summaryrefslogtreecommitdiff
path: root/net/nfc/nci/spi.c
blob: 6a93533c480e656914d83278068ebf10b4189b24 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2013  Intel Corporation. All rights reserved.
 */

#define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__

#include <linux/module.h>

#include <linux/export.h>
#include <linux/spi/spi.h>
#include <linux/crc-ccitt.h>
#include <net/nfc/nci_core.h>

#define NCI_SPI_ACK_SHIFT		6
#define NCI_SPI_MSB_PAYLOAD_MASK	0x3F

#define NCI_SPI_SEND_TIMEOUT	(NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
					NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)

#define NCI_SPI_DIRECT_WRITE	0x01
#define NCI_SPI_DIRECT_READ	0x02

#define ACKNOWLEDGE_NONE	0
#define ACKNOWLEDGE_ACK		1
#define ACKNOWLEDGE_NACK	2

#define CRC_INIT		0xFFFF

static int __nci_spi_send(struct nci_spi *nspi, const struct sk_buff *skb,
			  int cs_change)
{
	struct spi_message m;
	struct spi_transfer t;

	memset(&t, 0, sizeof(struct spi_transfer));
	/* a NULL skb means we just want the SPI chip select line to raise */
	if (skb) {
		t.tx_buf = skb->data;
		t.len = skb->len;
	} else {
		/* still set tx_buf non NULL to make the driver happy */
		t.tx_buf = &t;
		t.len = 0;
	}
	t.cs_change = cs_change;
	t.delay.value = nspi->xfer_udelay;
	t.delay.unit = SPI_DELAY_UNIT_USECS;
	t.speed_hz = nspi->xfer_speed_hz;

	spi_message_init(&m);
	spi_message_add_tail(&t, &m);

	return spi_sync(nspi->spi, &m);
}

int nci_spi_send(struct nci_spi *nspi,
		 struct completion *write_handshake_completion,
		 struct sk_buff *skb)
{
	unsigned int payload_len = skb->len;
	unsigned char *hdr;
	int ret;
	long completion_rc;

	/* add the NCI SPI header to the start of the buffer */
	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
	hdr[0] = NCI_SPI_DIRECT_WRITE;
	hdr[1] = nspi->acknowledge_mode;
	hdr[2] = payload_len >> 8;
	hdr[3] = payload_len & 0xFF;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
		u16 crc;

		crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
		skb_put_u8(skb, crc >> 8);
		skb_put_u8(skb, crc & 0xFF);
	}

	if (write_handshake_completion)	{
		/* Trick SPI driver to raise chip select */
		ret = __nci_spi_send(nspi, NULL, 1);
		if (ret)
			goto done;

		/* wait for NFC chip hardware handshake to complete */
		if (wait_for_completion_timeout(write_handshake_completion,
						msecs_to_jiffies(1000)) == 0) {
			ret = -ETIME;
			goto done;
		}
	}

	ret = __nci_spi_send(nspi, skb, 0);
	if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
		goto done;

	reinit_completion(&nspi->req_completion);
	completion_rc =	wait_for_completion_interruptible_timeout(
							&nspi->req_completion,
							NCI_SPI_SEND_TIMEOUT);

	if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK)
		ret = -EIO;

done:
	kfree_skb(skb);

	return ret;
}
EXPORT_SYMBOL_GPL(nci_spi_send);

/* ---- Interface to NCI SPI drivers ---- */

/**
 * nci_spi_allocate_spi - allocate a new nci spi
 *
 * @spi: SPI device
 * @acknowledge_mode: Acknowledge mode used by the NFC device
 * @delay: delay between transactions in us
 * @ndev: nci dev to send incoming nci frames to
 */
struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
				     u8 acknowledge_mode, unsigned int delay,
				     struct nci_dev *ndev)
{
	struct nci_spi *nspi;

	nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
	if (!nspi)
		return NULL;

	nspi->acknowledge_mode = acknowledge_mode;
	nspi->xfer_udelay = delay;
	/* Use controller max SPI speed by default */
	nspi->xfer_speed_hz = 0;
	nspi->spi = spi;
	nspi->ndev = ndev;
	init_completion(&nspi->req_completion);

	return nspi;
}
EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);

static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
{
	struct sk_buff *skb;
	unsigned char *hdr;
	u16 crc;
	int ret;

	skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);
	if (!skb)
		return -ENOMEM;

	/* add the NCI SPI header to the start of the buffer */
	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
	hdr[0] = NCI_SPI_DIRECT_WRITE;
	hdr[1] = NCI_SPI_CRC_ENABLED;
	hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
	hdr[3] = 0;

	crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
	skb_put_u8(skb, crc >> 8);
	skb_put_u8(skb, crc & 0xFF);

	ret = __nci_spi_send(nspi, skb, 0);

	kfree_skb(skb);

	return ret;
}

static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
{
	struct sk_buff *skb;
	struct spi_message m;
	unsigned char req[2], resp_hdr[2];
	struct spi_transfer tx, rx;
	unsigned short rx_len = 0;
	int ret;

	spi_message_init(&m);

	memset(&tx, 0, sizeof(struct spi_transfer));
	req[0] = NCI_SPI_DIRECT_READ;
	req[1] = nspi->acknowledge_mode;
	tx.tx_buf = req;
	tx.len = 2;
	tx.cs_change = 0;
	tx.speed_hz = nspi->xfer_speed_hz;
	spi_message_add_tail(&tx, &m);

	memset(&rx, 0, sizeof(struct spi_transfer));
	rx.rx_buf = resp_hdr;
	rx.len = 2;
	rx.cs_change = 1;
	rx.speed_hz = nspi->xfer_speed_hz;
	spi_message_add_tail(&rx, &m);

	ret = spi_sync(nspi->spi, &m);
	if (ret)
		return NULL;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
		rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
				resp_hdr[1] + NCI_SPI_CRC_LEN;
	else
		rx_len = (resp_hdr[0] << 8) | resp_hdr[1];

	skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
	if (!skb)
		return NULL;

	spi_message_init(&m);

	memset(&rx, 0, sizeof(struct spi_transfer));
	rx.rx_buf = skb_put(skb, rx_len);
	rx.len = rx_len;
	rx.cs_change = 0;
	rx.delay.value = nspi->xfer_udelay;
	rx.delay.unit = SPI_DELAY_UNIT_USECS;
	rx.speed_hz = nspi->xfer_speed_hz;
	spi_message_add_tail(&rx, &m);

	ret = spi_sync(nspi->spi, &m);
	if (ret)
		goto receive_error;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
		*(u8 *)skb_push(skb, 1) = resp_hdr[1];
		*(u8 *)skb_push(skb, 1) = resp_hdr[0];
	}

	return skb;

receive_error:
	kfree_skb(skb);

	return NULL;
}

static int nci_spi_check_crc(struct sk_buff *skb)
{
	u16 crc_data = (skb->data[skb->len - 2] << 8) |
			skb->data[skb->len - 1];
	int ret;

	ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
			== crc_data);

	skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);

	return ret;
}

static u8 nci_spi_get_ack(struct sk_buff *skb)
{
	u8 ret;

	ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;

	/* Remove NFCC part of the header: ACK, NACK and MSB payload len */
	skb_pull(skb, 2);

	return ret;
}

/**
 * nci_spi_read - read frame from NCI SPI drivers
 *
 * @nspi: The nci spi
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.
 *
 * It returns an allocated skb containing the frame on success, or NULL.
 */
struct sk_buff *nci_spi_read(struct nci_spi *nspi)
{
	struct sk_buff *skb;

	/* Retrieve frame from SPI */
	skb = __nci_spi_read(nspi);
	if (!skb)
		goto done;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
		if (!nci_spi_check_crc(skb)) {
			send_acknowledge(nspi, ACKNOWLEDGE_NACK);
			goto done;
		}

		/* In case of acknowledged mode: if ACK or NACK received,
		 * unblock completion of latest frame sent.
		 */
		nspi->req_result = nci_spi_get_ack(skb);
		if (nspi->req_result)
			complete(&nspi->req_completion);
	}

	/* If there is no payload (ACK/NACK only frame),
	 * free the socket buffer
	 */
	if (!skb->len) {
		kfree_skb(skb);
		skb = NULL;
		goto done;
	}

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
		send_acknowledge(nspi, ACKNOWLEDGE_ACK);

done:

	return skb;
}
EXPORT_SYMBOL_GPL(nci_spi_read);

MODULE_DESCRIPTION("NFC Controller Interface (NCI) SPI link layer");
MODULE_LICENSE("GPL");