1 // SPDX-License-Identifier: GPL-2.0
2 // SPI interface for ChromeOS Embedded Controller
3 //
4 // Copyright (C) 2012 Google, Inc
5 
6 #include <linux/delay.h>
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/of.h>
10 #include <linux/platform_data/cros_ec_commands.h>
11 #include <linux/platform_data/cros_ec_proto.h>
12 #include <linux/platform_device.h>
13 #include <linux/slab.h>
14 #include <linux/spi/spi.h>
15 #include <uapi/linux/sched/types.h>
16 
17 #include "cros_ec.h"
18 
19 /* The header byte, which follows the preamble */
20 #define EC_MSG_HEADER			0xec
21 
22 /*
23  * Number of EC preamble bytes we read at a time. Since it takes
24  * about 400-500us for the EC to respond there is not a lot of
25  * point in tuning this. If the EC could respond faster then
26  * we could increase this so that might expect the preamble and
27  * message to occur in a single transaction. However, the maximum
28  * SPI transfer size is 256 bytes, so at 5MHz we need a response
29  * time of perhaps <320us (200 bytes / 1600 bits).
30  */
31 #define EC_MSG_PREAMBLE_COUNT		32
32 
33 /*
34  * Allow for a long time for the EC to respond.  We support i2c
35  * tunneling and support fairly long messages for the tunnel (249
36  * bytes long at the moment).  If we're talking to a 100 kHz device
37  * on the other end and need to transfer ~256 bytes, then we need:
38  *  10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms
39  *
40  * We'll wait 8 times that to handle clock stretching and other
41  * paranoia.  Note that some battery gas gauge ICs claim to have a
42  * clock stretch of 144ms in rare situations.  That's incentive for
43  * not directly passing i2c through, but it's too late for that for
44  * existing hardware.
45  *
46  * It's pretty unlikely that we'll really see a 249 byte tunnel in
47  * anything other than testing.  If this was more common we might
48  * consider having slow commands like this require a GET_STATUS
49  * wait loop.  The 'flash write' command would be another candidate
50  * for this, clocking in at 2-3ms.
51  */
52 #define EC_MSG_DEADLINE_MS		200
53 
54 /*
55   * Time between raising the SPI chip select (for the end of a
56   * transaction) and dropping it again (for the next transaction).
57   * If we go too fast, the EC will miss the transaction. We know that we
58   * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be
59   * safe.
60   */
61 #define EC_SPI_RECOVERY_TIME_NS	(200 * 1000)
62 
63 /**
64  * struct cros_ec_spi - information about a SPI-connected EC
65  *
66  * @spi: SPI device we are connected to
67  * @last_transfer_ns: time that we last finished a transfer.
68  * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
69  *      is sent when we want to turn on CS at the start of a transaction.
70  * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
71  *      is sent when we want to turn off CS at the end of a transaction.
72  * @high_pri_worker: Used to schedule high priority work.
73  */
74 struct cros_ec_spi {
75 	struct spi_device *spi;
76 	s64 last_transfer_ns;
77 	unsigned int start_of_msg_delay;
78 	unsigned int end_of_msg_delay;
79 	struct kthread_worker *high_pri_worker;
80 };
81 
82 typedef int (*cros_ec_xfer_fn_t) (struct cros_ec_device *ec_dev,
83 				  struct cros_ec_command *ec_msg);
84 
85 /**
86  * struct cros_ec_xfer_work_params - params for our high priority workers
87  *
88  * @work: The work_struct needed to queue work
89  * @fn: The function to use to transfer
90  * @ec_dev: ChromeOS EC device
91  * @ec_msg: Message to transfer
92  * @ret: The return value of the function
93  */
94 
95 struct cros_ec_xfer_work_params {
96 	struct kthread_work work;
97 	cros_ec_xfer_fn_t fn;
98 	struct cros_ec_device *ec_dev;
99 	struct cros_ec_command *ec_msg;
100 	int ret;
101 };
102 
103 static void debug_packet(struct device *dev, const char *name, u8 *ptr,
104 			 int len)
105 {
106 #ifdef DEBUG
107 	int i;
108 
109 	dev_dbg(dev, "%s: ", name);
110 	for (i = 0; i < len; i++)
111 		pr_cont(" %02x", ptr[i]);
112 
113 	pr_cont("\n");
114 #endif
115 }
116 
117 static int terminate_request(struct cros_ec_device *ec_dev)
118 {
119 	struct cros_ec_spi *ec_spi = ec_dev->priv;
120 	struct spi_message msg;
121 	struct spi_transfer trans;
122 	int ret;
123 
124 	/*
125 	 * Turn off CS, possibly adding a delay to ensure the rising edge
126 	 * doesn't come too soon after the end of the data.
127 	 */
128 	spi_message_init(&msg);
129 	memset(&trans, 0, sizeof(trans));
130 	trans.delay.value = ec_spi->end_of_msg_delay;
131 	trans.delay.unit = SPI_DELAY_UNIT_USECS;
132 	spi_message_add_tail(&trans, &msg);
133 
134 	ret = spi_sync_locked(ec_spi->spi, &msg);
135 
136 	/* Reset end-of-response timer */
137 	ec_spi->last_transfer_ns = ktime_get_ns();
138 	if (ret < 0) {
139 		dev_err(ec_dev->dev,
140 			"cs-deassert spi transfer failed: %d\n",
141 			ret);
142 	}
143 
144 	return ret;
145 }
146 
147 /**
148  * receive_n_bytes - receive n bytes from the EC.
149  *
150  * Assumes buf is a pointer into the ec_dev->din buffer
151  *
152  * @ec_dev: ChromeOS EC device.
153  * @buf: Pointer to the buffer receiving the data.
154  * @n: Number of bytes received.
155  */
156 static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
157 {
158 	struct cros_ec_spi *ec_spi = ec_dev->priv;
159 	struct spi_transfer trans;
160 	struct spi_message msg;
161 	int ret;
162 
163 	BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);
164 
165 	memset(&trans, 0, sizeof(trans));
166 	trans.cs_change = 1;
167 	trans.rx_buf = buf;
168 	trans.len = n;
169 
170 	spi_message_init(&msg);
171 	spi_message_add_tail(&trans, &msg);
172 	ret = spi_sync_locked(ec_spi->spi, &msg);
173 	if (ret < 0)
174 		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
175 
176 	return ret;
177 }
178 
179 /**
180  * cros_ec_spi_receive_packet - Receive a packet from the EC.
181  *
182  * This function has two phases: reading the preamble bytes (since if we read
183  * data from the EC before it is ready to send, we just get preamble) and
184  * reading the actual message.
185  *
186  * The received data is placed into ec_dev->din.
187  *
188  * @ec_dev: ChromeOS EC device
189  * @need_len: Number of message bytes we need to read
190  */
191 static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
192 				      int need_len)
193 {
194 	struct ec_host_response *response;
195 	u8 *ptr, *end;
196 	int ret;
197 	unsigned long deadline;
198 	int todo;
199 
200 	BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
201 
202 	/* Receive data until we see the header byte */
203 	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
204 	while (true) {
205 		unsigned long start_jiffies = jiffies;
206 
207 		ret = receive_n_bytes(ec_dev,
208 				      ec_dev->din,
209 				      EC_MSG_PREAMBLE_COUNT);
210 		if (ret < 0)
211 			return ret;
212 
213 		ptr = ec_dev->din;
214 		for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
215 			if (*ptr == EC_SPI_FRAME_START) {
216 				dev_dbg(ec_dev->dev, "msg found at %zd\n",
217 					ptr - ec_dev->din);
218 				break;
219 			}
220 		}
221 		if (ptr != end)
222 			break;
223 
224 		/*
225 		 * Use the time at the start of the loop as a timeout.  This
226 		 * gives us one last shot at getting the transfer and is useful
227 		 * in case we got context switched out for a while.
228 		 */
229 		if (time_after(start_jiffies, deadline)) {
230 			dev_warn(ec_dev->dev, "EC failed to respond in time\n");
231 			return -ETIMEDOUT;
232 		}
233 	}
234 
235 	/*
236 	 * ptr now points to the header byte. Copy any valid data to the
237 	 * start of our buffer
238 	 */
239 	todo = end - ++ptr;
240 	BUG_ON(todo < 0 || todo > ec_dev->din_size);
241 	todo = min(todo, need_len);
242 	memmove(ec_dev->din, ptr, todo);
243 	ptr = ec_dev->din + todo;
244 	dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
245 		need_len, todo);
246 	need_len -= todo;
247 
248 	/* If the entire response struct wasn't read, get the rest of it. */
249 	if (todo < sizeof(*response)) {
250 		ret = receive_n_bytes(ec_dev, ptr, sizeof(*response) - todo);
251 		if (ret < 0)
252 			return -EBADMSG;
253 		ptr += (sizeof(*response) - todo);
254 		todo = sizeof(*response);
255 	}
256 
257 	response = (struct ec_host_response *)ec_dev->din;
258 
259 	/* Abort if data_len is too large. */
260 	if (response->data_len > ec_dev->din_size)
261 		return -EMSGSIZE;
262 
263 	/* Receive data until we have it all */
264 	while (need_len > 0) {
265 		/*
266 		 * We can't support transfers larger than the SPI FIFO size
267 		 * unless we have DMA. We don't have DMA on the ISP SPI ports
268 		 * for Exynos. We need a way of asking SPI driver for
269 		 * maximum-supported transfer size.
270 		 */
271 		todo = min(need_len, 256);
272 		dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
273 			todo, need_len, ptr - ec_dev->din);
274 
275 		ret = receive_n_bytes(ec_dev, ptr, todo);
276 		if (ret < 0)
277 			return ret;
278 
279 		ptr += todo;
280 		need_len -= todo;
281 	}
282 
283 	dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
284 
285 	return 0;
286 }
287 
288 /**
289  * cros_ec_spi_receive_response - Receive a response from the EC.
290  *
291  * This function has two phases: reading the preamble bytes (since if we read
292  * data from the EC before it is ready to send, we just get preamble) and
293  * reading the actual message.
294  *
295  * The received data is placed into ec_dev->din.
296  *
297  * @ec_dev: ChromeOS EC device
298  * @need_len: Number of message bytes we need to read
299  */
300 static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
301 					int need_len)
302 {
303 	u8 *ptr, *end;
304 	int ret;
305 	unsigned long deadline;
306 	int todo;
307 
308 	BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
309 
310 	/* Receive data until we see the header byte */
311 	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
312 	while (true) {
313 		unsigned long start_jiffies = jiffies;
314 
315 		ret = receive_n_bytes(ec_dev,
316 				      ec_dev->din,
317 				      EC_MSG_PREAMBLE_COUNT);
318 		if (ret < 0)
319 			return ret;
320 
321 		ptr = ec_dev->din;
322 		for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
323 			if (*ptr == EC_SPI_FRAME_START) {
324 				dev_dbg(ec_dev->dev, "msg found at %zd\n",
325 					ptr - ec_dev->din);
326 				break;
327 			}
328 		}
329 		if (ptr != end)
330 			break;
331 
332 		/*
333 		 * Use the time at the start of the loop as a timeout.  This
334 		 * gives us one last shot at getting the transfer and is useful
335 		 * in case we got context switched out for a while.
336 		 */
337 		if (time_after(start_jiffies, deadline)) {
338 			dev_warn(ec_dev->dev, "EC failed to respond in time\n");
339 			return -ETIMEDOUT;
340 		}
341 	}
342 
343 	/*
344 	 * ptr now points to the header byte. Copy any valid data to the
345 	 * start of our buffer
346 	 */
347 	todo = end - ++ptr;
348 	BUG_ON(todo < 0 || todo > ec_dev->din_size);
349 	todo = min(todo, need_len);
350 	memmove(ec_dev->din, ptr, todo);
351 	ptr = ec_dev->din + todo;
352 	dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
353 		 need_len, todo);
354 	need_len -= todo;
355 
356 	/* Receive data until we have it all */
357 	while (need_len > 0) {
358 		/*
359 		 * We can't support transfers larger than the SPI FIFO size
360 		 * unless we have DMA. We don't have DMA on the ISP SPI ports
361 		 * for Exynos. We need a way of asking SPI driver for
362 		 * maximum-supported transfer size.
363 		 */
364 		todo = min(need_len, 256);
365 		dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
366 			todo, need_len, ptr - ec_dev->din);
367 
368 		ret = receive_n_bytes(ec_dev, ptr, todo);
369 		if (ret < 0)
370 			return ret;
371 
372 		debug_packet(ec_dev->dev, "interim", ptr, todo);
373 		ptr += todo;
374 		need_len -= todo;
375 	}
376 
377 	dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
378 
379 	return 0;
380 }
381 
382 /**
383  * do_cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply
384  *
385  * @ec_dev: ChromeOS EC device
386  * @ec_msg: Message to transfer
387  */
388 static int do_cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
389 				   struct cros_ec_command *ec_msg)
390 {
391 	struct ec_host_response *response;
392 	struct cros_ec_spi *ec_spi = ec_dev->priv;
393 	struct spi_transfer trans, trans_delay;
394 	struct spi_message msg;
395 	int i, len;
396 	u8 *ptr;
397 	u8 *rx_buf;
398 	u8 sum;
399 	u8 rx_byte;
400 	int ret = 0, final_ret;
401 	unsigned long delay;
402 
403 	len = cros_ec_prepare_tx(ec_dev, ec_msg);
404 	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
405 
406 	/* If it's too soon to do another transaction, wait */
407 	delay = ktime_get_ns() - ec_spi->last_transfer_ns;
408 	if (delay < EC_SPI_RECOVERY_TIME_NS)
409 		ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
410 
411 	rx_buf = kzalloc(len, GFP_KERNEL);
412 	if (!rx_buf)
413 		return -ENOMEM;
414 
415 	spi_bus_lock(ec_spi->spi->master);
416 
417 	/*
418 	 * Leave a gap between CS assertion and clocking of data to allow the
419 	 * EC time to wakeup.
420 	 */
421 	spi_message_init(&msg);
422 	if (ec_spi->start_of_msg_delay) {
423 		memset(&trans_delay, 0, sizeof(trans_delay));
424 		trans_delay.delay.value = ec_spi->start_of_msg_delay;
425 		trans_delay.delay.unit = SPI_DELAY_UNIT_USECS;
426 		spi_message_add_tail(&trans_delay, &msg);
427 	}
428 
429 	/* Transmit phase - send our message */
430 	memset(&trans, 0, sizeof(trans));
431 	trans.tx_buf = ec_dev->dout;
432 	trans.rx_buf = rx_buf;
433 	trans.len = len;
434 	trans.cs_change = 1;
435 	spi_message_add_tail(&trans, &msg);
436 	ret = spi_sync_locked(ec_spi->spi, &msg);
437 
438 	/* Get the response */
439 	if (!ret) {
440 		/* Verify that EC can process command */
441 		for (i = 0; i < len; i++) {
442 			rx_byte = rx_buf[i];
443 			/*
444 			 * Seeing the PAST_END, RX_BAD_DATA, or NOT_READY
445 			 * markers are all signs that the EC didn't fully
446 			 * receive our command. e.g., if the EC is flashing
447 			 * itself, it can't respond to any commands and instead
448 			 * clocks out EC_SPI_PAST_END from its SPI hardware
449 			 * buffer. Similar occurrences can happen if the AP is
450 			 * too slow to clock out data after asserting CS -- the
451 			 * EC will abort and fill its buffer with
452 			 * EC_SPI_RX_BAD_DATA.
453 			 *
454 			 * In all cases, these errors should be safe to retry.
455 			 * Report -EAGAIN and let the caller decide what to do
456 			 * about that.
457 			 */
458 			if (rx_byte == EC_SPI_PAST_END  ||
459 			    rx_byte == EC_SPI_RX_BAD_DATA ||
460 			    rx_byte == EC_SPI_NOT_READY) {
461 				ret = -EAGAIN;
462 				break;
463 			}
464 		}
465 	}
466 
467 	if (!ret)
468 		ret = cros_ec_spi_receive_packet(ec_dev,
469 				ec_msg->insize + sizeof(*response));
470 	else if (ret != -EAGAIN)
471 		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
472 
473 	final_ret = terminate_request(ec_dev);
474 
475 	spi_bus_unlock(ec_spi->spi->master);
476 
477 	if (!ret)
478 		ret = final_ret;
479 	if (ret < 0)
480 		goto exit;
481 
482 	ptr = ec_dev->din;
483 
484 	/* check response error code */
485 	response = (struct ec_host_response *)ptr;
486 	ec_msg->result = response->result;
487 
488 	ret = cros_ec_check_result(ec_dev, ec_msg);
489 	if (ret)
490 		goto exit;
491 
492 	len = response->data_len;
493 	sum = 0;
494 	if (len > ec_msg->insize) {
495 		dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
496 			len, ec_msg->insize);
497 		ret = -EMSGSIZE;
498 		goto exit;
499 	}
500 
501 	for (i = 0; i < sizeof(*response); i++)
502 		sum += ptr[i];
503 
504 	/* copy response packet payload and compute checksum */
505 	memcpy(ec_msg->data, ptr + sizeof(*response), len);
506 	for (i = 0; i < len; i++)
507 		sum += ec_msg->data[i];
508 
509 	if (sum) {
510 		dev_err(ec_dev->dev,
511 			"bad packet checksum, calculated %x\n",
512 			sum);
513 		ret = -EBADMSG;
514 		goto exit;
515 	}
516 
517 	ret = len;
518 exit:
519 	kfree(rx_buf);
520 	if (ec_msg->command == EC_CMD_REBOOT_EC)
521 		msleep(EC_REBOOT_DELAY_MS);
522 
523 	return ret;
524 }
525 
526 /**
527  * do_cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply
528  *
529  * @ec_dev: ChromeOS EC device
530  * @ec_msg: Message to transfer
531  */
532 static int do_cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
533 				   struct cros_ec_command *ec_msg)
534 {
535 	struct cros_ec_spi *ec_spi = ec_dev->priv;
536 	struct spi_transfer trans;
537 	struct spi_message msg;
538 	int i, len;
539 	u8 *ptr;
540 	u8 *rx_buf;
541 	u8 rx_byte;
542 	int sum;
543 	int ret = 0, final_ret;
544 	unsigned long delay;
545 
546 	len = cros_ec_prepare_tx(ec_dev, ec_msg);
547 	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
548 
549 	/* If it's too soon to do another transaction, wait */
550 	delay = ktime_get_ns() - ec_spi->last_transfer_ns;
551 	if (delay < EC_SPI_RECOVERY_TIME_NS)
552 		ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
553 
554 	rx_buf = kzalloc(len, GFP_KERNEL);
555 	if (!rx_buf)
556 		return -ENOMEM;
557 
558 	spi_bus_lock(ec_spi->spi->master);
559 
560 	/* Transmit phase - send our message */
561 	debug_packet(ec_dev->dev, "out", ec_dev->dout, len);
562 	memset(&trans, 0, sizeof(trans));
563 	trans.tx_buf = ec_dev->dout;
564 	trans.rx_buf = rx_buf;
565 	trans.len = len;
566 	trans.cs_change = 1;
567 	spi_message_init(&msg);
568 	spi_message_add_tail(&trans, &msg);
569 	ret = spi_sync_locked(ec_spi->spi, &msg);
570 
571 	/* Get the response */
572 	if (!ret) {
573 		/* Verify that EC can process command */
574 		for (i = 0; i < len; i++) {
575 			rx_byte = rx_buf[i];
576 			/* See comments in cros_ec_pkt_xfer_spi() */
577 			if (rx_byte == EC_SPI_PAST_END  ||
578 			    rx_byte == EC_SPI_RX_BAD_DATA ||
579 			    rx_byte == EC_SPI_NOT_READY) {
580 				ret = -EAGAIN;
581 				break;
582 			}
583 		}
584 	}
585 
586 	if (!ret)
587 		ret = cros_ec_spi_receive_response(ec_dev,
588 				ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
589 	else if (ret != -EAGAIN)
590 		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
591 
592 	final_ret = terminate_request(ec_dev);
593 
594 	spi_bus_unlock(ec_spi->spi->master);
595 
596 	if (!ret)
597 		ret = final_ret;
598 	if (ret < 0)
599 		goto exit;
600 
601 	ptr = ec_dev->din;
602 
603 	/* check response error code */
604 	ec_msg->result = ptr[0];
605 	ret = cros_ec_check_result(ec_dev, ec_msg);
606 	if (ret)
607 		goto exit;
608 
609 	len = ptr[1];
610 	sum = ptr[0] + ptr[1];
611 	if (len > ec_msg->insize) {
612 		dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
613 			len, ec_msg->insize);
614 		ret = -ENOSPC;
615 		goto exit;
616 	}
617 
618 	/* copy response packet payload and compute checksum */
619 	for (i = 0; i < len; i++) {
620 		sum += ptr[i + 2];
621 		if (ec_msg->insize)
622 			ec_msg->data[i] = ptr[i + 2];
623 	}
624 	sum &= 0xff;
625 
626 	debug_packet(ec_dev->dev, "in", ptr, len + 3);
627 
628 	if (sum != ptr[len + 2]) {
629 		dev_err(ec_dev->dev,
630 			"bad packet checksum, expected %02x, got %02x\n",
631 			sum, ptr[len + 2]);
632 		ret = -EBADMSG;
633 		goto exit;
634 	}
635 
636 	ret = len;
637 exit:
638 	kfree(rx_buf);
639 	if (ec_msg->command == EC_CMD_REBOOT_EC)
640 		msleep(EC_REBOOT_DELAY_MS);
641 
642 	return ret;
643 }
644 
645 static void cros_ec_xfer_high_pri_work(struct kthread_work *work)
646 {
647 	struct cros_ec_xfer_work_params *params;
648 
649 	params = container_of(work, struct cros_ec_xfer_work_params, work);
650 	params->ret = params->fn(params->ec_dev, params->ec_msg);
651 }
652 
653 static int cros_ec_xfer_high_pri(struct cros_ec_device *ec_dev,
654 				 struct cros_ec_command *ec_msg,
655 				 cros_ec_xfer_fn_t fn)
656 {
657 	struct cros_ec_spi *ec_spi = ec_dev->priv;
658 	struct cros_ec_xfer_work_params params = {
659 		.work = KTHREAD_WORK_INIT(params.work,
660 					  cros_ec_xfer_high_pri_work),
661 		.ec_dev = ec_dev,
662 		.ec_msg = ec_msg,
663 		.fn = fn,
664 	};
665 
666 	/*
667 	 * This looks a bit ridiculous.  Why do the work on a
668 	 * different thread if we're just going to block waiting for
669 	 * the thread to finish?  The key here is that the thread is
670 	 * running at high priority but the calling context might not
671 	 * be.  We need to be at high priority to avoid getting
672 	 * context switched out for too long and the EC giving up on
673 	 * the transfer.
674 	 */
675 	kthread_queue_work(ec_spi->high_pri_worker, &params.work);
676 	kthread_flush_work(&params.work);
677 
678 	return params.ret;
679 }
680 
681 static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
682 				struct cros_ec_command *ec_msg)
683 {
684 	return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_pkt_xfer_spi);
685 }
686 
687 static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
688 				struct cros_ec_command *ec_msg)
689 {
690 	return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_cmd_xfer_spi);
691 }
692 
693 static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
694 {
695 	struct device_node *np = dev->of_node;
696 	u32 val;
697 	int ret;
698 
699 	ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val);
700 	if (!ret)
701 		ec_spi->start_of_msg_delay = val;
702 
703 	ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
704 	if (!ret)
705 		ec_spi->end_of_msg_delay = val;
706 }
707 
708 static void cros_ec_spi_high_pri_release(void *worker)
709 {
710 	kthread_destroy_worker(worker);
711 }
712 
713 static int cros_ec_spi_devm_high_pri_alloc(struct device *dev,
714 					   struct cros_ec_spi *ec_spi)
715 {
716 	int err;
717 
718 	ec_spi->high_pri_worker =
719 		kthread_create_worker(0, "cros_ec_spi_high_pri");
720 
721 	if (IS_ERR(ec_spi->high_pri_worker)) {
722 		err = PTR_ERR(ec_spi->high_pri_worker);
723 		dev_err(dev, "Can't create cros_ec high pri worker: %d\n", err);
724 		return err;
725 	}
726 
727 	err = devm_add_action_or_reset(dev, cros_ec_spi_high_pri_release,
728 				       ec_spi->high_pri_worker);
729 	if (err)
730 		return err;
731 
732 	sched_set_fifo(ec_spi->high_pri_worker->task);
733 
734 	return 0;
735 }
736 
737 static int cros_ec_spi_probe(struct spi_device *spi)
738 {
739 	struct device *dev = &spi->dev;
740 	struct cros_ec_device *ec_dev;
741 	struct cros_ec_spi *ec_spi;
742 	int err;
743 
744 	spi->rt = true;
745 	err = spi_setup(spi);
746 	if (err < 0)
747 		return err;
748 
749 	ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL);
750 	if (ec_spi == NULL)
751 		return -ENOMEM;
752 	ec_spi->spi = spi;
753 	ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
754 	if (!ec_dev)
755 		return -ENOMEM;
756 
757 	/* Check for any DT properties */
758 	cros_ec_spi_dt_probe(ec_spi, dev);
759 
760 	spi_set_drvdata(spi, ec_dev);
761 	ec_dev->dev = dev;
762 	ec_dev->priv = ec_spi;
763 	ec_dev->irq = spi->irq;
764 	ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi;
765 	ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi;
766 	ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
767 	ec_dev->din_size = EC_MSG_PREAMBLE_COUNT +
768 			   sizeof(struct ec_host_response) +
769 			   sizeof(struct ec_response_get_protocol_info);
770 	ec_dev->dout_size = sizeof(struct ec_host_request);
771 
772 	ec_spi->last_transfer_ns = ktime_get_ns();
773 
774 	err = cros_ec_spi_devm_high_pri_alloc(dev, ec_spi);
775 	if (err)
776 		return err;
777 
778 	err = cros_ec_register(ec_dev);
779 	if (err) {
780 		dev_err(dev, "cannot register EC\n");
781 		return err;
782 	}
783 
784 	device_init_wakeup(&spi->dev, true);
785 
786 	return 0;
787 }
788 
789 static int cros_ec_spi_remove(struct spi_device *spi)
790 {
791 	struct cros_ec_device *ec_dev = spi_get_drvdata(spi);
792 
793 	return cros_ec_unregister(ec_dev);
794 }
795 
796 #ifdef CONFIG_PM_SLEEP
797 static int cros_ec_spi_suspend(struct device *dev)
798 {
799 	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
800 
801 	return cros_ec_suspend(ec_dev);
802 }
803 
804 static int cros_ec_spi_resume(struct device *dev)
805 {
806 	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
807 
808 	return cros_ec_resume(ec_dev);
809 }
810 #endif
811 
812 static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend,
813 			 cros_ec_spi_resume);
814 
815 static const struct of_device_id cros_ec_spi_of_match[] = {
816 	{ .compatible = "google,cros-ec-spi", },
817 	{ /* sentinel */ },
818 };
819 MODULE_DEVICE_TABLE(of, cros_ec_spi_of_match);
820 
821 static const struct spi_device_id cros_ec_spi_id[] = {
822 	{ "cros-ec-spi", 0 },
823 	{ }
824 };
825 MODULE_DEVICE_TABLE(spi, cros_ec_spi_id);
826 
827 static struct spi_driver cros_ec_driver_spi = {
828 	.driver	= {
829 		.name	= "cros-ec-spi",
830 		.of_match_table = cros_ec_spi_of_match,
831 		.pm	= &cros_ec_spi_pm_ops,
832 	},
833 	.probe		= cros_ec_spi_probe,
834 	.remove		= cros_ec_spi_remove,
835 	.id_table	= cros_ec_spi_id,
836 };
837 
838 module_spi_driver(cros_ec_driver_spi);
839 
840 MODULE_LICENSE("GPL v2");
841 MODULE_DESCRIPTION("SPI interface for ChromeOS Embedded Controller");
842