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 "../iio.h"
34 #include "magnet.h"
35
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 iio_dev *indio_dev;
93 struct attribute_group attrs;
94 struct mutex lock;
95 u8 asa[3];
96 long raw_to_gauss[3];
97 unsigned long mode;
98 u8 reg_cache[AK8975_MAX_REGS];
99 int eoc_gpio;
100 int eoc_irq;
101 };
102
103 /*
104 * Helper function to write to the I2C device's registers.
105 */
ak8975_write_data(struct i2c_client * client,u8 reg,u8 val,u8 mask,u8 shift)106 static int ak8975_write_data(struct i2c_client *client,
107 u8 reg, u8 val, u8 mask, u8 shift)
108 {
109 u8 regval;
110 struct i2c_msg msg;
111 u8 w_data[2];
112 int ret = 0;
113
114 struct ak8975_data *data = i2c_get_clientdata(client);
115
116 regval = data->reg_cache[reg];
117 regval &= ~mask;
118 regval |= val << shift;
119
120 w_data[0] = reg;
121 w_data[1] = regval;
122
123 msg.addr = client->addr;
124 msg.flags = 0;
125 msg.len = 2;
126 msg.buf = w_data;
127
128 ret = i2c_transfer(client->adapter, &msg, 1);
129 if (ret < 0) {
130 dev_err(&client->dev, "Write to device fails status %x\n", ret);
131 return ret;
132 }
133 data->reg_cache[reg] = regval;
134
135 return 0;
136 }
137
138 /*
139 * Helper function to read a contiguous set of the I2C device's registers.
140 */
ak8975_read_data(struct i2c_client * client,u8 reg,u8 length,u8 * buffer)141 static int ak8975_read_data(struct i2c_client *client,
142 u8 reg, u8 length, u8 *buffer)
143 {
144 struct i2c_msg msg[2];
145 u8 w_data[2];
146 int ret;
147
148 w_data[0] = reg;
149
150 msg[0].addr = client->addr;
151 msg[0].flags = I2C_M_NOSTART; /* set repeated start and write */
152 msg[0].len = 1;
153 msg[0].buf = w_data;
154
155 msg[1].addr = client->addr;
156 msg[1].flags = I2C_M_RD;
157 msg[1].len = length;
158 msg[1].buf = buffer;
159
160 ret = i2c_transfer(client->adapter, msg, 2);
161 if (ret < 0) {
162 dev_err(&client->dev, "Read from device fails\n");
163 return ret;
164 }
165
166 return 0;
167 }
168
169 /*
170 * Perform some start-of-day setup, including reading the asa calibration
171 * values and caching them.
172 */
ak8975_setup(struct i2c_client * client)173 static int ak8975_setup(struct i2c_client *client)
174 {
175 struct ak8975_data *data = i2c_get_clientdata(client);
176 u8 device_id;
177 int ret;
178
179 /* Confirm that the device we're talking to is really an AK8975. */
180 ret = ak8975_read_data(client, AK8975_REG_WIA, 1, &device_id);
181 if (ret < 0) {
182 dev_err(&client->dev, "Error reading WIA\n");
183 return ret;
184 }
185 if (device_id != AK8975_DEVICE_ID) {
186 dev_err(&client->dev, "Device ak8975 not found\n");
187 return -ENODEV;
188 }
189
190 /* Write the fused rom access mode. */
191 ret = ak8975_write_data(client,
192 AK8975_REG_CNTL,
193 AK8975_REG_CNTL_MODE_FUSE_ROM,
194 AK8975_REG_CNTL_MODE_MASK,
195 AK8975_REG_CNTL_MODE_SHIFT);
196 if (ret < 0) {
197 dev_err(&client->dev, "Error in setting fuse access mode\n");
198 return ret;
199 }
200
201 /* Get asa data and store in the device data. */
202 ret = ak8975_read_data(client, AK8975_REG_ASAX, 3, data->asa);
203 if (ret < 0) {
204 dev_err(&client->dev, "Not able to read asa data\n");
205 return ret;
206 }
207
208 /* Precalculate scale factor for each axis and
209 store in the device data. */
210 data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
211 data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
212 data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
213
214 return 0;
215 }
216
217 /*
218 * Shows the device's mode. 0 = off, 1 = on.
219 */
show_mode(struct device * dev,struct device_attribute * devattr,char * buf)220 static ssize_t show_mode(struct device *dev, struct device_attribute *devattr,
221 char *buf)
222 {
223 struct iio_dev *indio_dev = dev_get_drvdata(dev);
224 struct ak8975_data *data = indio_dev->dev_data;
225
226 return sprintf(buf, "%lu\n", data->mode);
227 }
228
229 /*
230 * Sets the device's mode. 0 = off, 1 = on. The device's mode must be on
231 * for the magn raw attributes to be available.
232 */
store_mode(struct device * dev,struct device_attribute * devattr,const char * buf,size_t count)233 static ssize_t store_mode(struct device *dev, struct device_attribute *devattr,
234 const char *buf, size_t count)
235 {
236 struct iio_dev *indio_dev = dev_get_drvdata(dev);
237 struct ak8975_data *data = indio_dev->dev_data;
238 struct i2c_client *client = data->client;
239 unsigned long oval;
240 int ret;
241
242 /* Convert mode string and do some basic sanity checking on it.
243 only 0 or 1 are valid. */
244 if (strict_strtoul(buf, 10, &oval))
245 return -EINVAL;
246
247 if (oval > 1) {
248 dev_err(dev, "mode value is not supported\n");
249 return -EINVAL;
250 }
251
252 mutex_lock(&data->lock);
253
254 /* Write the mode to the device. */
255 if (data->mode != oval) {
256 ret = ak8975_write_data(client,
257 AK8975_REG_CNTL,
258 (u8)oval,
259 AK8975_REG_CNTL_MODE_MASK,
260 AK8975_REG_CNTL_MODE_SHIFT);
261
262 if (ret < 0) {
263 dev_err(&client->dev, "Error in setting mode\n");
264 mutex_unlock(&data->lock);
265 return ret;
266 }
267 data->mode = oval;
268 }
269
270 mutex_unlock(&data->lock);
271
272 return count;
273 }
274
275 /*
276 * Emits the scale factor to bring the raw value into Gauss units.
277 *
278 * This scale factor is axis-dependent, and is derived from 3 calibration
279 * factors ASA(x), ASA(y), and ASA(z).
280 *
281 * These ASA values are read from the sensor device at start of day, and
282 * cached in the device context struct.
283 *
284 * Adjusting the flux value with the sensitivity adjustment value should be
285 * done via the following formula:
286 *
287 * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
288 *
289 * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
290 * is the resultant adjusted value.
291 *
292 * We reduce the formula to:
293 *
294 * Hadj = H * (ASA + 128) / 256
295 *
296 * H is in the range of -4096 to 4095. The magnetometer has a range of
297 * +-1229uT. To go from the raw value to uT is:
298 *
299 * HuT = H * 1229/4096, or roughly, 3/10.
300 *
301 * Since 1uT = 100 gauss, our final scale factor becomes:
302 *
303 * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
304 * Hadj = H * ((ASA + 128) * 30 / 256
305 *
306 * Since ASA doesn't change, we cache the resultant scale factor into the
307 * device context in ak8975_setup().
308 */
show_scale(struct device * dev,struct device_attribute * devattr,char * buf)309 static ssize_t show_scale(struct device *dev, struct device_attribute *devattr,
310 char *buf)
311 {
312 struct iio_dev *indio_dev = dev_get_drvdata(dev);
313 struct ak8975_data *data = indio_dev->dev_data;
314 struct iio_dev_attr *this_attr = to_iio_dev_attr(devattr);
315
316 return sprintf(buf, "%ld\n", data->raw_to_gauss[this_attr->address]);
317 }
318
319 /*
320 * Emits the raw flux value for the x, y, or z axis.
321 */
show_raw(struct device * dev,struct device_attribute * devattr,char * buf)322 static ssize_t show_raw(struct device *dev, struct device_attribute *devattr,
323 char *buf)
324 {
325 struct iio_dev *indio_dev = dev_get_drvdata(dev);
326 struct ak8975_data *data = indio_dev->dev_data;
327 struct i2c_client *client = data->client;
328 struct iio_dev_attr *this_attr = to_iio_dev_attr(devattr);
329 u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
330 u16 meas_reg;
331 s16 raw;
332 u8 read_status;
333 int ret;
334
335 mutex_lock(&data->lock);
336
337 if (data->mode == 0) {
338 dev_err(&client->dev, "Operating mode is in power down mode\n");
339 ret = -EBUSY;
340 goto exit;
341 }
342
343 /* Set up the device for taking a sample. */
344 ret = ak8975_write_data(client,
345 AK8975_REG_CNTL,
346 AK8975_REG_CNTL_MODE_ONCE,
347 AK8975_REG_CNTL_MODE_MASK,
348 AK8975_REG_CNTL_MODE_SHIFT);
349 if (ret < 0) {
350 dev_err(&client->dev, "Error in setting operating mode\n");
351 goto exit;
352 }
353
354 /* Wait for the conversion to complete. */
355 while (timeout_ms) {
356 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
357 if (gpio_get_value(data->eoc_gpio))
358 break;
359 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
360 }
361 if (!timeout_ms) {
362 dev_err(&client->dev, "Conversion timeout happened\n");
363 ret = -EINVAL;
364 goto exit;
365 }
366
367 ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
368 if (ret < 0) {
369 dev_err(&client->dev, "Error in reading ST1\n");
370 goto exit;
371 }
372
373 if (read_status & AK8975_REG_ST1_DRDY_MASK) {
374 ret = ak8975_read_data(client, AK8975_REG_ST2, 1, &read_status);
375 if (ret < 0) {
376 dev_err(&client->dev, "Error in reading ST2\n");
377 goto exit;
378 }
379 if (read_status & (AK8975_REG_ST2_DERR_MASK |
380 AK8975_REG_ST2_HOFL_MASK)) {
381 dev_err(&client->dev, "ST2 status error 0x%x\n",
382 read_status);
383 ret = -EINVAL;
384 goto exit;
385 }
386 }
387
388 /* Read the flux value from the appropriate register
389 (the register is specified in the iio device attributes). */
390 ret = ak8975_read_data(client, this_attr->address, 2, (u8 *)&meas_reg);
391 if (ret < 0) {
392 dev_err(&client->dev, "Read axis data fails\n");
393 goto exit;
394 }
395
396 mutex_unlock(&data->lock);
397
398 /* Endian conversion of the measured values. */
399 raw = (s16) (le16_to_cpu(meas_reg));
400
401 /* Clamp to valid range. */
402 raw = clamp_t(s16, raw, -4096, 4095);
403
404 return sprintf(buf, "%d\n", raw);
405
406 exit:
407 mutex_unlock(&data->lock);
408 return ret;
409 }
410
411 static IIO_DEVICE_ATTR(mode, S_IRUGO | S_IWUSR, show_mode, store_mode, 0);
412 static IIO_DEV_ATTR_MAGN_X_SCALE(S_IRUGO, show_scale, NULL, 0);
413 static IIO_DEV_ATTR_MAGN_Y_SCALE(S_IRUGO, show_scale, NULL, 1);
414 static IIO_DEV_ATTR_MAGN_Z_SCALE(S_IRUGO, show_scale, NULL, 2);
415 static IIO_DEV_ATTR_MAGN_X(show_raw, AK8975_REG_HXL);
416 static IIO_DEV_ATTR_MAGN_Y(show_raw, AK8975_REG_HYL);
417 static IIO_DEV_ATTR_MAGN_Z(show_raw, AK8975_REG_HZL);
418
419 static struct attribute *ak8975_attr[] = {
420 &iio_dev_attr_mode.dev_attr.attr,
421 &iio_dev_attr_magn_x_scale.dev_attr.attr,
422 &iio_dev_attr_magn_y_scale.dev_attr.attr,
423 &iio_dev_attr_magn_z_scale.dev_attr.attr,
424 &iio_dev_attr_magn_x_raw.dev_attr.attr,
425 &iio_dev_attr_magn_y_raw.dev_attr.attr,
426 &iio_dev_attr_magn_z_raw.dev_attr.attr,
427 NULL
428 };
429
430 static struct attribute_group ak8975_attr_group = {
431 .attrs = ak8975_attr,
432 };
433
ak8975_probe(struct i2c_client * client,const struct i2c_device_id * id)434 static int ak8975_probe(struct i2c_client *client,
435 const struct i2c_device_id *id)
436 {
437 struct ak8975_data *data;
438 int err;
439
440 /* Allocate our device context. */
441 data = kzalloc(sizeof(struct ak8975_data), GFP_KERNEL);
442 if (!data) {
443 dev_err(&client->dev, "Memory allocation fails\n");
444 err = -ENOMEM;
445 goto exit;
446 }
447
448 i2c_set_clientdata(client, data);
449 data->client = client;
450
451 mutex_init(&data->lock);
452
453 /* Grab and set up the supplied GPIO. */
454 data->eoc_irq = client->irq;
455 data->eoc_gpio = irq_to_gpio(client->irq);
456
457 if (!data->eoc_gpio) {
458 dev_err(&client->dev, "failed, no valid GPIO\n");
459 err = -EINVAL;
460 goto exit_free;
461 }
462
463 err = gpio_request(data->eoc_gpio, "ak_8975");
464 if (err < 0) {
465 dev_err(&client->dev, "failed to request GPIO %d, error %d\n",
466 data->eoc_gpio, err);
467 goto exit_free;
468 }
469
470 err = gpio_direction_input(data->eoc_gpio);
471 if (err < 0) {
472 dev_err(&client->dev, "Failed to configure input direction for"
473 " GPIO %d, error %d\n", data->eoc_gpio, err);
474 goto exit_gpio;
475 }
476
477 /* Perform some basic start-of-day setup of the device. */
478 err = ak8975_setup(client);
479 if (err < 0) {
480 dev_err(&client->dev, "AK8975 initialization fails\n");
481 goto exit_gpio;
482 }
483
484 /* Register with IIO */
485 data->indio_dev = iio_allocate_device();
486 if (data->indio_dev == NULL) {
487 err = -ENOMEM;
488 goto exit_gpio;
489 }
490
491 data->indio_dev->dev.parent = &client->dev;
492 data->indio_dev->attrs = &ak8975_attr_group;
493 data->indio_dev->dev_data = (void *)(data);
494 data->indio_dev->driver_module = THIS_MODULE;
495 data->indio_dev->modes = INDIO_DIRECT_MODE;
496
497 err = iio_device_register(data->indio_dev);
498 if (err < 0)
499 goto exit_free_iio;
500
501 return 0;
502
503 exit_free_iio:
504 iio_free_device(data->indio_dev);
505 exit_gpio:
506 gpio_free(data->eoc_gpio);
507 exit_free:
508 kfree(data);
509 exit:
510 return err;
511 }
512
ak8975_remove(struct i2c_client * client)513 static int ak8975_remove(struct i2c_client *client)
514 {
515 struct ak8975_data *data = i2c_get_clientdata(client);
516
517 iio_device_unregister(data->indio_dev);
518 iio_free_device(data->indio_dev);
519
520 gpio_free(data->eoc_gpio);
521
522 kfree(data);
523
524 return 0;
525 }
526
527 static const struct i2c_device_id ak8975_id[] = {
528 {"ak8975", 0},
529 {}
530 };
531
532 MODULE_DEVICE_TABLE(i2c, ak8975_id);
533
534 static struct i2c_driver ak8975_driver = {
535 .driver = {
536 .name = "ak8975",
537 },
538 .probe = ak8975_probe,
539 .remove = __devexit_p(ak8975_remove),
540 .id_table = ak8975_id,
541 };
542
ak8975_init(void)543 static int __init ak8975_init(void)
544 {
545 return i2c_add_driver(&ak8975_driver);
546 }
547
ak8975_exit(void)548 static void __exit ak8975_exit(void)
549 {
550 i2c_del_driver(&ak8975_driver);
551 }
552
553 module_init(ak8975_init);
554 module_exit(ak8975_exit);
555
556 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
557 MODULE_DESCRIPTION("AK8975 magnetometer driver");
558 MODULE_LICENSE("GPL");
559