i2c.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * I2C Link Layer for ST21NFCA HCI based Driver
  4 * Copyright (C) 2014  STMicroelectronics SAS. All rights reserved.
  5 */
  6
  7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8
  9#include <linux/crc-ccitt.h>
 10#include <linux/module.h>
 11#include <linux/i2c.h>
 12#include <linux/gpio/consumer.h>
 13#include <linux/of_irq.h>
 14#include <linux/acpi.h>
 15#include <linux/interrupt.h>
 16#include <linux/delay.h>
 17#include <linux/nfc.h>
 18#include <linux/firmware.h>
 19
 20#include <net/nfc/hci.h>
 21#include <net/nfc/llc.h>
 22#include <net/nfc/nfc.h>
 23
 24#include "st21nfca.h"
 25
 26/*
 27 * Every frame starts with ST21NFCA_SOF_EOF and ends with ST21NFCA_SOF_EOF.
 28 * Because ST21NFCA_SOF_EOF is a possible data value, there is a mecanism
 29 * called byte stuffing has been introduced.
 30 *
 31 * if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
 32 * - insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
 33 * - xor byte with ST21NFCA_BYTE_STUFFING_MASK
 34 */
 35#define ST21NFCA_SOF_EOF		0x7e
 36#define ST21NFCA_BYTE_STUFFING_MASK	0x20
 37#define ST21NFCA_ESCAPE_BYTE_STUFFING	0x7d
 38
 39/* SOF + 00 */
 40#define ST21NFCA_FRAME_HEADROOM			2
 41
 42/* 2 bytes crc + EOF */
 43#define ST21NFCA_FRAME_TAILROOM 3
 44#define IS_START_OF_FRAME(buf) (buf[0] == ST21NFCA_SOF_EOF && \
 45				buf[1] == 0)
 46
 47#define ST21NFCA_HCI_DRIVER_NAME "st21nfca_hci"
 48#define ST21NFCA_HCI_I2C_DRIVER_NAME "st21nfca_hci_i2c"
 49
 50struct st21nfca_i2c_phy {
 51	struct i2c_client *i2c_dev;
 52	struct nfc_hci_dev *hdev;
 53
 54	struct gpio_desc *gpiod_ena;
 55	struct st21nfca_se_status se_status;
 56
 57	struct sk_buff *pending_skb;
 58	int current_read_len;
 59	/*
 60	 * crc might have fail because i2c macro
 61	 * is disable due to other interface activity
 62	 */
 63	int crc_trials;
 64
 65	int powered;
 66	int run_mode;
 67
 68	/*
 69	 * < 0 if hardware error occured (e.g. i2c err)
 70	 * and prevents normal operation.
 71	 */
 72	int hard_fault;
 73	struct mutex phy_lock;
 74};
 75
 76static const u8 len_seq[] = { 16, 24, 12, 29 };
 77static const u16 wait_tab[] = { 2, 3, 5, 15, 20, 40};
 78
 79#define I2C_DUMP_SKB(info, skb)					\
 80do {								\
 81	pr_debug("%s:\n", info);				\
 82	print_hex_dump(KERN_DEBUG, "i2c: ", DUMP_PREFIX_OFFSET,	\
 83		       16, 1, (skb)->data, (skb)->len, 0);	\
 84} while (0)
 85
 86/*
 87 * In order to get the CLF in a known state we generate an internal reboot
 88 * using a proprietary command.
 89 * Once the reboot is completed, we expect to receive a ST21NFCA_SOF_EOF
 90 * fill buffer.
 91 */
 92static int st21nfca_hci_platform_init(struct st21nfca_i2c_phy *phy)
 93{
 94	u16 wait_reboot[] = { 50, 300, 1000 };
 95	char reboot_cmd[] = { 0x7E, 0x66, 0x48, 0xF6, 0x7E };
 96	u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE];
 97	int i, r = -1;
 98
 99	for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
100		r = i2c_master_send(phy->i2c_dev, reboot_cmd,
101				    sizeof(reboot_cmd));
102		if (r < 0)
103			msleep(wait_reboot[i]);
104	}
105	if (r < 0)
106		return r;
107
108	/* CLF is spending about 20ms to do an internal reboot */
109	msleep(20);
110	r = -1;
111	for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
112		r = i2c_master_recv(phy->i2c_dev, tmp,
113				    ST21NFCA_HCI_LLC_MAX_SIZE);
114		if (r < 0)
115			msleep(wait_reboot[i]);
116	}
117	if (r < 0)
118		return r;
119
120	for (i = 0; i < ST21NFCA_HCI_LLC_MAX_SIZE &&
121		tmp[i] == ST21NFCA_SOF_EOF; i++)
122		;
123
124	if (r != ST21NFCA_HCI_LLC_MAX_SIZE)
125		return -ENODEV;
126
127	usleep_range(1000, 1500);
128	return 0;
129}
130
131static int st21nfca_hci_i2c_enable(void *phy_id)
132{
133	struct st21nfca_i2c_phy *phy = phy_id;
134
135	gpiod_set_value(phy->gpiod_ena, 1);
136	phy->powered = 1;
137	phy->run_mode = ST21NFCA_HCI_MODE;
138
139	usleep_range(10000, 15000);
140
141	return 0;
142}
143
144static void st21nfca_hci_i2c_disable(void *phy_id)
145{
146	struct st21nfca_i2c_phy *phy = phy_id;
147
148	gpiod_set_value(phy->gpiod_ena, 0);
149
150	phy->powered = 0;
151}
152
153static void st21nfca_hci_add_len_crc(struct sk_buff *skb)
154{
155	u16 crc;
156	u8 tmp;
157
158	*(u8 *)skb_push(skb, 1) = 0;
159
160	crc = crc_ccitt(0xffff, skb->data, skb->len);
161	crc = ~crc;
162
163	tmp = crc & 0x00ff;
164	skb_put_u8(skb, tmp);
165
166	tmp = (crc >> 8) & 0x00ff;
167	skb_put_u8(skb, tmp);
168}
169
170static void st21nfca_hci_remove_len_crc(struct sk_buff *skb)
171{
172	skb_pull(skb, ST21NFCA_FRAME_HEADROOM);
173	skb_trim(skb, skb->len - ST21NFCA_FRAME_TAILROOM);
174}
175
176/*
177 * Writing a frame must not return the number of written bytes.
178 * It must return either zero for success, or <0 for error.
179 * In addition, it must not alter the skb
180 */
181static int st21nfca_hci_i2c_write(void *phy_id, struct sk_buff *skb)
182{
183	int r = -1, i, j;
184	struct st21nfca_i2c_phy *phy = phy_id;
185	struct i2c_client *client = phy->i2c_dev;
186	u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE * 2];
187
188	I2C_DUMP_SKB("st21nfca_hci_i2c_write", skb);
189
190	if (phy->hard_fault != 0)
191		return phy->hard_fault;
192
193	/*
194	 * Compute CRC before byte stuffing computation on frame
195	 * Note st21nfca_hci_add_len_crc is doing a byte stuffing
196	 * on its own value
197	 */
198	st21nfca_hci_add_len_crc(skb);
199
200	/* add ST21NFCA_SOF_EOF on tail */
201	skb_put_u8(skb, ST21NFCA_SOF_EOF);
202	/* add ST21NFCA_SOF_EOF on head */
203	*(u8 *)skb_push(skb, 1) = ST21NFCA_SOF_EOF;
204
205	/*
206	 * Compute byte stuffing
207	 * if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
208	 * insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
209	 * xor byte with ST21NFCA_BYTE_STUFFING_MASK
210	 */
211	tmp[0] = skb->data[0];
212	for (i = 1, j = 1; i < skb->len - 1; i++, j++) {
213		if (skb->data[i] == ST21NFCA_SOF_EOF
214		    || skb->data[i] == ST21NFCA_ESCAPE_BYTE_STUFFING) {
215			tmp[j] = ST21NFCA_ESCAPE_BYTE_STUFFING;
216			j++;
217			tmp[j] = skb->data[i] ^ ST21NFCA_BYTE_STUFFING_MASK;
218		} else {
219			tmp[j] = skb->data[i];
220		}
221	}
222	tmp[j] = skb->data[i];
223	j++;
224
225	/*
226	 * Manage sleep mode
227	 * Try 3 times to send data with delay between each
228	 */
229	mutex_lock(&phy->phy_lock);
230	for (i = 0; i < ARRAY_SIZE(wait_tab) && r < 0; i++) {
231		r = i2c_master_send(client, tmp, j);
232		if (r < 0)
233			msleep(wait_tab[i]);
234	}
235	mutex_unlock(&phy->phy_lock);
236
237	if (r >= 0) {
238		if (r != j)
239			r = -EREMOTEIO;
240		else
241			r = 0;
242	}
243
244	st21nfca_hci_remove_len_crc(skb);
245
246	return r;
247}
248
249static int get_frame_size(u8 *buf, int buflen)
250{
251	int len = 0;
252
253	if (buf[len + 1] == ST21NFCA_SOF_EOF)
254		return 0;
255
256	for (len = 1; len < buflen && buf[len] != ST21NFCA_SOF_EOF; len++)
257		;
258
259	return len;
260}
261
262static int check_crc(u8 *buf, int buflen)
263{
264	u16 crc;
265
266	crc = crc_ccitt(0xffff, buf, buflen - 2);
267	crc = ~crc;
268
269	if (buf[buflen - 2] != (crc & 0xff) || buf[buflen - 1] != (crc >> 8)) {
270		pr_err(ST21NFCA_HCI_DRIVER_NAME
271		       ": CRC error 0x%x != 0x%x 0x%x\n", crc, buf[buflen - 1],
272		       buf[buflen - 2]);
273
274		pr_info(DRIVER_DESC ": %s : BAD CRC\n", __func__);
275		print_hex_dump(KERN_DEBUG, "crc: ", DUMP_PREFIX_NONE,
276			       16, 2, buf, buflen, false);
277		return -EPERM;
278	}
279	return 0;
280}
281
282/*
283 * Prepare received data for upper layer.
284 * Received data include byte stuffing, crc and sof/eof
285 * which is not usable by hci part.
286 * returns:
287 * frame size without sof/eof, header and byte stuffing
288 * -EBADMSG : frame was incorrect and discarded
289 */
290static int st21nfca_hci_i2c_repack(struct sk_buff *skb)
291{
292	int i, j, r, size;
293
294	if (skb->len < 1 || (skb->len > 1 && skb->data[1] != 0))
295		return -EBADMSG;
296
297	size = get_frame_size(skb->data, skb->len);
298	if (size > 0) {
299		skb_trim(skb, size);
300		/* remove ST21NFCA byte stuffing for upper layer */
301		for (i = 1, j = 0; i < skb->len; i++) {
302			if (skb->data[i + j] ==
303					(u8) ST21NFCA_ESCAPE_BYTE_STUFFING) {
304				skb->data[i] = skb->data[i + j + 1]
305						| ST21NFCA_BYTE_STUFFING_MASK;
306				i++;
307				j++;
308			}
309			skb->data[i] = skb->data[i + j];
310		}
311		/* remove byte stuffing useless byte */
312		skb_trim(skb, i - j);
313		/* remove ST21NFCA_SOF_EOF from head */
314		skb_pull(skb, 1);
315
316		r = check_crc(skb->data, skb->len);
317		if (r != 0)
318			return -EBADMSG;
319
320		/* remove headbyte */
321		skb_pull(skb, 1);
322		/* remove crc. Byte Stuffing is already removed here */
323		skb_trim(skb, skb->len - 2);
324		return skb->len;
325	}
326	return 0;
327}
328
329/*
330 * Reads an shdlc frame and returns it in a newly allocated sk_buff. Guarantees
331 * that i2c bus will be flushed and that next read will start on a new frame.
332 * returned skb contains only LLC header and payload.
333 * returns:
334 * frame size : if received frame is complete (find ST21NFCA_SOF_EOF at
335 * end of read)
336 * -EAGAIN : if received frame is incomplete (not find ST21NFCA_SOF_EOF
337 * at end of read)
338 * -EREMOTEIO : i2c read error (fatal)
339 * -EBADMSG : frame was incorrect and discarded
340 * (value returned from st21nfca_hci_i2c_repack)
341 * -EIO : if no ST21NFCA_SOF_EOF is found after reaching
342 * the read length end sequence
343 */
344static int st21nfca_hci_i2c_read(struct st21nfca_i2c_phy *phy,
345				 struct sk_buff *skb)
346{
347	int r, i;
348	u8 len;
349	u8 buf[ST21NFCA_HCI_LLC_MAX_PAYLOAD];
350	struct i2c_client *client = phy->i2c_dev;
351
352	if (phy->current_read_len < ARRAY_SIZE(len_seq)) {
353		len = len_seq[phy->current_read_len];
354
355		/*
356		 * Add retry mecanism
357		 * Operation on I2C interface may fail in case of operation on
358		 * RF or SWP interface
359		 */
360		r = 0;
361		mutex_lock(&phy->phy_lock);
362		for (i = 0; i < ARRAY_SIZE(wait_tab) && r <= 0; i++) {
363			r = i2c_master_recv(client, buf, len);
364			if (r < 0)
365				msleep(wait_tab[i]);
366		}
367		mutex_unlock(&phy->phy_lock);
368
369		if (r != len) {
370			phy->current_read_len = 0;
371			return -EREMOTEIO;
372		}
373
374		/*
375		 * The first read sequence does not start with SOF.
376		 * Data is corrupeted so we drop it.
377		 */
378		if (!phy->current_read_len && !IS_START_OF_FRAME(buf)) {
379			skb_trim(skb, 0);
380			phy->current_read_len = 0;
381			return -EIO;
382		} else if (phy->current_read_len && IS_START_OF_FRAME(buf)) {
383			/*
384			 * Previous frame transmission was interrupted and
385			 * the frame got repeated.
386			 * Received frame start with ST21NFCA_SOF_EOF + 00.
387			 */
388			skb_trim(skb, 0);
389			phy->current_read_len = 0;
390		}
391
392		skb_put_data(skb, buf, len);
393
394		if (skb->data[skb->len - 1] == ST21NFCA_SOF_EOF) {
395			phy->current_read_len = 0;
396			return st21nfca_hci_i2c_repack(skb);
397		}
398		phy->current_read_len++;
399		return -EAGAIN;
400	}
401	return -EIO;
402}
403
404/*
405 * Reads an shdlc frame from the chip. This is not as straightforward as it
406 * seems. The frame format is data-crc, and corruption can occur anywhere
407 * while transiting on i2c bus, such that we could read an invalid data.
408 * The tricky case is when we read a corrupted data or crc. We must detect
409 * this here in order to determine that data can be transmitted to the hci
410 * core. This is the reason why we check the crc here.
411 * The CLF will repeat a frame until we send a RR on that frame.
412 *
413 * On ST21NFCA, IRQ goes in idle when read starts. As no size information are
414 * available in the incoming data, other IRQ might come. Every IRQ will trigger
415 * a read sequence with different length and will fill the current frame.
416 * The reception is complete once we reach a ST21NFCA_SOF_EOF.
417 */
418static irqreturn_t st21nfca_hci_irq_thread_fn(int irq, void *phy_id)
419{
420	struct st21nfca_i2c_phy *phy = phy_id;
421
422	int r;
423
424	if (!phy || irq != phy->i2c_dev->irq) {
425		WARN_ON_ONCE(1);
426		return IRQ_NONE;
427	}
428
429	if (phy->hard_fault != 0)
430		return IRQ_HANDLED;
431
432	r = st21nfca_hci_i2c_read(phy, phy->pending_skb);
433	if (r == -EREMOTEIO) {
434		phy->hard_fault = r;
435
436		nfc_hci_recv_frame(phy->hdev, NULL);
437
438		return IRQ_HANDLED;
439	} else if (r == -EAGAIN || r == -EIO) {
440		return IRQ_HANDLED;
441	} else if (r == -EBADMSG && phy->crc_trials < ARRAY_SIZE(wait_tab)) {
442		/*
443		 * With ST21NFCA, only one interface (I2C, RF or SWP)
444		 * may be active at a time.
445		 * Having incorrect crc is usually due to i2c macrocell
446		 * deactivation in the middle of a transmission.
447		 * It may generate corrupted data on i2c.
448		 * We give sometime to get i2c back.
449		 * The complete frame will be repeated.
450		 */
451		msleep(wait_tab[phy->crc_trials]);
452		phy->crc_trials++;
453		phy->current_read_len = 0;
454		kfree_skb(phy->pending_skb);
455	} else if (r > 0) {
456		/*
457		 * We succeeded to read data from the CLF and
458		 * data is valid.
459		 * Reset counter.
460		 */
461		nfc_hci_recv_frame(phy->hdev, phy->pending_skb);
462		phy->crc_trials = 0;
463	} else {
464		kfree_skb(phy->pending_skb);
465	}
466
467	phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
468	if (phy->pending_skb == NULL) {
469		phy->hard_fault = -ENOMEM;
470		nfc_hci_recv_frame(phy->hdev, NULL);
471	}
472
473	return IRQ_HANDLED;
474}
475
476static const struct nfc_phy_ops i2c_phy_ops = {
477	.write = st21nfca_hci_i2c_write,
478	.enable = st21nfca_hci_i2c_enable,
479	.disable = st21nfca_hci_i2c_disable,
480};
481
482static const struct acpi_gpio_params enable_gpios = { 1, 0, false };
483
484static const struct acpi_gpio_mapping acpi_st21nfca_gpios[] = {
485	{ "enable-gpios", &enable_gpios, 1 },
486	{},
487};
488
489static int st21nfca_hci_i2c_probe(struct i2c_client *client)
490{
491	struct device *dev = &client->dev;
492	struct st21nfca_i2c_phy *phy;
493	int r;
494
495	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
496		nfc_err(&client->dev, "Need I2C_FUNC_I2C\n");
497		return -ENODEV;
498	}
499
500	phy = devm_kzalloc(&client->dev, sizeof(struct st21nfca_i2c_phy),
501			   GFP_KERNEL);
502	if (!phy)
503		return -ENOMEM;
504
505	phy->i2c_dev = client;
506	phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
507	if (phy->pending_skb == NULL)
508		return -ENOMEM;
509
510	phy->current_read_len = 0;
511	phy->crc_trials = 0;
512	mutex_init(&phy->phy_lock);
513	i2c_set_clientdata(client, phy);
514
515	r = devm_acpi_dev_add_driver_gpios(dev, acpi_st21nfca_gpios);
516	if (r)
517		dev_dbg(dev, "Unable to add GPIO mapping table\n");
518
519	/* Get EN GPIO from resource provider */
520	phy->gpiod_ena = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
521	if (IS_ERR(phy->gpiod_ena)) {
522		nfc_err(dev, "Unable to get ENABLE GPIO\n");
523		r = PTR_ERR(phy->gpiod_ena);
524		goto out_free;
525	}
526
527	phy->se_status.is_ese_present =
528			device_property_read_bool(&client->dev, "ese-present");
529	phy->se_status.is_uicc_present =
530			device_property_read_bool(&client->dev, "uicc-present");
531
532	r = st21nfca_hci_platform_init(phy);
533	if (r < 0) {
534		nfc_err(&client->dev, "Unable to reboot st21nfca\n");
535		goto out_free;
536	}
537
538	r = devm_request_threaded_irq(&client->dev, client->irq, NULL,
539				st21nfca_hci_irq_thread_fn,
540				IRQF_ONESHOT,
541				ST21NFCA_HCI_DRIVER_NAME, phy);
542	if (r < 0) {
543		nfc_err(&client->dev, "Unable to register IRQ handler\n");
544		goto out_free;
545	}
546
547	r = st21nfca_hci_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
548			       ST21NFCA_FRAME_HEADROOM,
549			       ST21NFCA_FRAME_TAILROOM,
550			       ST21NFCA_HCI_LLC_MAX_PAYLOAD,
551			       &phy->hdev,
552			       &phy->se_status);
553	if (r)
554		goto out_free;
555
556	return 0;
557
558out_free:
559	kfree_skb(phy->pending_skb);
560	return r;
561}
562
563static void st21nfca_hci_i2c_remove(struct i2c_client *client)
564{
565	struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);
566
567	st21nfca_hci_remove(phy->hdev);
568
569	if (phy->powered)
570		st21nfca_hci_i2c_disable(phy);
571	kfree_skb(phy->pending_skb);
572}
573
574static const struct i2c_device_id st21nfca_hci_i2c_id_table[] = {
575	{ ST21NFCA_HCI_DRIVER_NAME },
576	{}
577};
578MODULE_DEVICE_TABLE(i2c, st21nfca_hci_i2c_id_table);
579
580static const struct acpi_device_id st21nfca_hci_i2c_acpi_match[] __maybe_unused = {
581	{"SMO2100", 0},
582	{}
583};
584MODULE_DEVICE_TABLE(acpi, st21nfca_hci_i2c_acpi_match);
585
586static const struct of_device_id of_st21nfca_i2c_match[] __maybe_unused = {
587	{ .compatible = "st,st21nfca-i2c", },
588	{ .compatible = "st,st21nfca_i2c", },
589	{}
590};
591MODULE_DEVICE_TABLE(of, of_st21nfca_i2c_match);
592
593static struct i2c_driver st21nfca_hci_i2c_driver = {
594	.driver = {
595		.name = ST21NFCA_HCI_I2C_DRIVER_NAME,
596		.of_match_table = of_match_ptr(of_st21nfca_i2c_match),
597		.acpi_match_table = ACPI_PTR(st21nfca_hci_i2c_acpi_match),
598	},
599	.probe = st21nfca_hci_i2c_probe,
600	.id_table = st21nfca_hci_i2c_id_table,
601	.remove = st21nfca_hci_i2c_remove,
602};
603module_i2c_driver(st21nfca_hci_i2c_driver);
604
605MODULE_LICENSE("GPL");
606MODULE_DESCRIPTION(DRIVER_DESC);