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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 #include <linux/acpi.h>
 35 
 36 #include <linux/iio/iio.h>
 37 #include <linux/iio/sysfs.h>
 38 /*
 39  * Register definitions, as well as various shifts and masks to get at the
 40  * individual fields of the registers.
 41  */
 42 #define AK8975_REG_WIA                  0x00
 43 #define AK8975_DEVICE_ID                0x48
 44 
 45 #define AK8975_REG_INFO                 0x01
 46 
 47 #define AK8975_REG_ST1                  0x02
 48 #define AK8975_REG_ST1_DRDY_SHIFT       0
 49 #define AK8975_REG_ST1_DRDY_MASK        (1 << AK8975_REG_ST1_DRDY_SHIFT)
 50 
 51 #define AK8975_REG_HXL                  0x03
 52 #define AK8975_REG_HXH                  0x04
 53 #define AK8975_REG_HYL                  0x05
 54 #define AK8975_REG_HYH                  0x06
 55 #define AK8975_REG_HZL                  0x07
 56 #define AK8975_REG_HZH                  0x08
 57 #define AK8975_REG_ST2                  0x09
 58 #define AK8975_REG_ST2_DERR_SHIFT       2
 59 #define AK8975_REG_ST2_DERR_MASK        (1 << AK8975_REG_ST2_DERR_SHIFT)
 60 
 61 #define AK8975_REG_ST2_HOFL_SHIFT       3
 62 #define AK8975_REG_ST2_HOFL_MASK        (1 << AK8975_REG_ST2_HOFL_SHIFT)
 63 
 64 #define AK8975_REG_CNTL                 0x0A
 65 #define AK8975_REG_CNTL_MODE_SHIFT      0
 66 #define AK8975_REG_CNTL_MODE_MASK       (0xF << AK8975_REG_CNTL_MODE_SHIFT)
 67 #define AK8975_REG_CNTL_MODE_POWER_DOWN 0
 68 #define AK8975_REG_CNTL_MODE_ONCE       1
 69 #define AK8975_REG_CNTL_MODE_SELF_TEST  8
 70 #define AK8975_REG_CNTL_MODE_FUSE_ROM   0xF
 71 
 72 #define AK8975_REG_RSVC                 0x0B
 73 #define AK8975_REG_ASTC                 0x0C
 74 #define AK8975_REG_TS1                  0x0D
 75 #define AK8975_REG_TS2                  0x0E
 76 #define AK8975_REG_I2CDIS               0x0F
 77 #define AK8975_REG_ASAX                 0x10
 78 #define AK8975_REG_ASAY                 0x11
 79 #define AK8975_REG_ASAZ                 0x12
 80 
 81 #define AK8975_MAX_REGS                 AK8975_REG_ASAZ
 82 
 83 /*
 84  * Miscellaneous values.
 85  */
 86 #define AK8975_MAX_CONVERSION_TIMEOUT   500
 87 #define AK8975_CONVERSION_DONE_POLL_TIME 10
 88 #define AK8975_DATA_READY_TIMEOUT       ((100*HZ)/1000)
 89 #define RAW_TO_GAUSS_8975(asa) ((((asa) + 128) * 3000) / 256)
 90 #define RAW_TO_GAUSS_8963(asa) ((((asa) + 128) * 6000) / 256)
 91 
 92 /* Compatible Asahi Kasei Compass parts */
 93 enum asahi_compass_chipset {
 94         AK8975,
 95         AK8963,
 96 };
 97 
 98 /*
 99  * Per-instance context data for the device.
100  */
101 struct ak8975_data {
102         struct i2c_client       *client;
103         struct attribute_group  attrs;
104         struct mutex            lock;
105         u8                      asa[3];
106         long                    raw_to_gauss[3];
107         u8                      reg_cache[AK8975_MAX_REGS];
108         int                     eoc_gpio;
109         int                     eoc_irq;
110         wait_queue_head_t       data_ready_queue;
111         unsigned long           flags;
112         enum asahi_compass_chipset chipset;
113 };
114 
115 static const int ak8975_index_to_reg[] = {
116         AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
117 };
118 
119 /*
120  * Helper function to write to the I2C device's registers.
121  */
122 static int ak8975_write_data(struct i2c_client *client,
123                              u8 reg, u8 val, u8 mask, u8 shift)
124 {
125         struct iio_dev *indio_dev = i2c_get_clientdata(client);
126         struct ak8975_data *data = iio_priv(indio_dev);
127         u8 regval;
128         int ret;
129 
130         regval = (data->reg_cache[reg] & ~mask) | (val << shift);
131         ret = i2c_smbus_write_byte_data(client, reg, regval);
132         if (ret < 0) {
133                 dev_err(&client->dev, "Write to device fails status %x\n", ret);
134                 return ret;
135         }
136         data->reg_cache[reg] = regval;
137 
138         return 0;
139 }
140 
141 /*
142  * Handle data ready irq
143  */
144 static irqreturn_t ak8975_irq_handler(int irq, void *data)
145 {
146         struct ak8975_data *ak8975 = data;
147 
148         set_bit(0, &ak8975->flags);
149         wake_up(&ak8975->data_ready_queue);
150 
151         return IRQ_HANDLED;
152 }
153 
154 /*
155  * Install data ready interrupt handler
156  */
157 static int ak8975_setup_irq(struct ak8975_data *data)
158 {
159         struct i2c_client *client = data->client;
160         int rc;
161         int irq;
162 
163         if (client->irq)
164                 irq = client->irq;
165         else
166                 irq = gpio_to_irq(data->eoc_gpio);
167 
168         rc = devm_request_irq(&client->dev, irq, ak8975_irq_handler,
169                          IRQF_TRIGGER_RISING | IRQF_ONESHOT,
170                          dev_name(&client->dev), data);
171         if (rc < 0) {
172                 dev_err(&client->dev,
173                         "irq %d request failed, (gpio %d): %d\n",
174                         irq, data->eoc_gpio, rc);
175                 return rc;
176         }
177 
178         init_waitqueue_head(&data->data_ready_queue);
179         clear_bit(0, &data->flags);
180         data->eoc_irq = irq;
181 
182         return rc;
183 }
184 
185 
186 /*
187  * Perform some start-of-day setup, including reading the asa calibration
188  * values and caching them.
189  */
190 static int ak8975_setup(struct i2c_client *client)
191 {
192         struct iio_dev *indio_dev = i2c_get_clientdata(client);
193         struct ak8975_data *data = iio_priv(indio_dev);
194         u8 device_id;
195         int ret;
196 
197         /* Confirm that the device we're talking to is really an AK8975. */
198         ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
199         if (ret < 0) {
200                 dev_err(&client->dev, "Error reading WIA\n");
201                 return ret;
202         }
203         device_id = ret;
204         if (device_id != AK8975_DEVICE_ID) {
205                 dev_err(&client->dev, "Device ak8975 not found\n");
206                 return -ENODEV;
207         }
208 
209         /* Write the fused rom access mode. */
210         ret = ak8975_write_data(client,
211                                 AK8975_REG_CNTL,
212                                 AK8975_REG_CNTL_MODE_FUSE_ROM,
213                                 AK8975_REG_CNTL_MODE_MASK,
214                                 AK8975_REG_CNTL_MODE_SHIFT);
215         if (ret < 0) {
216                 dev_err(&client->dev, "Error in setting fuse access mode\n");
217                 return ret;
218         }
219 
220         /* Get asa data and store in the device data. */
221         ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
222                                             3, data->asa);
223         if (ret < 0) {
224                 dev_err(&client->dev, "Not able to read asa data\n");
225                 return ret;
226         }
227 
228         /* After reading fuse ROM data set power-down mode */
229         ret = ak8975_write_data(client,
230                                 AK8975_REG_CNTL,
231                                 AK8975_REG_CNTL_MODE_POWER_DOWN,
232                                 AK8975_REG_CNTL_MODE_MASK,
233                                 AK8975_REG_CNTL_MODE_SHIFT);
234 
235         if (data->eoc_gpio > 0 || client->irq) {
236                 ret = ak8975_setup_irq(data);
237                 if (ret < 0) {
238                         dev_err(&client->dev,
239                                 "Error setting data ready interrupt\n");
240                         return ret;
241                 }
242         }
243 
244         if (ret < 0) {
245                 dev_err(&client->dev, "Error in setting power-down mode\n");
246                 return ret;
247         }
248 
249 /*
250  * Precalculate scale factor (in Gauss units) for each axis and
251  * store in the device data.
252  *
253  * This scale factor is axis-dependent, and is derived from 3 calibration
254  * factors ASA(x), ASA(y), and ASA(z).
255  *
256  * These ASA values are read from the sensor device at start of day, and
257  * cached in the device context struct.
258  *
259  * Adjusting the flux value with the sensitivity adjustment value should be
260  * done via the following formula:
261  *
262  * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
263  *
264  * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
265  * is the resultant adjusted value.
266  *
267  * We reduce the formula to:
268  *
269  * Hadj = H * (ASA + 128) / 256
270  *
271  * H is in the range of -4096 to 4095.  The magnetometer has a range of
272  * +-1229uT.  To go from the raw value to uT is:
273  *
274  * HuT = H * 1229/4096, or roughly, 3/10.
275  *
276  * Since 1uT = 0.01 gauss, our final scale factor becomes:
277  *
278  * Hadj = H * ((ASA + 128) / 256) * 3/10 * 1/100
279  * Hadj = H * ((ASA + 128) * 0.003) / 256
280  *
281  * Since ASA doesn't change, we cache the resultant scale factor into the
282  * device context in ak8975_setup().
283  */
284         if (data->chipset == AK8963) {
285                 /*
286                  * H range is +-8190 and magnetometer range is +-4912.
287                  * So HuT using the above explanation for 8975,
288                  * 4912/8190 = ~ 6/10.
289                  * So the Hadj should use 6/10 instead of 3/10.
290                  */
291                 data->raw_to_gauss[0] = RAW_TO_GAUSS_8963(data->asa[0]);
292                 data->raw_to_gauss[1] = RAW_TO_GAUSS_8963(data->asa[1]);
293                 data->raw_to_gauss[2] = RAW_TO_GAUSS_8963(data->asa[2]);
294         } else {
295                 data->raw_to_gauss[0] = RAW_TO_GAUSS_8975(data->asa[0]);
296                 data->raw_to_gauss[1] = RAW_TO_GAUSS_8975(data->asa[1]);
297                 data->raw_to_gauss[2] = RAW_TO_GAUSS_8975(data->asa[2]);
298         }
299 
300         return 0;
301 }
302 
303 static int wait_conversion_complete_gpio(struct ak8975_data *data)
304 {
305         struct i2c_client *client = data->client;
306         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
307         int ret;
308 
309         /* Wait for the conversion to complete. */
310         while (timeout_ms) {
311                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
312                 if (gpio_get_value(data->eoc_gpio))
313                         break;
314                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
315         }
316         if (!timeout_ms) {
317                 dev_err(&client->dev, "Conversion timeout happened\n");
318                 return -EINVAL;
319         }
320 
321         ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
322         if (ret < 0)
323                 dev_err(&client->dev, "Error in reading ST1\n");
324 
325         return ret;
326 }
327 
328 static int wait_conversion_complete_polled(struct ak8975_data *data)
329 {
330         struct i2c_client *client = data->client;
331         u8 read_status;
332         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
333         int ret;
334 
335         /* Wait for the conversion to complete. */
336         while (timeout_ms) {
337                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
338                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
339                 if (ret < 0) {
340                         dev_err(&client->dev, "Error in reading ST1\n");
341                         return ret;
342                 }
343                 read_status = ret;
344                 if (read_status)
345                         break;
346                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
347         }
348         if (!timeout_ms) {
349                 dev_err(&client->dev, "Conversion timeout happened\n");
350                 return -EINVAL;
351         }
352 
353         return read_status;
354 }
355 
356 /* Returns 0 if the end of conversion interrupt occured or -ETIME otherwise */
357 static int wait_conversion_complete_interrupt(struct ak8975_data *data)
358 {
359         int ret;
360 
361         ret = wait_event_timeout(data->data_ready_queue,
362                                  test_bit(0, &data->flags),
363                                  AK8975_DATA_READY_TIMEOUT);
364         clear_bit(0, &data->flags);
365 
366         return ret > 0 ? 0 : -ETIME;
367 }
368 
369 /*
370  * Emits the raw flux value for the x, y, or z axis.
371  */
372 static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
373 {
374         struct ak8975_data *data = iio_priv(indio_dev);
375         struct i2c_client *client = data->client;
376         int ret;
377 
378         mutex_lock(&data->lock);
379 
380         /* Set up the device for taking a sample. */
381         ret = ak8975_write_data(client,
382                                 AK8975_REG_CNTL,
383                                 AK8975_REG_CNTL_MODE_ONCE,
384                                 AK8975_REG_CNTL_MODE_MASK,
385                                 AK8975_REG_CNTL_MODE_SHIFT);
386         if (ret < 0) {
387                 dev_err(&client->dev, "Error in setting operating mode\n");
388                 goto exit;
389         }
390 
391         /* Wait for the conversion to complete. */
392         if (data->eoc_irq)
393                 ret = wait_conversion_complete_interrupt(data);
394         else if (gpio_is_valid(data->eoc_gpio))
395                 ret = wait_conversion_complete_gpio(data);
396         else
397                 ret = wait_conversion_complete_polled(data);
398         if (ret < 0)
399                 goto exit;
400 
401         /* This will be executed only for non-interrupt based waiting case */
402         if (ret & AK8975_REG_ST1_DRDY_MASK) {
403                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
404                 if (ret < 0) {
405                         dev_err(&client->dev, "Error in reading ST2\n");
406                         goto exit;
407                 }
408                 if (ret & (AK8975_REG_ST2_DERR_MASK |
409                            AK8975_REG_ST2_HOFL_MASK)) {
410                         dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
411                         ret = -EINVAL;
412                         goto exit;
413                 }
414         }
415 
416         /* Read the flux value from the appropriate register
417            (the register is specified in the iio device attributes). */
418         ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
419         if (ret < 0) {
420                 dev_err(&client->dev, "Read axis data fails\n");
421                 goto exit;
422         }
423 
424         mutex_unlock(&data->lock);
425 
426         /* Clamp to valid range. */
427         *val = clamp_t(s16, ret, -4096, 4095);
428         return IIO_VAL_INT;
429 
430 exit:
431         mutex_unlock(&data->lock);
432         return ret;
433 }
434 
435 static int ak8975_read_raw(struct iio_dev *indio_dev,
436                            struct iio_chan_spec const *chan,
437                            int *val, int *val2,
438                            long mask)
439 {
440         struct ak8975_data *data = iio_priv(indio_dev);
441 
442         switch (mask) {
443         case IIO_CHAN_INFO_RAW:
444                 return ak8975_read_axis(indio_dev, chan->address, val);
445         case IIO_CHAN_INFO_SCALE:
446                 *val = 0;
447                 *val2 = data->raw_to_gauss[chan->address];
448                 return IIO_VAL_INT_PLUS_MICRO;
449         }
450         return -EINVAL;
451 }
452 
453 #define AK8975_CHANNEL(axis, index)                                     \
454         {                                                               \
455                 .type = IIO_MAGN,                                       \
456                 .modified = 1,                                          \
457                 .channel2 = IIO_MOD_##axis,                             \
458                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |          \
459                              BIT(IIO_CHAN_INFO_SCALE),                  \
460                 .address = index,                                       \
461         }
462 
463 static const struct iio_chan_spec ak8975_channels[] = {
464         AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
465 };
466 
467 static const struct iio_info ak8975_info = {
468         .read_raw = &ak8975_read_raw,
469         .driver_module = THIS_MODULE,
470 };
471 
472 static const struct acpi_device_id ak_acpi_match[] = {
473         {"AK8975", AK8975},
474         {"AK8963", AK8963},
475         {"INVN6500", AK8963},
476         { },
477 };
478 MODULE_DEVICE_TABLE(acpi, ak_acpi_match);
479 
480 static char *ak8975_match_acpi_device(struct device *dev,
481                                 enum asahi_compass_chipset *chipset)
482 {
483         const struct acpi_device_id *id;
484 
485         id = acpi_match_device(dev->driver->acpi_match_table, dev);
486         if (!id)
487                 return NULL;
488         *chipset = (int)id->driver_data;
489 
490         return (char *)dev_name(dev);
491 }
492 
493 static int ak8975_probe(struct i2c_client *client,
494                         const struct i2c_device_id *id)
495 {
496         struct ak8975_data *data;
497         struct iio_dev *indio_dev;
498         int eoc_gpio;
499         int err;
500         char *name = NULL;
501 
502         /* Grab and set up the supplied GPIO. */
503         if (client->dev.platform_data)
504                 eoc_gpio = *(int *)(client->dev.platform_data);
505         else if (client->dev.of_node)
506                 eoc_gpio = of_get_gpio(client->dev.of_node, 0);
507         else
508                 eoc_gpio = -1;
509 
510         if (eoc_gpio == -EPROBE_DEFER)
511                 return -EPROBE_DEFER;
512 
513         /* We may not have a GPIO based IRQ to scan, that is fine, we will
514            poll if so */
515         if (gpio_is_valid(eoc_gpio)) {
516                 err = devm_gpio_request_one(&client->dev, eoc_gpio,
517                                                         GPIOF_IN, "ak_8975");
518                 if (err < 0) {
519                         dev_err(&client->dev,
520                                 "failed to request GPIO %d, error %d\n",
521                                                         eoc_gpio, err);
522                         return err;
523                 }
524         }
525 
526         /* Register with IIO */
527         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
528         if (indio_dev == NULL)
529                 return -ENOMEM;
530 
531         data = iio_priv(indio_dev);
532         i2c_set_clientdata(client, indio_dev);
533 
534         data->client = client;
535         data->eoc_gpio = eoc_gpio;
536         data->eoc_irq = 0;
537 
538         /* id will be NULL when enumerated via ACPI */
539         if (id) {
540                 data->chipset =
541                         (enum asahi_compass_chipset)(id->driver_data);
542                 name = (char *) id->name;
543         } else if (ACPI_HANDLE(&client->dev))
544                 name = ak8975_match_acpi_device(&client->dev, &data->chipset);
545         else
546                 return -ENOSYS;
547 
548         dev_dbg(&client->dev, "Asahi compass chip %s\n", name);
549 
550         /* Perform some basic start-of-day setup of the device. */
551         err = ak8975_setup(client);
552         if (err < 0) {
553                 dev_err(&client->dev, "AK8975 initialization fails\n");
554                 return err;
555         }
556 
557         data->client = client;
558         mutex_init(&data->lock);
559         data->eoc_gpio = eoc_gpio;
560         indio_dev->dev.parent = &client->dev;
561         indio_dev->channels = ak8975_channels;
562         indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
563         indio_dev->info = &ak8975_info;
564         indio_dev->modes = INDIO_DIRECT_MODE;
565         indio_dev->name = name;
566         err = devm_iio_device_register(&client->dev, indio_dev);
567         if (err < 0)
568                 return err;
569 
570         return 0;
571 }
572 
573 static const struct i2c_device_id ak8975_id[] = {
574         {"ak8975", AK8975},
575         {"ak8963", AK8963},
576         {}
577 };
578 
579 MODULE_DEVICE_TABLE(i2c, ak8975_id);
580 
581 static const struct of_device_id ak8975_of_match[] = {
582         { .compatible = "asahi-kasei,ak8975", },
583         { .compatible = "ak8975", },
584         { }
585 };
586 MODULE_DEVICE_TABLE(of, ak8975_of_match);
587 
588 static struct i2c_driver ak8975_driver = {
589         .driver = {
590                 .name   = "ak8975",
591                 .of_match_table = ak8975_of_match,
592                 .acpi_match_table = ACPI_PTR(ak_acpi_match),
593         },
594         .probe          = ak8975_probe,
595         .id_table       = ak8975_id,
596 };
597 module_i2c_driver(ak8975_driver);
598 
599 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
600 MODULE_DESCRIPTION("AK8975 magnetometer driver");
601 MODULE_LICENSE("GPL");
602 

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