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/err.h>
  28 #include <linux/mutex.h>
  29 #include <linux/delay.h>
  30
  31 #include <linux/gpio.h>
  32 #include <linux/of_gpio.h>
  33
  34 #include <linux/iio/iio.h>
  35 #include <linux/iio/sysfs.h>
  36 /*
  37  * Register definitions, as well as various shifts and masks to get at the
  38  * individual fields of the registers.
  39  */
  40 #define AK8975_REG_WIA                  0x00
  41 #define AK8975_DEVICE_ID                0x48
  42
  43 #define AK8975_REG_INFO                 0x01
  44
  45 #define AK8975_REG_ST1                  0x02
  46 #define AK8975_REG_ST1_DRDY_SHIFT       0
  47 #define AK8975_REG_ST1_DRDY_MASK        (1 << AK8975_REG_ST1_DRDY_SHIFT)
  48
  49 #define AK8975_REG_HXL                  0x03
  50 #define AK8975_REG_HXH                  0x04
  51 #define AK8975_REG_HYL                  0x05
  52 #define AK8975_REG_HYH                  0x06
  53 #define AK8975_REG_HZL                  0x07
  54 #define AK8975_REG_HZH                  0x08
  55 #define AK8975_REG_ST2                  0x09
  56 #define AK8975_REG_ST2_DERR_SHIFT       2
  57 #define AK8975_REG_ST2_DERR_MASK        (1 << AK8975_REG_ST2_DERR_SHIFT)
  58
  59 #define AK8975_REG_ST2_HOFL_SHIFT       3
  60 #define AK8975_REG_ST2_HOFL_MASK        (1 << AK8975_REG_ST2_HOFL_SHIFT)
  61
  62 #define AK8975_REG_CNTL                 0x0A
  63 #define AK8975_REG_CNTL_MODE_SHIFT      0
  64 #define AK8975_REG_CNTL_MODE_MASK       (0xF << AK8975_REG_CNTL_MODE_SHIFT)
  65 #define AK8975_REG_CNTL_MODE_POWER_DOWN 0
  66 #define AK8975_REG_CNTL_MODE_ONCE       1
  67 #define AK8975_REG_CNTL_MODE_SELF_TEST  8
  68 #define AK8975_REG_CNTL_MODE_FUSE_ROM   0xF
  69
  70 #define AK8975_REG_RSVC                 0x0B
  71 #define AK8975_REG_ASTC                 0x0C
  72 #define AK8975_REG_TS1                  0x0D
  73 #define AK8975_REG_TS2                  0x0E
  74 #define AK8975_REG_I2CDIS               0x0F
  75 #define AK8975_REG_ASAX                 0x10
  76 #define AK8975_REG_ASAY                 0x11
  77 #define AK8975_REG_ASAZ                 0x12
  78
  79 #define AK8975_MAX_REGS                 AK8975_REG_ASAZ
  80
  81 /*
  82  * Miscellaneous values.
  83  */
  84 #define AK8975_MAX_CONVERSION_TIMEOUT   500
  85 #define AK8975_CONVERSION_DONE_POLL_TIME 10
  86
  87 /*
  88  * Per-instance context data for the device.
  89  */
  90 struct ak8975_data {
  91         struct i2c_client       *client;
  92         struct attribute_group  attrs;
  93         struct mutex            lock;
  94         u8                      asa[3];
  95         long                    raw_to_gauss[3];
  96         u8                      reg_cache[AK8975_MAX_REGS];
  97         int                     eoc_gpio;
  98 };
  99
 100 static const int ak8975_index_to_reg[] = {
 101         AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
 102 };
 103
 104 /*
 105  * Helper function to write to the I2C device's registers.
 106  */
 107 static int ak8975_write_data(struct i2c_client *client,
 108                              u8 reg, u8 val, u8 mask, u8 shift)
 109 {
 110         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 111         struct ak8975_data *data = iio_priv(indio_dev);
 112         u8 regval;
 113         int ret;
 114
 115         regval = (data->reg_cache[reg] & ~mask) | (val << shift);
 116         ret = i2c_smbus_write_byte_data(client, reg, regval);
 117         if (ret < 0) {
 118                 dev_err(&client->dev, "Write to device fails status %x\n", ret);
 119                 return ret;
 120         }
 121         data->reg_cache[reg] = regval;
 122
 123         return 0;
 124 }
 125
 126 /*
 127  * Perform some start-of-day setup, including reading the asa calibration
 128  * values and caching them.
 129  */
 130 static int ak8975_setup(struct i2c_client *client)
 131 {
 132         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 133         struct ak8975_data *data = iio_priv(indio_dev);
 134         u8 device_id;
 135         int ret;
 136
 137         /* Confirm that the device we're talking to is really an AK8975. */
 138         ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
 139         if (ret < 0) {
 140                 dev_err(&client->dev, "Error reading WIA\n");
 141                 return ret;
 142         }
 143         device_id = ret;
 144         if (device_id != AK8975_DEVICE_ID) {
 145                 dev_err(&client->dev, "Device ak8975 not found\n");
 146                 return -ENODEV;
 147         }
 148
 149         /* Write the fused rom access mode. */
 150         ret = ak8975_write_data(client,
 151                                 AK8975_REG_CNTL,
 152                                 AK8975_REG_CNTL_MODE_FUSE_ROM,
 153                                 AK8975_REG_CNTL_MODE_MASK,
 154                                 AK8975_REG_CNTL_MODE_SHIFT);
 155         if (ret < 0) {
 156                 dev_err(&client->dev, "Error in setting fuse access mode\n");
 157                 return ret;
 158         }
 159
 160         /* Get asa data and store in the device data. */
 161         ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
 162                                             3, data->asa);
 163         if (ret < 0) {
 164                 dev_err(&client->dev, "Not able to read asa data\n");
 165                 return ret;
 166         }
 167
 168         /* After reading fuse ROM data set power-down mode */
 169         ret = ak8975_write_data(client,
 170                                 AK8975_REG_CNTL,
 171                                 AK8975_REG_CNTL_MODE_POWER_DOWN,
 172                                 AK8975_REG_CNTL_MODE_MASK,
 173                                 AK8975_REG_CNTL_MODE_SHIFT);
 174         if (ret < 0) {
 175                 dev_err(&client->dev, "Error in setting power-down mode\n");
 176                 return ret;
 177         }
 178
 179 /*
 180  * Precalculate scale factor (in Gauss units) for each axis and
 181  * store in the device data.
 182  *
 183  * This scale factor is axis-dependent, and is derived from 3 calibration
 184  * factors ASA(x), ASA(y), and ASA(z).
 185  *
 186  * These ASA values are read from the sensor device at start of day, and
 187  * cached in the device context struct.
 188  *
 189  * Adjusting the flux value with the sensitivity adjustment value should be
 190  * done via the following formula:
 191  *
 192  * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
 193  *
 194  * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
 195  * is the resultant adjusted value.
 196  *
 197  * We reduce the formula to:
 198  *
 199  * Hadj = H * (ASA + 128) / 256
 200  *
 201  * H is in the range of -4096 to 4095.  The magnetometer has a range of
 202  * +-1229uT.  To go from the raw value to uT is:
 203  *
 204  * HuT = H * 1229/4096, or roughly, 3/10.
 205  *
 206  * Since 1uT = 100 gauss, our final scale factor becomes:
 207  *
 208  * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
 209  * Hadj = H * ((ASA + 128) * 30 / 256
 210  *
 211  * Since ASA doesn't change, we cache the resultant scale factor into the
 212  * device context in ak8975_setup().
 213  */
 214         data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
 215         data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
 216         data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
 217
 218         return 0;
 219 }
 220
 221 static int wait_conversion_complete_gpio(struct ak8975_data *data)
 222 {
 223         struct i2c_client *client = data->client;
 224         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 225         int ret;
 226
 227         /* Wait for the conversion to complete. */
 228         while (timeout_ms) {
 229                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 230                 if (gpio_get_value(data->eoc_gpio))
 231                         break;
 232                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 233         }
 234         if (!timeout_ms) {
 235                 dev_err(&client->dev, "Conversion timeout happened\n");
 236                 return -EINVAL;
 237         }
 238
 239         ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 240         if (ret < 0)
 241                 dev_err(&client->dev, "Error in reading ST1\n");
 242
 243         return ret;
 244 }
 245
 246 static int wait_conversion_complete_polled(struct ak8975_data *data)
 247 {
 248         struct i2c_client *client = data->client;
 249         u8 read_status;
 250         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 251         int ret;
 252
 253         /* Wait for the conversion to complete. */
 254         while (timeout_ms) {
 255                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 256                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 257                 if (ret < 0) {
 258                         dev_err(&client->dev, "Error in reading ST1\n");
 259                         return ret;
 260                 }
 261                 read_status = ret;
 262                 if (read_status)
 263                         break;
 264                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 265         }
 266         if (!timeout_ms) {
 267                 dev_err(&client->dev, "Conversion timeout happened\n");
 268                 return -EINVAL;
 269         }
 270         return read_status;
 271 }
 272
 273 /*
 274  * Emits the raw flux value for the x, y, or z axis.
 275  */
 276 static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 277 {
 278         struct ak8975_data *data = iio_priv(indio_dev);
 279         struct i2c_client *client = data->client;
 280         u16 meas_reg;
 281         s16 raw;
 282         int ret;
 283
 284         mutex_lock(&data->lock);
 285
 286         /* Set up the device for taking a sample. */
 287         ret = ak8975_write_data(client,
 288                                 AK8975_REG_CNTL,
 289                                 AK8975_REG_CNTL_MODE_ONCE,
 290                                 AK8975_REG_CNTL_MODE_MASK,
 291                                 AK8975_REG_CNTL_MODE_SHIFT);
 292         if (ret < 0) {
 293                 dev_err(&client->dev, "Error in setting operating mode\n");
 294                 goto exit;
 295         }
 296
 297         /* Wait for the conversion to complete. */
 298         if (gpio_is_valid(data->eoc_gpio))
 299                 ret = wait_conversion_complete_gpio(data);
 300         else
 301                 ret = wait_conversion_complete_polled(data);
 302         if (ret < 0)
 303                 goto exit;
 304
 305         if (ret & AK8975_REG_ST1_DRDY_MASK) {
 306                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
 307                 if (ret < 0) {
 308                         dev_err(&client->dev, "Error in reading ST2\n");
 309                         goto exit;
 310                 }
 311                 if (ret & (AK8975_REG_ST2_DERR_MASK |
 312                            AK8975_REG_ST2_HOFL_MASK)) {
 313                         dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
 314                         ret = -EINVAL;
 315                         goto exit;
 316                 }
 317         }
 318
 319         /* Read the flux value from the appropriate register
 320            (the register is specified in the iio device attributes). */
 321         ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
 322         if (ret < 0) {
 323                 dev_err(&client->dev, "Read axis data fails\n");
 324                 goto exit;
 325         }
 326         meas_reg = ret;
 327
 328         mutex_unlock(&data->lock);
 329
 330         /* Endian conversion of the measured values. */
 331         raw = (s16) (le16_to_cpu(meas_reg));
 332
 333         /* Clamp to valid range. */
 334         raw = clamp_t(s16, raw, -4096, 4095);
 335         *val = raw;
 336         return IIO_VAL_INT;
 337
 338 exit:
 339         mutex_unlock(&data->lock);
 340         return ret;
 341 }
 342
 343 static int ak8975_read_raw(struct iio_dev *indio_dev,
 344                            struct iio_chan_spec const *chan,
 345                            int *val, int *val2,
 346                            long mask)
 347 {
 348         struct ak8975_data *data = iio_priv(indio_dev);
 349
 350         switch (mask) {
 351         case IIO_CHAN_INFO_RAW:
 352                 return ak8975_read_axis(indio_dev, chan->address, val);
 353         case IIO_CHAN_INFO_SCALE:
 354                 *val = data->raw_to_gauss[chan->address];
 355                 return IIO_VAL_INT;
 356         }
 357         return -EINVAL;
 358 }
 359
 360 #define AK8975_CHANNEL(axis, index)                                     \
 361         {                                                               \
 362                 .type = IIO_MAGN,                                       \
 363                 .modified = 1,                                          \
 364                 .channel2 = IIO_MOD_##axis,                             \
 365                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |          \
 366                              BIT(IIO_CHAN_INFO_SCALE),                  \
 367                 .address = index,                                       \
 368         }
 369
 370 static const struct iio_chan_spec ak8975_channels[] = {
 371         AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
 372 };
 373
 374 static const struct iio_info ak8975_info = {
 375         .read_raw = &ak8975_read_raw,
 376         .driver_module = THIS_MODULE,
 377 };
 378
 379 static int ak8975_probe(struct i2c_client *client,
 380                         const struct i2c_device_id *id)
 381 {
 382         struct ak8975_data *data;
 383         struct iio_dev *indio_dev;
 384         int eoc_gpio;
 385         int err;
 386
 387         /* Grab and set up the supplied GPIO. */
 388         if (client->dev.platform_data)
 389                 eoc_gpio = *(int *)(client->dev.platform_data);
 390         else if (client->dev.of_node)
 391                 eoc_gpio = of_get_gpio(client->dev.of_node, 0);
 392         else
 393                 eoc_gpio = -1;
 394
 395         if (eoc_gpio == -EPROBE_DEFER)
 396                 return -EPROBE_DEFER;
 397
 398         /* We may not have a GPIO based IRQ to scan, that is fine, we will
 399            poll if so */
 400         if (gpio_is_valid(eoc_gpio)) {
 401                 err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
 402                 if (err < 0) {
 403                         dev_err(&client->dev,
 404                                 "failed to request GPIO %d, error %d\n",
 405                                                         eoc_gpio, err);
 406                         goto exit;
 407                 }
 408         }
 409
 410         /* Register with IIO */
 411         indio_dev = iio_device_alloc(sizeof(*data));
 412         if (indio_dev == NULL) {
 413                 err = -ENOMEM;
 414                 goto exit_gpio;
 415         }
 416         data = iio_priv(indio_dev);
 417         i2c_set_clientdata(client, indio_dev);
 418         /* Perform some basic start-of-day setup of the device. */
 419         err = ak8975_setup(client);
 420         if (err < 0) {
 421                 dev_err(&client->dev, "AK8975 initialization fails\n");
 422                 goto exit_free_iio;
 423         }
 424
 425         data->client = client;
 426         mutex_init(&data->lock);
 427         data->eoc_gpio = eoc_gpio;
 428         indio_dev->dev.parent = &client->dev;
 429         indio_dev->channels = ak8975_channels;
 430         indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
 431         indio_dev->info = &ak8975_info;
 432         indio_dev->modes = INDIO_DIRECT_MODE;
 433
 434         err = iio_device_register(indio_dev);
 435         if (err < 0)
 436                 goto exit_free_iio;
 437
 438         return 0;
 439
 440 exit_free_iio:
 441         iio_device_free(indio_dev);
 442 exit_gpio:
 443         if (gpio_is_valid(eoc_gpio))
 444                 gpio_free(eoc_gpio);
 445 exit:
 446         return err;
 447 }
 448
 449 static int ak8975_remove(struct i2c_client *client)
 450 {
 451         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 452         struct ak8975_data *data = iio_priv(indio_dev);
 453
 454         iio_device_unregister(indio_dev);
 455
 456         if (gpio_is_valid(data->eoc_gpio))
 457                 gpio_free(data->eoc_gpio);
 458
 459         iio_device_free(indio_dev);
 460
 461         return 0;
 462 }
 463
 464 static const struct i2c_device_id ak8975_id[] = {
 465         {"ak8975", 0},
 466         {}
 467 };
 468
 469 MODULE_DEVICE_TABLE(i2c, ak8975_id);
 470
 471 static const struct of_device_id ak8975_of_match[] = {
 472         { .compatible = "asahi-kasei,ak8975", },
 473         { .compatible = "ak8975", },
 474         { }
 475 };
 476 MODULE_DEVICE_TABLE(of, ak8975_of_match);
 477
 478 static struct i2c_driver ak8975_driver = {
 479         .driver = {
 480                 .name   = "ak8975",
 481                 .of_match_table = ak8975_of_match,
 482         },
 483         .probe          = ak8975_probe,
 484         .remove         = ak8975_remove,
 485         .id_table       = ak8975_id,
 486 };
 487 module_i2c_driver(ak8975_driver);
 488
 489 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 490 MODULE_DESCRIPTION("AK8975 magnetometer driver");
 491 MODULE_LICENSE("GPL");