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 #define RAW_TO_GAUSS(asa) ((((asa) + 128) * 3000) / 256)
  89
  90 /*
  91  * Per-instance context data for the device.
  92  */
  93 struct ak8975_data {
  94         struct i2c_client       *client;
  95         struct attribute_group  attrs;
  96         struct mutex            lock;
  97         u8                      asa[3];
  98         long                    raw_to_gauss[3];
  99         u8                      reg_cache[AK8975_MAX_REGS];
 100         int                     eoc_gpio;
 101         int                     eoc_irq;
 102         wait_queue_head_t       data_ready_queue;
 103         unsigned long           flags;
 104 };
 105
 106 static const int ak8975_index_to_reg[] = {
 107         AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
 108 };
 109
 110 /*
 111  * Helper function to write to the I2C device's registers.
 112  */
 113 static int ak8975_write_data(struct i2c_client *client,
 114                              u8 reg, u8 val, u8 mask, u8 shift)
 115 {
 116         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 117         struct ak8975_data *data = iio_priv(indio_dev);
 118         u8 regval;
 119         int ret;
 120
 121         regval = (data->reg_cache[reg] & ~mask) | (val << shift);
 122         ret = i2c_smbus_write_byte_data(client, reg, regval);
 123         if (ret < 0) {
 124                 dev_err(&client->dev, "Write to device fails status %x\n", ret);
 125                 return ret;
 126         }
 127         data->reg_cache[reg] = regval;
 128
 129         return 0;
 130 }
 131
 132 /*
 133  * Handle data ready irq
 134  */
 135 static irqreturn_t ak8975_irq_handler(int irq, void *data)
 136 {
 137         struct ak8975_data *ak8975 = data;
 138
 139         set_bit(0, &ak8975->flags);
 140         wake_up(&ak8975->data_ready_queue);
 141
 142         return IRQ_HANDLED;
 143 }
 144
 145 /*
 146  * Install data ready interrupt handler
 147  */
 148 static int ak8975_setup_irq(struct ak8975_data *data)
 149 {
 150         struct i2c_client *client = data->client;
 151         int rc;
 152         int irq;
 153
 154         if (client->irq)
 155                 irq = client->irq;
 156         else
 157                 irq = gpio_to_irq(data->eoc_gpio);
 158
 159         rc = request_irq(irq, ak8975_irq_handler,
 160                          IRQF_TRIGGER_RISING | IRQF_ONESHOT,
 161                          dev_name(&client->dev), data);
 162         if (rc < 0) {
 163                 dev_err(&client->dev,
 164                         "irq %d request failed, (gpio %d): %d\n",
 165                         irq, data->eoc_gpio, rc);
 166                 return rc;
 167         }
 168
 169         init_waitqueue_head(&data->data_ready_queue);
 170         clear_bit(0, &data->flags);
 171         data->eoc_irq = irq;
 172
 173         return rc;
 174 }
 175
 176
 177 /*
 178  * Perform some start-of-day setup, including reading the asa calibration
 179  * values and caching them.
 180  */
 181 static int ak8975_setup(struct i2c_client *client)
 182 {
 183         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 184         struct ak8975_data *data = iio_priv(indio_dev);
 185         u8 device_id;
 186         int ret;
 187
 188         /* Confirm that the device we're talking to is really an AK8975. */
 189         ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
 190         if (ret < 0) {
 191                 dev_err(&client->dev, "Error reading WIA\n");
 192                 return ret;
 193         }
 194         device_id = ret;
 195         if (device_id != AK8975_DEVICE_ID) {
 196                 dev_err(&client->dev, "Device ak8975 not found\n");
 197                 return -ENODEV;
 198         }
 199
 200         /* Write the fused rom access mode. */
 201         ret = ak8975_write_data(client,
 202                                 AK8975_REG_CNTL,
 203                                 AK8975_REG_CNTL_MODE_FUSE_ROM,
 204                                 AK8975_REG_CNTL_MODE_MASK,
 205                                 AK8975_REG_CNTL_MODE_SHIFT);
 206         if (ret < 0) {
 207                 dev_err(&client->dev, "Error in setting fuse access mode\n");
 208                 return ret;
 209         }
 210
 211         /* Get asa data and store in the device data. */
 212         ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
 213                                             3, data->asa);
 214         if (ret < 0) {
 215                 dev_err(&client->dev, "Not able to read asa data\n");
 216                 return ret;
 217         }
 218
 219         /* After reading fuse ROM data set power-down mode */
 220         ret = ak8975_write_data(client,
 221                                 AK8975_REG_CNTL,
 222                                 AK8975_REG_CNTL_MODE_POWER_DOWN,
 223                                 AK8975_REG_CNTL_MODE_MASK,
 224                                 AK8975_REG_CNTL_MODE_SHIFT);
 225
 226         if (data->eoc_gpio > 0 || client->irq) {
 227                 ret = ak8975_setup_irq(data);
 228                 if (ret < 0) {
 229                         dev_err(&client->dev,
 230                                 "Error setting data ready interrupt\n");
 231                         return ret;
 232                 }
 233         }
 234
 235         if (ret < 0) {
 236                 dev_err(&client->dev, "Error in setting power-down mode\n");
 237                 return ret;
 238         }
 239
 240 /*
 241  * Precalculate scale factor (in Gauss units) for each axis and
 242  * store in the device data.
 243  *
 244  * This scale factor is axis-dependent, and is derived from 3 calibration
 245  * factors ASA(x), ASA(y), and ASA(z).
 246  *
 247  * These ASA values are read from the sensor device at start of day, and
 248  * cached in the device context struct.
 249  *
 250  * Adjusting the flux value with the sensitivity adjustment value should be
 251  * done via the following formula:
 252  *
 253  * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
 254  *
 255  * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
 256  * is the resultant adjusted value.
 257  *
 258  * We reduce the formula to:
 259  *
 260  * Hadj = H * (ASA + 128) / 256
 261  *
 262  * H is in the range of -4096 to 4095.  The magnetometer has a range of
 263  * +-1229uT.  To go from the raw value to uT is:
 264  *
 265  * HuT = H * 1229/4096, or roughly, 3/10.
 266  *
 267  * Since 1uT = 0.01 gauss, our final scale factor becomes:
 268  *
 269  * Hadj = H * ((ASA + 128) / 256) * 3/10 * 1/100
 270  * Hadj = H * ((ASA + 128) * 0.003) / 256
 271  *
 272  * Since ASA doesn't change, we cache the resultant scale factor into the
 273  * device context in ak8975_setup().
 274  */
 275         data->raw_to_gauss[0] = RAW_TO_GAUSS(data->asa[0]);
 276         data->raw_to_gauss[1] = RAW_TO_GAUSS(data->asa[1]);
 277         data->raw_to_gauss[2] = RAW_TO_GAUSS(data->asa[2]);
 278
 279         return 0;
 280 }
 281
 282 static int wait_conversion_complete_gpio(struct ak8975_data *data)
 283 {
 284         struct i2c_client *client = data->client;
 285         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 286         int ret;
 287
 288         /* Wait for the conversion to complete. */
 289         while (timeout_ms) {
 290                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 291                 if (gpio_get_value(data->eoc_gpio))
 292                         break;
 293                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 294         }
 295         if (!timeout_ms) {
 296                 dev_err(&client->dev, "Conversion timeout happened\n");
 297                 return -EINVAL;
 298         }
 299
 300         ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 301         if (ret < 0)
 302                 dev_err(&client->dev, "Error in reading ST1\n");
 303
 304         return ret;
 305 }
 306
 307 static int wait_conversion_complete_polled(struct ak8975_data *data)
 308 {
 309         struct i2c_client *client = data->client;
 310         u8 read_status;
 311         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 312         int ret;
 313
 314         /* Wait for the conversion to complete. */
 315         while (timeout_ms) {
 316                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 317                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 318                 if (ret < 0) {
 319                         dev_err(&client->dev, "Error in reading ST1\n");
 320                         return ret;
 321                 }
 322                 read_status = ret;
 323                 if (read_status)
 324                         break;
 325                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 326         }
 327         if (!timeout_ms) {
 328                 dev_err(&client->dev, "Conversion timeout happened\n");
 329                 return -EINVAL;
 330         }
 331
 332         return read_status;
 333 }
 334
 335 /* Returns 0 if the end of conversion interrupt occured or -ETIME otherwise */
 336 static int wait_conversion_complete_interrupt(struct ak8975_data *data)
 337 {
 338         int ret;
 339
 340         ret = wait_event_timeout(data->data_ready_queue,
 341                                  test_bit(0, &data->flags),
 342                                  AK8975_DATA_READY_TIMEOUT);
 343         clear_bit(0, &data->flags);
 344
 345         return ret > 0 ? 0 : -ETIME;
 346 }
 347
 348 /*
 349  * Emits the raw flux value for the x, y, or z axis.
 350  */
 351 static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 352 {
 353         struct ak8975_data *data = iio_priv(indio_dev);
 354         struct i2c_client *client = data->client;
 355         u16 meas_reg;
 356         s16 raw;
 357         int ret;
 358
 359         mutex_lock(&data->lock);
 360
 361         /* Set up the device for taking a sample. */
 362         ret = ak8975_write_data(client,
 363                                 AK8975_REG_CNTL,
 364                                 AK8975_REG_CNTL_MODE_ONCE,
 365                                 AK8975_REG_CNTL_MODE_MASK,
 366                                 AK8975_REG_CNTL_MODE_SHIFT);
 367         if (ret < 0) {
 368                 dev_err(&client->dev, "Error in setting operating mode\n");
 369                 goto exit;
 370         }
 371
 372         /* Wait for the conversion to complete. */
 373         if (data->eoc_irq)
 374                 ret = wait_conversion_complete_interrupt(data);
 375         else if (gpio_is_valid(data->eoc_gpio))
 376                 ret = wait_conversion_complete_gpio(data);
 377         else
 378                 ret = wait_conversion_complete_polled(data);
 379         if (ret < 0)
 380                 goto exit;
 381
 382         /* This will be executed only for non-interrupt based waiting case */
 383         if (ret & AK8975_REG_ST1_DRDY_MASK) {
 384                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
 385                 if (ret < 0) {
 386                         dev_err(&client->dev, "Error in reading ST2\n");
 387                         goto exit;
 388                 }
 389                 if (ret & (AK8975_REG_ST2_DERR_MASK |
 390                            AK8975_REG_ST2_HOFL_MASK)) {
 391                         dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
 392                         ret = -EINVAL;
 393                         goto exit;
 394                 }
 395         }
 396
 397         /* Read the flux value from the appropriate register
 398            (the register is specified in the iio device attributes). */
 399         ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
 400         if (ret < 0) {
 401                 dev_err(&client->dev, "Read axis data fails\n");
 402                 goto exit;
 403         }
 404         meas_reg = ret;
 405
 406         mutex_unlock(&data->lock);
 407
 408         /* Endian conversion of the measured values. */
 409         raw = (s16) (le16_to_cpu(meas_reg));
 410
 411         /* Clamp to valid range. */
 412         raw = clamp_t(s16, raw, -4096, 4095);
 413         *val = raw;
 414         return IIO_VAL_INT;
 415
 416 exit:
 417         mutex_unlock(&data->lock);
 418         return ret;
 419 }
 420
 421 static int ak8975_read_raw(struct iio_dev *indio_dev,
 422                            struct iio_chan_spec const *chan,
 423                            int *val, int *val2,
 424                            long mask)
 425 {
 426         struct ak8975_data *data = iio_priv(indio_dev);
 427
 428         switch (mask) {
 429         case IIO_CHAN_INFO_RAW:
 430                 return ak8975_read_axis(indio_dev, chan->address, val);
 431         case IIO_CHAN_INFO_SCALE:
 432                 *val = 0;
 433                 *val2 = data->raw_to_gauss[chan->address];
 434                 return IIO_VAL_INT_PLUS_MICRO;
 435         }
 436         return -EINVAL;
 437 }
 438
 439 #define AK8975_CHANNEL(axis, index)                                     \
 440         {                                                               \
 441                 .type = IIO_MAGN,                                       \
 442                 .modified = 1,                                          \
 443                 .channel2 = IIO_MOD_##axis,                             \
 444                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |          \
 445                              BIT(IIO_CHAN_INFO_SCALE),                  \
 446                 .address = index,                                       \
 447         }
 448
 449 static const struct iio_chan_spec ak8975_channels[] = {
 450         AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
 451 };
 452
 453 static const struct iio_info ak8975_info = {
 454         .read_raw = &ak8975_read_raw,
 455         .driver_module = THIS_MODULE,
 456 };
 457
 458 static int ak8975_probe(struct i2c_client *client,
 459                         const struct i2c_device_id *id)
 460 {
 461         struct ak8975_data *data;
 462         struct iio_dev *indio_dev;
 463         int eoc_gpio;
 464         int err;
 465
 466         /* Grab and set up the supplied GPIO. */
 467         if (client->dev.platform_data)
 468                 eoc_gpio = *(int *)(client->dev.platform_data);
 469         else if (client->dev.of_node)
 470                 eoc_gpio = of_get_gpio(client->dev.of_node, 0);
 471         else
 472                 eoc_gpio = -1;
 473
 474         if (eoc_gpio == -EPROBE_DEFER)
 475                 return -EPROBE_DEFER;
 476
 477         /* We may not have a GPIO based IRQ to scan, that is fine, we will
 478            poll if so */
 479         if (gpio_is_valid(eoc_gpio)) {
 480                 err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
 481                 if (err < 0) {
 482                         dev_err(&client->dev,
 483                                 "failed to request GPIO %d, error %d\n",
 484                                                         eoc_gpio, err);
 485                         goto exit;
 486                 }
 487         }
 488
 489         /* Register with IIO */
 490         indio_dev = iio_device_alloc(sizeof(*data));
 491         if (indio_dev == NULL) {
 492                 err = -ENOMEM;
 493                 goto exit_gpio;
 494         }
 495         data = iio_priv(indio_dev);
 496         i2c_set_clientdata(client, indio_dev);
 497
 498         data->client = client;
 499         data->eoc_gpio = eoc_gpio;
 500         data->eoc_irq = 0;
 501
 502         /* Perform some basic start-of-day setup of the device. */
 503         err = ak8975_setup(client);
 504         if (err < 0) {
 505                 dev_err(&client->dev, "AK8975 initialization fails\n");
 506                 goto exit_free_iio;
 507         }
 508
 509         data->client = client;
 510         mutex_init(&data->lock);
 511         data->eoc_gpio = eoc_gpio;
 512         indio_dev->dev.parent = &client->dev;
 513         indio_dev->channels = ak8975_channels;
 514         indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
 515         indio_dev->info = &ak8975_info;
 516         indio_dev->modes = INDIO_DIRECT_MODE;
 517
 518         err = iio_device_register(indio_dev);
 519         if (err < 0)
 520                 goto exit_free_iio;
 521
 522         return 0;
 523
 524 exit_free_iio:
 525         iio_device_free(indio_dev);
 526         if (data->eoc_irq)
 527                 free_irq(data->eoc_irq, data);
 528 exit_gpio:
 529         if (gpio_is_valid(eoc_gpio))
 530                 gpio_free(eoc_gpio);
 531 exit:
 532         return err;
 533 }
 534
 535 static int ak8975_remove(struct i2c_client *client)
 536 {
 537         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 538         struct ak8975_data *data = iio_priv(indio_dev);
 539
 540         iio_device_unregister(indio_dev);
 541
 542         if (data->eoc_irq)
 543                 free_irq(data->eoc_irq, data);
 544
 545         if (gpio_is_valid(data->eoc_gpio))
 546                 gpio_free(data->eoc_gpio);
 547
 548         iio_device_free(indio_dev);
 549
 550         return 0;
 551 }
 552
 553 static const struct i2c_device_id ak8975_id[] = {
 554         {"ak8975", 0},
 555         {}
 556 };
 557
 558 MODULE_DEVICE_TABLE(i2c, ak8975_id);
 559
 560 static const struct of_device_id ak8975_of_match[] = {
 561         { .compatible = "asahi-kasei,ak8975", },
 562         { .compatible = "ak8975", },
 563         { }
 564 };
 565 MODULE_DEVICE_TABLE(of, ak8975_of_match);
 566
 567 static struct i2c_driver ak8975_driver = {
 568         .driver = {
 569                 .name   = "ak8975",
 570                 .of_match_table = ak8975_of_match,
 571         },
 572         .probe          = ak8975_probe,
 573         .remove         = ak8975_remove,
 574         .id_table       = ak8975_id,
 575 };
 576 module_i2c_driver(ak8975_driver);
 577
 578 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 579 MODULE_DESCRIPTION("AK8975 magnetometer driver");
 580 MODULE_LICENSE("GPL");