iio:temperature: Add MAX31856 thermocouple support
[linux-2.6-block.git] / drivers / iio / temperature / max31856.c
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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/module.h>
10#include <linux/init.h>
11#include <linux/err.h>
12#include <linux/spi/spi.h>
13#include <linux/iio/iio.h>
14#include <linux/iio/sysfs.h>
15#include <dt-bindings/iio/temperature/thermocouple.h>
16/*
17 * The MSB of the register value determines whether the following byte will
18 * be written or read. If it is 0, one or more byte reads will follow.
19 */
20#define MAX31856_RD_WR_BIT BIT(7)
21
22#define MAX31856_CR0_AUTOCONVERT BIT(7)
23#define MAX31856_CR0_1SHOT BIT(6)
24#define MAX31856_CR0_OCFAULT BIT(4)
25#define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
26#define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
27#define MAX31856_FAULT_OVUV BIT(1)
28#define MAX31856_FAULT_OPEN BIT(0)
29
30/* The MAX31856 registers */
31#define MAX31856_CR0_REG 0x00
32#define MAX31856_CR1_REG 0x01
33#define MAX31856_MASK_REG 0x02
34#define MAX31856_CJHF_REG 0x03
35#define MAX31856_CJLF_REG 0x04
36#define MAX31856_LTHFTH_REG 0x05
37#define MAX31856_LTHFTL_REG 0x06
38#define MAX31856_LTLFTH_REG 0x07
39#define MAX31856_LTLFTL_REG 0x08
40#define MAX31856_CJTO_REG 0x09
41#define MAX31856_CJTH_REG 0x0A
42#define MAX31856_CJTL_REG 0x0B
43#define MAX31856_LTCBH_REG 0x0C
44#define MAX31856_LTCBM_REG 0x0D
45#define MAX31856_LTCBL_REG 0x0E
46#define MAX31856_SR_REG 0x0F
47
48static const struct iio_chan_spec max31856_channels[] = {
49 { /* Thermocouple Temperature */
50 .type = IIO_TEMP,
51 .info_mask_separate =
52 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
53 },
54 { /* Cold Junction Temperature */
55 .type = IIO_TEMP,
56 .channel2 = IIO_MOD_TEMP_AMBIENT,
57 .modified = 1,
58 .info_mask_separate =
59 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
60 },
61};
62
63struct max31856_data {
64 struct spi_device *spi;
65 u32 thermocouple_type;
66};
67
68static int max31856_read(struct max31856_data *data, u8 reg,
69 u8 val[], unsigned int read_size)
70{
71 return spi_write_then_read(data->spi, &reg, 1, val, read_size);
72}
73
74static int max31856_write(struct max31856_data *data, u8 reg,
75 unsigned int val)
76{
77 u8 buf[2];
78
79 buf[0] = reg | (MAX31856_RD_WR_BIT);
80 buf[1] = val;
81
82 return spi_write(data->spi, buf, 2);
83}
84
85static int max31856_init(struct max31856_data *data)
86{
87 int ret;
88 u8 reg_cr0_val, reg_cr1_val;
89
90 /* Start by changing to Off mode before making changes as
91 * some settings are recommended to be set only when the device
92 * is off
93 */
94 ret = max31856_read(data, MAX31856_CR0_REG, &reg_cr0_val, 1);
95 if (ret)
96 return ret;
97
98 reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT;
99 ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
100 if (ret)
101 return ret;
102
103 /* Set thermocouple type based on dts property */
104 ret = max31856_read(data, MAX31856_CR1_REG, &reg_cr1_val, 1);
105 if (ret)
106 return ret;
107
108 reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
109 reg_cr1_val |= data->thermocouple_type;
110 ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
111 if (ret)
112 return ret;
113
114 /*
115 * Enable Open circuit fault detection
116 * Read datasheet for more information: Table 4.
117 * Value 01 means : Enabled (Once every 16 conversions)
118 */
119 reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK;
120 reg_cr0_val |= MAX31856_CR0_OCFAULT;
121
122 /* Set Auto Conversion Mode */
123 reg_cr0_val &= ~MAX31856_CR0_1SHOT;
124 reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;
125
126 return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
127}
128
129static int max31856_thermocouple_read(struct max31856_data *data,
130 struct iio_chan_spec const *chan,
131 int *val)
132{
133 int ret, offset_cjto;
134 u8 reg_val[3];
135
136 switch (chan->channel2) {
137 case IIO_NO_MOD:
138 /*
139 * Multibyte Read
140 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG
141 */
142 ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3);
143 if (ret)
144 return ret;
145 /* Skip last 5 dead bits of LTCBL */
146 *val = (reg_val[0] << 16 | reg_val[1] << 8 | reg_val[2]) >> 5;
147 /* Check 7th bit of LTCBH reg. value for sign*/
148 if (reg_val[0] & 0x80)
149 *val -= 0x80000;
150 break;
151
152 case IIO_MOD_TEMP_AMBIENT:
153 /*
154 * Multibyte Read
155 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG
156 */
157 ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3);
158 if (ret)
159 return ret;
160 /* Get Cold Junction Temp. offset register value */
161 offset_cjto = reg_val[0];
162 /* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */
163 *val = (reg_val[1] << 8 | reg_val[2]) >> 2;
164 /* As per datasheet add offset into CJTH and CJTL */
165 *val += offset_cjto;
166 /* Check 7th bit of CJTH reg. value for sign */
167 if (reg_val[1] & 0x80)
168 *val -= 0x4000;
169 break;
170
171 default:
172 return -EINVAL;
173 }
174
175 ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1);
176 if (ret)
177 return ret;
178 /* Check for over/under voltage or open circuit fault */
179 if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN))
180 return -EIO;
181
182 return ret;
183}
184
185static int max31856_read_raw(struct iio_dev *indio_dev,
186 struct iio_chan_spec const *chan,
187 int *val, int *val2, long mask)
188{
189 struct max31856_data *data = iio_priv(indio_dev);
190 int ret;
191
192 switch (mask) {
193 case IIO_CHAN_INFO_RAW:
194 ret = max31856_thermocouple_read(data, chan, val);
195 if (ret)
196 return ret;
197 return IIO_VAL_INT;
198 case IIO_CHAN_INFO_SCALE:
199 switch (chan->channel2) {
200 case IIO_MOD_TEMP_AMBIENT:
201 /* Cold junction Temp. Data resolution is 0.015625 */
202 *val = 15;
203 *val2 = 625000; /* 1000 * 0.015625 */
204 ret = IIO_VAL_INT_PLUS_MICRO;
205 break;
206 default:
207 /* Thermocouple Temp. Data resolution is 0.0078125 */
208 *val = 7;
209 *val2 = 812500; /* 1000 * 0.0078125) */
210 return IIO_VAL_INT_PLUS_MICRO;
211 }
212 break;
213 }
214
215 return ret;
216}
217
218static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
219{
220 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
221 struct max31856_data *data = iio_priv(indio_dev);
222 u8 reg_val;
223 int ret;
224 bool fault;
225
226 ret = max31856_read(data, MAX31856_SR_REG, &reg_val, 1);
227 if (ret)
228 return ret;
229
230 fault = reg_val & faultbit;
231
232 return sprintf(buf, "%d\n", fault);
233}
234
235static ssize_t show_fault_ovuv(struct device *dev,
236 struct device_attribute *attr,
237 char *buf)
238{
239 return show_fault(dev, MAX31856_FAULT_OVUV, buf);
240}
241
242static ssize_t show_fault_oc(struct device *dev,
243 struct device_attribute *attr,
244 char *buf)
245{
246 return show_fault(dev, MAX31856_FAULT_OPEN, buf);
247}
248
249static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
250static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
251
252static struct attribute *max31856_attributes[] = {
253 &iio_dev_attr_fault_ovuv.dev_attr.attr,
254 &iio_dev_attr_fault_oc.dev_attr.attr,
255 NULL,
256};
257
258static const struct attribute_group max31856_group = {
259 .attrs = max31856_attributes,
260};
261
262static const struct iio_info max31856_info = {
263 .read_raw = max31856_read_raw,
264 .attrs = &max31856_group,
265};
266
267static int max31856_probe(struct spi_device *spi)
268{
269 const struct spi_device_id *id = spi_get_device_id(spi);
270 struct iio_dev *indio_dev;
271 struct max31856_data *data;
272 int ret;
273
274 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
275 if (!indio_dev)
276 return -ENOMEM;
277
278 data = iio_priv(indio_dev);
279 data->spi = spi;
280
281 spi_set_drvdata(spi, indio_dev);
282
283 indio_dev->info = &max31856_info;
284 indio_dev->name = id->name;
285 indio_dev->modes = INDIO_DIRECT_MODE;
286 indio_dev->channels = max31856_channels;
287 indio_dev->num_channels = ARRAY_SIZE(max31856_channels);
288
289 ret = of_property_read_u32(spi->dev.of_node, "thermocouple-type",
290 &data->thermocouple_type);
291
292 if (ret) {
293 dev_info(&spi->dev,
294 "Could not read thermocouple type DT property, configuring as a K-Type\n");
295 data->thermocouple_type = THERMOCOUPLE_TYPE_K;
296 }
297
298 /*
299 * no need to translate values as the supported types
300 * have the same value as the #defines
301 */
302 switch (data->thermocouple_type) {
303 case THERMOCOUPLE_TYPE_B:
304 case THERMOCOUPLE_TYPE_E:
305 case THERMOCOUPLE_TYPE_J:
306 case THERMOCOUPLE_TYPE_K:
307 case THERMOCOUPLE_TYPE_N:
308 case THERMOCOUPLE_TYPE_R:
309 case THERMOCOUPLE_TYPE_S:
310 case THERMOCOUPLE_TYPE_T:
311 break;
312 default:
313 dev_err(&spi->dev,
314 "error: thermocouple-type %u not supported by max31856\n"
315 , data->thermocouple_type);
316 return -EINVAL;
317 }
318
319 ret = max31856_init(data);
320 if (ret) {
321 dev_err(&spi->dev, "error: Failed to configure max31856\n");
322 return ret;
323 }
324
325 return devm_iio_device_register(&spi->dev, indio_dev);
326}
327
328static const struct spi_device_id max31856_id[] = {
329 { "max31856", 0 },
330 { }
331};
332MODULE_DEVICE_TABLE(spi, max31856_id);
333
334static const struct of_device_id max31856_of_match[] = {
335 { .compatible = "maxim,max31856" },
336 { }
337};
338MODULE_DEVICE_TABLE(of, max31856_of_match);
339
340static struct spi_driver max31856_driver = {
341 .driver = {
342 .name = "max31856",
343 .of_match_table = max31856_of_match,
344 },
345 .probe = max31856_probe,
346 .id_table = max31856_id,
347};
348module_spi_driver(max31856_driver);
349
350MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>");
351MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");
352MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver");
353MODULE_LICENSE("GPL");