drivers/iio/magnetometer/ak8975.c

   1 /*
   2  * A sensor driver for the magnetometer AK8975.
   3  *
   4  * Magnetic compass sensor driver for monitoring magnetic flux information.
   5  *
   6  * Copyright (c) 2010, NVIDIA Corporation.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful, but WITHOUT
  14  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  16  * more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/kernel.h>
  25 #include <linux/slab.h>
  26 #include <linux/i2c.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/err.h>
  29 #include <linux/mutex.h>
  30 #include <linux/delay.h>
  31 #include <linux/bitops.h>
  32 #include <linux/gpio.h>
  33 #include <linux/of_gpio.h>
  34
  35 #include <linux/iio/iio.h>
  36 #include <linux/iio/sysfs.h>
  37 /*
  38  * Register definitions, as well as various shifts and masks to get at the
  39  * individual fields of the registers.
  40  */
  41 #define AK8975_REG_WIA                  0x00
  42 #define AK8975_DEVICE_ID                0x48
  43
  44 #define AK8975_REG_INFO                 0x01
  45
  46 #define AK8975_REG_ST1                  0x02
  47 #define AK8975_REG_ST1_DRDY_SHIFT       0
  48 #define AK8975_REG_ST1_DRDY_MASK        (1 << AK8975_REG_ST1_DRDY_SHIFT)
  49
  50 #define AK8975_REG_HXL                  0x03
  51 #define AK8975_REG_HXH                  0x04
  52 #define AK8975_REG_HYL                  0x05
  53 #define AK8975_REG_HYH                  0x06
  54 #define AK8975_REG_HZL                  0x07
  55 #define AK8975_REG_HZH                  0x08
  56 #define AK8975_REG_ST2                  0x09
  57 #define AK8975_REG_ST2_DERR_SHIFT       2
  58 #define AK8975_REG_ST2_DERR_MASK        (1 << AK8975_REG_ST2_DERR_SHIFT)
  59
  60 #define AK8975_REG_ST2_HOFL_SHIFT       3
  61 #define AK8975_REG_ST2_HOFL_MASK        (1 << AK8975_REG_ST2_HOFL_SHIFT)
  62
  63 #define AK8975_REG_CNTL                 0x0A
  64 #define AK8975_REG_CNTL_MODE_SHIFT      0
  65 #define AK8975_REG_CNTL_MODE_MASK       (0xF << AK8975_REG_CNTL_MODE_SHIFT)
  66 #define AK8975_REG_CNTL_MODE_POWER_DOWN 0
  67 #define AK8975_REG_CNTL_MODE_ONCE       1
  68 #define AK8975_REG_CNTL_MODE_SELF_TEST  8
  69 #define AK8975_REG_CNTL_MODE_FUSE_ROM   0xF
  70
  71 #define AK8975_REG_RSVC                 0x0B
  72 #define AK8975_REG_ASTC                 0x0C
  73 #define AK8975_REG_TS1                  0x0D
  74 #define AK8975_REG_TS2                  0x0E
  75 #define AK8975_REG_I2CDIS               0x0F
  76 #define AK8975_REG_ASAX                 0x10
  77 #define AK8975_REG_ASAY                 0x11
  78 #define AK8975_REG_ASAZ                 0x12
  79
  80 #define AK8975_MAX_REGS                 AK8975_REG_ASAZ
  81
  82 /*
  83  * Miscellaneous values.
  84  */
  85 #define AK8975_MAX_CONVERSION_TIMEOUT   500
  86 #define AK8975_CONVERSION_DONE_POLL_TIME 10
  87 #define AK8975_DATA_READY_TIMEOUT       ((100*HZ)/1000)
  88
  89 /*
  90  * Per-instance context data for the device.
  91  */
  92 struct ak8975_data {
  93         struct i2c_client       *client;
  94         struct attribute_group  attrs;
  95         struct mutex            lock;
  96         u8                      asa[3];
  97         long                    raw_to_gauss[3];
  98         u8                      reg_cache[AK8975_MAX_REGS];
  99         int                     eoc_gpio;
 100         int                     eoc_irq;
 101         wait_queue_head_t       data_ready_queue;
 102         unsigned long           flags;
 103 };
 104
 105 static const int ak8975_index_to_reg[] = {
 106         AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
 107 };
 108
 109 /*
 110  * Helper function to write to the I2C device's registers.
 111  */
 112 static int ak8975_write_data(struct i2c_client *client,
 113                              u8 reg, u8 val, u8 mask, u8 shift)
 114 {
 115         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 116         struct ak8975_data *data = iio_priv(indio_dev);
 117         u8 regval;
 118         int ret;
 119
 120         regval = (data->reg_cache[reg] & ~mask) | (val << shift);
 121         ret = i2c_smbus_write_byte_data(client, reg, regval);
 122         if (ret < 0) {
 123                 dev_err(&client->dev, "Write to device fails status %x\n", ret);
 124                 return ret;
 125         }
 126         data->reg_cache[reg] = regval;
 127
 128         return 0;
 129 }
 130
 131 /*
 132  * Handle data ready irq
 133  */
 134 static irqreturn_t ak8975_irq_handler(int irq, void *data)
 135 {
 136         struct ak8975_data *ak8975 = data;
 137
 138         set_bit(0, &ak8975->flags);
 139         wake_up(&ak8975->data_ready_queue);
 140
 141         return IRQ_HANDLED;
 142 }
 143
 144 /*
 145  * Install data ready interrupt handler
 146  */
 147 static int ak8975_setup_irq(struct ak8975_data *data)
 148 {
 149         struct i2c_client *client = data->client;
 150         int rc;
 151         int irq;
 152
 153         if (client->irq)
 154                 irq = client->irq;
 155         else
 156                 irq = gpio_to_irq(data->eoc_gpio);
 157
 158         rc = request_irq(irq, ak8975_irq_handler,
 159                          IRQF_TRIGGER_RISING | IRQF_ONESHOT,
 160                          dev_name(&client->dev), data);
 161         if (rc < 0) {
 162                 dev_err(&client->dev,
 163                         "irq %d request failed, (gpio %d): %d\n",
 164                         irq, data->eoc_gpio, rc);
 165                 return rc;
 166         }
 167
 168         init_waitqueue_head(&data->data_ready_queue);
 169         clear_bit(0, &data->flags);
 170         data->eoc_irq = irq;
 171
 172         return rc;
 173 }
 174
 175
 176 /*
 177  * Perform some start-of-day setup, including reading the asa calibration
 178  * values and caching them.
 179  */
 180 static int ak8975_setup(struct i2c_client *client)
 181 {
 182         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 183         struct ak8975_data *data = iio_priv(indio_dev);
 184         u8 device_id;
 185         int ret;
 186
 187         /* Confirm that the device we're talking to is really an AK8975. */
 188         ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
 189         if (ret < 0) {
 190                 dev_err(&client->dev, "Error reading WIA\n");
 191                 return ret;
 192         }
 193         device_id = ret;
 194         if (device_id != AK8975_DEVICE_ID) {
 195                 dev_err(&client->dev, "Device ak8975 not found\n");
 196                 return -ENODEV;
 197         }
 198
 199         /* Write the fused rom access mode. */
 200         ret = ak8975_write_data(client,
 201                                 AK8975_REG_CNTL,
 202                                 AK8975_REG_CNTL_MODE_FUSE_ROM,
 203                                 AK8975_REG_CNTL_MODE_MASK,
 204                                 AK8975_REG_CNTL_MODE_SHIFT);
 205         if (ret < 0) {
 206                 dev_err(&client->dev, "Error in setting fuse access mode\n");
 207                 return ret;
 208         }
 209
 210         /* Get asa data and store in the device data. */
 211         ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
 212                                             3, data->asa);
 213         if (ret < 0) {
 214                 dev_err(&client->dev, "Not able to read asa data\n");
 215                 return ret;
 216         }
 217
 218         /* After reading fuse ROM data set power-down mode */
 219         ret = ak8975_write_data(client,
 220                                 AK8975_REG_CNTL,
 221                                 AK8975_REG_CNTL_MODE_POWER_DOWN,
 222                                 AK8975_REG_CNTL_MODE_MASK,
 223                                 AK8975_REG_CNTL_MODE_SHIFT);
 224
 225         if (data->eoc_gpio > 0 || client->irq) {
 226                 ret = ak8975_setup_irq(data);
 227                 if (ret < 0) {
 228                         dev_err(&client->dev,
 229                                 "Error setting data ready interrupt\n");
 230                         return ret;
 231                 }
 232         }
 233
 234         if (ret < 0) {
 235                 dev_err(&client->dev, "Error in setting power-down mode\n");
 236                 return ret;
 237         }
 238
 239 /*
 240  * Precalculate scale factor (in Gauss units) for each axis and
 241  * store in the device data.
 242  *
 243  * This scale factor is axis-dependent, and is derived from 3 calibration
 244  * factors ASA(x), ASA(y), and ASA(z).
 245  *
 246  * These ASA values are read from the sensor device at start of day, and
 247  * cached in the device context struct.
 248  *
 249  * Adjusting the flux value with the sensitivity adjustment value should be
 250  * done via the following formula:
 251  *
 252  * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
 253  *
 254  * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
 255  * is the resultant adjusted value.
 256  *
 257  * We reduce the formula to:
 258  *
 259  * Hadj = H * (ASA + 128) / 256
 260  *
 261  * H is in the range of -4096 to 4095.  The magnetometer has a range of
 262  * +-1229uT.  To go from the raw value to uT is:
 263  *
 264  * HuT = H * 1229/4096, or roughly, 3/10.
 265  *
 266  * Since 1uT = 0.01 gauss, our final scale factor becomes:
 267  *
 268  * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
 269  * Hadj = H * ((ASA + 128) * 30 / 256
 270  *
 271  * Since ASA doesn't change, we cache the resultant scale factor into the
 272  * device context in ak8975_setup().
 273  */
 274         data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
 275         data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
 276         data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
 277
 278         return 0;
 279 }
 280
 281 static int wait_conversion_complete_gpio(struct ak8975_data *data)
 282 {
 283         struct i2c_client *client = data->client;
 284         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 285         int ret;
 286
 287         /* Wait for the conversion to complete. */
 288         while (timeout_ms) {
 289                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 290                 if (gpio_get_value(data->eoc_gpio))
 291                         break;
 292                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 293         }
 294         if (!timeout_ms) {
 295                 dev_err(&client->dev, "Conversion timeout happened\n");
 296                 return -EINVAL;
 297         }
 298
 299         ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 300         if (ret < 0)
 301                 dev_err(&client->dev, "Error in reading ST1\n");
 302
 303         return ret;
 304 }
 305
 306 static int wait_conversion_complete_polled(struct ak8975_data *data)
 307 {
 308         struct i2c_client *client = data->client;
 309         u8 read_status;
 310         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 311         int ret;
 312
 313         /* Wait for the conversion to complete. */
 314         while (timeout_ms) {
 315                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 316                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 317                 if (ret < 0) {
 318                         dev_err(&client->dev, "Error in reading ST1\n");
 319                         return ret;
 320                 }
 321                 read_status = ret;
 322                 if (read_status)
 323                         break;
 324                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 325         }
 326         if (!timeout_ms) {
 327                 dev_err(&client->dev, "Conversion timeout happened\n");
 328                 return -EINVAL;
 329         }
 330
 331         return read_status;
 332 }
 333
 334 /* Returns 0 if the end of conversion interrupt occured or -ETIME otherwise */
 335 static int wait_conversion_complete_interrupt(struct ak8975_data *data)
 336 {
 337         int ret;
 338
 339         ret = wait_event_timeout(data->data_ready_queue,
 340                                  test_bit(0, &data->flags),
 341                                  AK8975_DATA_READY_TIMEOUT);
 342         clear_bit(0, &data->flags);
 343
 344         return ret > 0 ? 0 : -ETIME;
 345 }
 346
 347 /*
 348  * Emits the raw flux value for the x, y, or z axis.
 349  */
 350 static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 351 {
 352         struct ak8975_data *data = iio_priv(indio_dev);
 353         struct i2c_client *client = data->client;
 354         u16 meas_reg;
 355         s16 raw;
 356         int ret;
 357
 358         mutex_lock(&data->lock);
 359
 360         /* Set up the device for taking a sample. */
 361         ret = ak8975_write_data(client,
 362                                 AK8975_REG_CNTL,
 363                                 AK8975_REG_CNTL_MODE_ONCE,
 364                                 AK8975_REG_CNTL_MODE_MASK,
 365                                 AK8975_REG_CNTL_MODE_SHIFT);
 366         if (ret < 0) {
 367                 dev_err(&client->dev, "Error in setting operating mode\n");
 368                 goto exit;
 369         }
 370
 371         /* Wait for the conversion to complete. */
 372         if (data->eoc_irq)
 373                 ret = wait_conversion_complete_interrupt(data);
 374         else if (gpio_is_valid(data->eoc_gpio))
 375                 ret = wait_conversion_complete_gpio(data);
 376         else
 377                 ret = wait_conversion_complete_polled(data);
 378         if (ret < 0)
 379                 goto exit;
 380
 381         /* This will be executed only for non-interrupt based waiting case */
 382         if (ret & AK8975_REG_ST1_DRDY_MASK) {
 383                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
 384                 if (ret < 0) {
 385                         dev_err(&client->dev, "Error in reading ST2\n");
 386                         goto exit;
 387                 }
 388                 if (ret & (AK8975_REG_ST2_DERR_MASK |
 389                            AK8975_REG_ST2_HOFL_MASK)) {
 390                         dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
 391                         ret = -EINVAL;
 392                         goto exit;
 393                 }
 394         }
 395
 396         /* Read the flux value from the appropriate register
 397            (the register is specified in the iio device attributes). */
 398         ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
 399         if (ret < 0) {
 400                 dev_err(&client->dev, "Read axis data fails\n");
 401                 goto exit;
 402         }
 403         meas_reg = ret;
 404
 405         mutex_unlock(&data->lock);
 406
 407         /* Endian conversion of the measured values. */
 408         raw = (s16) (le16_to_cpu(meas_reg));
 409
 410         /* Clamp to valid range. */
 411         raw = clamp_t(s16, raw, -4096, 4095);
 412         *val = raw;
 413         return IIO_VAL_INT;
 414
 415 exit:
 416         mutex_unlock(&data->lock);
 417         return ret;
 418 }
 419
 420 static int ak8975_read_raw(struct iio_dev *indio_dev,
 421                            struct iio_chan_spec const *chan,
 422                            int *val, int *val2,
 423                            long mask)
 424 {
 425         struct ak8975_data *data = iio_priv(indio_dev);
 426
 427         switch (mask) {
 428         case IIO_CHAN_INFO_RAW:
 429                 return ak8975_read_axis(indio_dev, chan->address, val);
 430         case IIO_CHAN_INFO_SCALE:
 431                 *val = data->raw_to_gauss[chan->address];
 432                 return IIO_VAL_INT;
 433         }
 434         return -EINVAL;
 435 }
 436
 437 #define AK8975_CHANNEL(axis, index)                                     \
 438         {                                                               \
 439                 .type = IIO_MAGN,                                       \
 440                 .modified = 1,                                          \
 441                 .channel2 = IIO_MOD_##axis,                             \
 442                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |          \
 443                              BIT(IIO_CHAN_INFO_SCALE),                  \
 444                 .address = index,                                       \
 445         }
 446
 447 static const struct iio_chan_spec ak8975_channels[] = {
 448         AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
 449 };
 450
 451 static const struct iio_info ak8975_info = {
 452         .read_raw = &ak8975_read_raw,
 453         .driver_module = THIS_MODULE,
 454 };
 455
 456 static int ak8975_probe(struct i2c_client *client,
 457                         const struct i2c_device_id *id)
 458 {
 459         struct ak8975_data *data;
 460         struct iio_dev *indio_dev;
 461         int eoc_gpio;
 462         int err;
 463
 464         /* Grab and set up the supplied GPIO. */
 465         if (client->dev.platform_data)
 466                 eoc_gpio = *(int *)(client->dev.platform_data);
 467         else if (client->dev.of_node)
 468                 eoc_gpio = of_get_gpio(client->dev.of_node, 0);
 469         else
 470                 eoc_gpio = -1;
 471
 472         if (eoc_gpio == -EPROBE_DEFER)
 473                 return -EPROBE_DEFER;
 474
 475         /* We may not have a GPIO based IRQ to scan, that is fine, we will
 476            poll if so */
 477         if (gpio_is_valid(eoc_gpio)) {
 478                 err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
 479                 if (err < 0) {
 480                         dev_err(&client->dev,
 481                                 "failed to request GPIO %d, error %d\n",
 482                                                         eoc_gpio, err);
 483                         goto exit;
 484                 }
 485         }
 486
 487         /* Register with IIO */
 488         indio_dev = iio_device_alloc(sizeof(*data));
 489         if (indio_dev == NULL) {
 490                 err = -ENOMEM;
 491                 goto exit_gpio;
 492         }
 493         data = iio_priv(indio_dev);
 494         i2c_set_clientdata(client, indio_dev);
 495
 496         data->client = client;
 497         data->eoc_gpio = eoc_gpio;
 498         data->eoc_irq = 0;
 499
 500         /* Perform some basic start-of-day setup of the device. */
 501         err = ak8975_setup(client);
 502         if (err < 0) {
 503                 dev_err(&client->dev, "AK8975 initialization fails\n");
 504                 goto exit_free_iio;
 505         }
 506
 507         data->client = client;
 508         mutex_init(&data->lock);
 509         data->eoc_gpio = eoc_gpio;
 510         indio_dev->dev.parent = &client->dev;
 511         indio_dev->channels = ak8975_channels;
 512         indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
 513         indio_dev->info = &ak8975_info;
 514         indio_dev->modes = INDIO_DIRECT_MODE;
 515
 516         err = iio_device_register(indio_dev);
 517         if (err < 0)
 518                 goto exit_free_iio;
 519
 520         return 0;
 521
 522 exit_free_iio:
 523         iio_device_free(indio_dev);
 524         if (data->eoc_irq)
 525                 free_irq(data->eoc_irq, data);
 526 exit_gpio:
 527         if (gpio_is_valid(eoc_gpio))
 528                 gpio_free(eoc_gpio);
 529 exit:
 530         return err;
 531 }
 532
 533 static int ak8975_remove(struct i2c_client *client)
 534 {
 535         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 536         struct ak8975_data *data = iio_priv(indio_dev);
 537
 538         iio_device_unregister(indio_dev);
 539
 540         if (data->eoc_irq)
 541                 free_irq(data->eoc_irq, data);
 542
 543         if (gpio_is_valid(data->eoc_gpio))
 544                 gpio_free(data->eoc_gpio);
 545
 546         iio_device_free(indio_dev);
 547
 548         return 0;
 549 }
 550
 551 static const struct i2c_device_id ak8975_id[] = {
 552         {"ak8975", 0},
 553         {}
 554 };
 555
 556 MODULE_DEVICE_TABLE(i2c, ak8975_id);
 557
 558 static const struct of_device_id ak8975_of_match[] = {
 559         { .compatible = "asahi-kasei,ak8975", },
 560         { .compatible = "ak8975", },
 561         { }
 562 };
 563 MODULE_DEVICE_TABLE(of, ak8975_of_match);
 564
 565 static struct i2c_driver ak8975_driver = {
 566         .driver = {
 567                 .name   = "ak8975",
 568                 .of_match_table = ak8975_of_match,
 569         },
 570         .probe          = ak8975_probe,
 571         .remove         = ak8975_remove,
 572         .id_table       = ak8975_id,
 573 };
 574 module_i2c_driver(ak8975_driver);
 575
 576 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 577 MODULE_DESCRIPTION("AK8975 magnetometer driver");
 578 MODULE_LICENSE("GPL");