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
__nci_spi_send(struct nci_spi * nspi,struct sk_buff * skb,int cs_change)41 static 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
nci_spi_send(struct nci_spi * nspi,struct completion * write_handshake_completion,struct sk_buff * skb)66 int 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
116 done:
117 kfree_skb(skb);
118
119 return ret;
120 }
121 EXPORT_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 */
nci_spi_allocate_spi(struct spi_device * spi,u8 acknowledge_mode,unsigned int delay,struct nci_dev * ndev)133 struct 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 }
152 EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);
153
send_acknowledge(struct nci_spi * nspi,u8 acknowledge)154 static 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
__nci_spi_read(struct nci_spi * nspi)181 static 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
240 receive_error:
241 kfree_skb(skb);
242
243 return NULL;
244 }
245
nci_spi_check_crc(struct sk_buff * skb)246 static 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
nci_spi_get_ack(struct sk_buff * skb)260 static 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 */
nci_spi_read(struct nci_spi * nspi)283 struct 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
318 done:
319
320 return skb;
321 }
322 EXPORT_SYMBOL_GPL(nci_spi_read);
323