xref: /linux/drivers/iio/adc/ad4000.c (revision c532de5a67a70f8533d495f8f2aaa9a0491c3ad0)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * AD4000 SPI ADC driver
4  *
5  * Copyright 2024 Analog Devices Inc.
6  */
7 #include <linux/bits.h>
8 #include <linux/bitfield.h>
9 #include <linux/byteorder/generic.h>
10 #include <linux/cleanup.h>
11 #include <linux/device.h>
12 #include <linux/err.h>
13 #include <linux/math.h>
14 #include <linux/module.h>
15 #include <linux/mod_devicetable.h>
16 #include <linux/gpio/consumer.h>
17 #include <linux/regulator/consumer.h>
18 #include <linux/spi/spi.h>
19 #include <linux/units.h>
20 #include <linux/util_macros.h>
21 #include <linux/iio/iio.h>
22 
23 #include <linux/iio/buffer.h>
24 #include <linux/iio/triggered_buffer.h>
25 #include <linux/iio/trigger_consumer.h>
26 
27 #define AD4000_READ_COMMAND	0x54
28 #define AD4000_WRITE_COMMAND	0x14
29 
30 #define AD4000_CONFIG_REG_DEFAULT	0xE1
31 
32 /* AD4000 Configuration Register programmable bits */
33 #define AD4000_CFG_SPAN_COMP		BIT(3) /* Input span compression  */
34 #define AD4000_CFG_HIGHZ		BIT(2) /* High impedance mode  */
35 
36 #define AD4000_SCALE_OPTIONS		2
37 
38 #define AD4000_TQUIET1_NS		190
39 #define AD4000_TQUIET2_NS		60
40 #define AD4000_TCONV_NS			320
41 
42 #define __AD4000_DIFF_CHANNEL(_sign, _real_bits, _storage_bits, _reg_access)	\
43 {										\
44 	.type = IIO_VOLTAGE,							\
45 	.indexed = 1,								\
46 	.differential = 1,							\
47 	.channel = 0,								\
48 	.channel2 = 1,								\
49 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |				\
50 			      BIT(IIO_CHAN_INFO_SCALE),				\
51 	.info_mask_separate_available = _reg_access ? BIT(IIO_CHAN_INFO_SCALE) : 0,\
52 	.scan_type = {								\
53 		.sign = _sign,							\
54 		.realbits = _real_bits,						\
55 		.storagebits = _storage_bits,					\
56 		.shift = _storage_bits - _real_bits,				\
57 		.endianness = IIO_BE,						\
58 	},									\
59 }
60 
61 #define AD4000_DIFF_CHANNEL(_sign, _real_bits, _reg_access)			\
62 	__AD4000_DIFF_CHANNEL((_sign), (_real_bits),				\
63 				     ((_real_bits) > 16 ? 32 : 16), (_reg_access))
64 
65 #define __AD4000_PSEUDO_DIFF_CHANNEL(_sign, _real_bits, _storage_bits, _reg_access)\
66 {										\
67 	.type = IIO_VOLTAGE,							\
68 	.indexed = 1,								\
69 	.channel = 0,								\
70 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |				\
71 			      BIT(IIO_CHAN_INFO_SCALE) |			\
72 			      BIT(IIO_CHAN_INFO_OFFSET),			\
73 	.info_mask_separate_available = _reg_access ? BIT(IIO_CHAN_INFO_SCALE) : 0,\
74 	.scan_type = {								\
75 		.sign = _sign,							\
76 		.realbits = _real_bits,						\
77 		.storagebits = _storage_bits,					\
78 		.shift = _storage_bits - _real_bits,				\
79 		.endianness = IIO_BE,						\
80 	},									\
81 }
82 
83 #define AD4000_PSEUDO_DIFF_CHANNEL(_sign, _real_bits, _reg_access)		\
84 	__AD4000_PSEUDO_DIFF_CHANNEL((_sign), (_real_bits),			\
85 				     ((_real_bits) > 16 ? 32 : 16), (_reg_access))
86 
87 static const char * const ad4000_power_supplies[] = {
88 	"vdd", "vio"
89 };
90 
91 enum ad4000_sdi {
92 	AD4000_SDI_MOSI,
93 	AD4000_SDI_VIO,
94 	AD4000_SDI_CS,
95 	AD4000_SDI_GND,
96 };
97 
98 /* maps adi,sdi-pin property value to enum */
99 static const char * const ad4000_sdi_pin[] = {
100 	[AD4000_SDI_MOSI] = "sdi",
101 	[AD4000_SDI_VIO] = "high",
102 	[AD4000_SDI_CS] = "cs",
103 	[AD4000_SDI_GND] = "low",
104 };
105 
106 /* Gains stored as fractions of 1000 so they can be expressed by integers. */
107 static const int ad4000_gains[] = {
108 	454, 909, 1000, 1900,
109 };
110 
111 struct ad4000_chip_info {
112 	const char *dev_name;
113 	struct iio_chan_spec chan_spec;
114 	struct iio_chan_spec reg_access_chan_spec;
115 	bool has_hardware_gain;
116 };
117 
118 static const struct ad4000_chip_info ad4000_chip_info = {
119 	.dev_name = "ad4000",
120 	.chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 16, 0),
121 	.reg_access_chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 16, 1),
122 };
123 
124 static const struct ad4000_chip_info ad4001_chip_info = {
125 	.dev_name = "ad4001",
126 	.chan_spec = AD4000_DIFF_CHANNEL('s', 16, 0),
127 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 16, 1),
128 };
129 
130 static const struct ad4000_chip_info ad4002_chip_info = {
131 	.dev_name = "ad4002",
132 	.chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 18, 0),
133 	.reg_access_chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 18, 1),
134 };
135 
136 static const struct ad4000_chip_info ad4003_chip_info = {
137 	.dev_name = "ad4003",
138 	.chan_spec = AD4000_DIFF_CHANNEL('s', 18, 0),
139 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 18, 1),
140 };
141 
142 static const struct ad4000_chip_info ad4004_chip_info = {
143 	.dev_name = "ad4004",
144 	.chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 16, 0),
145 	.reg_access_chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 16, 1),
146 };
147 
148 static const struct ad4000_chip_info ad4005_chip_info = {
149 	.dev_name = "ad4005",
150 	.chan_spec = AD4000_DIFF_CHANNEL('s', 16, 0),
151 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 16, 1),
152 };
153 
154 static const struct ad4000_chip_info ad4006_chip_info = {
155 	.dev_name = "ad4006",
156 	.chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 18, 0),
157 	.reg_access_chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 18, 1),
158 };
159 
160 static const struct ad4000_chip_info ad4007_chip_info = {
161 	.dev_name = "ad4007",
162 	.chan_spec = AD4000_DIFF_CHANNEL('s', 18, 0),
163 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 18, 1),
164 };
165 
166 static const struct ad4000_chip_info ad4008_chip_info = {
167 	.dev_name = "ad4008",
168 	.chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 16, 0),
169 	.reg_access_chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 16, 1),
170 };
171 
172 static const struct ad4000_chip_info ad4010_chip_info = {
173 	.dev_name = "ad4010",
174 	.chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 18, 0),
175 	.reg_access_chan_spec = AD4000_PSEUDO_DIFF_CHANNEL('u', 18, 1),
176 };
177 
178 static const struct ad4000_chip_info ad4011_chip_info = {
179 	.dev_name = "ad4011",
180 	.chan_spec = AD4000_DIFF_CHANNEL('s', 18, 0),
181 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 18, 1),
182 };
183 
184 static const struct ad4000_chip_info ad4020_chip_info = {
185 	.dev_name = "ad4020",
186 	.chan_spec = AD4000_DIFF_CHANNEL('s', 20, 0),
187 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 20, 1),
188 };
189 
190 static const struct ad4000_chip_info ad4021_chip_info = {
191 	.dev_name = "ad4021",
192 	.chan_spec = AD4000_DIFF_CHANNEL('s', 20, 0),
193 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 20, 1),
194 };
195 
196 static const struct ad4000_chip_info ad4022_chip_info = {
197 	.dev_name = "ad4022",
198 	.chan_spec = AD4000_DIFF_CHANNEL('s', 20, 0),
199 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 20, 1),
200 };
201 
202 static const struct ad4000_chip_info adaq4001_chip_info = {
203 	.dev_name = "adaq4001",
204 	.chan_spec = AD4000_DIFF_CHANNEL('s', 16, 0),
205 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 16, 1),
206 	.has_hardware_gain = true,
207 };
208 
209 static const struct ad4000_chip_info adaq4003_chip_info = {
210 	.dev_name = "adaq4003",
211 	.chan_spec = AD4000_DIFF_CHANNEL('s', 18, 0),
212 	.reg_access_chan_spec = AD4000_DIFF_CHANNEL('s', 18, 1),
213 	.has_hardware_gain = true,
214 };
215 
216 struct ad4000_state {
217 	struct spi_device *spi;
218 	struct gpio_desc *cnv_gpio;
219 	struct spi_transfer xfers[2];
220 	struct spi_message msg;
221 	struct mutex lock; /* Protect read modify write cycle */
222 	int vref_mv;
223 	enum ad4000_sdi sdi_pin;
224 	bool span_comp;
225 	u16 gain_milli;
226 	int scale_tbl[AD4000_SCALE_OPTIONS][2];
227 
228 	/*
229 	 * DMA (thus cache coherency maintenance) requires the transfer buffers
230 	 * to live in their own cache lines.
231 	 */
232 	struct {
233 		union {
234 			__be16 sample_buf16;
235 			__be32 sample_buf32;
236 		} data;
237 		s64 timestamp __aligned(8);
238 	} scan __aligned(IIO_DMA_MINALIGN);
239 	u8 tx_buf[2];
240 	u8 rx_buf[2];
241 };
242 
243 static void ad4000_fill_scale_tbl(struct ad4000_state *st,
244 				  struct iio_chan_spec const *chan)
245 {
246 	int val, tmp0, tmp1;
247 	int scale_bits;
248 	u64 tmp2;
249 
250 	/*
251 	 * ADCs that output two's complement code have one less bit to express
252 	 * voltage magnitude.
253 	 */
254 	if (chan->scan_type.sign == 's')
255 		scale_bits = chan->scan_type.realbits - 1;
256 	else
257 		scale_bits = chan->scan_type.realbits;
258 
259 	/*
260 	 * The gain is stored as a fraction of 1000 and, as we need to
261 	 * divide vref_mv by the gain, we invert the gain/1000 fraction.
262 	 * Also multiply by an extra MILLI to preserve precision.
263 	 * Thus, we have MILLI * MILLI equals MICRO as fraction numerator.
264 	 */
265 	val = mult_frac(st->vref_mv, MICRO, st->gain_milli);
266 
267 	/* Would multiply by NANO here but we multiplied by extra MILLI */
268 	tmp2 = shift_right((u64)val * MICRO, scale_bits);
269 	tmp0 = div_s64_rem(tmp2, NANO, &tmp1);
270 
271 	/* Store scale for when span compression is disabled */
272 	st->scale_tbl[0][0] = tmp0; /* Integer part */
273 	st->scale_tbl[0][1] = abs(tmp1); /* Fractional part */
274 
275 	/* Store scale for when span compression is enabled */
276 	st->scale_tbl[1][0] = tmp0;
277 
278 	/* The integer part is always zero so don't bother to divide it. */
279 	if (chan->differential)
280 		st->scale_tbl[1][1] = DIV_ROUND_CLOSEST(abs(tmp1) * 4, 5);
281 	else
282 		st->scale_tbl[1][1] = DIV_ROUND_CLOSEST(abs(tmp1) * 9, 10);
283 }
284 
285 static int ad4000_write_reg(struct ad4000_state *st, uint8_t val)
286 {
287 	st->tx_buf[0] = AD4000_WRITE_COMMAND;
288 	st->tx_buf[1] = val;
289 	return spi_write(st->spi, st->tx_buf, ARRAY_SIZE(st->tx_buf));
290 }
291 
292 static int ad4000_read_reg(struct ad4000_state *st, unsigned int *val)
293 {
294 	struct spi_transfer t = {
295 		.tx_buf = st->tx_buf,
296 		.rx_buf = st->rx_buf,
297 		.len = 2,
298 	};
299 	int ret;
300 
301 	st->tx_buf[0] = AD4000_READ_COMMAND;
302 	ret = spi_sync_transfer(st->spi, &t, 1);
303 	if (ret < 0)
304 		return ret;
305 
306 	*val = st->rx_buf[1];
307 	return ret;
308 }
309 
310 static int ad4000_convert_and_acquire(struct ad4000_state *st)
311 {
312 	int ret;
313 
314 	/*
315 	 * In 4-wire mode, the CNV line is held high for the entire conversion
316 	 * and acquisition process. In other modes, the CNV GPIO is optional
317 	 * and, if provided, replaces controller CS. If CNV GPIO is not defined
318 	 * gpiod_set_value_cansleep() has no effect.
319 	 */
320 	gpiod_set_value_cansleep(st->cnv_gpio, 1);
321 	ret = spi_sync(st->spi, &st->msg);
322 	gpiod_set_value_cansleep(st->cnv_gpio, 0);
323 
324 	return ret;
325 }
326 
327 static int ad4000_single_conversion(struct iio_dev *indio_dev,
328 				    const struct iio_chan_spec *chan, int *val)
329 {
330 	struct ad4000_state *st = iio_priv(indio_dev);
331 	u32 sample;
332 	int ret;
333 
334 	ret = ad4000_convert_and_acquire(st);
335 	if (ret < 0)
336 		return ret;
337 
338 	if (chan->scan_type.storagebits > 16)
339 		sample = be32_to_cpu(st->scan.data.sample_buf32);
340 	else
341 		sample = be16_to_cpu(st->scan.data.sample_buf16);
342 
343 	sample >>= chan->scan_type.shift;
344 
345 	if (chan->scan_type.sign == 's')
346 		*val = sign_extend32(sample, chan->scan_type.realbits - 1);
347 
348 	return IIO_VAL_INT;
349 }
350 
351 static int ad4000_read_raw(struct iio_dev *indio_dev,
352 			   struct iio_chan_spec const *chan, int *val,
353 			   int *val2, long info)
354 {
355 	struct ad4000_state *st = iio_priv(indio_dev);
356 
357 	switch (info) {
358 	case IIO_CHAN_INFO_RAW:
359 		iio_device_claim_direct_scoped(return -EBUSY, indio_dev)
360 			return ad4000_single_conversion(indio_dev, chan, val);
361 		unreachable();
362 	case IIO_CHAN_INFO_SCALE:
363 		*val = st->scale_tbl[st->span_comp][0];
364 		*val2 = st->scale_tbl[st->span_comp][1];
365 		return IIO_VAL_INT_PLUS_NANO;
366 	case IIO_CHAN_INFO_OFFSET:
367 		*val = 0;
368 		if (st->span_comp)
369 			*val = mult_frac(st->vref_mv, 1, 10);
370 
371 		return IIO_VAL_INT;
372 	default:
373 		return -EINVAL;
374 	}
375 }
376 
377 static int ad4000_read_avail(struct iio_dev *indio_dev,
378 			     struct iio_chan_spec const *chan,
379 			     const int **vals, int *type, int *length,
380 			     long info)
381 {
382 	struct ad4000_state *st = iio_priv(indio_dev);
383 
384 	switch (info) {
385 	case IIO_CHAN_INFO_SCALE:
386 		*vals = (int *)st->scale_tbl;
387 		*length = AD4000_SCALE_OPTIONS * 2;
388 		*type = IIO_VAL_INT_PLUS_NANO;
389 		return IIO_AVAIL_LIST;
390 	default:
391 		return -EINVAL;
392 	}
393 }
394 
395 static int ad4000_write_raw_get_fmt(struct iio_dev *indio_dev,
396 				    struct iio_chan_spec const *chan, long mask)
397 {
398 	switch (mask) {
399 	case IIO_CHAN_INFO_SCALE:
400 		return IIO_VAL_INT_PLUS_NANO;
401 	default:
402 		return IIO_VAL_INT_PLUS_MICRO;
403 	}
404 }
405 
406 static int ad4000_write_raw(struct iio_dev *indio_dev,
407 			    struct iio_chan_spec const *chan, int val, int val2,
408 			    long mask)
409 {
410 	struct ad4000_state *st = iio_priv(indio_dev);
411 	unsigned int reg_val;
412 	bool span_comp_en;
413 	int ret;
414 
415 	switch (mask) {
416 	case IIO_CHAN_INFO_SCALE:
417 		iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
418 			guard(mutex)(&st->lock);
419 
420 			ret = ad4000_read_reg(st, &reg_val);
421 			if (ret < 0)
422 				return ret;
423 
424 			span_comp_en = val2 == st->scale_tbl[1][1];
425 			reg_val &= ~AD4000_CFG_SPAN_COMP;
426 			reg_val |= FIELD_PREP(AD4000_CFG_SPAN_COMP, span_comp_en);
427 
428 			ret = ad4000_write_reg(st, reg_val);
429 			if (ret < 0)
430 				return ret;
431 
432 			st->span_comp = span_comp_en;
433 			return 0;
434 		}
435 		unreachable();
436 	default:
437 		return -EINVAL;
438 	}
439 }
440 
441 static irqreturn_t ad4000_trigger_handler(int irq, void *p)
442 {
443 	struct iio_poll_func *pf = p;
444 	struct iio_dev *indio_dev = pf->indio_dev;
445 	struct ad4000_state *st = iio_priv(indio_dev);
446 	int ret;
447 
448 	ret = ad4000_convert_and_acquire(st);
449 	if (ret < 0)
450 		goto err_out;
451 
452 	iio_push_to_buffers_with_timestamp(indio_dev, &st->scan, pf->timestamp);
453 
454 err_out:
455 	iio_trigger_notify_done(indio_dev->trig);
456 	return IRQ_HANDLED;
457 }
458 
459 static const struct iio_info ad4000_reg_access_info = {
460 	.read_raw = &ad4000_read_raw,
461 	.read_avail = &ad4000_read_avail,
462 	.write_raw = &ad4000_write_raw,
463 	.write_raw_get_fmt = &ad4000_write_raw_get_fmt,
464 };
465 
466 static const struct iio_info ad4000_info = {
467 	.read_raw = &ad4000_read_raw,
468 };
469 
470 /*
471  * This executes a data sample transfer for when the device connections are
472  * in "3-wire" mode, selected when the adi,sdi-pin device tree property is
473  * absent or set to "high". In this connection mode, the ADC SDI pin is
474  * connected to MOSI or to VIO and ADC CNV pin is connected either to a SPI
475  * controller CS or to a GPIO.
476  * AD4000 series of devices initiate conversions on the rising edge of CNV pin.
477  *
478  * If the CNV pin is connected to an SPI controller CS line (which is by default
479  * active low), the ADC readings would have a latency (delay) of one read.
480  * Moreover, since we also do ADC sampling for filling the buffer on triggered
481  * buffer mode, the timestamps of buffer readings would be disarranged.
482  * To prevent the read latency and reduce the time discrepancy between the
483  * sample read request and the time of actual sampling by the ADC, do a
484  * preparatory transfer to pulse the CS/CNV line.
485  */
486 static int ad4000_prepare_3wire_mode_message(struct ad4000_state *st,
487 					     const struct iio_chan_spec *chan)
488 {
489 	unsigned int cnv_pulse_time = AD4000_TCONV_NS;
490 	struct spi_transfer *xfers = st->xfers;
491 
492 	xfers[0].cs_change = 1;
493 	xfers[0].cs_change_delay.value = cnv_pulse_time;
494 	xfers[0].cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
495 
496 	xfers[1].rx_buf = &st->scan.data;
497 	xfers[1].len = BITS_TO_BYTES(chan->scan_type.storagebits);
498 	xfers[1].delay.value = AD4000_TQUIET2_NS;
499 	xfers[1].delay.unit = SPI_DELAY_UNIT_NSECS;
500 
501 	spi_message_init_with_transfers(&st->msg, st->xfers, 2);
502 
503 	return devm_spi_optimize_message(&st->spi->dev, st->spi, &st->msg);
504 }
505 
506 /*
507  * This executes a data sample transfer for when the device connections are
508  * in "4-wire" mode, selected when the adi,sdi-pin device tree property is
509  * set to "cs". In this connection mode, the controller CS pin is connected to
510  * ADC SDI pin and a GPIO is connected to ADC CNV pin.
511  * The GPIO connected to ADC CNV pin is set outside of the SPI transfer.
512  */
513 static int ad4000_prepare_4wire_mode_message(struct ad4000_state *st,
514 					     const struct iio_chan_spec *chan)
515 {
516 	unsigned int cnv_to_sdi_time = AD4000_TCONV_NS;
517 	struct spi_transfer *xfers = st->xfers;
518 
519 	/*
520 	 * Dummy transfer to cause enough delay between CNV going high and SDI
521 	 * going low.
522 	 */
523 	xfers[0].cs_off = 1;
524 	xfers[0].delay.value = cnv_to_sdi_time;
525 	xfers[0].delay.unit = SPI_DELAY_UNIT_NSECS;
526 
527 	xfers[1].rx_buf = &st->scan.data;
528 	xfers[1].len = BITS_TO_BYTES(chan->scan_type.storagebits);
529 
530 	spi_message_init_with_transfers(&st->msg, st->xfers, 2);
531 
532 	return devm_spi_optimize_message(&st->spi->dev, st->spi, &st->msg);
533 }
534 
535 static int ad4000_config(struct ad4000_state *st)
536 {
537 	unsigned int reg_val = AD4000_CONFIG_REG_DEFAULT;
538 
539 	if (device_property_present(&st->spi->dev, "adi,high-z-input"))
540 		reg_val |= FIELD_PREP(AD4000_CFG_HIGHZ, 1);
541 
542 	return ad4000_write_reg(st, reg_val);
543 }
544 
545 static int ad4000_probe(struct spi_device *spi)
546 {
547 	const struct ad4000_chip_info *chip;
548 	struct device *dev = &spi->dev;
549 	struct iio_dev *indio_dev;
550 	struct ad4000_state *st;
551 	int gain_idx, ret;
552 
553 	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
554 	if (!indio_dev)
555 		return -ENOMEM;
556 
557 	chip = spi_get_device_match_data(spi);
558 	if (!chip)
559 		return -EINVAL;
560 
561 	st = iio_priv(indio_dev);
562 	st->spi = spi;
563 
564 	ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(ad4000_power_supplies),
565 					     ad4000_power_supplies);
566 	if (ret)
567 		return dev_err_probe(dev, ret, "Failed to enable power supplies\n");
568 
569 	ret = devm_regulator_get_enable_read_voltage(dev, "ref");
570 	if (ret < 0)
571 		return dev_err_probe(dev, ret,
572 				     "Failed to get ref regulator reference\n");
573 	st->vref_mv = ret / 1000;
574 
575 	st->cnv_gpio = devm_gpiod_get_optional(dev, "cnv", GPIOD_OUT_HIGH);
576 	if (IS_ERR(st->cnv_gpio))
577 		return dev_err_probe(dev, PTR_ERR(st->cnv_gpio),
578 				     "Failed to get CNV GPIO");
579 
580 	ret = device_property_match_property_string(dev, "adi,sdi-pin",
581 						    ad4000_sdi_pin,
582 						    ARRAY_SIZE(ad4000_sdi_pin));
583 	if (ret < 0 && ret != -EINVAL)
584 		return dev_err_probe(dev, ret,
585 				     "getting adi,sdi-pin property failed\n");
586 
587 	/* Default to usual SPI connections if pin properties are not present */
588 	st->sdi_pin = ret == -EINVAL ? AD4000_SDI_MOSI : ret;
589 	switch (st->sdi_pin) {
590 	case AD4000_SDI_MOSI:
591 		indio_dev->info = &ad4000_reg_access_info;
592 		indio_dev->channels = &chip->reg_access_chan_spec;
593 
594 		/*
595 		 * In "3-wire mode", the ADC SDI line must be kept high when
596 		 * data is not being clocked out of the controller.
597 		 * Request the SPI controller to make MOSI idle high.
598 		 */
599 		spi->mode |= SPI_MOSI_IDLE_HIGH;
600 		ret = spi_setup(spi);
601 		if (ret < 0)
602 			return ret;
603 
604 		ret = ad4000_prepare_3wire_mode_message(st, indio_dev->channels);
605 		if (ret)
606 			return ret;
607 
608 		ret = ad4000_config(st);
609 		if (ret < 0)
610 			return dev_err_probe(dev, ret, "Failed to config device\n");
611 
612 		break;
613 	case AD4000_SDI_VIO:
614 		indio_dev->info = &ad4000_info;
615 		indio_dev->channels = &chip->chan_spec;
616 		ret = ad4000_prepare_3wire_mode_message(st, indio_dev->channels);
617 		if (ret)
618 			return ret;
619 
620 		break;
621 	case AD4000_SDI_CS:
622 		indio_dev->info = &ad4000_info;
623 		indio_dev->channels = &chip->chan_spec;
624 		ret = ad4000_prepare_4wire_mode_message(st, indio_dev->channels);
625 		if (ret)
626 			return ret;
627 
628 		break;
629 	case AD4000_SDI_GND:
630 		return dev_err_probe(dev, -EPROTONOSUPPORT,
631 				     "Unsupported connection mode\n");
632 
633 	default:
634 		return dev_err_probe(dev, -EINVAL, "Unrecognized connection mode\n");
635 	}
636 
637 	indio_dev->name = chip->dev_name;
638 	indio_dev->num_channels = 1;
639 
640 	devm_mutex_init(dev, &st->lock);
641 
642 	st->gain_milli = 1000;
643 	if (chip->has_hardware_gain) {
644 		ret = device_property_read_u16(dev, "adi,gain-milli",
645 					       &st->gain_milli);
646 		if (!ret) {
647 			/* Match gain value from dt to one of supported gains */
648 			gain_idx = find_closest(st->gain_milli, ad4000_gains,
649 						ARRAY_SIZE(ad4000_gains));
650 			st->gain_milli = ad4000_gains[gain_idx];
651 		} else {
652 			return dev_err_probe(dev, ret,
653 					     "Failed to read gain property\n");
654 		}
655 	}
656 
657 	ad4000_fill_scale_tbl(st, indio_dev->channels);
658 
659 	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
660 					      &iio_pollfunc_store_time,
661 					      &ad4000_trigger_handler, NULL);
662 	if (ret)
663 		return ret;
664 
665 	return devm_iio_device_register(dev, indio_dev);
666 }
667 
668 static const struct spi_device_id ad4000_id[] = {
669 	{ "ad4000", (kernel_ulong_t)&ad4000_chip_info },
670 	{ "ad4001", (kernel_ulong_t)&ad4001_chip_info },
671 	{ "ad4002", (kernel_ulong_t)&ad4002_chip_info },
672 	{ "ad4003", (kernel_ulong_t)&ad4003_chip_info },
673 	{ "ad4004", (kernel_ulong_t)&ad4004_chip_info },
674 	{ "ad4005", (kernel_ulong_t)&ad4005_chip_info },
675 	{ "ad4006", (kernel_ulong_t)&ad4006_chip_info },
676 	{ "ad4007", (kernel_ulong_t)&ad4007_chip_info },
677 	{ "ad4008", (kernel_ulong_t)&ad4008_chip_info },
678 	{ "ad4010", (kernel_ulong_t)&ad4010_chip_info },
679 	{ "ad4011", (kernel_ulong_t)&ad4011_chip_info },
680 	{ "ad4020", (kernel_ulong_t)&ad4020_chip_info },
681 	{ "ad4021", (kernel_ulong_t)&ad4021_chip_info },
682 	{ "ad4022", (kernel_ulong_t)&ad4022_chip_info },
683 	{ "adaq4001", (kernel_ulong_t)&adaq4001_chip_info },
684 	{ "adaq4003", (kernel_ulong_t)&adaq4003_chip_info },
685 	{ }
686 };
687 MODULE_DEVICE_TABLE(spi, ad4000_id);
688 
689 static const struct of_device_id ad4000_of_match[] = {
690 	{ .compatible = "adi,ad4000", .data = &ad4000_chip_info },
691 	{ .compatible = "adi,ad4001", .data = &ad4001_chip_info },
692 	{ .compatible = "adi,ad4002", .data = &ad4002_chip_info },
693 	{ .compatible = "adi,ad4003", .data = &ad4003_chip_info },
694 	{ .compatible = "adi,ad4004", .data = &ad4004_chip_info },
695 	{ .compatible = "adi,ad4005", .data = &ad4005_chip_info },
696 	{ .compatible = "adi,ad4006", .data = &ad4006_chip_info },
697 	{ .compatible = "adi,ad4007", .data = &ad4007_chip_info },
698 	{ .compatible = "adi,ad4008", .data = &ad4008_chip_info },
699 	{ .compatible = "adi,ad4010", .data = &ad4010_chip_info },
700 	{ .compatible = "adi,ad4011", .data = &ad4011_chip_info },
701 	{ .compatible = "adi,ad4020", .data = &ad4020_chip_info },
702 	{ .compatible = "adi,ad4021", .data = &ad4021_chip_info },
703 	{ .compatible = "adi,ad4022", .data = &ad4022_chip_info },
704 	{ .compatible = "adi,adaq4001", .data = &adaq4001_chip_info },
705 	{ .compatible = "adi,adaq4003", .data = &adaq4003_chip_info },
706 	{ }
707 };
708 MODULE_DEVICE_TABLE(of, ad4000_of_match);
709 
710 static struct spi_driver ad4000_driver = {
711 	.driver = {
712 		.name   = "ad4000",
713 		.of_match_table = ad4000_of_match,
714 	},
715 	.probe          = ad4000_probe,
716 	.id_table       = ad4000_id,
717 };
718 module_spi_driver(ad4000_driver);
719 
720 MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt@analog.com>");
721 MODULE_DESCRIPTION("Analog Devices AD4000 ADC driver");
722 MODULE_LICENSE("GPL");
723