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
54static 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
74struct max31856_data {
75	struct spi_device *spi;
76	u32 thermocouple_type;
77	bool filter_50hz;
78	int averaging;
79};
80
81static const char max31856_tc_types[] = {
82	'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'
83};
84
85static 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
91static 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
102static 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
155static 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
211static 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
253static 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
265static 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
309static 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
326static 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
333static 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
340static 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
350static 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
379static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
380static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
381static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644,
382		       show_filter, set_filter, 0);
383
384static 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
391static const struct attribute_group max31856_group = {
392	.attrs = max31856_attributes,
393};
394
395static 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
402static 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
464static const struct spi_device_id max31856_id[] = {
465	{ "max31856", 0 },
466	{ }
467};
468MODULE_DEVICE_TABLE(spi, max31856_id);
469
470static const struct of_device_id max31856_of_match[] = {
471	{ .compatible = "maxim,max31856" },
472	{ }
473};
474MODULE_DEVICE_TABLE(of, max31856_of_match);
475
476static 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};
484module_spi_driver(max31856_driver);
485
486MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>");
487MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");
488MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver");
489MODULE_LICENSE("GPL");
490