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Linux/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");
581 

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