1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * STMicroelectronics st_lsm6dsx FIFO buffer library driver
4  *
5  * LSM6DS3/LSM6DS3H/LSM6DSL/LSM6DSM/ISM330DLC/LSM6DS3TR-C:
6  * The FIFO buffer can be configured to store data from gyroscope and
7  * accelerometer. Samples are queued without any tag according to a
8  * specific pattern based on 'FIFO data sets' (6 bytes each):
9  *  - 1st data set is reserved for gyroscope data
10  *  - 2nd data set is reserved for accelerometer data
11  * The FIFO pattern changes depending on the ODRs and decimation factors
12  * assigned to the FIFO data sets. The first sequence of data stored in FIFO
13  * buffer contains the data of all the enabled FIFO data sets
14  * (e.g. Gx, Gy, Gz, Ax, Ay, Az), then data are repeated depending on the
15  * value of the decimation factor and ODR set for each FIFO data set.
16  *
17  * LSM6DSO/LSM6DSOX/ASM330LHH/LSM6DSR/LSM6DSRX/ISM330DHCX:
18  * The FIFO buffer can be configured to store data from gyroscope and
19  * accelerometer. Each sample is queued with a tag (1B) indicating data
20  * source (gyroscope, accelerometer, hw timer).
21  *
22  * FIFO supported modes:
23  *  - BYPASS: FIFO disabled
24  *  - CONTINUOUS: FIFO enabled. When the buffer is full, the FIFO index
25  *    restarts from the beginning and the oldest sample is overwritten
26  *
27  * Copyright 2016 STMicroelectronics Inc.
28  *
29  * Lorenzo Bianconi <lorenzo.bianconi@st.com>
30  * Denis Ciocca <denis.ciocca@st.com>
31  */
32 #include <linux/module.h>
33 #include <linux/iio/kfifo_buf.h>
34 #include <linux/iio/iio.h>
35 #include <linux/iio/buffer.h>
36 #include <linux/regmap.h>
37 #include <linux/bitfield.h>
38 
39 #include <linux/platform_data/st_sensors_pdata.h>
40 
41 #include "st_lsm6dsx.h"
42 
43 #define ST_LSM6DSX_REG_FIFO_MODE_ADDR		0x0a
44 #define ST_LSM6DSX_FIFO_MODE_MASK		GENMASK(2, 0)
45 #define ST_LSM6DSX_FIFO_ODR_MASK		GENMASK(6, 3)
46 #define ST_LSM6DSX_FIFO_EMPTY_MASK		BIT(12)
47 #define ST_LSM6DSX_REG_FIFO_OUTL_ADDR		0x3e
48 #define ST_LSM6DSX_REG_FIFO_OUT_TAG_ADDR	0x78
49 #define ST_LSM6DSX_REG_TS_RESET_ADDR		0x42
50 
51 #define ST_LSM6DSX_MAX_FIFO_ODR_VAL		0x08
52 
53 #define ST_LSM6DSX_TS_RESET_VAL			0xaa
54 
55 struct st_lsm6dsx_decimator_entry {
56 	u8 decimator;
57 	u8 val;
58 };
59 
60 enum st_lsm6dsx_fifo_tag {
61 	ST_LSM6DSX_GYRO_TAG = 0x01,
62 	ST_LSM6DSX_ACC_TAG = 0x02,
63 	ST_LSM6DSX_TS_TAG = 0x04,
64 	ST_LSM6DSX_EXT0_TAG = 0x0f,
65 	ST_LSM6DSX_EXT1_TAG = 0x10,
66 	ST_LSM6DSX_EXT2_TAG = 0x11,
67 };
68 
69 static const
70 struct st_lsm6dsx_decimator_entry st_lsm6dsx_decimator_table[] = {
71 	{  0, 0x0 },
72 	{  1, 0x1 },
73 	{  2, 0x2 },
74 	{  3, 0x3 },
75 	{  4, 0x4 },
76 	{  8, 0x5 },
77 	{ 16, 0x6 },
78 	{ 32, 0x7 },
79 };
80 
81 static int st_lsm6dsx_get_decimator_val(u8 val)
82 {
83 	const int max_size = ARRAY_SIZE(st_lsm6dsx_decimator_table);
84 	int i;
85 
86 	for (i = 0; i < max_size; i++)
87 		if (st_lsm6dsx_decimator_table[i].decimator == val)
88 			break;
89 
90 	return i == max_size ? 0 : st_lsm6dsx_decimator_table[i].val;
91 }
92 
93 static void st_lsm6dsx_get_max_min_odr(struct st_lsm6dsx_hw *hw,
94 				       u32 *max_odr, u32 *min_odr)
95 {
96 	struct st_lsm6dsx_sensor *sensor;
97 	int i;
98 
99 	*max_odr = 0, *min_odr = ~0;
100 	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
101 		if (!hw->iio_devs[i])
102 			continue;
103 
104 		sensor = iio_priv(hw->iio_devs[i]);
105 
106 		if (!(hw->enable_mask & BIT(sensor->id)))
107 			continue;
108 
109 		*max_odr = max_t(u32, *max_odr, sensor->odr);
110 		*min_odr = min_t(u32, *min_odr, sensor->odr);
111 	}
112 }
113 
114 static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
115 {
116 	const struct st_lsm6dsx_reg *ts_dec_reg;
117 	struct st_lsm6dsx_sensor *sensor;
118 	u16 sip = 0, ts_sip = 0;
119 	u32 max_odr, min_odr;
120 	int err = 0, i;
121 	u8 data;
122 
123 	st_lsm6dsx_get_max_min_odr(hw, &max_odr, &min_odr);
124 
125 	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
126 		const struct st_lsm6dsx_reg *dec_reg;
127 
128 		if (!hw->iio_devs[i])
129 			continue;
130 
131 		sensor = iio_priv(hw->iio_devs[i]);
132 		/* update fifo decimators and sample in pattern */
133 		if (hw->enable_mask & BIT(sensor->id)) {
134 			sensor->sip = sensor->odr / min_odr;
135 			sensor->decimator = max_odr / sensor->odr;
136 			data = st_lsm6dsx_get_decimator_val(sensor->decimator);
137 		} else {
138 			sensor->sip = 0;
139 			sensor->decimator = 0;
140 			data = 0;
141 		}
142 		ts_sip = max_t(u16, ts_sip, sensor->sip);
143 
144 		dec_reg = &hw->settings->decimator[sensor->id];
145 		if (dec_reg->addr) {
146 			int val = ST_LSM6DSX_SHIFT_VAL(data, dec_reg->mask);
147 
148 			err = st_lsm6dsx_update_bits_locked(hw, dec_reg->addr,
149 							    dec_reg->mask,
150 							    val);
151 			if (err < 0)
152 				return err;
153 		}
154 		sip += sensor->sip;
155 	}
156 	hw->sip = sip + ts_sip;
157 	hw->ts_sip = ts_sip;
158 
159 	/*
160 	 * update hw ts decimator if necessary. Decimator for hw timestamp
161 	 * is always 1 or 0 in order to have a ts sample for each data
162 	 * sample in FIFO
163 	 */
164 	ts_dec_reg = &hw->settings->ts_settings.decimator;
165 	if (ts_dec_reg->addr) {
166 		int val, ts_dec = !!hw->ts_sip;
167 
168 		val = ST_LSM6DSX_SHIFT_VAL(ts_dec, ts_dec_reg->mask);
169 		err = st_lsm6dsx_update_bits_locked(hw, ts_dec_reg->addr,
170 						    ts_dec_reg->mask, val);
171 	}
172 	return err;
173 }
174 
175 int st_lsm6dsx_set_fifo_mode(struct st_lsm6dsx_hw *hw,
176 			     enum st_lsm6dsx_fifo_mode fifo_mode)
177 {
178 	unsigned int data;
179 	int err;
180 
181 	data = FIELD_PREP(ST_LSM6DSX_FIFO_MODE_MASK, fifo_mode);
182 	err = st_lsm6dsx_update_bits_locked(hw, ST_LSM6DSX_REG_FIFO_MODE_ADDR,
183 					    ST_LSM6DSX_FIFO_MODE_MASK, data);
184 	if (err < 0)
185 		return err;
186 
187 	hw->fifo_mode = fifo_mode;
188 
189 	return 0;
190 }
191 
192 static int st_lsm6dsx_set_fifo_odr(struct st_lsm6dsx_sensor *sensor,
193 				   bool enable)
194 {
195 	struct st_lsm6dsx_hw *hw = sensor->hw;
196 	const struct st_lsm6dsx_reg *batch_reg;
197 	u8 data;
198 
199 	batch_reg = &hw->settings->batch[sensor->id];
200 	if (batch_reg->addr) {
201 		int val;
202 
203 		if (enable) {
204 			int err;
205 
206 			err = st_lsm6dsx_check_odr(sensor, sensor->odr,
207 						   &data);
208 			if (err < 0)
209 				return err;
210 		} else {
211 			data = 0;
212 		}
213 		val = ST_LSM6DSX_SHIFT_VAL(data, batch_reg->mask);
214 		return st_lsm6dsx_update_bits_locked(hw, batch_reg->addr,
215 						     batch_reg->mask, val);
216 	} else {
217 		data = hw->enable_mask ? ST_LSM6DSX_MAX_FIFO_ODR_VAL : 0;
218 		return st_lsm6dsx_update_bits_locked(hw,
219 					ST_LSM6DSX_REG_FIFO_MODE_ADDR,
220 					ST_LSM6DSX_FIFO_ODR_MASK,
221 					FIELD_PREP(ST_LSM6DSX_FIFO_ODR_MASK,
222 						   data));
223 	}
224 }
225 
226 int st_lsm6dsx_update_watermark(struct st_lsm6dsx_sensor *sensor, u16 watermark)
227 {
228 	u16 fifo_watermark = ~0, cur_watermark, fifo_th_mask;
229 	struct st_lsm6dsx_hw *hw = sensor->hw;
230 	struct st_lsm6dsx_sensor *cur_sensor;
231 	int i, err, data;
232 	__le16 wdata;
233 
234 	if (!hw->sip)
235 		return 0;
236 
237 	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
238 		if (!hw->iio_devs[i])
239 			continue;
240 
241 		cur_sensor = iio_priv(hw->iio_devs[i]);
242 
243 		if (!(hw->enable_mask & BIT(cur_sensor->id)))
244 			continue;
245 
246 		cur_watermark = (cur_sensor == sensor) ? watermark
247 						       : cur_sensor->watermark;
248 
249 		fifo_watermark = min_t(u16, fifo_watermark, cur_watermark);
250 	}
251 
252 	fifo_watermark = max_t(u16, fifo_watermark, hw->sip);
253 	fifo_watermark = (fifo_watermark / hw->sip) * hw->sip;
254 	fifo_watermark = fifo_watermark * hw->settings->fifo_ops.th_wl;
255 
256 	mutex_lock(&hw->page_lock);
257 	err = regmap_read(hw->regmap, hw->settings->fifo_ops.fifo_th.addr + 1,
258 			  &data);
259 	if (err < 0)
260 		goto out;
261 
262 	fifo_th_mask = hw->settings->fifo_ops.fifo_th.mask;
263 	fifo_watermark = ((data << 8) & ~fifo_th_mask) |
264 			 (fifo_watermark & fifo_th_mask);
265 
266 	wdata = cpu_to_le16(fifo_watermark);
267 	err = regmap_bulk_write(hw->regmap,
268 				hw->settings->fifo_ops.fifo_th.addr,
269 				&wdata, sizeof(wdata));
270 out:
271 	mutex_unlock(&hw->page_lock);
272 	return err;
273 }
274 
275 static int st_lsm6dsx_reset_hw_ts(struct st_lsm6dsx_hw *hw)
276 {
277 	struct st_lsm6dsx_sensor *sensor;
278 	int i, err;
279 
280 	/* reset hw ts counter */
281 	err = st_lsm6dsx_write_locked(hw, ST_LSM6DSX_REG_TS_RESET_ADDR,
282 				      ST_LSM6DSX_TS_RESET_VAL);
283 	if (err < 0)
284 		return err;
285 
286 	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
287 		if (!hw->iio_devs[i])
288 			continue;
289 
290 		sensor = iio_priv(hw->iio_devs[i]);
291 		/*
292 		 * store enable buffer timestamp as reference for
293 		 * hw timestamp
294 		 */
295 		sensor->ts_ref = iio_get_time_ns(hw->iio_devs[i]);
296 	}
297 	return 0;
298 }
299 
300 /*
301  * Set max bulk read to ST_LSM6DSX_MAX_WORD_LEN/ST_LSM6DSX_MAX_TAGGED_WORD_LEN
302  * in order to avoid a kmalloc for each bus access
303  */
304 static inline int st_lsm6dsx_read_block(struct st_lsm6dsx_hw *hw, u8 addr,
305 					u8 *data, unsigned int data_len,
306 					unsigned int max_word_len)
307 {
308 	unsigned int word_len, read_len = 0;
309 	int err;
310 
311 	while (read_len < data_len) {
312 		word_len = min_t(unsigned int, data_len - read_len,
313 				 max_word_len);
314 		err = st_lsm6dsx_read_locked(hw, addr, data + read_len,
315 					     word_len);
316 		if (err < 0)
317 			return err;
318 		read_len += word_len;
319 	}
320 	return 0;
321 }
322 
323 #define ST_LSM6DSX_IIO_BUFF_SIZE	(ALIGN(ST_LSM6DSX_SAMPLE_SIZE, \
324 					       sizeof(s64)) + sizeof(s64))
325 /**
326  * st_lsm6dsx_read_fifo() - hw FIFO read routine
327  * @hw: Pointer to instance of struct st_lsm6dsx_hw.
328  *
329  * Read samples from the hw FIFO and push them to IIO buffers.
330  *
331  * Return: Number of bytes read from the FIFO
332  */
333 int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
334 {
335 	u16 fifo_len, pattern_len = hw->sip * ST_LSM6DSX_SAMPLE_SIZE;
336 	u16 fifo_diff_mask = hw->settings->fifo_ops.fifo_diff.mask;
337 	int err, acc_sip, gyro_sip, ts_sip, read_len, offset;
338 	struct st_lsm6dsx_sensor *acc_sensor, *gyro_sensor;
339 	u8 gyro_buff[ST_LSM6DSX_IIO_BUFF_SIZE];
340 	u8 acc_buff[ST_LSM6DSX_IIO_BUFF_SIZE];
341 	bool reset_ts = false;
342 	__le16 fifo_status;
343 	s64 ts = 0;
344 
345 	err = st_lsm6dsx_read_locked(hw,
346 				     hw->settings->fifo_ops.fifo_diff.addr,
347 				     &fifo_status, sizeof(fifo_status));
348 	if (err < 0) {
349 		dev_err(hw->dev, "failed to read fifo status (err=%d)\n",
350 			err);
351 		return err;
352 	}
353 
354 	if (fifo_status & cpu_to_le16(ST_LSM6DSX_FIFO_EMPTY_MASK))
355 		return 0;
356 
357 	fifo_len = (le16_to_cpu(fifo_status) & fifo_diff_mask) *
358 		   ST_LSM6DSX_CHAN_SIZE;
359 	fifo_len = (fifo_len / pattern_len) * pattern_len;
360 
361 	acc_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_ACC]);
362 	gyro_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_GYRO]);
363 
364 	for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
365 		err = st_lsm6dsx_read_block(hw, ST_LSM6DSX_REG_FIFO_OUTL_ADDR,
366 					    hw->buff, pattern_len,
367 					    ST_LSM6DSX_MAX_WORD_LEN);
368 		if (err < 0) {
369 			dev_err(hw->dev,
370 				"failed to read pattern from fifo (err=%d)\n",
371 				err);
372 			return err;
373 		}
374 
375 		/*
376 		 * Data are written to the FIFO with a specific pattern
377 		 * depending on the configured ODRs. The first sequence of data
378 		 * stored in FIFO contains the data of all enabled sensors
379 		 * (e.g. Gx, Gy, Gz, Ax, Ay, Az, Ts), then data are repeated
380 		 * depending on the value of the decimation factor set for each
381 		 * sensor.
382 		 *
383 		 * Supposing the FIFO is storing data from gyroscope and
384 		 * accelerometer at different ODRs:
385 		 *   - gyroscope ODR = 208Hz, accelerometer ODR = 104Hz
386 		 * Since the gyroscope ODR is twice the accelerometer one, the
387 		 * following pattern is repeated every 9 samples:
388 		 *   - Gx, Gy, Gz, Ax, Ay, Az, Ts, Gx, Gy, Gz, Ts, Gx, ..
389 		 */
390 		gyro_sip = gyro_sensor->sip;
391 		acc_sip = acc_sensor->sip;
392 		ts_sip = hw->ts_sip;
393 		offset = 0;
394 
395 		while (acc_sip > 0 || gyro_sip > 0) {
396 			if (gyro_sip > 0) {
397 				memcpy(gyro_buff, &hw->buff[offset],
398 				       ST_LSM6DSX_SAMPLE_SIZE);
399 				offset += ST_LSM6DSX_SAMPLE_SIZE;
400 			}
401 			if (acc_sip > 0) {
402 				memcpy(acc_buff, &hw->buff[offset],
403 				       ST_LSM6DSX_SAMPLE_SIZE);
404 				offset += ST_LSM6DSX_SAMPLE_SIZE;
405 			}
406 
407 			if (ts_sip-- > 0) {
408 				u8 data[ST_LSM6DSX_SAMPLE_SIZE];
409 
410 				memcpy(data, &hw->buff[offset], sizeof(data));
411 				/*
412 				 * hw timestamp is 3B long and it is stored
413 				 * in FIFO using 6B as 4th FIFO data set
414 				 * according to this schema:
415 				 * B0 = ts[15:8], B1 = ts[23:16], B3 = ts[7:0]
416 				 */
417 				ts = data[1] << 16 | data[0] << 8 | data[3];
418 				/*
419 				 * check if hw timestamp engine is going to
420 				 * reset (the sensor generates an interrupt
421 				 * to signal the hw timestamp will reset in
422 				 * 1.638s)
423 				 */
424 				if (!reset_ts && ts >= 0xff0000)
425 					reset_ts = true;
426 				ts *= hw->ts_gain;
427 
428 				offset += ST_LSM6DSX_SAMPLE_SIZE;
429 			}
430 
431 			if (gyro_sip-- > 0)
432 				iio_push_to_buffers_with_timestamp(
433 					hw->iio_devs[ST_LSM6DSX_ID_GYRO],
434 					gyro_buff, gyro_sensor->ts_ref + ts);
435 			if (acc_sip-- > 0)
436 				iio_push_to_buffers_with_timestamp(
437 					hw->iio_devs[ST_LSM6DSX_ID_ACC],
438 					acc_buff, acc_sensor->ts_ref + ts);
439 		}
440 	}
441 
442 	if (unlikely(reset_ts)) {
443 		err = st_lsm6dsx_reset_hw_ts(hw);
444 		if (err < 0) {
445 			dev_err(hw->dev, "failed to reset hw ts (err=%d)\n",
446 				err);
447 			return err;
448 		}
449 	}
450 	return read_len;
451 }
452 
453 #define ST_LSM6DSX_INVALID_SAMPLE	0x7ffd
454 static int
455 st_lsm6dsx_push_tagged_data(struct st_lsm6dsx_hw *hw, u8 tag,
456 			    u8 *data, s64 ts)
457 {
458 	s16 val = le16_to_cpu(*(__le16 *)data);
459 	struct st_lsm6dsx_sensor *sensor;
460 	struct iio_dev *iio_dev;
461 
462 	/* invalid sample during bootstrap phase */
463 	if (val >= ST_LSM6DSX_INVALID_SAMPLE)
464 		return -EINVAL;
465 
466 	/*
467 	 * EXT_TAG are managed in FIFO fashion so ST_LSM6DSX_EXT0_TAG
468 	 * corresponds to the first enabled channel, ST_LSM6DSX_EXT1_TAG
469 	 * to the second one and ST_LSM6DSX_EXT2_TAG to the last enabled
470 	 * channel
471 	 */
472 	switch (tag) {
473 	case ST_LSM6DSX_GYRO_TAG:
474 		iio_dev = hw->iio_devs[ST_LSM6DSX_ID_GYRO];
475 		break;
476 	case ST_LSM6DSX_ACC_TAG:
477 		iio_dev = hw->iio_devs[ST_LSM6DSX_ID_ACC];
478 		break;
479 	case ST_LSM6DSX_EXT0_TAG:
480 		if (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT0))
481 			iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT0];
482 		else if (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT1))
483 			iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT1];
484 		else
485 			iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];
486 		break;
487 	case ST_LSM6DSX_EXT1_TAG:
488 		if ((hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT0)) &&
489 		    (hw->enable_mask & BIT(ST_LSM6DSX_ID_EXT1)))
490 			iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT1];
491 		else
492 			iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];
493 		break;
494 	case ST_LSM6DSX_EXT2_TAG:
495 		iio_dev = hw->iio_devs[ST_LSM6DSX_ID_EXT2];
496 		break;
497 	default:
498 		return -EINVAL;
499 	}
500 
501 	sensor = iio_priv(iio_dev);
502 	iio_push_to_buffers_with_timestamp(iio_dev, data,
503 					   ts + sensor->ts_ref);
504 
505 	return 0;
506 }
507 
508 /**
509  * st_lsm6dsx_read_tagged_fifo() - tagged hw FIFO read routine
510  * @hw: Pointer to instance of struct st_lsm6dsx_hw.
511  *
512  * Read samples from the hw FIFO and push them to IIO buffers.
513  *
514  * Return: Number of bytes read from the FIFO
515  */
516 int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw)
517 {
518 	u16 pattern_len = hw->sip * ST_LSM6DSX_TAGGED_SAMPLE_SIZE;
519 	u16 fifo_len, fifo_diff_mask;
520 	u8 iio_buff[ST_LSM6DSX_IIO_BUFF_SIZE], tag;
521 	bool reset_ts = false;
522 	int i, err, read_len;
523 	__le16 fifo_status;
524 	s64 ts = 0;
525 
526 	err = st_lsm6dsx_read_locked(hw,
527 				     hw->settings->fifo_ops.fifo_diff.addr,
528 				     &fifo_status, sizeof(fifo_status));
529 	if (err < 0) {
530 		dev_err(hw->dev, "failed to read fifo status (err=%d)\n",
531 			err);
532 		return err;
533 	}
534 
535 	fifo_diff_mask = hw->settings->fifo_ops.fifo_diff.mask;
536 	fifo_len = (le16_to_cpu(fifo_status) & fifo_diff_mask) *
537 		   ST_LSM6DSX_TAGGED_SAMPLE_SIZE;
538 	if (!fifo_len)
539 		return 0;
540 
541 	for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
542 		err = st_lsm6dsx_read_block(hw,
543 					    ST_LSM6DSX_REG_FIFO_OUT_TAG_ADDR,
544 					    hw->buff, pattern_len,
545 					    ST_LSM6DSX_MAX_TAGGED_WORD_LEN);
546 		if (err < 0) {
547 			dev_err(hw->dev,
548 				"failed to read pattern from fifo (err=%d)\n",
549 				err);
550 			return err;
551 		}
552 
553 		for (i = 0; i < pattern_len;
554 		     i += ST_LSM6DSX_TAGGED_SAMPLE_SIZE) {
555 			memcpy(iio_buff, &hw->buff[i + ST_LSM6DSX_TAG_SIZE],
556 			       ST_LSM6DSX_SAMPLE_SIZE);
557 
558 			tag = hw->buff[i] >> 3;
559 			if (tag == ST_LSM6DSX_TS_TAG) {
560 				/*
561 				 * hw timestamp is 4B long and it is stored
562 				 * in FIFO according to this schema:
563 				 * B0 = ts[7:0], B1 = ts[15:8], B2 = ts[23:16],
564 				 * B3 = ts[31:24]
565 				 */
566 				ts = le32_to_cpu(*((__le32 *)iio_buff));
567 				/*
568 				 * check if hw timestamp engine is going to
569 				 * reset (the sensor generates an interrupt
570 				 * to signal the hw timestamp will reset in
571 				 * 1.638s)
572 				 */
573 				if (!reset_ts && ts >= 0xffff0000)
574 					reset_ts = true;
575 				ts *= hw->ts_gain;
576 			} else {
577 				st_lsm6dsx_push_tagged_data(hw, tag, iio_buff,
578 							    ts);
579 			}
580 		}
581 	}
582 
583 	if (unlikely(reset_ts)) {
584 		err = st_lsm6dsx_reset_hw_ts(hw);
585 		if (err < 0)
586 			return err;
587 	}
588 	return read_len;
589 }
590 
591 int st_lsm6dsx_flush_fifo(struct st_lsm6dsx_hw *hw)
592 {
593 	int err;
594 
595 	if (!hw->settings->fifo_ops.read_fifo)
596 		return -ENOTSUPP;
597 
598 	mutex_lock(&hw->fifo_lock);
599 
600 	hw->settings->fifo_ops.read_fifo(hw);
601 	err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_BYPASS);
602 
603 	mutex_unlock(&hw->fifo_lock);
604 
605 	return err;
606 }
607 
608 int st_lsm6dsx_update_fifo(struct st_lsm6dsx_sensor *sensor, bool enable)
609 {
610 	struct st_lsm6dsx_hw *hw = sensor->hw;
611 	int err;
612 
613 	mutex_lock(&hw->conf_lock);
614 
615 	if (hw->fifo_mode != ST_LSM6DSX_FIFO_BYPASS) {
616 		err = st_lsm6dsx_flush_fifo(hw);
617 		if (err < 0)
618 			goto out;
619 	}
620 
621 	if (sensor->id == ST_LSM6DSX_ID_EXT0 ||
622 	    sensor->id == ST_LSM6DSX_ID_EXT1 ||
623 	    sensor->id == ST_LSM6DSX_ID_EXT2) {
624 		err = st_lsm6dsx_shub_set_enable(sensor, enable);
625 		if (err < 0)
626 			goto out;
627 	} else {
628 		err = st_lsm6dsx_sensor_set_enable(sensor, enable);
629 		if (err < 0)
630 			goto out;
631 
632 		err = st_lsm6dsx_set_fifo_odr(sensor, enable);
633 		if (err < 0)
634 			goto out;
635 	}
636 
637 	err = st_lsm6dsx_update_decimators(hw);
638 	if (err < 0)
639 		goto out;
640 
641 	err = st_lsm6dsx_update_watermark(sensor, sensor->watermark);
642 	if (err < 0)
643 		goto out;
644 
645 	if (hw->enable_mask) {
646 		/* reset hw ts counter */
647 		err = st_lsm6dsx_reset_hw_ts(hw);
648 		if (err < 0)
649 			goto out;
650 
651 		err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
652 	}
653 
654 out:
655 	mutex_unlock(&hw->conf_lock);
656 
657 	return err;
658 }
659 
660 static int st_lsm6dsx_buffer_preenable(struct iio_dev *iio_dev)
661 {
662 	struct st_lsm6dsx_sensor *sensor = iio_priv(iio_dev);
663 	struct st_lsm6dsx_hw *hw = sensor->hw;
664 
665 	if (!hw->settings->fifo_ops.update_fifo)
666 		return -ENOTSUPP;
667 
668 	return hw->settings->fifo_ops.update_fifo(sensor, true);
669 }
670 
671 static int st_lsm6dsx_buffer_postdisable(struct iio_dev *iio_dev)
672 {
673 	struct st_lsm6dsx_sensor *sensor = iio_priv(iio_dev);
674 	struct st_lsm6dsx_hw *hw = sensor->hw;
675 
676 	if (!hw->settings->fifo_ops.update_fifo)
677 		return -ENOTSUPP;
678 
679 	return hw->settings->fifo_ops.update_fifo(sensor, false);
680 }
681 
682 static const struct iio_buffer_setup_ops st_lsm6dsx_buffer_ops = {
683 	.preenable = st_lsm6dsx_buffer_preenable,
684 	.postdisable = st_lsm6dsx_buffer_postdisable,
685 };
686 
687 int st_lsm6dsx_fifo_setup(struct st_lsm6dsx_hw *hw)
688 {
689 	struct iio_buffer *buffer;
690 	int i;
691 
692 	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
693 		if (!hw->iio_devs[i])
694 			continue;
695 
696 		buffer = devm_iio_kfifo_allocate(hw->dev);
697 		if (!buffer)
698 			return -ENOMEM;
699 
700 		iio_device_attach_buffer(hw->iio_devs[i], buffer);
701 		hw->iio_devs[i]->modes |= INDIO_BUFFER_SOFTWARE;
702 		hw->iio_devs[i]->setup_ops = &st_lsm6dsx_buffer_ops;
703 	}
704 
705 	return 0;
706 }
707