1/*
2 * Copyright (C) 2013  Intel Corporation. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms and conditions of the GNU General Public License,
6 * version 2, as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
11 * more details.
12 *
13 * You should have received a copy of the GNU General Public License along with
14 * this program; if not, write to the Free Software Foundation, Inc.,
15 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
16 *
17 */
18
19#define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__
20
21#include <linux/export.h>
22#include <linux/spi/spi.h>
23#include <linux/crc-ccitt.h>
24#include <net/nfc/nci_core.h>
25
26#define NCI_SPI_ACK_SHIFT		6
27#define NCI_SPI_MSB_PAYLOAD_MASK	0x3F
28
29#define NCI_SPI_SEND_TIMEOUT	(NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
30					NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)
31
32#define NCI_SPI_DIRECT_WRITE	0x01
33#define NCI_SPI_DIRECT_READ	0x02
34
35#define ACKNOWLEDGE_NONE	0
36#define ACKNOWLEDGE_ACK		1
37#define ACKNOWLEDGE_NACK	2
38
39#define CRC_INIT		0xFFFF
40
41static int __nci_spi_send(struct nci_spi *nspi, struct sk_buff *skb,
42			  int cs_change)
43{
44	struct spi_message m;
45	struct spi_transfer t;
46
47	memset(&t, 0, sizeof(struct spi_transfer));
48	/* a NULL skb means we just want the SPI chip select line to raise */
49	if (skb) {
50		t.tx_buf = skb->data;
51		t.len = skb->len;
52	} else {
53		/* still set tx_buf non NULL to make the driver happy */
54		t.tx_buf = &t;
55		t.len = 0;
56	}
57	t.cs_change = cs_change;
58	t.delay_usecs = nspi->xfer_udelay;
59
60	spi_message_init(&m);
61	spi_message_add_tail(&t, &m);
62
63	return spi_sync(nspi->spi, &m);
64}
65
66int nci_spi_send(struct nci_spi *nspi,
67		 struct completion *write_handshake_completion,
68		 struct sk_buff *skb)
69{
70	unsigned int payload_len = skb->len;
71	unsigned char *hdr;
72	int ret;
73	long completion_rc;
74
75	/* add the NCI SPI header to the start of the buffer */
76	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
77	hdr[0] = NCI_SPI_DIRECT_WRITE;
78	hdr[1] = nspi->acknowledge_mode;
79	hdr[2] = payload_len >> 8;
80	hdr[3] = payload_len & 0xFF;
81
82	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
83		u16 crc;
84
85		crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
86		*skb_put(skb, 1) = crc >> 8;
87		*skb_put(skb, 1) = crc & 0xFF;
88	}
89
90	if (write_handshake_completion)	{
91		/* Trick SPI driver to raise chip select */
92		ret = __nci_spi_send(nspi, NULL, 1);
93		if (ret)
94			goto done;
95
96		/* wait for NFC chip hardware handshake to complete */
97		if (wait_for_completion_timeout(write_handshake_completion,
98						msecs_to_jiffies(1000)) == 0) {
99			ret = -ETIME;
100			goto done;
101		}
102	}
103
104	ret = __nci_spi_send(nspi, skb, 0);
105	if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
106		goto done;
107
108	reinit_completion(&nspi->req_completion);
109	completion_rc =	wait_for_completion_interruptible_timeout(
110							&nspi->req_completion,
111							NCI_SPI_SEND_TIMEOUT);
112
113	if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK)
114		ret = -EIO;
115
116done:
117	kfree_skb(skb);
118
119	return ret;
120}
121EXPORT_SYMBOL_GPL(nci_spi_send);
122
123/* ---- Interface to NCI SPI drivers ---- */
124
125/**
126 * nci_spi_allocate_spi - allocate a new nci spi
127 *
128 * @spi: SPI device
129 * @acknowledge_mode: Acknowledge mode used by the NFC device
130 * @delay: delay between transactions in us
131 * @ndev: nci dev to send incoming nci frames to
132 */
133struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
134				     u8 acknowledge_mode, unsigned int delay,
135				     struct nci_dev *ndev)
136{
137	struct nci_spi *nspi;
138
139	nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
140	if (!nspi)
141		return NULL;
142
143	nspi->acknowledge_mode = acknowledge_mode;
144	nspi->xfer_udelay = delay;
145
146	nspi->spi = spi;
147	nspi->ndev = ndev;
148	init_completion(&nspi->req_completion);
149
150	return nspi;
151}
152EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);
153
154static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
155{
156	struct sk_buff *skb;
157	unsigned char *hdr;
158	u16 crc;
159	int ret;
160
161	skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);
162
163	/* add the NCI SPI header to the start of the buffer */
164	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
165	hdr[0] = NCI_SPI_DIRECT_WRITE;
166	hdr[1] = NCI_SPI_CRC_ENABLED;
167	hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
168	hdr[3] = 0;
169
170	crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
171	*skb_put(skb, 1) = crc >> 8;
172	*skb_put(skb, 1) = crc & 0xFF;
173
174	ret = __nci_spi_send(nspi, skb, 0);
175
176	kfree_skb(skb);
177
178	return ret;
179}
180
181static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
182{
183	struct sk_buff *skb;
184	struct spi_message m;
185	unsigned char req[2], resp_hdr[2];
186	struct spi_transfer tx, rx;
187	unsigned short rx_len = 0;
188	int ret;
189
190	spi_message_init(&m);
191
192	memset(&tx, 0, sizeof(struct spi_transfer));
193	req[0] = NCI_SPI_DIRECT_READ;
194	req[1] = nspi->acknowledge_mode;
195	tx.tx_buf = req;
196	tx.len = 2;
197	tx.cs_change = 0;
198	spi_message_add_tail(&tx, &m);
199
200	memset(&rx, 0, sizeof(struct spi_transfer));
201	rx.rx_buf = resp_hdr;
202	rx.len = 2;
203	rx.cs_change = 1;
204	spi_message_add_tail(&rx, &m);
205
206	ret = spi_sync(nspi->spi, &m);
207	if (ret)
208		return NULL;
209
210	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
211		rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
212				resp_hdr[1] + NCI_SPI_CRC_LEN;
213	else
214		rx_len = (resp_hdr[0] << 8) | resp_hdr[1];
215
216	skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
217	if (!skb)
218		return NULL;
219
220	spi_message_init(&m);
221
222	memset(&rx, 0, sizeof(struct spi_transfer));
223	rx.rx_buf = skb_put(skb, rx_len);
224	rx.len = rx_len;
225	rx.cs_change = 0;
226	rx.delay_usecs = nspi->xfer_udelay;
227	spi_message_add_tail(&rx, &m);
228
229	ret = spi_sync(nspi->spi, &m);
230	if (ret)
231		goto receive_error;
232
233	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
234		*skb_push(skb, 1) = resp_hdr[1];
235		*skb_push(skb, 1) = resp_hdr[0];
236	}
237
238	return skb;
239
240receive_error:
241	kfree_skb(skb);
242
243	return NULL;
244}
245
246static int nci_spi_check_crc(struct sk_buff *skb)
247{
248	u16 crc_data = (skb->data[skb->len - 2] << 8) |
249			skb->data[skb->len - 1];
250	int ret;
251
252	ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
253			== crc_data);
254
255	skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);
256
257	return ret;
258}
259
260static u8 nci_spi_get_ack(struct sk_buff *skb)
261{
262	u8 ret;
263
264	ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;
265
266	/* Remove NFCC part of the header: ACK, NACK and MSB payload len */
267	skb_pull(skb, 2);
268
269	return ret;
270}
271
272/**
273 * nci_spi_read - read frame from NCI SPI drivers
274 *
275 * @nspi: The nci spi
276 * Context: can sleep
277 *
278 * This call may only be used from a context that may sleep.  The sleep
279 * is non-interruptible, and has no timeout.
280 *
281 * It returns an allocated skb containing the frame on success, or NULL.
282 */
283struct sk_buff *nci_spi_read(struct nci_spi *nspi)
284{
285	struct sk_buff *skb;
286
287	/* Retrieve frame from SPI */
288	skb = __nci_spi_read(nspi);
289	if (!skb)
290		goto done;
291
292	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
293		if (!nci_spi_check_crc(skb)) {
294			send_acknowledge(nspi, ACKNOWLEDGE_NACK);
295			goto done;
296		}
297
298		/* In case of acknowledged mode: if ACK or NACK received,
299		 * unblock completion of latest frame sent.
300		 */
301		nspi->req_result = nci_spi_get_ack(skb);
302		if (nspi->req_result)
303			complete(&nspi->req_completion);
304	}
305
306	/* If there is no payload (ACK/NACK only frame),
307	 * free the socket buffer
308	 */
309	if (!skb->len) {
310		kfree_skb(skb);
311		skb = NULL;
312		goto done;
313	}
314
315	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
316		send_acknowledge(nspi, ACKNOWLEDGE_ACK);
317
318done:
319
320	return skb;
321}
322EXPORT_SYMBOL_GPL(nci_spi_read);
323