1 // SPDX-License-Identifier: GPL-2.0
2 // SPI interface for ChromeOS Embedded Controller
4 // Copyright (C) 2012 Google, Inc
6 #include <linux/delay.h>
7 #include <linux/kernel.h>
8 #include <linux/module.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>
19 /* The header byte, which follows the preamble */
20 #define EC_MSG_HEADER 0xec
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).
31 #define EC_MSG_PREAMBLE_COUNT 32
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
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
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.
52 #define EC_MSG_DEADLINE_MS 200
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
61 #define EC_SPI_RECOVERY_TIME_NS (200 * 1000)
64 * struct cros_ec_spi - information about a SPI-connected EC
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.
75 struct spi_device *spi;
77 unsigned int start_of_msg_delay;
78 unsigned int end_of_msg_delay;
79 struct kthread_worker *high_pri_worker;
82 typedef int (*cros_ec_xfer_fn_t) (struct cros_ec_device *ec_dev,
83 struct cros_ec_command *ec_msg);
86 * struct cros_ec_xfer_work_params - params for our high priority workers
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
95 struct cros_ec_xfer_work_params {
96 struct kthread_work work;
98 struct cros_ec_device *ec_dev;
99 struct cros_ec_command *ec_msg;
103 static void debug_packet(struct device *dev, const char *name, u8 *ptr,
109 dev_dbg(dev, "%s: ", name);
110 for (i = 0; i < len; i++)
111 pr_cont(" %02x", ptr[i]);
117 static int terminate_request(struct cros_ec_device *ec_dev)
119 struct cros_ec_spi *ec_spi = ec_dev->priv;
120 struct spi_message msg;
121 struct spi_transfer trans;
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.
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);
134 ret = spi_sync_locked(ec_spi->spi, &msg);
136 /* Reset end-of-response timer */
137 ec_spi->last_transfer_ns = ktime_get_ns();
140 "cs-deassert spi transfer failed: %d\n",
148 * receive_n_bytes - receive n bytes from the EC.
150 * Assumes buf is a pointer into the ec_dev->din buffer
152 static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
154 struct cros_ec_spi *ec_spi = ec_dev->priv;
155 struct spi_transfer trans;
156 struct spi_message msg;
159 BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);
161 memset(&trans, 0, sizeof(trans));
166 spi_message_init(&msg);
167 spi_message_add_tail(&trans, &msg);
168 ret = spi_sync_locked(ec_spi->spi, &msg);
170 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
176 * cros_ec_spi_receive_packet - Receive a packet from the EC.
178 * This function has two phases: reading the preamble bytes (since if we read
179 * data from the EC before it is ready to send, we just get preamble) and
180 * reading the actual message.
182 * The received data is placed into ec_dev->din.
184 * @ec_dev: ChromeOS EC device
185 * @need_len: Number of message bytes we need to read
187 static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
190 struct ec_host_response *response;
193 unsigned long deadline;
196 BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
198 /* Receive data until we see the header byte */
199 deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
201 unsigned long start_jiffies = jiffies;
203 ret = receive_n_bytes(ec_dev,
205 EC_MSG_PREAMBLE_COUNT);
210 for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
211 if (*ptr == EC_SPI_FRAME_START) {
212 dev_dbg(ec_dev->dev, "msg found at %zd\n",
221 * Use the time at the start of the loop as a timeout. This
222 * gives us one last shot at getting the transfer and is useful
223 * in case we got context switched out for a while.
225 if (time_after(start_jiffies, deadline)) {
226 dev_warn(ec_dev->dev, "EC failed to respond in time\n");
232 * ptr now points to the header byte. Copy any valid data to the
233 * start of our buffer
236 BUG_ON(todo < 0 || todo > ec_dev->din_size);
237 todo = min(todo, need_len);
238 memmove(ec_dev->din, ptr, todo);
239 ptr = ec_dev->din + todo;
240 dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
244 /* If the entire response struct wasn't read, get the rest of it. */
245 if (todo < sizeof(*response)) {
246 ret = receive_n_bytes(ec_dev, ptr, sizeof(*response) - todo);
249 ptr += (sizeof(*response) - todo);
250 todo = sizeof(*response);
253 response = (struct ec_host_response *)ec_dev->din;
255 /* Abort if data_len is too large. */
256 if (response->data_len > ec_dev->din_size)
259 /* Receive data until we have it all */
260 while (need_len > 0) {
262 * We can't support transfers larger than the SPI FIFO size
263 * unless we have DMA. We don't have DMA on the ISP SPI ports
264 * for Exynos. We need a way of asking SPI driver for
265 * maximum-supported transfer size.
267 todo = min(need_len, 256);
268 dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
269 todo, need_len, ptr - ec_dev->din);
271 ret = receive_n_bytes(ec_dev, ptr, todo);
279 dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
285 * cros_ec_spi_receive_response - Receive a response from the EC.
287 * This function has two phases: reading the preamble bytes (since if we read
288 * data from the EC before it is ready to send, we just get preamble) and
289 * reading the actual message.
291 * The received data is placed into ec_dev->din.
293 * @ec_dev: ChromeOS EC device
294 * @need_len: Number of message bytes we need to read
296 static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
301 unsigned long deadline;
304 BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
306 /* Receive data until we see the header byte */
307 deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
309 unsigned long start_jiffies = jiffies;
311 ret = receive_n_bytes(ec_dev,
313 EC_MSG_PREAMBLE_COUNT);
318 for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
319 if (*ptr == EC_SPI_FRAME_START) {
320 dev_dbg(ec_dev->dev, "msg found at %zd\n",
329 * Use the time at the start of the loop as a timeout. This
330 * gives us one last shot at getting the transfer and is useful
331 * in case we got context switched out for a while.
333 if (time_after(start_jiffies, deadline)) {
334 dev_warn(ec_dev->dev, "EC failed to respond in time\n");
340 * ptr now points to the header byte. Copy any valid data to the
341 * start of our buffer
344 BUG_ON(todo < 0 || todo > ec_dev->din_size);
345 todo = min(todo, need_len);
346 memmove(ec_dev->din, ptr, todo);
347 ptr = ec_dev->din + todo;
348 dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
352 /* Receive data until we have it all */
353 while (need_len > 0) {
355 * We can't support transfers larger than the SPI FIFO size
356 * unless we have DMA. We don't have DMA on the ISP SPI ports
357 * for Exynos. We need a way of asking SPI driver for
358 * maximum-supported transfer size.
360 todo = min(need_len, 256);
361 dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
362 todo, need_len, ptr - ec_dev->din);
364 ret = receive_n_bytes(ec_dev, ptr, todo);
368 debug_packet(ec_dev->dev, "interim", ptr, todo);
373 dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
379 * do_cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply
381 * @ec_dev: ChromeOS EC device
382 * @ec_msg: Message to transfer
384 static int do_cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
385 struct cros_ec_command *ec_msg)
387 struct ec_host_response *response;
388 struct cros_ec_spi *ec_spi = ec_dev->priv;
389 struct spi_transfer trans, trans_delay;
390 struct spi_message msg;
396 int ret = 0, final_ret;
399 len = cros_ec_prepare_tx(ec_dev, ec_msg);
400 dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
402 /* If it's too soon to do another transaction, wait */
403 delay = ktime_get_ns() - ec_spi->last_transfer_ns;
404 if (delay < EC_SPI_RECOVERY_TIME_NS)
405 ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
407 rx_buf = kzalloc(len, GFP_KERNEL);
411 spi_bus_lock(ec_spi->spi->master);
414 * Leave a gap between CS assertion and clocking of data to allow the
417 spi_message_init(&msg);
418 if (ec_spi->start_of_msg_delay) {
419 memset(&trans_delay, 0, sizeof(trans_delay));
420 trans_delay.delay.value = ec_spi->start_of_msg_delay;
421 trans_delay.delay.unit = SPI_DELAY_UNIT_USECS;
422 spi_message_add_tail(&trans_delay, &msg);
425 /* Transmit phase - send our message */
426 memset(&trans, 0, sizeof(trans));
427 trans.tx_buf = ec_dev->dout;
428 trans.rx_buf = rx_buf;
431 spi_message_add_tail(&trans, &msg);
432 ret = spi_sync_locked(ec_spi->spi, &msg);
434 /* Get the response */
436 /* Verify that EC can process command */
437 for (i = 0; i < len; i++) {
440 * Seeing the PAST_END, RX_BAD_DATA, or NOT_READY
441 * markers are all signs that the EC didn't fully
442 * receive our command. e.g., if the EC is flashing
443 * itself, it can't respond to any commands and instead
444 * clocks out EC_SPI_PAST_END from its SPI hardware
445 * buffer. Similar occurrences can happen if the AP is
446 * too slow to clock out data after asserting CS -- the
447 * EC will abort and fill its buffer with
448 * EC_SPI_RX_BAD_DATA.
450 * In all cases, these errors should be safe to retry.
451 * Report -EAGAIN and let the caller decide what to do
454 if (rx_byte == EC_SPI_PAST_END ||
455 rx_byte == EC_SPI_RX_BAD_DATA ||
456 rx_byte == EC_SPI_NOT_READY) {
464 ret = cros_ec_spi_receive_packet(ec_dev,
465 ec_msg->insize + sizeof(*response));
466 else if (ret != -EAGAIN)
467 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
469 final_ret = terminate_request(ec_dev);
471 spi_bus_unlock(ec_spi->spi->master);
480 /* check response error code */
481 response = (struct ec_host_response *)ptr;
482 ec_msg->result = response->result;
484 ret = cros_ec_check_result(ec_dev, ec_msg);
488 len = response->data_len;
490 if (len > ec_msg->insize) {
491 dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
492 len, ec_msg->insize);
497 for (i = 0; i < sizeof(*response); i++)
500 /* copy response packet payload and compute checksum */
501 memcpy(ec_msg->data, ptr + sizeof(*response), len);
502 for (i = 0; i < len; i++)
503 sum += ec_msg->data[i];
507 "bad packet checksum, calculated %x\n",
516 if (ec_msg->command == EC_CMD_REBOOT_EC)
517 msleep(EC_REBOOT_DELAY_MS);
523 * do_cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply
525 * @ec_dev: ChromeOS EC device
526 * @ec_msg: Message to transfer
528 static int do_cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
529 struct cros_ec_command *ec_msg)
531 struct cros_ec_spi *ec_spi = ec_dev->priv;
532 struct spi_transfer trans;
533 struct spi_message msg;
539 int ret = 0, final_ret;
542 len = cros_ec_prepare_tx(ec_dev, ec_msg);
543 dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
545 /* If it's too soon to do another transaction, wait */
546 delay = ktime_get_ns() - ec_spi->last_transfer_ns;
547 if (delay < EC_SPI_RECOVERY_TIME_NS)
548 ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
550 rx_buf = kzalloc(len, GFP_KERNEL);
554 spi_bus_lock(ec_spi->spi->master);
556 /* Transmit phase - send our message */
557 debug_packet(ec_dev->dev, "out", ec_dev->dout, len);
558 memset(&trans, 0, sizeof(trans));
559 trans.tx_buf = ec_dev->dout;
560 trans.rx_buf = rx_buf;
563 spi_message_init(&msg);
564 spi_message_add_tail(&trans, &msg);
565 ret = spi_sync_locked(ec_spi->spi, &msg);
567 /* Get the response */
569 /* Verify that EC can process command */
570 for (i = 0; i < len; i++) {
572 /* See comments in cros_ec_pkt_xfer_spi() */
573 if (rx_byte == EC_SPI_PAST_END ||
574 rx_byte == EC_SPI_RX_BAD_DATA ||
575 rx_byte == EC_SPI_NOT_READY) {
583 ret = cros_ec_spi_receive_response(ec_dev,
584 ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
585 else if (ret != -EAGAIN)
586 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
588 final_ret = terminate_request(ec_dev);
590 spi_bus_unlock(ec_spi->spi->master);
599 /* check response error code */
600 ec_msg->result = ptr[0];
601 ret = cros_ec_check_result(ec_dev, ec_msg);
606 sum = ptr[0] + ptr[1];
607 if (len > ec_msg->insize) {
608 dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
609 len, ec_msg->insize);
614 /* copy response packet payload and compute checksum */
615 for (i = 0; i < len; i++) {
618 ec_msg->data[i] = ptr[i + 2];
622 debug_packet(ec_dev->dev, "in", ptr, len + 3);
624 if (sum != ptr[len + 2]) {
626 "bad packet checksum, expected %02x, got %02x\n",
635 if (ec_msg->command == EC_CMD_REBOOT_EC)
636 msleep(EC_REBOOT_DELAY_MS);
641 static void cros_ec_xfer_high_pri_work(struct kthread_work *work)
643 struct cros_ec_xfer_work_params *params;
645 params = container_of(work, struct cros_ec_xfer_work_params, work);
646 params->ret = params->fn(params->ec_dev, params->ec_msg);
649 static int cros_ec_xfer_high_pri(struct cros_ec_device *ec_dev,
650 struct cros_ec_command *ec_msg,
651 cros_ec_xfer_fn_t fn)
653 struct cros_ec_spi *ec_spi = ec_dev->priv;
654 struct cros_ec_xfer_work_params params = {
655 .work = KTHREAD_WORK_INIT(params.work,
656 cros_ec_xfer_high_pri_work),
663 * This looks a bit ridiculous. Why do the work on a
664 * different thread if we're just going to block waiting for
665 * the thread to finish? The key here is that the thread is
666 * running at high priority but the calling context might not
667 * be. We need to be at high priority to avoid getting
668 * context switched out for too long and the EC giving up on
671 kthread_queue_work(ec_spi->high_pri_worker, ¶ms.work);
672 kthread_flush_work(¶ms.work);
677 static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
678 struct cros_ec_command *ec_msg)
680 return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_pkt_xfer_spi);
683 static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
684 struct cros_ec_command *ec_msg)
686 return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_cmd_xfer_spi);
689 static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
691 struct device_node *np = dev->of_node;
695 ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val);
697 ec_spi->start_of_msg_delay = val;
699 ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
701 ec_spi->end_of_msg_delay = val;
704 static void cros_ec_spi_high_pri_release(void *worker)
706 kthread_destroy_worker(worker);
709 static int cros_ec_spi_devm_high_pri_alloc(struct device *dev,
710 struct cros_ec_spi *ec_spi)
714 ec_spi->high_pri_worker =
715 kthread_create_worker(0, "cros_ec_spi_high_pri");
717 if (IS_ERR(ec_spi->high_pri_worker)) {
718 err = PTR_ERR(ec_spi->high_pri_worker);
719 dev_err(dev, "Can't create cros_ec high pri worker: %d\n", err);
723 err = devm_add_action_or_reset(dev, cros_ec_spi_high_pri_release,
724 ec_spi->high_pri_worker);
728 sched_set_fifo(ec_spi->high_pri_worker->task);
733 static int cros_ec_spi_probe(struct spi_device *spi)
735 struct device *dev = &spi->dev;
736 struct cros_ec_device *ec_dev;
737 struct cros_ec_spi *ec_spi;
740 spi->bits_per_word = 8;
741 spi->mode = SPI_MODE_0;
743 err = spi_setup(spi);
747 ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL);
751 ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
755 /* Check for any DT properties */
756 cros_ec_spi_dt_probe(ec_spi, dev);
758 spi_set_drvdata(spi, ec_dev);
760 ec_dev->priv = ec_spi;
761 ec_dev->irq = spi->irq;
762 ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi;
763 ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi;
764 ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
765 ec_dev->din_size = EC_MSG_PREAMBLE_COUNT +
766 sizeof(struct ec_host_response) +
767 sizeof(struct ec_response_get_protocol_info);
768 ec_dev->dout_size = sizeof(struct ec_host_request);
770 ec_spi->last_transfer_ns = ktime_get_ns();
772 err = cros_ec_spi_devm_high_pri_alloc(dev, ec_spi);
776 err = cros_ec_register(ec_dev);
778 dev_err(dev, "cannot register EC\n");
782 device_init_wakeup(&spi->dev, true);
787 static int cros_ec_spi_remove(struct spi_device *spi)
789 struct cros_ec_device *ec_dev = spi_get_drvdata(spi);
791 return cros_ec_unregister(ec_dev);
794 #ifdef CONFIG_PM_SLEEP
795 static int cros_ec_spi_suspend(struct device *dev)
797 struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
799 return cros_ec_suspend(ec_dev);
802 static int cros_ec_spi_resume(struct device *dev)
804 struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
806 return cros_ec_resume(ec_dev);
810 static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend,
813 static const struct of_device_id cros_ec_spi_of_match[] = {
814 { .compatible = "google,cros-ec-spi", },
817 MODULE_DEVICE_TABLE(of, cros_ec_spi_of_match);
819 static const struct spi_device_id cros_ec_spi_id[] = {
820 { "cros-ec-spi", 0 },
823 MODULE_DEVICE_TABLE(spi, cros_ec_spi_id);
825 static struct spi_driver cros_ec_driver_spi = {
827 .name = "cros-ec-spi",
828 .of_match_table = cros_ec_spi_of_match,
829 .pm = &cros_ec_spi_pm_ops,
831 .probe = cros_ec_spi_probe,
832 .remove = cros_ec_spi_remove,
833 .id_table = cros_ec_spi_id,
836 module_spi_driver(cros_ec_driver_spi);
838 MODULE_LICENSE("GPL v2");
839 MODULE_DESCRIPTION("SPI interface for ChromeOS Embedded Controller");