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/mod_devicetable.h>
11 #include <linux/module.h>
12 #include <linux/init.h>
13 #include <linux/err.h>
14 #include <linux/property.h>
15 #include <linux/spi/spi.h>
16 #include <linux/iio/iio.h>
17 #include <linux/iio/sysfs.h>
18 #include <linux/util_macros.h>
19 #include <asm/unaligned.h>
20 #include <dt-bindings/iio/temperature/thermocouple.h>
21 /*
22 * The MSB of the register value determines whether the following byte will
23 * be written or read. If it is 0, one or more byte reads will follow.
24 */
25 #define MAX31856_RD_WR_BIT BIT(7)
26
27 #define MAX31856_CR0_AUTOCONVERT BIT(7)
28 #define MAX31856_CR0_1SHOT BIT(6)
29 #define MAX31856_CR0_OCFAULT BIT(4)
30 #define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
31 #define MAX31856_CR0_FILTER_50HZ BIT(0)
32 #define MAX31856_AVERAGING_MASK GENMASK(6, 4)
33 #define MAX31856_AVERAGING_SHIFT 4
34 #define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
35 #define MAX31856_FAULT_OVUV BIT(1)
36 #define MAX31856_FAULT_OPEN BIT(0)
37
38 /* The MAX31856 registers */
39 #define MAX31856_CR0_REG 0x00
40 #define MAX31856_CR1_REG 0x01
41 #define MAX31856_MASK_REG 0x02
42 #define MAX31856_CJHF_REG 0x03
43 #define MAX31856_CJLF_REG 0x04
44 #define MAX31856_LTHFTH_REG 0x05
45 #define MAX31856_LTHFTL_REG 0x06
46 #define MAX31856_LTLFTH_REG 0x07
47 #define MAX31856_LTLFTL_REG 0x08
48 #define MAX31856_CJTO_REG 0x09
49 #define MAX31856_CJTH_REG 0x0A
50 #define MAX31856_CJTL_REG 0x0B
51 #define MAX31856_LTCBH_REG 0x0C
52 #define MAX31856_LTCBM_REG 0x0D
53 #define MAX31856_LTCBL_REG 0x0E
54 #define MAX31856_SR_REG 0x0F
55
56 static const struct iio_chan_spec max31856_channels[] = {
57 { /* Thermocouple Temperature */
58 .type = IIO_TEMP,
59 .info_mask_separate =
60 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
61 BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),
62 .info_mask_shared_by_type =
63 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
64 },
65 { /* Cold Junction Temperature */
66 .type = IIO_TEMP,
67 .channel2 = IIO_MOD_TEMP_AMBIENT,
68 .modified = 1,
69 .info_mask_separate =
70 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
71 .info_mask_shared_by_type =
72 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
73 },
74 };
75
76 struct max31856_data {
77 struct spi_device *spi;
78 u32 thermocouple_type;
79 bool filter_50hz;
80 int averaging;
81 };
82
83 static const char max31856_tc_types[] = {
84 'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'
85 };
86
max31856_read(struct max31856_data * data,u8 reg,u8 val[],unsigned int read_size)87 static int max31856_read(struct max31856_data *data, u8 reg,
88 u8 val[], unsigned int read_size)
89 {
90 return spi_write_then_read(data->spi, ®, 1, val, read_size);
91 }
92
max31856_write(struct max31856_data * data,u8 reg,unsigned int val)93 static int max31856_write(struct max31856_data *data, u8 reg,
94 unsigned int val)
95 {
96 u8 buf[2];
97
98 buf[0] = reg | (MAX31856_RD_WR_BIT);
99 buf[1] = val;
100
101 return spi_write(data->spi, buf, 2);
102 }
103
max31856_init(struct max31856_data * data)104 static int max31856_init(struct max31856_data *data)
105 {
106 int ret;
107 u8 reg_cr0_val, reg_cr1_val;
108
109 /* Start by changing to Off mode before making changes as
110 * some settings are recommended to be set only when the device
111 * is off
112 */
113 ret = max31856_read(data, MAX31856_CR0_REG, ®_cr0_val, 1);
114 if (ret)
115 return ret;
116
117 reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT;
118 ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
119 if (ret)
120 return ret;
121
122 /* Set thermocouple type based on dts property */
123 ret = max31856_read(data, MAX31856_CR1_REG, ®_cr1_val, 1);
124 if (ret)
125 return ret;
126
127 reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
128 reg_cr1_val |= data->thermocouple_type;
129
130 reg_cr1_val &= ~MAX31856_AVERAGING_MASK;
131 reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT;
132
133 ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
134 if (ret)
135 return ret;
136
137 /*
138 * Enable Open circuit fault detection
139 * Read datasheet for more information: Table 4.
140 * Value 01 means : Enabled (Once every 16 conversions)
141 */
142 reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK;
143 reg_cr0_val |= MAX31856_CR0_OCFAULT;
144
145 /* Set Auto Conversion Mode */
146 reg_cr0_val &= ~MAX31856_CR0_1SHOT;
147 reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;
148
149 if (data->filter_50hz)
150 reg_cr0_val |= MAX31856_CR0_FILTER_50HZ;
151 else
152 reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ;
153
154 return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
155 }
156
max31856_thermocouple_read(struct max31856_data * data,struct iio_chan_spec const * chan,int * val)157 static int max31856_thermocouple_read(struct max31856_data *data,
158 struct iio_chan_spec const *chan,
159 int *val)
160 {
161 int ret, offset_cjto;
162 u8 reg_val[3];
163
164 switch (chan->channel2) {
165 case IIO_NO_MOD:
166 /*
167 * Multibyte Read
168 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG
169 */
170 ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3);
171 if (ret)
172 return ret;
173 /* Skip last 5 dead bits of LTCBL */
174 *val = get_unaligned_be24(®_val[0]) >> 5;
175 /* Check 7th bit of LTCBH reg. value for sign*/
176 if (reg_val[0] & 0x80)
177 *val -= 0x80000;
178 break;
179
180 case IIO_MOD_TEMP_AMBIENT:
181 /*
182 * Multibyte Read
183 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG
184 */
185 ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3);
186 if (ret)
187 return ret;
188 /* Get Cold Junction Temp. offset register value */
189 offset_cjto = reg_val[0];
190 /* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */
191 *val = get_unaligned_be16(®_val[1]) >> 2;
192 /* As per datasheet add offset into CJTH and CJTL */
193 *val += offset_cjto;
194 /* Check 7th bit of CJTH reg. value for sign */
195 if (reg_val[1] & 0x80)
196 *val -= 0x4000;
197 break;
198
199 default:
200 return -EINVAL;
201 }
202
203 ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1);
204 if (ret)
205 return ret;
206 /* Check for over/under voltage or open circuit fault */
207 if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN))
208 return -EIO;
209
210 return ret;
211 }
212
max31856_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)213 static int max31856_read_raw(struct iio_dev *indio_dev,
214 struct iio_chan_spec const *chan,
215 int *val, int *val2, long mask)
216 {
217 struct max31856_data *data = iio_priv(indio_dev);
218 int ret;
219
220 switch (mask) {
221 case IIO_CHAN_INFO_RAW:
222 ret = max31856_thermocouple_read(data, chan, val);
223 if (ret)
224 return ret;
225 return IIO_VAL_INT;
226 case IIO_CHAN_INFO_SCALE:
227 switch (chan->channel2) {
228 case IIO_MOD_TEMP_AMBIENT:
229 /* Cold junction Temp. Data resolution is 0.015625 */
230 *val = 15;
231 *val2 = 625000; /* 1000 * 0.015625 */
232 ret = IIO_VAL_INT_PLUS_MICRO;
233 break;
234 default:
235 /* Thermocouple Temp. Data resolution is 0.0078125 */
236 *val = 7;
237 *val2 = 812500; /* 1000 * 0.0078125) */
238 return IIO_VAL_INT_PLUS_MICRO;
239 }
240 break;
241 case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
242 *val = 1 << data->averaging;
243 return IIO_VAL_INT;
244 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
245 *val = max31856_tc_types[data->thermocouple_type];
246 return IIO_VAL_CHAR;
247 default:
248 ret = -EINVAL;
249 break;
250 }
251
252 return ret;
253 }
254
max31856_write_raw_get_fmt(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,long mask)255 static int max31856_write_raw_get_fmt(struct iio_dev *indio_dev,
256 struct iio_chan_spec const *chan,
257 long mask)
258 {
259 switch (mask) {
260 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
261 return IIO_VAL_CHAR;
262 default:
263 return IIO_VAL_INT;
264 }
265 }
266
max31856_write_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int val,int val2,long mask)267 static int max31856_write_raw(struct iio_dev *indio_dev,
268 struct iio_chan_spec const *chan,
269 int val, int val2, long mask)
270 {
271 struct max31856_data *data = iio_priv(indio_dev);
272 int msb;
273
274 switch (mask) {
275 case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
276 if (val > 16 || val < 1)
277 return -EINVAL;
278 msb = fls(val) - 1;
279 /* Round up to next 2pow if needed */
280 if (BIT(msb) < val)
281 msb++;
282
283 data->averaging = msb;
284 max31856_init(data);
285 break;
286 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
287 {
288 int tc_type = -1;
289 int i;
290
291 for (i = 0; i < ARRAY_SIZE(max31856_tc_types); i++) {
292 if (max31856_tc_types[i] == toupper(val)) {
293 tc_type = i;
294 break;
295 }
296 }
297 if (tc_type < 0)
298 return -EINVAL;
299
300 data->thermocouple_type = tc_type;
301 max31856_init(data);
302 break;
303 }
304 default:
305 return -EINVAL;
306 }
307
308 return 0;
309 }
310
show_fault(struct device * dev,u8 faultbit,char * buf)311 static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
312 {
313 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
314 struct max31856_data *data = iio_priv(indio_dev);
315 u8 reg_val;
316 int ret;
317 bool fault;
318
319 ret = max31856_read(data, MAX31856_SR_REG, ®_val, 1);
320 if (ret)
321 return ret;
322
323 fault = reg_val & faultbit;
324
325 return sysfs_emit(buf, "%d\n", fault);
326 }
327
show_fault_ovuv(struct device * dev,struct device_attribute * attr,char * buf)328 static ssize_t show_fault_ovuv(struct device *dev,
329 struct device_attribute *attr,
330 char *buf)
331 {
332 return show_fault(dev, MAX31856_FAULT_OVUV, buf);
333 }
334
show_fault_oc(struct device * dev,struct device_attribute * attr,char * buf)335 static ssize_t show_fault_oc(struct device *dev,
336 struct device_attribute *attr,
337 char *buf)
338 {
339 return show_fault(dev, MAX31856_FAULT_OPEN, buf);
340 }
341
show_filter(struct device * dev,struct device_attribute * attr,char * buf)342 static ssize_t show_filter(struct device *dev,
343 struct device_attribute *attr,
344 char *buf)
345 {
346 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
347 struct max31856_data *data = iio_priv(indio_dev);
348
349 return sysfs_emit(buf, "%d\n", data->filter_50hz ? 50 : 60);
350 }
351
set_filter(struct device * dev,struct device_attribute * attr,const char * buf,size_t len)352 static ssize_t set_filter(struct device *dev,
353 struct device_attribute *attr,
354 const char *buf,
355 size_t len)
356 {
357 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
358 struct max31856_data *data = iio_priv(indio_dev);
359 unsigned int freq;
360 int ret;
361
362 ret = kstrtouint(buf, 10, &freq);
363 if (ret)
364 return ret;
365
366 switch (freq) {
367 case 50:
368 data->filter_50hz = true;
369 break;
370 case 60:
371 data->filter_50hz = false;
372 break;
373 default:
374 return -EINVAL;
375 }
376
377 max31856_init(data);
378 return len;
379 }
380
381 static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
382 static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
383 static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644,
384 show_filter, set_filter, 0);
385
386 static struct attribute *max31856_attributes[] = {
387 &iio_dev_attr_fault_ovuv.dev_attr.attr,
388 &iio_dev_attr_fault_oc.dev_attr.attr,
389 &iio_dev_attr_in_temp_filter_notch_center_frequency.dev_attr.attr,
390 NULL,
391 };
392
393 static const struct attribute_group max31856_group = {
394 .attrs = max31856_attributes,
395 };
396
397 static const struct iio_info max31856_info = {
398 .read_raw = max31856_read_raw,
399 .write_raw = max31856_write_raw,
400 .write_raw_get_fmt = max31856_write_raw_get_fmt,
401 .attrs = &max31856_group,
402 };
403
max31856_probe(struct spi_device * spi)404 static int max31856_probe(struct spi_device *spi)
405 {
406 const struct spi_device_id *id = spi_get_device_id(spi);
407 struct iio_dev *indio_dev;
408 struct max31856_data *data;
409 int ret;
410
411 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
412 if (!indio_dev)
413 return -ENOMEM;
414
415 data = iio_priv(indio_dev);
416 data->spi = spi;
417 data->filter_50hz = false;
418
419 spi_set_drvdata(spi, indio_dev);
420
421 indio_dev->info = &max31856_info;
422 indio_dev->name = id->name;
423 indio_dev->modes = INDIO_DIRECT_MODE;
424 indio_dev->channels = max31856_channels;
425 indio_dev->num_channels = ARRAY_SIZE(max31856_channels);
426
427 ret = device_property_read_u32(&spi->dev, "thermocouple-type", &data->thermocouple_type);
428 if (ret) {
429 dev_info(&spi->dev,
430 "Could not read thermocouple type DT property, configuring as a K-Type\n");
431 data->thermocouple_type = THERMOCOUPLE_TYPE_K;
432 }
433
434 /*
435 * no need to translate values as the supported types
436 * have the same value as the #defines
437 */
438 switch (data->thermocouple_type) {
439 case THERMOCOUPLE_TYPE_B:
440 case THERMOCOUPLE_TYPE_E:
441 case THERMOCOUPLE_TYPE_J:
442 case THERMOCOUPLE_TYPE_K:
443 case THERMOCOUPLE_TYPE_N:
444 case THERMOCOUPLE_TYPE_R:
445 case THERMOCOUPLE_TYPE_S:
446 case THERMOCOUPLE_TYPE_T:
447 break;
448 default:
449 dev_err(&spi->dev,
450 "error: thermocouple-type %u not supported by max31856\n"
451 , data->thermocouple_type);
452 return -EINVAL;
453 }
454
455 ret = max31856_init(data);
456 if (ret) {
457 dev_err(&spi->dev, "error: Failed to configure max31856\n");
458 return ret;
459 }
460
461 return devm_iio_device_register(&spi->dev, indio_dev);
462 }
463
464 static const struct spi_device_id max31856_id[] = {
465 { "max31856", 0 },
466 { }
467 };
468 MODULE_DEVICE_TABLE(spi, max31856_id);
469
470 static const struct of_device_id max31856_of_match[] = {
471 { .compatible = "maxim,max31856" },
472 { }
473 };
474 MODULE_DEVICE_TABLE(of, max31856_of_match);
475
476 static struct spi_driver max31856_driver = {
477 .driver = {
478 .name = "max31856",
479 .of_match_table = max31856_of_match,
480 },
481 .probe = max31856_probe,
482 .id_table = max31856_id,
483 };
484 module_spi_driver(max31856_driver);
485
486 MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>");
487 MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");
488 MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver");
489 MODULE_LICENSE("GPL");
490