1 /* Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com>
2 * Copyright (c) 2012 Bosch Sensortec GmbH
3 * Copyright (c) 2012 Unixphere AB
4 *
5 * This driver supports the bmp085 and bmp18x digital barometric pressure
6 * and temperature sensors from Bosch Sensortec. The datasheets
7 * are available from their website:
8 * http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf
9 * http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP180-DS000-07.pdf
10 *
11 * A pressure measurement is issued by reading from pressure0_input.
12 * The return value ranges from 30000 to 110000 pascal with a resulution
13 * of 1 pascal (0.01 millibar) which enables measurements from 9000m above
14 * to 500m below sea level.
15 *
16 * The temperature can be read from temp0_input. Values range from
17 * -400 to 850 representing the ambient temperature in degree celsius
18 * multiplied by 10.The resolution is 0.1 celsius.
19 *
20 * Because ambient pressure is temperature dependent, a temperature
21 * measurement will be executed automatically even if the user is reading
22 * from pressure0_input. This happens if the last temperature measurement
23 * has been executed more then one second ago.
24 *
25 * To decrease RMS noise from pressure measurements, the bmp085 can
26 * autonomously calculate the average of up to eight samples. This is
27 * set up by writing to the oversampling sysfs file. Accepted values
28 * are 0, 1, 2 and 3. 2^x when x is the value written to this file
29 * specifies the number of samples used to calculate the ambient pressure.
30 * RMS noise is specified with six pascal (without averaging) and decreases
31 * down to 3 pascal when using an oversampling setting of 3.
32 *
33 * This program is free software; you can redistribute it and/or modify
34 * it under the terms of the GNU General Public License as published by
35 * the Free Software Foundation; either version 2 of the License, or
36 * (at your option) any later version.
37 *
38 * This program is distributed in the hope that it will be useful,
39 * but WITHOUT ANY WARRANTY; without even the implied warranty of
40 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
41 * GNU General Public License for more details.
42 *
43 * You should have received a copy of the GNU General Public License
44 * along with this program; if not, write to the Free Software
45 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
46 */
47
48 #include <linux/module.h>
49 #include <linux/device.h>
50 #include <linux/init.h>
51 #include <linux/slab.h>
52 #include <linux/delay.h>
53 #include <linux/of.h>
54 #include "bmp085.h"
55
56 #define BMP085_CHIP_ID 0x55
57 #define BMP085_CALIBRATION_DATA_START 0xAA
58 #define BMP085_CALIBRATION_DATA_LENGTH 11 /* 16 bit values */
59 #define BMP085_CHIP_ID_REG 0xD0
60 #define BMP085_CTRL_REG 0xF4
61 #define BMP085_TEMP_MEASUREMENT 0x2E
62 #define BMP085_PRESSURE_MEASUREMENT 0x34
63 #define BMP085_CONVERSION_REGISTER_MSB 0xF6
64 #define BMP085_CONVERSION_REGISTER_LSB 0xF7
65 #define BMP085_CONVERSION_REGISTER_XLSB 0xF8
66 #define BMP085_TEMP_CONVERSION_TIME 5
67
68 struct bmp085_calibration_data {
69 s16 AC1, AC2, AC3;
70 u16 AC4, AC5, AC6;
71 s16 B1, B2;
72 s16 MB, MC, MD;
73 };
74
75 struct bmp085_data {
76 struct device *dev;
77 struct regmap *regmap;
78 struct mutex lock;
79 struct bmp085_calibration_data calibration;
80 u8 oversampling_setting;
81 u32 raw_temperature;
82 u32 raw_pressure;
83 u32 temp_measurement_period;
84 unsigned long last_temp_measurement;
85 u8 chip_id;
86 s32 b6; /* calculated temperature correction coefficient */
87 };
88
bmp085_read_calibration_data(struct bmp085_data * data)89 static s32 bmp085_read_calibration_data(struct bmp085_data *data)
90 {
91 u16 tmp[BMP085_CALIBRATION_DATA_LENGTH];
92 struct bmp085_calibration_data *cali = &(data->calibration);
93 s32 status = regmap_bulk_read(data->regmap,
94 BMP085_CALIBRATION_DATA_START, (u8 *)tmp,
95 (BMP085_CALIBRATION_DATA_LENGTH << 1));
96 if (status < 0)
97 return status;
98
99 cali->AC1 = be16_to_cpu(tmp[0]);
100 cali->AC2 = be16_to_cpu(tmp[1]);
101 cali->AC3 = be16_to_cpu(tmp[2]);
102 cali->AC4 = be16_to_cpu(tmp[3]);
103 cali->AC5 = be16_to_cpu(tmp[4]);
104 cali->AC6 = be16_to_cpu(tmp[5]);
105 cali->B1 = be16_to_cpu(tmp[6]);
106 cali->B2 = be16_to_cpu(tmp[7]);
107 cali->MB = be16_to_cpu(tmp[8]);
108 cali->MC = be16_to_cpu(tmp[9]);
109 cali->MD = be16_to_cpu(tmp[10]);
110 return 0;
111 }
112
bmp085_update_raw_temperature(struct bmp085_data * data)113 static s32 bmp085_update_raw_temperature(struct bmp085_data *data)
114 {
115 u16 tmp;
116 s32 status;
117
118 mutex_lock(&data->lock);
119 status = regmap_write(data->regmap, BMP085_CTRL_REG,
120 BMP085_TEMP_MEASUREMENT);
121 if (status < 0) {
122 dev_err(data->dev,
123 "Error while requesting temperature measurement.\n");
124 goto exit;
125 }
126 msleep(BMP085_TEMP_CONVERSION_TIME);
127
128 status = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB,
129 &tmp, sizeof(tmp));
130 if (status < 0) {
131 dev_err(data->dev,
132 "Error while reading temperature measurement result\n");
133 goto exit;
134 }
135 data->raw_temperature = be16_to_cpu(tmp);
136 data->last_temp_measurement = jiffies;
137 status = 0; /* everything ok, return 0 */
138
139 exit:
140 mutex_unlock(&data->lock);
141 return status;
142 }
143
bmp085_update_raw_pressure(struct bmp085_data * data)144 static s32 bmp085_update_raw_pressure(struct bmp085_data *data)
145 {
146 u32 tmp = 0;
147 s32 status;
148
149 mutex_lock(&data->lock);
150 status = regmap_write(data->regmap, BMP085_CTRL_REG,
151 BMP085_PRESSURE_MEASUREMENT +
152 (data->oversampling_setting << 6));
153 if (status < 0) {
154 dev_err(data->dev,
155 "Error while requesting pressure measurement.\n");
156 goto exit;
157 }
158
159 /* wait for the end of conversion */
160 msleep(2+(3 << data->oversampling_setting));
161
162 /* copy data into a u32 (4 bytes), but skip the first byte. */
163 status = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB,
164 ((u8 *)&tmp)+1, 3);
165 if (status < 0) {
166 dev_err(data->dev,
167 "Error while reading pressure measurement results\n");
168 goto exit;
169 }
170 data->raw_pressure = be32_to_cpu((tmp));
171 data->raw_pressure >>= (8-data->oversampling_setting);
172 status = 0; /* everything ok, return 0 */
173
174 exit:
175 mutex_unlock(&data->lock);
176 return status;
177 }
178
179 /*
180 * This function starts the temperature measurement and returns the value
181 * in tenth of a degree celsius.
182 */
bmp085_get_temperature(struct bmp085_data * data,int * temperature)183 static s32 bmp085_get_temperature(struct bmp085_data *data, int *temperature)
184 {
185 struct bmp085_calibration_data *cali = &data->calibration;
186 long x1, x2;
187 int status;
188
189 status = bmp085_update_raw_temperature(data);
190 if (status < 0)
191 goto exit;
192
193 x1 = ((data->raw_temperature - cali->AC6) * cali->AC5) >> 15;
194 x2 = (cali->MC << 11) / (x1 + cali->MD);
195 data->b6 = x1 + x2 - 4000;
196 /* if NULL just update b6. Used for pressure only measurements */
197 if (temperature != NULL)
198 *temperature = (x1+x2+8) >> 4;
199
200 exit:
201 return status;
202 }
203
204 /*
205 * This function starts the pressure measurement and returns the value
206 * in millibar. Since the pressure depends on the ambient temperature,
207 * a temperature measurement is executed according to the given temperature
208 * measurement period (default is 1 sec boundary). This period could vary
209 * and needs to be adjusted according to the sensor environment, i.e. if big
210 * temperature variations then the temperature needs to be read out often.
211 */
bmp085_get_pressure(struct bmp085_data * data,int * pressure)212 static s32 bmp085_get_pressure(struct bmp085_data *data, int *pressure)
213 {
214 struct bmp085_calibration_data *cali = &data->calibration;
215 s32 x1, x2, x3, b3;
216 u32 b4, b7;
217 s32 p;
218 int status;
219
220 /* alt least every second force an update of the ambient temperature */
221 if ((data->last_temp_measurement == 0) ||
222 time_is_before_jiffies(data->last_temp_measurement + 1*HZ)) {
223 status = bmp085_get_temperature(data, NULL);
224 if (status < 0)
225 return status;
226 }
227
228 status = bmp085_update_raw_pressure(data);
229 if (status < 0)
230 return status;
231
232 x1 = (data->b6 * data->b6) >> 12;
233 x1 *= cali->B2;
234 x1 >>= 11;
235
236 x2 = cali->AC2 * data->b6;
237 x2 >>= 11;
238
239 x3 = x1 + x2;
240
241 b3 = (((((s32)cali->AC1) * 4 + x3) << data->oversampling_setting) + 2);
242 b3 >>= 2;
243
244 x1 = (cali->AC3 * data->b6) >> 13;
245 x2 = (cali->B1 * ((data->b6 * data->b6) >> 12)) >> 16;
246 x3 = (x1 + x2 + 2) >> 2;
247 b4 = (cali->AC4 * (u32)(x3 + 32768)) >> 15;
248
249 b7 = ((u32)data->raw_pressure - b3) *
250 (50000 >> data->oversampling_setting);
251 p = ((b7 < 0x80000000) ? ((b7 << 1) / b4) : ((b7 / b4) * 2));
252
253 x1 = p >> 8;
254 x1 *= x1;
255 x1 = (x1 * 3038) >> 16;
256 x2 = (-7357 * p) >> 16;
257 p += (x1 + x2 + 3791) >> 4;
258
259 *pressure = p;
260
261 return 0;
262 }
263
264 /*
265 * This function sets the chip-internal oversampling. Valid values are 0..3.
266 * The chip will use 2^oversampling samples for internal averaging.
267 * This influences the measurement time and the accuracy; larger values
268 * increase both. The datasheet gives an overview on how measurement time,
269 * accuracy and noise correlate.
270 */
bmp085_set_oversampling(struct bmp085_data * data,unsigned char oversampling)271 static void bmp085_set_oversampling(struct bmp085_data *data,
272 unsigned char oversampling)
273 {
274 if (oversampling > 3)
275 oversampling = 3;
276 data->oversampling_setting = oversampling;
277 }
278
279 /*
280 * Returns the currently selected oversampling. Range: 0..3
281 */
bmp085_get_oversampling(struct bmp085_data * data)282 static unsigned char bmp085_get_oversampling(struct bmp085_data *data)
283 {
284 return data->oversampling_setting;
285 }
286
287 /* sysfs callbacks */
set_oversampling(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)288 static ssize_t set_oversampling(struct device *dev,
289 struct device_attribute *attr,
290 const char *buf, size_t count)
291 {
292 struct bmp085_data *data = dev_get_drvdata(dev);
293 unsigned long oversampling;
294 int err = kstrtoul(buf, 10, &oversampling);
295
296 if (err == 0) {
297 mutex_lock(&data->lock);
298 bmp085_set_oversampling(data, oversampling);
299 mutex_unlock(&data->lock);
300 return count;
301 }
302
303 return err;
304 }
305
show_oversampling(struct device * dev,struct device_attribute * attr,char * buf)306 static ssize_t show_oversampling(struct device *dev,
307 struct device_attribute *attr, char *buf)
308 {
309 struct bmp085_data *data = dev_get_drvdata(dev);
310
311 return sprintf(buf, "%u\n", bmp085_get_oversampling(data));
312 }
313 static DEVICE_ATTR(oversampling, S_IWUSR | S_IRUGO,
314 show_oversampling, set_oversampling);
315
316
show_temperature(struct device * dev,struct device_attribute * attr,char * buf)317 static ssize_t show_temperature(struct device *dev,
318 struct device_attribute *attr, char *buf)
319 {
320 int temperature;
321 int status;
322 struct bmp085_data *data = dev_get_drvdata(dev);
323
324 status = bmp085_get_temperature(data, &temperature);
325 if (status < 0)
326 return status;
327 else
328 return sprintf(buf, "%d\n", temperature);
329 }
330 static DEVICE_ATTR(temp0_input, S_IRUGO, show_temperature, NULL);
331
332
show_pressure(struct device * dev,struct device_attribute * attr,char * buf)333 static ssize_t show_pressure(struct device *dev,
334 struct device_attribute *attr, char *buf)
335 {
336 int pressure;
337 int status;
338 struct bmp085_data *data = dev_get_drvdata(dev);
339
340 status = bmp085_get_pressure(data, &pressure);
341 if (status < 0)
342 return status;
343 else
344 return sprintf(buf, "%d\n", pressure);
345 }
346 static DEVICE_ATTR(pressure0_input, S_IRUGO, show_pressure, NULL);
347
348
349 static struct attribute *bmp085_attributes[] = {
350 &dev_attr_temp0_input.attr,
351 &dev_attr_pressure0_input.attr,
352 &dev_attr_oversampling.attr,
353 NULL
354 };
355
356 static const struct attribute_group bmp085_attr_group = {
357 .attrs = bmp085_attributes,
358 };
359
bmp085_detect(struct device * dev)360 int bmp085_detect(struct device *dev)
361 {
362 struct bmp085_data *data = dev_get_drvdata(dev);
363 unsigned int id;
364 int ret;
365
366 ret = regmap_read(data->regmap, BMP085_CHIP_ID_REG, &id);
367 if (ret < 0)
368 return ret;
369
370 if (id != data->chip_id)
371 return -ENODEV;
372
373 return 0;
374 }
375 EXPORT_SYMBOL_GPL(bmp085_detect);
376
bmp085_get_of_properties(struct bmp085_data * data)377 static void __init bmp085_get_of_properties(struct bmp085_data *data)
378 {
379 #ifdef CONFIG_OF
380 struct device_node *np = data->dev->of_node;
381 u32 prop;
382
383 if (!np)
384 return;
385
386 if (!of_property_read_u32(np, "chip-id", &prop))
387 data->chip_id = prop & 0xff;
388
389 if (!of_property_read_u32(np, "temp-measurement-period", &prop))
390 data->temp_measurement_period = (prop/100)*HZ;
391
392 if (!of_property_read_u32(np, "default-oversampling", &prop))
393 data->oversampling_setting = prop & 0xff;
394 #endif
395 }
396
bmp085_init_client(struct bmp085_data * data)397 static int bmp085_init_client(struct bmp085_data *data)
398 {
399 int status = bmp085_read_calibration_data(data);
400
401 if (status < 0)
402 return status;
403
404 /* default settings */
405 data->chip_id = BMP085_CHIP_ID;
406 data->last_temp_measurement = 0;
407 data->temp_measurement_period = 1*HZ;
408 data->oversampling_setting = 3;
409
410 bmp085_get_of_properties(data);
411
412 mutex_init(&data->lock);
413
414 return 0;
415 }
416
417 struct regmap_config bmp085_regmap_config = {
418 .reg_bits = 8,
419 .val_bits = 8
420 };
421 EXPORT_SYMBOL_GPL(bmp085_regmap_config);
422
bmp085_probe(struct device * dev,struct regmap * regmap)423 int bmp085_probe(struct device *dev, struct regmap *regmap)
424 {
425 struct bmp085_data *data;
426 int err = 0;
427
428 data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL);
429 if (!data) {
430 err = -ENOMEM;
431 goto exit;
432 }
433
434 dev_set_drvdata(dev, data);
435 data->dev = dev;
436 data->regmap = regmap;
437
438 /* Initialize the BMP085 chip */
439 err = bmp085_init_client(data);
440 if (err < 0)
441 goto exit_free;
442
443 err = bmp085_detect(dev);
444 if (err < 0) {
445 dev_err(dev, "%s: chip_id failed!\n", BMP085_NAME);
446 goto exit_free;
447 }
448
449 /* Register sysfs hooks */
450 err = sysfs_create_group(&dev->kobj, &bmp085_attr_group);
451 if (err)
452 goto exit_free;
453
454 dev_info(dev, "Successfully initialized %s!\n", BMP085_NAME);
455
456 return 0;
457
458 exit_free:
459 kfree(data);
460 exit:
461 return err;
462 }
463 EXPORT_SYMBOL_GPL(bmp085_probe);
464
bmp085_remove(struct device * dev)465 int bmp085_remove(struct device *dev)
466 {
467 struct bmp085_data *data = dev_get_drvdata(dev);
468
469 sysfs_remove_group(&data->dev->kobj, &bmp085_attr_group);
470 kfree(data);
471
472 return 0;
473 }
474 EXPORT_SYMBOL_GPL(bmp085_remove);
475
476 MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com>");
477 MODULE_DESCRIPTION("BMP085 driver");
478 MODULE_LICENSE("GPL");
479