maxim_thermocouple.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * maxim_thermocouple.c  - Support for Maxim thermocouple chips
  4 *
  5 * Copyright (C) 2016-2018 Matt Ranostay
  6 * Author: <matt.ranostay@konsulko.com>
  7 */
  8
  9#include <linux/init.h>
 10#include <linux/mod_devicetable.h>
 11#include <linux/module.h>
 12#include <linux/err.h>
 13#include <linux/spi/spi.h>
 14#include <linux/types.h>
 15#include <linux/iio/iio.h>
 16#include <linux/iio/sysfs.h>
 17#include <linux/iio/trigger.h>
 18#include <linux/iio/buffer.h>
 19#include <linux/iio/triggered_buffer.h>
 20#include <linux/iio/trigger_consumer.h>
 21
 22#define MAXIM_THERMOCOUPLE_DRV_NAME	"maxim_thermocouple"
 23
 24enum {
 25	MAX6675,
 26	MAX31855,
 27	MAX31855K,
 28	MAX31855J,
 29	MAX31855N,
 30	MAX31855S,
 31	MAX31855T,
 32	MAX31855E,
 33	MAX31855R,
 34};
 35
 36static const char maxim_tc_types[] = {
 37	'K', '?', 'K', 'J', 'N', 'S', 'T', 'E', 'R'
 38};
 39
 40static const struct iio_chan_spec max6675_channels[] = {
 41	{	/* thermocouple temperature */
 42		.type = IIO_TEMP,
 43		.info_mask_separate =
 44			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
 45			BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),
 46		.scan_index = 0,
 47		.scan_type = {
 48			.sign = 's',
 49			.realbits = 13,
 50			.storagebits = 16,
 51			.shift = 3,
 52			.endianness = IIO_BE,
 53		},
 54	},
 55	IIO_CHAN_SOFT_TIMESTAMP(1),
 56};
 57
 58static const struct iio_chan_spec max31855_channels[] = {
 59	{	/* thermocouple temperature */
 60		.type = IIO_TEMP,
 61		.address = 2,
 62		.info_mask_separate =
 63			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
 64			BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),
 65		.scan_index = 0,
 66		.scan_type = {
 67			.sign = 's',
 68			.realbits = 14,
 69			.storagebits = 16,
 70			.shift = 2,
 71			.endianness = IIO_BE,
 72		},
 73	},
 74	{	/* cold junction temperature */
 75		.type = IIO_TEMP,
 76		.address = 0,
 77		.channel2 = IIO_MOD_TEMP_AMBIENT,
 78		.modified = 1,
 79		.info_mask_separate =
 80			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
 81		.scan_index = 1,
 82		.scan_type = {
 83			.sign = 's',
 84			.realbits = 12,
 85			.storagebits = 16,
 86			.shift = 4,
 87			.endianness = IIO_BE,
 88		},
 89	},
 90	IIO_CHAN_SOFT_TIMESTAMP(2),
 91};
 92
 93static const unsigned long max31855_scan_masks[] = {0x3, 0};
 94
 95struct maxim_thermocouple_chip {
 96	const struct iio_chan_spec *channels;
 97	const unsigned long *scan_masks;
 98	u8 num_channels;
 99	u8 read_size;
100
101	/* bit-check for valid input */
102	u32 status_bit;
103};
104
105static const struct maxim_thermocouple_chip maxim_thermocouple_chips[] = {
106	[MAX6675] = {
107			.channels = max6675_channels,
108			.num_channels = ARRAY_SIZE(max6675_channels),
109			.read_size = 2,
110			.status_bit = BIT(2),
111		},
112	[MAX31855] = {
113			.channels = max31855_channels,
114			.num_channels = ARRAY_SIZE(max31855_channels),
115			.read_size = 4,
116			.scan_masks = max31855_scan_masks,
117			.status_bit = BIT(16),
118		},
119};
120
121struct maxim_thermocouple_data {
122	struct spi_device *spi;
123	const struct maxim_thermocouple_chip *chip;
124	char tc_type;
125	/* Buffer for reading up to 2 hardware channels. */
126	struct {
127		union {
128			__be16 raw16;
129			__be32 raw32;
130			__be16 raw[2];
131		};
132		aligned_s64 timestamp;
133	} buffer __aligned(IIO_DMA_MINALIGN);
134};
135
136static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
137				   struct iio_chan_spec const *chan, int *val)
138{
139	unsigned int storage_bytes = data->chip->read_size;
140	unsigned int shift = chan->scan_type.shift + (chan->address * 8);
141	int ret;
142
143	switch (storage_bytes) {
144	case 2:
145		ret = spi_read(data->spi, &data->buffer.raw16, storage_bytes);
146		*val = be16_to_cpu(data->buffer.raw16);
147		break;
148	case 4:
149		ret = spi_read(data->spi, &data->buffer.raw32, storage_bytes);
150		*val = be32_to_cpu(data->buffer.raw32);
151		break;
152	default:
153		ret = -EINVAL;
154	}
155
156	if (ret)
157		return ret;
158
159	/* check to be sure this is a valid reading */
160	if (*val & data->chip->status_bit)
161		return -EINVAL;
162
163	*val = sign_extend32(*val >> shift, chan->scan_type.realbits - 1);
164
165	return 0;
166}
167
168static irqreturn_t maxim_thermocouple_trigger_handler(int irq, void *private)
169{
170	struct iio_poll_func *pf = private;
171	struct iio_dev *indio_dev = pf->indio_dev;
172	struct maxim_thermocouple_data *data = iio_priv(indio_dev);
173	int ret;
174
175	ret = spi_read(data->spi, data->buffer.raw, data->chip->read_size);
176	if (!ret) {
177		iio_push_to_buffers_with_ts(indio_dev, &data->buffer,
178					    sizeof(data->buffer),
179					    iio_get_time_ns(indio_dev));
180	}
181
182	iio_trigger_notify_done(indio_dev->trig);
183
184	return IRQ_HANDLED;
185}
186
187static int maxim_thermocouple_read_raw(struct iio_dev *indio_dev,
188				       struct iio_chan_spec const *chan,
189				       int *val, int *val2, long mask)
190{
191	struct maxim_thermocouple_data *data = iio_priv(indio_dev);
192	int ret;
193
194	switch (mask) {
195	case IIO_CHAN_INFO_RAW:
196		if (!iio_device_claim_direct(indio_dev))
197			return -EBUSY;
198
199		ret = maxim_thermocouple_read(data, chan, val);
200		iio_device_release_direct(indio_dev);
201		if (ret)
202			return ret;
203
204		return IIO_VAL_INT;
205	case IIO_CHAN_INFO_SCALE:
206		switch (chan->channel2) {
207		case IIO_MOD_TEMP_AMBIENT:
208			*val = 62;
209			*val2 = 500000; /* 1000 * 0.0625 */
210			return IIO_VAL_INT_PLUS_MICRO;
211		default:
212			*val = 250; /* 1000 * 0.25 */
213			return IIO_VAL_INT;
214		}
215	case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
216		*val = data->tc_type;
217		return IIO_VAL_CHAR;
218	default:
219		return -EINVAL;
220	}
221}
222
223static const struct iio_info maxim_thermocouple_info = {
224	.read_raw = maxim_thermocouple_read_raw,
225};
226
227static int maxim_thermocouple_probe(struct spi_device *spi)
228{
229	const struct spi_device_id *id = spi_get_device_id(spi);
230	struct iio_dev *indio_dev;
231	struct maxim_thermocouple_data *data;
232	const int chip_type = (id->driver_data == MAX6675) ? MAX6675 : MAX31855;
233	const struct maxim_thermocouple_chip *chip =
234		&maxim_thermocouple_chips[chip_type];
235	int ret;
236
237	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
238	if (!indio_dev)
239		return -ENOMEM;
240
241	indio_dev->info = &maxim_thermocouple_info;
242	indio_dev->name = MAXIM_THERMOCOUPLE_DRV_NAME;
243	indio_dev->channels = chip->channels;
244	indio_dev->available_scan_masks = chip->scan_masks;
245	indio_dev->num_channels = chip->num_channels;
246	indio_dev->modes = INDIO_DIRECT_MODE;
247
248	data = iio_priv(indio_dev);
249	data->spi = spi;
250	data->chip = chip;
251	data->tc_type = maxim_tc_types[id->driver_data];
252
253	ret = devm_iio_triggered_buffer_setup(&spi->dev,
254				indio_dev, NULL,
255				maxim_thermocouple_trigger_handler, NULL);
256	if (ret)
257		return ret;
258
259	if (id->driver_data == MAX31855)
260		dev_warn(&spi->dev, "generic max31855 ID is deprecated\nplease use more specific part type");
261
262	return devm_iio_device_register(&spi->dev, indio_dev);
263}
264
265static const struct spi_device_id maxim_thermocouple_id[] = {
266	{"max6675", MAX6675},
267	{"max31855", MAX31855},
268	{"max31855k", MAX31855K},
269	{"max31855j", MAX31855J},
270	{"max31855n", MAX31855N},
271	{"max31855s", MAX31855S},
272	{"max31855t", MAX31855T},
273	{"max31855e", MAX31855E},
274	{"max31855r", MAX31855R},
275	{ }
276};
277MODULE_DEVICE_TABLE(spi, maxim_thermocouple_id);
278
279static const struct of_device_id maxim_thermocouple_of_match[] = {
280        { .compatible = "maxim,max6675" },
281        { .compatible = "maxim,max31855" },
282	{ .compatible = "maxim,max31855k" },
283	{ .compatible = "maxim,max31855j" },
284	{ .compatible = "maxim,max31855n" },
285	{ .compatible = "maxim,max31855s" },
286	{ .compatible = "maxim,max31855t" },
287	{ .compatible = "maxim,max31855e" },
288	{ .compatible = "maxim,max31855r" },
289        { },
290};
291MODULE_DEVICE_TABLE(of, maxim_thermocouple_of_match);
292
293static struct spi_driver maxim_thermocouple_driver = {
294	.driver = {
295		.name	= MAXIM_THERMOCOUPLE_DRV_NAME,
296		.of_match_table = maxim_thermocouple_of_match,
297	},
298	.probe		= maxim_thermocouple_probe,
299	.id_table	= maxim_thermocouple_id,
300};
301module_spi_driver(maxim_thermocouple_driver);
302
303MODULE_AUTHOR("Matt Ranostay <matt.ranostay@konsulko.com>");
304MODULE_DESCRIPTION("Maxim thermocouple sensors");
305MODULE_LICENSE("GPL");