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/spi/spi.h>
14 #include <linux/iio/iio.h>
15 #include <linux/iio/sysfs.h>
16 #include <linux/util_macros.h>
17 #include <asm/unaligned.h>
18 #include <dt-bindings/iio/temperature/thermocouple.h>
19 /*
20  * The MSB of the register value determines whether the following byte will
21  * be written or read. If it is 0, one or more byte reads will follow.
22  */
23 #define MAX31856_RD_WR_BIT         BIT(7)
24 
25 #define MAX31856_CR0_AUTOCONVERT   BIT(7)
26 #define MAX31856_CR0_1SHOT         BIT(6)
27 #define MAX31856_CR0_OCFAULT       BIT(4)
28 #define MAX31856_CR0_OCFAULT_MASK  GENMASK(5, 4)
29 #define MAX31856_CR0_FILTER_50HZ   BIT(0)
30 #define MAX31856_AVERAGING_MASK    GENMASK(6, 4)
31 #define MAX31856_AVERAGING_SHIFT   4
32 #define MAX31856_TC_TYPE_MASK      GENMASK(3, 0)
33 #define MAX31856_FAULT_OVUV        BIT(1)
34 #define MAX31856_FAULT_OPEN        BIT(0)
35 
36 /* The MAX31856 registers */
37 #define MAX31856_CR0_REG           0x00
38 #define MAX31856_CR1_REG           0x01
39 #define MAX31856_MASK_REG          0x02
40 #define MAX31856_CJHF_REG          0x03
41 #define MAX31856_CJLF_REG          0x04
42 #define MAX31856_LTHFTH_REG        0x05
43 #define MAX31856_LTHFTL_REG        0x06
44 #define MAX31856_LTLFTH_REG        0x07
45 #define MAX31856_LTLFTL_REG        0x08
46 #define MAX31856_CJTO_REG          0x09
47 #define MAX31856_CJTH_REG          0x0A
48 #define MAX31856_CJTL_REG          0x0B
49 #define MAX31856_LTCBH_REG         0x0C
50 #define MAX31856_LTCBM_REG         0x0D
51 #define MAX31856_LTCBL_REG         0x0E
52 #define MAX31856_SR_REG            0x0F
53 
54 static const struct iio_chan_spec max31856_channels[] = {
55 	{	/* Thermocouple Temperature */
56 		.type = IIO_TEMP,
57 		.info_mask_separate =
58 			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
59 			BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),
60 		.info_mask_shared_by_type =
61 			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
62 	},
63 	{	/* Cold Junction Temperature */
64 		.type = IIO_TEMP,
65 		.channel2 = IIO_MOD_TEMP_AMBIENT,
66 		.modified = 1,
67 		.info_mask_separate =
68 			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
69 		.info_mask_shared_by_type =
70 			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
71 	},
72 };
73 
74 struct max31856_data {
75 	struct spi_device *spi;
76 	u32 thermocouple_type;
77 	bool filter_50hz;
78 	int averaging;
79 };
80 
81 static const char max31856_tc_types[] = {
82 	'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'
83 };
84 
85 static int max31856_read(struct max31856_data *data, u8 reg,
86 			 u8 val[], unsigned int read_size)
87 {
88 	return spi_write_then_read(data->spi, &reg, 1, val, read_size);
89 }
90 
91 static int max31856_write(struct max31856_data *data, u8 reg,
92 			  unsigned int val)
93 {
94 	u8 buf[2];
95 
96 	buf[0] = reg | (MAX31856_RD_WR_BIT);
97 	buf[1] = val;
98 
99 	return spi_write(data->spi, buf, 2);
100 }
101 
102 static int max31856_init(struct max31856_data *data)
103 {
104 	int ret;
105 	u8 reg_cr0_val, reg_cr1_val;
106 
107 	/* Start by changing to Off mode before making changes as
108 	 * some settings are recommended to be set only when the device
109 	 * is off
110 	 */
111 	ret = max31856_read(data, MAX31856_CR0_REG, &reg_cr0_val, 1);
112 	if (ret)
113 		return ret;
114 
115 	reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT;
116 	ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
117 	if (ret)
118 		return ret;
119 
120 	/* Set thermocouple type based on dts property */
121 	ret = max31856_read(data, MAX31856_CR1_REG, &reg_cr1_val, 1);
122 	if (ret)
123 		return ret;
124 
125 	reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
126 	reg_cr1_val |= data->thermocouple_type;
127 
128 	reg_cr1_val &= ~MAX31856_AVERAGING_MASK;
129 	reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT;
130 
131 	ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
132 	if (ret)
133 		return ret;
134 
135 	/*
136 	 * Enable Open circuit fault detection
137 	 * Read datasheet for more information: Table 4.
138 	 * Value 01 means : Enabled (Once every 16 conversions)
139 	 */
140 	reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK;
141 	reg_cr0_val |= MAX31856_CR0_OCFAULT;
142 
143 	/* Set Auto Conversion Mode */
144 	reg_cr0_val &= ~MAX31856_CR0_1SHOT;
145 	reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;
146 
147 	if (data->filter_50hz)
148 		reg_cr0_val |= MAX31856_CR0_FILTER_50HZ;
149 	else
150 		reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ;
151 
152 	return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
153 }
154 
155 static int max31856_thermocouple_read(struct max31856_data *data,
156 				      struct iio_chan_spec const *chan,
157 				      int *val)
158 {
159 	int ret, offset_cjto;
160 	u8 reg_val[3];
161 
162 	switch (chan->channel2) {
163 	case IIO_NO_MOD:
164 		/*
165 		 * Multibyte Read
166 		 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG
167 		 */
168 		ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3);
169 		if (ret)
170 			return ret;
171 		/* Skip last 5 dead bits of LTCBL */
172 		*val = get_unaligned_be24(&reg_val[0]) >> 5;
173 		/* Check 7th bit of LTCBH reg. value for sign*/
174 		if (reg_val[0] & 0x80)
175 			*val -= 0x80000;
176 		break;
177 
178 	case IIO_MOD_TEMP_AMBIENT:
179 		/*
180 		 * Multibyte Read
181 		 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG
182 		 */
183 		ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3);
184 		if (ret)
185 			return ret;
186 		/* Get Cold Junction Temp. offset register value */
187 		offset_cjto = reg_val[0];
188 		/* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */
189 		*val = get_unaligned_be16(&reg_val[1]) >> 2;
190 		/* As per datasheet add offset into CJTH and CJTL */
191 		*val += offset_cjto;
192 		/* Check 7th bit of CJTH reg. value for sign */
193 		if (reg_val[1] & 0x80)
194 			*val -= 0x4000;
195 		break;
196 
197 	default:
198 		return -EINVAL;
199 	}
200 
201 	ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1);
202 	if (ret)
203 		return ret;
204 	/* Check for over/under voltage or open circuit fault */
205 	if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN))
206 		return -EIO;
207 
208 	return ret;
209 }
210 
211 static int max31856_read_raw(struct iio_dev *indio_dev,
212 			     struct iio_chan_spec const *chan,
213 			     int *val, int *val2, long mask)
214 {
215 	struct max31856_data *data = iio_priv(indio_dev);
216 	int ret;
217 
218 	switch (mask) {
219 	case IIO_CHAN_INFO_RAW:
220 		ret = max31856_thermocouple_read(data, chan, val);
221 		if (ret)
222 			return ret;
223 		return IIO_VAL_INT;
224 	case IIO_CHAN_INFO_SCALE:
225 		switch (chan->channel2) {
226 		case IIO_MOD_TEMP_AMBIENT:
227 			/* Cold junction Temp. Data resolution is 0.015625 */
228 			*val = 15;
229 			*val2 = 625000; /* 1000 * 0.015625 */
230 			ret = IIO_VAL_INT_PLUS_MICRO;
231 			break;
232 		default:
233 			/* Thermocouple Temp. Data resolution is 0.0078125 */
234 			*val = 7;
235 			*val2 = 812500; /* 1000 * 0.0078125) */
236 			return IIO_VAL_INT_PLUS_MICRO;
237 		}
238 		break;
239 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
240 		*val = 1 << data->averaging;
241 		return IIO_VAL_INT;
242 	case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
243 		*val = max31856_tc_types[data->thermocouple_type];
244 		return IIO_VAL_CHAR;
245 	default:
246 		ret = -EINVAL;
247 		break;
248 	}
249 
250 	return ret;
251 }
252 
253 static int max31856_write_raw_get_fmt(struct iio_dev *indio_dev,
254 				      struct iio_chan_spec const *chan,
255 				      long mask)
256 {
257 	switch (mask) {
258 	case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
259 		return IIO_VAL_CHAR;
260 	default:
261 		return IIO_VAL_INT;
262 	}
263 }
264 
265 static int max31856_write_raw(struct iio_dev *indio_dev,
266 			      struct iio_chan_spec const *chan,
267 			      int val, int val2, long mask)
268 {
269 	struct max31856_data *data = iio_priv(indio_dev);
270 	int msb;
271 
272 	switch (mask) {
273 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
274 		if (val > 16 || val < 1)
275 			return -EINVAL;
276 		msb = fls(val) - 1;
277 		/* Round up to next 2pow if needed */
278 		if (BIT(msb) < val)
279 			msb++;
280 
281 		data->averaging = msb;
282 		max31856_init(data);
283 		break;
284 	case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
285 	{
286 		int tc_type = -1;
287 		int i;
288 
289 		for (i = 0; i < ARRAY_SIZE(max31856_tc_types); i++) {
290 			if (max31856_tc_types[i] == toupper(val)) {
291 				tc_type = i;
292 				break;
293 			}
294 		}
295 		if (tc_type < 0)
296 			return -EINVAL;
297 
298 		data->thermocouple_type = tc_type;
299 		max31856_init(data);
300 		break;
301 	}
302 	default:
303 		return -EINVAL;
304 	}
305 
306 	return 0;
307 }
308 
309 static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
310 {
311 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
312 	struct max31856_data *data = iio_priv(indio_dev);
313 	u8 reg_val;
314 	int ret;
315 	bool fault;
316 
317 	ret = max31856_read(data, MAX31856_SR_REG, &reg_val, 1);
318 	if (ret)
319 		return ret;
320 
321 	fault = reg_val & faultbit;
322 
323 	return sprintf(buf, "%d\n", fault);
324 }
325 
326 static ssize_t show_fault_ovuv(struct device *dev,
327 			       struct device_attribute *attr,
328 			       char *buf)
329 {
330 	return show_fault(dev, MAX31856_FAULT_OVUV, buf);
331 }
332 
333 static ssize_t show_fault_oc(struct device *dev,
334 			     struct device_attribute *attr,
335 			     char *buf)
336 {
337 	return show_fault(dev, MAX31856_FAULT_OPEN, buf);
338 }
339 
340 static ssize_t show_filter(struct device *dev,
341 			   struct device_attribute *attr,
342 			   char *buf)
343 {
344 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
345 	struct max31856_data *data = iio_priv(indio_dev);
346 
347 	return sprintf(buf, "%d\n", data->filter_50hz ? 50 : 60);
348 }
349 
350 static ssize_t set_filter(struct device *dev,
351 			  struct device_attribute *attr,
352 			  const char *buf,
353 			  size_t len)
354 {
355 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
356 	struct max31856_data *data = iio_priv(indio_dev);
357 	unsigned int freq;
358 	int ret;
359 
360 	ret = kstrtouint(buf, 10, &freq);
361 	if (ret)
362 		return ret;
363 
364 	switch (freq) {
365 	case 50:
366 		data->filter_50hz = true;
367 		break;
368 	case 60:
369 		data->filter_50hz = false;
370 		break;
371 	default:
372 		return -EINVAL;
373 	}
374 
375 	max31856_init(data);
376 	return len;
377 }
378 
379 static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
380 static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
381 static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644,
382 		       show_filter, set_filter, 0);
383 
384 static struct attribute *max31856_attributes[] = {
385 	&iio_dev_attr_fault_ovuv.dev_attr.attr,
386 	&iio_dev_attr_fault_oc.dev_attr.attr,
387 	&iio_dev_attr_in_temp_filter_notch_center_frequency.dev_attr.attr,
388 	NULL,
389 };
390 
391 static const struct attribute_group max31856_group = {
392 	.attrs = max31856_attributes,
393 };
394 
395 static const struct iio_info max31856_info = {
396 	.read_raw = max31856_read_raw,
397 	.write_raw = max31856_write_raw,
398 	.write_raw_get_fmt = max31856_write_raw_get_fmt,
399 	.attrs = &max31856_group,
400 };
401 
402 static int max31856_probe(struct spi_device *spi)
403 {
404 	const struct spi_device_id *id = spi_get_device_id(spi);
405 	struct iio_dev *indio_dev;
406 	struct max31856_data *data;
407 	int ret;
408 
409 	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
410 	if (!indio_dev)
411 		return -ENOMEM;
412 
413 	data = iio_priv(indio_dev);
414 	data->spi = spi;
415 	data->filter_50hz = false;
416 
417 	spi_set_drvdata(spi, indio_dev);
418 
419 	indio_dev->info = &max31856_info;
420 	indio_dev->name = id->name;
421 	indio_dev->modes = INDIO_DIRECT_MODE;
422 	indio_dev->channels = max31856_channels;
423 	indio_dev->num_channels = ARRAY_SIZE(max31856_channels);
424 
425 	ret = of_property_read_u32(spi->dev.of_node, "thermocouple-type",
426 				   &data->thermocouple_type);
427 
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