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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 | ||
48 | static 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 | ||
63 | struct max31856_data { | |
64 | struct spi_device *spi; | |
65 | u32 thermocouple_type; | |
66 | }; | |
67 | ||
68 | static 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, ®, 1, val, read_size); | |
72 | } | |
73 | ||
74 | static 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 | ||
85 | static 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, ®_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, ®_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 | ||
129 | static 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 | ||
185 | static 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 | ||
218 | static 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, ®_val, 1); | |
227 | if (ret) | |
228 | return ret; | |
229 | ||
230 | fault = reg_val & faultbit; | |
231 | ||
232 | return sprintf(buf, "%d\n", fault); | |
233 | } | |
234 | ||
235 | static 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 | ||
242 | static 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 | ||
249 | static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0); | |
250 | static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0); | |
251 | ||
252 | static 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 | ||
258 | static const struct attribute_group max31856_group = { | |
259 | .attrs = max31856_attributes, | |
260 | }; | |
261 | ||
262 | static const struct iio_info max31856_info = { | |
263 | .read_raw = max31856_read_raw, | |
264 | .attrs = &max31856_group, | |
265 | }; | |
266 | ||
267 | static 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 | ||
328 | static const struct spi_device_id max31856_id[] = { | |
329 | { "max31856", 0 }, | |
330 | { } | |
331 | }; | |
332 | MODULE_DEVICE_TABLE(spi, max31856_id); | |
333 | ||
334 | static const struct of_device_id max31856_of_match[] = { | |
335 | { .compatible = "maxim,max31856" }, | |
336 | { } | |
337 | }; | |
338 | MODULE_DEVICE_TABLE(of, max31856_of_match); | |
339 | ||
340 | static 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 | }; | |
348 | module_spi_driver(max31856_driver); | |
349 | ||
350 | MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>"); | |
351 | MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>"); | |
352 | MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver"); | |
353 | MODULE_LICENSE("GPL"); |