drivers/staging/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/input/ak8975.h>
  33
  34 #include "../iio.h"
  35 #include "magnet.h"
  36
  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
  88 /*
  89  * Per-instance context data for the device.
  90  */
  91 struct ak8975_data {
  92         struct i2c_client       *client;
  93         struct iio_dev          *indio_dev;
  94         struct attribute_group  attrs;
  95         struct mutex            lock;
  96         u8                      asa[3];
  97         long                    raw_to_gauss[3];
  98         unsigned long           mode;
  99         u8                      reg_cache[AK8975_MAX_REGS];
 100         int                     eoc_gpio;
 101         int                     eoc_irq;
 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         u8 regval;
 111         struct i2c_msg msg;
 112         u8 w_data[2];
 113         int ret = 0;
 114
 115         struct ak8975_data *data = i2c_get_clientdata(client);
 116
 117         regval = data->reg_cache[reg];
 118         regval &= ~mask;
 119         regval |= val << shift;
 120
 121         w_data[0] = reg;
 122         w_data[1] = regval;
 123
 124         msg.addr = client->addr;
 125         msg.flags = 0;
 126         msg.len = 2;
 127         msg.buf = w_data;
 128
 129         ret = i2c_transfer(client->adapter, &msg, 1);
 130         if (ret < 0) {
 131                 dev_err(&client->dev, "Write to device fails status %x\n", ret);
 132                 return ret;
 133         }
 134         data->reg_cache[reg] = regval;
 135
 136         return 0;
 137 }
 138
 139 /*
 140  * Helper function to read a contiguous set of the I2C device's registers.
 141  */
 142 static int ak8975_read_data(struct i2c_client *client,
 143                             u8 reg, u8 length, u8 *buffer)
 144 {
 145         struct i2c_msg msg[2];
 146         u8 w_data[2];
 147         int ret;
 148
 149         w_data[0] = reg;
 150
 151         msg[0].addr = client->addr;
 152         msg[0].flags = I2C_M_NOSTART;   /* set repeated start and write */
 153         msg[0].len = 1;
 154         msg[0].buf = w_data;
 155
 156         msg[1].addr = client->addr;
 157         msg[1].flags = I2C_M_RD;
 158         msg[1].len = length;
 159         msg[1].buf = buffer;
 160
 161         ret = i2c_transfer(client->adapter, msg, 2);
 162         if (ret < 0) {
 163                 dev_err(&client->dev, "Read from device fails\n");
 164                 return ret;
 165         }
 166
 167         return 0;
 168 }
 169
 170 /*
 171  * Perform some start-of-day setup, including reading the asa calibration
 172  * values and caching them.
 173  */
 174 static int ak8975_setup(struct i2c_client *client)
 175 {
 176         struct ak8975_data *data = i2c_get_clientdata(client);
 177         u8 device_id;
 178         int ret;
 179
 180         /* Confirm that the device we're talking to is really an AK8975. */
 181         ret = ak8975_read_data(client, AK8975_REG_WIA, 1, &device_id);
 182         if (ret < 0) {
 183                 dev_err(&client->dev, "Error reading WIA\n");
 184                 return ret;
 185         }
 186         if (device_id != AK8975_DEVICE_ID) {
 187                 dev_err(&client->dev, "Device ak8975 not found\n");
 188                 return -ENODEV;
 189         }
 190
 191         /* Write the fused rom access mode. */
 192         ret = ak8975_write_data(client,
 193                                 AK8975_REG_CNTL,
 194                                 AK8975_REG_CNTL_MODE_FUSE_ROM,
 195                                 AK8975_REG_CNTL_MODE_MASK,
 196                                 AK8975_REG_CNTL_MODE_SHIFT);
 197         if (ret < 0) {
 198                 dev_err(&client->dev, "Error in setting fuse access mode\n");
 199                 return ret;
 200         }
 201
 202         /* Get asa data and store in the device data. */
 203         ret = ak8975_read_data(client, AK8975_REG_ASAX, 3, data->asa);
 204         if (ret < 0) {
 205                 dev_err(&client->dev, "Not able to read asa data\n");
 206                 return ret;
 207         }
 208
 209         /* Precalculate scale factor for each axis and
 210            store in the device data. */
 211         data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
 212         data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
 213         data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
 214
 215         return 0;
 216 }
 217
 218 /*
 219  * Shows the device's mode.  0 = off, 1 = on.
 220  */
 221 static ssize_t show_mode(struct device *dev, struct device_attribute *devattr,
 222                          char *buf)
 223 {
 224         struct iio_dev *indio_dev = dev_get_drvdata(dev);
 225         struct ak8975_data *data = indio_dev->dev_data;
 226
 227         return sprintf(buf, "%lu\n", data->mode);
 228 }
 229
 230 /*
 231  * Sets the device's mode.  0 = off, 1 = on.  The device's mode must be on
 232  * for the magn raw attributes to be available.
 233  */
 234 static ssize_t store_mode(struct device *dev, struct device_attribute *devattr,
 235                           const char *buf, size_t count)
 236 {
 237         struct iio_dev *indio_dev = dev_get_drvdata(dev);
 238         struct ak8975_data *data = indio_dev->dev_data;
 239         struct i2c_client *client = data->client;
 240         unsigned long oval;
 241         int ret;
 242
 243         /* Convert mode string and do some basic sanity checking on it.
 244            only 0 or 1 are valid. */
 245         if (strict_strtoul(buf, 10, &oval))
 246                 return -EINVAL;
 247
 248         if (oval > 1) {
 249                 dev_err(dev, "mode value is not supported\n");
 250                 return -EINVAL;
 251         }
 252
 253         mutex_lock(&data->lock);
 254
 255         /* Write the mode to the device. */
 256         if (data->mode != oval) {
 257                 ret = ak8975_write_data(client,
 258                                         AK8975_REG_CNTL,
 259                                         (u8)oval,
 260                                         AK8975_REG_CNTL_MODE_MASK,
 261                                         AK8975_REG_CNTL_MODE_SHIFT);
 262
 263                 if (ret < 0) {
 264                         dev_err(&client->dev, "Error in setting mode\n");
 265                         mutex_unlock(&data->lock);
 266                         return ret;
 267                 }
 268                 data->mode = oval;
 269         }
 270
 271         mutex_unlock(&data->lock);
 272
 273         return count;
 274 }
 275
 276 /*
 277  * Emits the scale factor to bring the raw value into Gauss units.
 278  *
 279  * This scale factor is axis-dependent, and is derived from 3 calibration
 280  * factors ASA(x), ASA(y), and ASA(z).
 281  *
 282  * These ASA values are read from the sensor device at start of day, and
 283  * cached in the device context struct.
 284  *
 285  * Adjusting the flux value with the sensitivity adjustment value should be
 286  * done via the following formula:
 287  *
 288  * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
 289  *
 290  * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
 291  * is the resultant adjusted value.
 292  *
 293  * We reduce the formula to:
 294  *
 295  * Hadj = H * (ASA + 128) / 256
 296  *
 297  * H is in the range of -4096 to 4095.  The magnetometer has a range of
 298  * +-1229uT.  To go from the raw value to uT is:
 299  *
 300  * HuT = H * 1229/4096, or roughly, 3/10.
 301  *
 302  * Since 1uT = 100 gauss, our final scale factor becomes:
 303  *
 304  * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
 305  * Hadj = H * ((ASA + 128) * 30 / 256
 306  *
 307  * Since ASA doesn't change, we cache the resultant scale factor into the
 308  * device context in ak8975_setup().
 309  */
 310 static ssize_t show_scale(struct device *dev, struct device_attribute *devattr,
 311                           char *buf)
 312 {
 313         struct iio_dev *indio_dev = dev_get_drvdata(dev);
 314         struct ak8975_data *data = indio_dev->dev_data;
 315         struct iio_dev_attr *this_attr = to_iio_dev_attr(devattr);
 316
 317         return sprintf(buf, "%ld\n", data->raw_to_gauss[this_attr->address]);
 318 }
 319
 320 /*
 321  * Emits the raw flux value for the x, y, or z axis.
 322  */
 323 static ssize_t show_raw(struct device *dev, struct device_attribute *devattr,
 324                         char *buf)
 325 {
 326         struct iio_dev *indio_dev = dev_get_drvdata(dev);
 327         struct ak8975_data *data = indio_dev->dev_data;
 328         struct i2c_client *client = data->client;
 329         struct iio_dev_attr *this_attr = to_iio_dev_attr(devattr);
 330         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 331         u16 meas_reg;
 332         s16 raw;
 333         u8 read_status;
 334         int ret;
 335
 336         mutex_lock(&data->lock);
 337
 338         if (data->mode == 0) {
 339                 dev_err(&client->dev, "Operating mode is in power down mode\n");
 340                 ret = -EBUSY;
 341                 goto exit;
 342         }
 343
 344         /* Set up the device for taking a sample. */
 345         ret = ak8975_write_data(client,
 346                                 AK8975_REG_CNTL,
 347                                 AK8975_REG_CNTL_MODE_ONCE,
 348                                 AK8975_REG_CNTL_MODE_MASK,
 349                                 AK8975_REG_CNTL_MODE_SHIFT);
 350         if (ret < 0) {
 351                 dev_err(&client->dev, "Error in setting operating mode\n");
 352                 goto exit;
 353         }
 354
 355         /* Wait for the conversion to complete. */
 356         while (timeout_ms) {
 357                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 358                 if (gpio_get_value(data->eoc_gpio))
 359                         break;
 360                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 361         }
 362         if (!timeout_ms) {
 363                 dev_err(&client->dev, "Conversion timeout happened\n");
 364                 ret = -EINVAL;
 365                 goto exit;
 366         }
 367
 368         ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
 369         if (ret < 0) {
 370                 dev_err(&client->dev, "Error in reading ST1\n");
 371                 goto exit;
 372         }
 373
 374         if (read_status & AK8975_REG_ST1_DRDY_MASK) {
 375                 ret = ak8975_read_data(client, AK8975_REG_ST2, 1, &read_status);
 376                 if (ret < 0) {
 377                         dev_err(&client->dev, "Error in reading ST2\n");
 378                         goto exit;
 379                 }
 380                 if (read_status & (AK8975_REG_ST2_DERR_MASK |
 381                                    AK8975_REG_ST2_HOFL_MASK)) {
 382                         dev_err(&client->dev, "ST2 status error 0x%x\n",
 383                                 read_status);
 384                         ret = -EINVAL;
 385                         goto exit;
 386                 }
 387         }
 388
 389         /* Read the flux value from the appropriate register
 390            (the register is specified in the iio device attributes). */
 391         ret = ak8975_read_data(client, this_attr->address, 2, (u8 *)&meas_reg);
 392         if (ret < 0) {
 393                 dev_err(&client->dev, "Read axis data fails\n");
 394                 goto exit;
 395         }
 396
 397         mutex_unlock(&data->lock);
 398
 399         /* Endian conversion of the measured values. */
 400         raw = (s16) (le16_to_cpu(meas_reg));
 401
 402         /* Clamp to valid range. */
 403         raw = clamp_t(s16, raw, -4096, 4095);
 404
 405         return sprintf(buf, "%d\n", raw);
 406
 407 exit:
 408         mutex_unlock(&data->lock);
 409         return ret;
 410 }
 411
 412 static IIO_DEVICE_ATTR(mode, S_IRUGO | S_IWUSR, show_mode, store_mode, 0);
 413 static IIO_DEV_ATTR_MAGN_X_SCALE(S_IRUGO, show_scale, NULL, 0);
 414 static IIO_DEV_ATTR_MAGN_Y_SCALE(S_IRUGO, show_scale, NULL, 1);
 415 static IIO_DEV_ATTR_MAGN_Z_SCALE(S_IRUGO, show_scale, NULL, 2);
 416 static IIO_DEV_ATTR_MAGN_X(show_raw, AK8975_REG_HXL);
 417 static IIO_DEV_ATTR_MAGN_Y(show_raw, AK8975_REG_HYL);
 418 static IIO_DEV_ATTR_MAGN_Z(show_raw, AK8975_REG_HZL);
 419
 420 static struct attribute *ak8975_attr[] = {
 421         &iio_dev_attr_mode.dev_attr.attr,
 422         &iio_dev_attr_magn_x_scale.dev_attr.attr,
 423         &iio_dev_attr_magn_y_scale.dev_attr.attr,
 424         &iio_dev_attr_magn_z_scale.dev_attr.attr,
 425         &iio_dev_attr_magn_x_raw.dev_attr.attr,
 426         &iio_dev_attr_magn_y_raw.dev_attr.attr,
 427         &iio_dev_attr_magn_z_raw.dev_attr.attr,
 428         NULL
 429 };
 430
 431 static struct attribute_group ak8975_attr_group = {
 432         .attrs = ak8975_attr,
 433 };
 434
 435 static int ak8975_probe(struct i2c_client *client,
 436                         const struct i2c_device_id *id)
 437 {
 438         struct ak8975_data *data;
 439         struct ak8975_platform_data *pdata;
 440         int err;
 441
 442         /* Allocate our device context. */
 443         data = kzalloc(sizeof(struct ak8975_data), GFP_KERNEL);
 444         if (!data) {
 445                 dev_err(&client->dev, "Memory allocation fails\n");
 446                 err = -ENOMEM;
 447                 goto exit;
 448         }
 449
 450         i2c_set_clientdata(client, data);
 451         data->client = client;
 452
 453         mutex_init(&data->lock);
 454
 455         /* Grab and set up the supplied GPIO. */
 456         data->eoc_irq = client->irq;
 457         pdata = client->dev.platform_data;
 458         if (pdata)
 459                 data->eoc_gpio = pdata->gpio;
 460         else
 461                 data->eoc_gpio = irq_to_gpio(client->irq);
 462
 463         if (!data->eoc_gpio) {
 464                 dev_err(&client->dev, "failed, no valid GPIO\n");
 465                 err = -EINVAL;
 466                 goto exit_free;
 467         }
 468
 469         err = gpio_request(data->eoc_gpio, "ak_8975");
 470         if (err < 0) {
 471                 dev_err(&client->dev, "failed to request GPIO %d, error %d\n",
 472                         data->eoc_gpio, err);
 473                 goto exit_free;
 474         }
 475
 476         err = gpio_direction_input(data->eoc_gpio);
 477         if (err < 0) {
 478                 dev_err(&client->dev, "Failed to configure input direction for"
 479                         " GPIO %d, error %d\n", data->eoc_gpio, err);
 480                 goto exit_gpio;
 481         }
 482
 483         /* Perform some basic start-of-day setup of the device. */
 484         err = ak8975_setup(client);
 485         if (err < 0) {
 486                 dev_err(&client->dev, "AK8975 initialization fails\n");
 487                 goto exit_gpio;
 488         }
 489
 490         /* Register with IIO */
 491         data->indio_dev = iio_allocate_device();
 492         if (data->indio_dev == NULL) {
 493                 err = -ENOMEM;
 494                 goto exit_gpio;
 495         }
 496
 497         data->indio_dev->dev.parent = &client->dev;
 498         data->indio_dev->attrs = &ak8975_attr_group;
 499         data->indio_dev->dev_data = (void *)(data);
 500         data->indio_dev->driver_module = THIS_MODULE;
 501         data->indio_dev->modes = INDIO_DIRECT_MODE;
 502
 503         err = iio_device_register(data->indio_dev);
 504         if (err < 0)
 505                 goto exit_free_iio;
 506
 507         return 0;
 508
 509 exit_free_iio:
 510         iio_free_device(data->indio_dev);
 511 exit_gpio:
 512         gpio_free(data->eoc_gpio);
 513 exit_free:
 514         kfree(data);
 515 exit:
 516         return err;
 517 }
 518
 519 static int ak8975_remove(struct i2c_client *client)
 520 {
 521         struct ak8975_data *data = i2c_get_clientdata(client);
 522
 523         iio_device_unregister(data->indio_dev);
 524         iio_free_device(data->indio_dev);
 525
 526         gpio_free(data->eoc_gpio);
 527
 528         kfree(data);
 529
 530         return 0;
 531 }
 532
 533 static const struct i2c_device_id ak8975_id[] = {
 534         {"ak8975", 0},
 535         {}
 536 };
 537
 538 MODULE_DEVICE_TABLE(i2c, ak8975_id);
 539
 540 static struct i2c_driver ak8975_driver = {
 541         .driver = {
 542                 .name   = "ak8975",
 543         },
 544         .probe          = ak8975_probe,
 545         .remove         = __devexit_p(ak8975_remove),
 546         .id_table       = ak8975_id,
 547 };
 548
 549 static int __init ak8975_init(void)
 550 {
 551         return i2c_add_driver(&ak8975_driver);
 552 }
 553
 554 static void __exit ak8975_exit(void)
 555 {
 556         i2c_del_driver(&ak8975_driver);
 557 }
 558
 559 module_init(ak8975_init);
 560 module_exit(ak8975_exit);
 561
 562 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 563 MODULE_DESCRIPTION("AK8975 magnetometer driver");
 564 MODULE_LICENSE("GPL");