platform:i2c-gpio");