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