linux/drivers/staging/iio/magnetometer/ak8975.c
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   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
  33#include <linux/iio/iio.h>
  34#include <linux/iio/sysfs.h>
  35/*
  36 * Register definitions, as well as various shifts and masks to get at the
  37 * individual fields of the registers.
  38 */
  39#define AK8975_REG_WIA                  0x00
  40#define AK8975_DEVICE_ID                0x48
  41
  42#define AK8975_REG_INFO                 0x01
  43
  44#define AK8975_REG_ST1                  0x02
  45#define AK8975_REG_ST1_DRDY_SHIFT       0
  46#define AK8975_REG_ST1_DRDY_MASK        (1 << AK8975_REG_ST1_DRDY_SHIFT)
  47
  48#define AK8975_REG_HXL                  0x03
  49#define AK8975_REG_HXH                  0x04
  50#define AK8975_REG_HYL                  0x05
  51#define AK8975_REG_HYH                  0x06
  52#define AK8975_REG_HZL                  0x07
  53#define AK8975_REG_HZH                  0x08
  54#define AK8975_REG_ST2                  0x09
  55#define AK8975_REG_ST2_DERR_SHIFT       2
  56#define AK8975_REG_ST2_DERR_MASK        (1 << AK8975_REG_ST2_DERR_SHIFT)
  57
  58#define AK8975_REG_ST2_HOFL_SHIFT       3
  59#define AK8975_REG_ST2_HOFL_MASK        (1 << AK8975_REG_ST2_HOFL_SHIFT)
  60
  61#define AK8975_REG_CNTL                 0x0A
  62#define AK8975_REG_CNTL_MODE_SHIFT      0
  63#define AK8975_REG_CNTL_MODE_MASK       (0xF << AK8975_REG_CNTL_MODE_SHIFT)
  64#define AK8975_REG_CNTL_MODE_POWER_DOWN 0
  65#define AK8975_REG_CNTL_MODE_ONCE       1
  66#define AK8975_REG_CNTL_MODE_SELF_TEST  8
  67#define AK8975_REG_CNTL_MODE_FUSE_ROM   0xF
  68
  69#define AK8975_REG_RSVC                 0x0B
  70#define AK8975_REG_ASTC                 0x0C
  71#define AK8975_REG_TS1                  0x0D
  72#define AK8975_REG_TS2                  0x0E
  73#define AK8975_REG_I2CDIS               0x0F
  74#define AK8975_REG_ASAX                 0x10
  75#define AK8975_REG_ASAY                 0x11
  76#define AK8975_REG_ASAZ                 0x12
  77
  78#define AK8975_MAX_REGS                 AK8975_REG_ASAZ
  79
  80/*
  81 * Miscellaneous values.
  82 */
  83#define AK8975_MAX_CONVERSION_TIMEOUT   500
  84#define AK8975_CONVERSION_DONE_POLL_TIME 10
  85
  86/*
  87 * Per-instance context data for the device.
  88 */
  89struct ak8975_data {
  90        struct i2c_client       *client;
  91        struct attribute_group  attrs;
  92        struct mutex            lock;
  93        u8                      asa[3];
  94        long                    raw_to_gauss[3];
  95        u8                      reg_cache[AK8975_MAX_REGS];
  96        int                     eoc_gpio;
  97        int                     eoc_irq;
  98};
  99
 100static 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 */
 107static 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 * Helper function to read a contiguous set of the I2C device's registers.
 128 */
 129static int ak8975_read_data(struct i2c_client *client,
 130                            u8 reg, u8 length, u8 *buffer)
 131{
 132        int ret;
 133        struct i2c_msg msg[2] = {
 134                {
 135                        .addr = client->addr,
 136                        .flags = I2C_M_NOSTART,
 137                        .len = 1,
 138                        .buf = &reg,
 139                }, {
 140                        .addr = client->addr,
 141                        .flags = I2C_M_RD,
 142                        .len = length,
 143                        .buf = buffer,
 144                }
 145        };
 146
 147        ret = i2c_transfer(client->adapter, msg, 2);
 148        if (ret < 0) {
 149                dev_err(&client->dev, "Read from device fails\n");
 150                return ret;
 151        }
 152
 153        return 0;
 154}
 155
 156/*
 157 * Perform some start-of-day setup, including reading the asa calibration
 158 * values and caching them.
 159 */
 160static int ak8975_setup(struct i2c_client *client)
 161{
 162        struct iio_dev *indio_dev = i2c_get_clientdata(client);
 163        struct ak8975_data *data = iio_priv(indio_dev);
 164        u8 device_id;
 165        int ret;
 166
 167        /* Confirm that the device we're talking to is really an AK8975. */
 168        ret = ak8975_read_data(client, AK8975_REG_WIA, 1, &device_id);
 169        if (ret < 0) {
 170                dev_err(&client->dev, "Error reading WIA\n");
 171                return ret;
 172        }
 173        if (device_id != AK8975_DEVICE_ID) {
 174                dev_err(&client->dev, "Device ak8975 not found\n");
 175                return -ENODEV;
 176        }
 177
 178        /* Write the fused rom access mode. */
 179        ret = ak8975_write_data(client,
 180                                AK8975_REG_CNTL,
 181                                AK8975_REG_CNTL_MODE_FUSE_ROM,
 182                                AK8975_REG_CNTL_MODE_MASK,
 183                                AK8975_REG_CNTL_MODE_SHIFT);
 184        if (ret < 0) {
 185                dev_err(&client->dev, "Error in setting fuse access mode\n");
 186                return ret;
 187        }
 188
 189        /* Get asa data and store in the device data. */
 190        ret = ak8975_read_data(client, AK8975_REG_ASAX, 3, data->asa);
 191        if (ret < 0) {
 192                dev_err(&client->dev, "Not able to read asa data\n");
 193                return ret;
 194        }
 195
 196        /* After reading fuse ROM data set power-down mode */
 197        ret = ak8975_write_data(client,
 198                                AK8975_REG_CNTL,
 199                                AK8975_REG_CNTL_MODE_POWER_DOWN,
 200                                AK8975_REG_CNTL_MODE_MASK,
 201                                AK8975_REG_CNTL_MODE_SHIFT);
 202        if (ret < 0) {
 203                dev_err(&client->dev, "Error in setting power-down mode\n");
 204                return ret;
 205        }
 206
 207/*
 208 * Precalculate scale factor (in Gauss units) for each axis and
 209 * store in the device data.
 210 *
 211 * This scale factor is axis-dependent, and is derived from 3 calibration
 212 * factors ASA(x), ASA(y), and ASA(z).
 213 *
 214 * These ASA values are read from the sensor device at start of day, and
 215 * cached in the device context struct.
 216 *
 217 * Adjusting the flux value with the sensitivity adjustment value should be
 218 * done via the following formula:
 219 *
 220 * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
 221 *
 222 * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
 223 * is the resultant adjusted value.
 224 *
 225 * We reduce the formula to:
 226 *
 227 * Hadj = H * (ASA + 128) / 256
 228 *
 229 * H is in the range of -4096 to 4095.  The magnetometer has a range of
 230 * +-1229uT.  To go from the raw value to uT is:
 231 *
 232 * HuT = H * 1229/4096, or roughly, 3/10.
 233 *
 234 * Since 1uT = 100 gauss, our final scale factor becomes:
 235 *
 236 * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
 237 * Hadj = H * ((ASA + 128) * 30 / 256
 238 *
 239 * Since ASA doesn't change, we cache the resultant scale factor into the
 240 * device context in ak8975_setup().
 241 */
 242        data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
 243        data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
 244        data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
 245
 246        return 0;
 247}
 248
 249static int wait_conversion_complete_gpio(struct ak8975_data *data)
 250{
 251        struct i2c_client *client = data->client;
 252        u8 read_status;
 253        u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 254        int ret;
 255
 256        /* Wait for the conversion to complete. */
 257        while (timeout_ms) {
 258                msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 259                if (gpio_get_value(data->eoc_gpio))
 260                        break;
 261                timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 262        }
 263        if (!timeout_ms) {
 264                dev_err(&client->dev, "Conversion timeout happened\n");
 265                return -EINVAL;
 266        }
 267
 268        ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
 269        if (ret < 0) {
 270                dev_err(&client->dev, "Error in reading ST1\n");
 271                return ret;
 272        }
 273        return read_status;
 274}
 275
 276static int wait_conversion_complete_polled(struct ak8975_data *data)
 277{
 278        struct i2c_client *client = data->client;
 279        u8 read_status;
 280        u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 281        int ret;
 282
 283        /* Wait for the conversion to complete. */
 284        while (timeout_ms) {
 285                msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 286                ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
 287                if (ret < 0) {
 288                        dev_err(&client->dev, "Error in reading ST1\n");
 289                        return ret;
 290                }
 291                if (read_status)
 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        return read_status;
 300}
 301
 302/*
 303 * Emits the raw flux value for the x, y, or z axis.
 304 */
 305static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 306{
 307        struct ak8975_data *data = iio_priv(indio_dev);
 308        struct i2c_client *client = data->client;
 309        u16 meas_reg;
 310        s16 raw;
 311        u8 read_status;
 312        int ret;
 313
 314        mutex_lock(&data->lock);
 315
 316        /* Set up the device for taking a sample. */
 317        ret = ak8975_write_data(client,
 318                                AK8975_REG_CNTL,
 319                                AK8975_REG_CNTL_MODE_ONCE,
 320                                AK8975_REG_CNTL_MODE_MASK,
 321                                AK8975_REG_CNTL_MODE_SHIFT);
 322        if (ret < 0) {
 323                dev_err(&client->dev, "Error in setting operating mode\n");
 324                goto exit;
 325        }
 326
 327        /* Wait for the conversion to complete. */
 328        if (gpio_is_valid(data->eoc_gpio))
 329                ret = wait_conversion_complete_gpio(data);
 330        else
 331                ret = wait_conversion_complete_polled(data);
 332        if (ret < 0)
 333                goto exit;
 334
 335        read_status = ret;
 336
 337        if (read_status & AK8975_REG_ST1_DRDY_MASK) {
 338                ret = ak8975_read_data(client, AK8975_REG_ST2, 1, &read_status);
 339                if (ret < 0) {
 340                        dev_err(&client->dev, "Error in reading ST2\n");
 341                        goto exit;
 342                }
 343                if (read_status & (AK8975_REG_ST2_DERR_MASK |
 344                                   AK8975_REG_ST2_HOFL_MASK)) {
 345                        dev_err(&client->dev, "ST2 status error 0x%x\n",
 346                                read_status);
 347                        ret = -EINVAL;
 348                        goto exit;
 349                }
 350        }
 351
 352        /* Read the flux value from the appropriate register
 353           (the register is specified in the iio device attributes). */
 354        ret = ak8975_read_data(client, ak8975_index_to_reg[index],
 355                               2, (u8 *)&meas_reg);
 356        if (ret < 0) {
 357                dev_err(&client->dev, "Read axis data fails\n");
 358                goto exit;
 359        }
 360
 361        mutex_unlock(&data->lock);
 362
 363        /* Endian conversion of the measured values. */
 364        raw = (s16) (le16_to_cpu(meas_reg));
 365
 366        /* Clamp to valid range. */
 367        raw = clamp_t(s16, raw, -4096, 4095);
 368        *val = raw;
 369        return IIO_VAL_INT;
 370
 371exit:
 372        mutex_unlock(&data->lock);
 373        return ret;
 374}
 375
 376static int ak8975_read_raw(struct iio_dev *indio_dev,
 377                           struct iio_chan_spec const *chan,
 378                           int *val, int *val2,
 379                           long mask)
 380{
 381        struct ak8975_data *data = iio_priv(indio_dev);
 382
 383        switch (mask) {
 384        case IIO_CHAN_INFO_RAW:
 385                return ak8975_read_axis(indio_dev, chan->address, val);
 386        case IIO_CHAN_INFO_SCALE:
 387                *val = data->raw_to_gauss[chan->address];
 388                return IIO_VAL_INT;
 389        }
 390        return -EINVAL;
 391}
 392
 393#define AK8975_CHANNEL(axis, index)                                     \
 394        {                                                               \
 395                .type = IIO_MAGN,                                       \
 396                .modified = 1,                                          \
 397                .channel2 = IIO_MOD_##axis,                             \
 398                .info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT |           \
 399                             IIO_CHAN_INFO_SCALE_SEPARATE_BIT,          \
 400                .address = index,                                       \
 401        }
 402
 403static const struct iio_chan_spec ak8975_channels[] = {
 404        AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
 405};
 406
 407static const struct iio_info ak8975_info = {
 408        .read_raw = &ak8975_read_raw,
 409        .driver_module = THIS_MODULE,
 410};
 411
 412static int __devinit ak8975_probe(struct i2c_client *client,
 413                        const struct i2c_device_id *id)
 414{
 415        struct ak8975_data *data;
 416        struct iio_dev *indio_dev;
 417        int eoc_gpio;
 418        int err;
 419
 420        /* Grab and set up the supplied GPIO. */
 421        if (client->dev.platform_data == NULL)
 422                eoc_gpio = -1;
 423        else
 424                eoc_gpio = *(int *)(client->dev.platform_data);
 425
 426        /* We may not have a GPIO based IRQ to scan, that is fine, we will
 427           poll if so */
 428        if (gpio_is_valid(eoc_gpio)) {
 429                err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
 430                if (err < 0) {
 431                        dev_err(&client->dev,
 432                                "failed to request GPIO %d, error %d\n",
 433                                                        eoc_gpio, err);
 434                        goto exit;
 435                }
 436        }
 437
 438        /* Register with IIO */
 439        indio_dev = iio_device_alloc(sizeof(*data));
 440        if (indio_dev == NULL) {
 441                err = -ENOMEM;
 442                goto exit_gpio;
 443        }
 444        data = iio_priv(indio_dev);
 445        i2c_set_clientdata(client, indio_dev);
 446        /* Perform some basic start-of-day setup of the device. */
 447        err = ak8975_setup(client);
 448        if (err < 0) {
 449                dev_err(&client->dev, "AK8975 initialization fails\n");
 450                goto exit_free_iio;
 451        }
 452
 453        data->client = client;
 454        mutex_init(&data->lock);
 455        data->eoc_irq = client->irq;
 456        data->eoc_gpio = eoc_gpio;
 457        indio_dev->dev.parent = &client->dev;
 458        indio_dev->channels = ak8975_channels;
 459        indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
 460        indio_dev->info = &ak8975_info;
 461        indio_dev->modes = INDIO_DIRECT_MODE;
 462
 463        err = iio_device_register(indio_dev);
 464        if (err < 0)
 465                goto exit_free_iio;
 466
 467        return 0;
 468
 469exit_free_iio:
 470        iio_device_free(indio_dev);
 471exit_gpio:
 472        if (gpio_is_valid(eoc_gpio))
 473                gpio_free(eoc_gpio);
 474exit:
 475        return err;
 476}
 477
 478static int __devexit ak8975_remove(struct i2c_client *client)
 479{
 480        struct iio_dev *indio_dev = i2c_get_clientdata(client);
 481        struct ak8975_data *data = iio_priv(indio_dev);
 482
 483        iio_device_unregister(indio_dev);
 484
 485        if (gpio_is_valid(data->eoc_gpio))
 486                gpio_free(data->eoc_gpio);
 487
 488        iio_device_free(indio_dev);
 489
 490        return 0;
 491}
 492
 493static const struct i2c_device_id ak8975_id[] = {
 494        {"ak8975", 0},
 495        {}
 496};
 497
 498MODULE_DEVICE_TABLE(i2c, ak8975_id);
 499
 500static const struct of_device_id ak8975_of_match[] = {
 501        { .compatible = "asahi-kasei,ak8975", },
 502        { .compatible = "ak8975", },
 503        { }
 504};
 505MODULE_DEVICE_TABLE(of, ak8975_of_match);
 506
 507static struct i2c_driver ak8975_driver = {
 508        .driver = {
 509                .name   = "ak8975",
 510                .of_match_table = ak8975_of_match,
 511        },
 512        .probe          = ak8975_probe,
 513        .remove         = __devexit_p(ak8975_remove),
 514        .id_table       = ak8975_id,
 515};
 516module_i2c_driver(ak8975_driver);
 517
 518MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 519MODULE_DESCRIPTION("AK8975 magnetometer driver");
 520MODULE_LICENSE("GPL");
 521