1 // SPDX-License-Identifier: GPL-2.0
2 /* max31856.c
3 *
4 * Maxim MAX31856 thermocouple sensor driver
5 *
6 * Copyright (C) 2018-2019 Rockwell Collins
7 */
8
9 #include <linux/ctype.h>
10 #include <linux/module.h>
11 #include <linux/init.h>
12 #include <linux/err.h>
13 #include <linux/property.h>
14 #include <linux/spi/spi.h>
15 #include <linux/iio/iio.h>
16 #include <linux/iio/sysfs.h>
17 #include <linux/util_macros.h>
18 #include <linux/unaligned.h>
19 #include <dt-bindings/iio/temperature/thermocouple.h>
20 /*
21 * The MSB of the register value determines whether the following byte will
22 * be written or read. If it is 0, one or more byte reads will follow.
23 */
24 #define MAX31856_RD_WR_BIT BIT(7)
25
26 #define MAX31856_CR0_AUTOCONVERT BIT(7)
27 #define MAX31856_CR0_1SHOT BIT(6)
28 #define MAX31856_CR0_OCFAULT BIT(4)
29 #define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
30 #define MAX31856_CR0_FILTER_50HZ BIT(0)
31 #define MAX31856_AVERAGING_MASK GENMASK(6, 4)
32 #define MAX31856_AVERAGING_SHIFT 4
33 #define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
34 #define MAX31856_FAULT_OVUV BIT(1)
35 #define MAX31856_FAULT_OPEN BIT(0)
36
37 /* The MAX31856 registers */
38 #define MAX31856_CR0_REG 0x00
39 #define MAX31856_CR1_REG 0x01
40 #define MAX31856_MASK_REG 0x02
41 #define MAX31856_CJHF_REG 0x03
42 #define MAX31856_CJLF_REG 0x04
43 #define MAX31856_LTHFTH_REG 0x05
44 #define MAX31856_LTHFTL_REG 0x06
45 #define MAX31856_LTLFTH_REG 0x07
46 #define MAX31856_LTLFTL_REG 0x08
47 #define MAX31856_CJTO_REG 0x09
48 #define MAX31856_CJTH_REG 0x0A
49 #define MAX31856_CJTL_REG 0x0B
50 #define MAX31856_LTCBH_REG 0x0C
51 #define MAX31856_LTCBM_REG 0x0D
52 #define MAX31856_LTCBL_REG 0x0E
53 #define MAX31856_SR_REG 0x0F
54
55 static const struct iio_chan_spec max31856_channels[] = {
56 { /* Thermocouple Temperature */
57 .type = IIO_TEMP,
58 .info_mask_separate =
59 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
60 BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),
61 .info_mask_shared_by_type =
62 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
63 },
64 { /* Cold Junction Temperature */
65 .type = IIO_TEMP,
66 .channel2 = IIO_MOD_TEMP_AMBIENT,
67 .modified = 1,
68 .info_mask_separate =
69 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
70 .info_mask_shared_by_type =
71 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
72 },
73 };
74
75 struct max31856_data {
76 struct spi_device *spi;
77 u32 thermocouple_type;
78 bool filter_50hz;
79 int averaging;
80 };
81
82 static const char max31856_tc_types[] = {
83 'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'
84 };
85
max31856_read(struct max31856_data * data,u8 reg,u8 val[],unsigned int read_size)86 static int max31856_read(struct max31856_data *data, u8 reg,
87 u8 val[], unsigned int read_size)
88 {
89 return spi_write_then_read(data->spi, ®, 1, val, read_size);
90 }
91
max31856_write(struct max31856_data * data,u8 reg,unsigned int val)92 static int max31856_write(struct max31856_data *data, u8 reg,
93 unsigned int val)
94 {
95 u8 buf[2];
96
97 buf[0] = reg | (MAX31856_RD_WR_BIT);
98 buf[1] = val;
99
100 return spi_write(data->spi, buf, 2);
101 }
102
max31856_init(struct max31856_data * data)103 static int max31856_init(struct max31856_data *data)
104 {
105 int ret;
106 u8 reg_cr0_val, reg_cr1_val;
107
108 /* Start by changing to Off mode before making changes as
109 * some settings are recommended to be set only when the device
110 * is off
111 */
112 ret = max31856_read(data, MAX31856_CR0_REG, ®_cr0_val, 1);
113 if (ret)
114 return ret;
115
116 reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT;
117 ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
118 if (ret)
119 return ret;
120
121 /* Set thermocouple type based on dts property */
122 ret = max31856_read(data, MAX31856_CR1_REG, ®_cr1_val, 1);
123 if (ret)
124 return ret;
125
126 reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
127 reg_cr1_val |= data->thermocouple_type;
128
129 reg_cr1_val &= ~MAX31856_AVERAGING_MASK;
130 reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT;
131
132 ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
133 if (ret)
134 return ret;
135
136 /*
137 * Enable Open circuit fault detection
138 * Read datasheet for more information: Table 4.
139 * Value 01 means : Enabled (Once every 16 conversions)
140 */
141 reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK;
142 reg_cr0_val |= MAX31856_CR0_OCFAULT;
143
144 /* Set Auto Conversion Mode */
145 reg_cr0_val &= ~MAX31856_CR0_1SHOT;
146 reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;
147
148 if (data->filter_50hz)
149 reg_cr0_val |= MAX31856_CR0_FILTER_50HZ;
150 else
151 reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ;
152
153 return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
154 }
155
max31856_thermocouple_read(struct max31856_data * data,struct iio_chan_spec const * chan,int * val)156 static int max31856_thermocouple_read(struct max31856_data *data,
157 struct iio_chan_spec const *chan,
158 int *val)
159 {
160 int ret, offset_cjto;
161 u8 reg_val[3];
162
163 switch (chan->channel2) {
164 case IIO_NO_MOD:
165 /*
166 * Multibyte Read
167 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG
168 */
169 ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3);
170 if (ret)
171 return ret;
172 /* Skip last 5 dead bits of LTCBL */
173 *val = get_unaligned_be24(®_val[0]) >> 5;
174 /* Check 7th bit of LTCBH reg. value for sign*/
175 if (reg_val[0] & 0x80)
176 *val -= 0x80000;
177 break;
178
179 case IIO_MOD_TEMP_AMBIENT:
180 /*
181 * Multibyte Read
182 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG
183 */
184 ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3);
185 if (ret)
186 return ret;
187 /* Get Cold Junction Temp. offset register value */
188 offset_cjto = reg_val[0];
189 /* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */
190 *val = get_unaligned_be16(®_val[1]) >> 2;
191 /* As per datasheet add offset into CJTH and CJTL */
192 *val += offset_cjto;
193 /* Check 7th bit of CJTH reg. value for sign */
194 if (reg_val[1] & 0x80)
195 *val -= 0x4000;
196 break;
197
198 default:
199 return -EINVAL;
200 }
201
202 ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1);
203 if (ret)
204 return ret;
205 /* Check for over/under voltage or open circuit fault */
206 if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN))
207 return -EIO;
208
209 return ret;
210 }
211
max31856_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)212 static int max31856_read_raw(struct iio_dev *indio_dev,
213 struct iio_chan_spec const *chan,
214 int *val, int *val2, long mask)
215 {
216 struct max31856_data *data = iio_priv(indio_dev);
217 int ret;
218
219 switch (mask) {
220 case IIO_CHAN_INFO_RAW:
221 ret = max31856_thermocouple_read(data, chan, val);
222 if (ret)
223 return ret;
224 return IIO_VAL_INT;
225 case IIO_CHAN_INFO_SCALE:
226 switch (chan->channel2) {
227 case IIO_MOD_TEMP_AMBIENT:
228 /* Cold junction Temp. Data resolution is 0.015625 */
229 *val = 15;
230 *val2 = 625000; /* 1000 * 0.015625 */
231 ret = IIO_VAL_INT_PLUS_MICRO;
232 break;
233 default:
234 /* Thermocouple Temp. Data resolution is 0.0078125 */
235 *val = 7;
236 *val2 = 812500; /* 1000 * 0.0078125) */
237 return IIO_VAL_INT_PLUS_MICRO;
238 }
239 break;
240 case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
241 *val = 1 << data->averaging;
242 return IIO_VAL_INT;
243 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
244 *val = max31856_tc_types[data->thermocouple_type];
245 return IIO_VAL_CHAR;
246 default:
247 ret = -EINVAL;
248 break;
249 }
250
251 return ret;
252 }
253
max31856_write_raw_get_fmt(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,long mask)254 static int max31856_write_raw_get_fmt(struct iio_dev *indio_dev,
255 struct iio_chan_spec const *chan,
256 long mask)
257 {
258 switch (mask) {
259 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
260 return IIO_VAL_CHAR;
261 default:
262 return IIO_VAL_INT;
263 }
264 }
265
max31856_write_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int val,int val2,long mask)266 static int max31856_write_raw(struct iio_dev *indio_dev,
267 struct iio_chan_spec const *chan,
268 int val, int val2, long mask)
269 {
270 struct max31856_data *data = iio_priv(indio_dev);
271 int msb;
272
273 switch (mask) {
274 case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
275 if (val > 16 || val < 1)
276 return -EINVAL;
277 msb = fls(val) - 1;
278 /* Round up to next 2pow if needed */
279 if (BIT(msb) < val)
280 msb++;
281
282 data->averaging = msb;
283 max31856_init(data);
284 break;
285 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
286 {
287 int tc_type = -1;
288 int i;
289
290 for (i = 0; i < ARRAY_SIZE(max31856_tc_types); i++) {
291 if (max31856_tc_types[i] == toupper(val)) {
292 tc_type = i;
293 break;
294 }
295 }
296 if (tc_type < 0)
297 return -EINVAL;
298
299 data->thermocouple_type = tc_type;
300 max31856_init(data);
301 break;
302 }
303 default:
304 return -EINVAL;
305 }
306
307 return 0;
308 }
309
show_fault(struct device * dev,u8 faultbit,char * buf)310 static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
311 {
312 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
313 struct max31856_data *data = iio_priv(indio_dev);
314 u8 reg_val;
315 int ret;
316 bool fault;
317
318 ret = max31856_read(data, MAX31856_SR_REG, ®_val, 1);
319 if (ret)
320 return ret;
321
322 fault = reg_val & faultbit;
323
324 return sysfs_emit(buf, "%d\n", fault);
325 }
326
show_fault_ovuv(struct device * dev,struct device_attribute * attr,char * buf)327 static ssize_t show_fault_ovuv(struct device *dev,
328 struct device_attribute *attr,
329 char *buf)
330 {
331 return show_fault(dev, MAX31856_FAULT_OVUV, buf);
332 }
333
show_fault_oc(struct device * dev,struct device_attribute * attr,char * buf)334 static ssize_t show_fault_oc(struct device *dev,
335 struct device_attribute *attr,
336 char *buf)
337 {
338 return show_fault(dev, MAX31856_FAULT_OPEN, buf);
339 }
340
show_filter(struct device * dev,struct device_attribute * attr,char * buf)341 static ssize_t show_filter(struct device *dev,
342 struct device_attribute *attr,
343 char *buf)
344 {
345 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
346 struct max31856_data *data = iio_priv(indio_dev);
347
348 return sysfs_emit(buf, "%d\n", data->filter_50hz ? 50 : 60);
349 }
350
set_filter(struct device * dev,struct device_attribute * attr,const char * buf,size_t len)351 static ssize_t set_filter(struct device *dev,
352 struct device_attribute *attr,
353 const char *buf,
354 size_t len)
355 {
356 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
357 struct max31856_data *data = iio_priv(indio_dev);
358 unsigned int freq;
359 int ret;
360
361 ret = kstrtouint(buf, 10, &freq);
362 if (ret)
363 return ret;
364
365 switch (freq) {
366 case 50:
367 data->filter_50hz = true;
368 break;
369 case 60:
370 data->filter_50hz = false;
371 break;
372 default:
373 return -EINVAL;
374 }
375
376 max31856_init(data);
377 return len;
378 }
379
380 static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
381 static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
382 static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644,
383 show_filter, set_filter, 0);
384
385 static struct attribute *max31856_attributes[] = {
386 &iio_dev_attr_fault_ovuv.dev_attr.attr,
387 &iio_dev_attr_fault_oc.dev_attr.attr,
388 &iio_dev_attr_in_temp_filter_notch_center_frequency.dev_attr.attr,
389 NULL,
390 };
391
392 static const struct attribute_group max31856_group = {
393 .attrs = max31856_attributes,
394 };
395
396 static const struct iio_info max31856_info = {
397 .read_raw = max31856_read_raw,
398 .write_raw = max31856_write_raw,
399 .write_raw_get_fmt = max31856_write_raw_get_fmt,
400 .attrs = &max31856_group,
401 };
402
max31856_probe(struct spi_device * spi)403 static int max31856_probe(struct spi_device *spi)
404 {
405 const struct spi_device_id *id = spi_get_device_id(spi);
406 struct iio_dev *indio_dev;
407 struct max31856_data *data;
408 int ret;
409
410 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
411 if (!indio_dev)
412 return -ENOMEM;
413
414 data = iio_priv(indio_dev);
415 data->spi = spi;
416 data->filter_50hz = false;
417
418 spi_set_drvdata(spi, indio_dev);
419
420 indio_dev->info = &max31856_info;
421 indio_dev->name = id->name;
422 indio_dev->modes = INDIO_DIRECT_MODE;
423 indio_dev->channels = max31856_channels;
424 indio_dev->num_channels = ARRAY_SIZE(max31856_channels);
425
426 ret = device_property_read_u32(&spi->dev, "thermocouple-type", &data->thermocouple_type);
427 if (ret) {
428 dev_info(&spi->dev,
429 "Could not read thermocouple type DT property, configuring as a K-Type\n");
430 data->thermocouple_type = THERMOCOUPLE_TYPE_K;
431 }
432
433 /*
434 * no need to translate values as the supported types
435 * have the same value as the #defines
436 */
437 switch (data->thermocouple_type) {
438 case THERMOCOUPLE_TYPE_B:
439 case THERMOCOUPLE_TYPE_E:
440 case THERMOCOUPLE_TYPE_J:
441 case THERMOCOUPLE_TYPE_K:
442 case THERMOCOUPLE_TYPE_N:
443 case THERMOCOUPLE_TYPE_R:
444 case THERMOCOUPLE_TYPE_S:
445 case THERMOCOUPLE_TYPE_T:
446 break;
447 default:
448 dev_err(&spi->dev,
449 "error: thermocouple-type %u not supported by max31856\n"
450 , data->thermocouple_type);
451 return -EINVAL;
452 }
453
454 ret = max31856_init(data);
455 if (ret) {
456 dev_err(&spi->dev, "error: Failed to configure max31856\n");
457 return ret;
458 }
459
460 return devm_iio_device_register(&spi->dev, indio_dev);
461 }
462
463 static const struct spi_device_id max31856_id[] = {
464 { .name = "max31856" },
465 { }
466 };
467 MODULE_DEVICE_TABLE(spi, max31856_id);
468
469 static const struct of_device_id max31856_of_match[] = {
470 { .compatible = "maxim,max31856" },
471 { }
472 };
473 MODULE_DEVICE_TABLE(of, max31856_of_match);
474
475 static struct spi_driver max31856_driver = {
476 .driver = {
477 .name = "max31856",
478 .of_match_table = max31856_of_match,
479 },
480 .probe = max31856_probe,
481 .id_table = max31856_id,
482 };
483 module_spi_driver(max31856_driver);
484
485 MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>");
486 MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");
487 MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver");
488 MODULE_LICENSE("GPL");
489