1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2013 Intel Corporation. All rights reserved.
4 */
5
6 #define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__
7
8 #include <linux/module.h>
9
10 #include <linux/export.h>
11 #include <linux/spi/spi.h>
12 #include <linux/crc-ccitt.h>
13 #include <net/nfc/nci_core.h>
14
15 #define NCI_SPI_ACK_SHIFT 6
16 #define NCI_SPI_MSB_PAYLOAD_MASK 0x3F
17
18 #define NCI_SPI_SEND_TIMEOUT (NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
19 NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)
20
21 #define NCI_SPI_DIRECT_WRITE 0x01
22 #define NCI_SPI_DIRECT_READ 0x02
23
24 #define ACKNOWLEDGE_NONE 0
25 #define ACKNOWLEDGE_ACK 1
26 #define ACKNOWLEDGE_NACK 2
27
28 #define CRC_INIT 0xFFFF
29
__nci_spi_send(struct nci_spi * nspi,struct sk_buff * skb,int cs_change)30 static int __nci_spi_send(struct nci_spi *nspi, struct sk_buff *skb,
31 int cs_change)
32 {
33 struct spi_message m;
34 struct spi_transfer t;
35
36 memset(&t, 0, sizeof(struct spi_transfer));
37 /* a NULL skb means we just want the SPI chip select line to raise */
38 if (skb) {
39 t.tx_buf = skb->data;
40 t.len = skb->len;
41 } else {
42 /* still set tx_buf non NULL to make the driver happy */
43 t.tx_buf = &t;
44 t.len = 0;
45 }
46 t.cs_change = cs_change;
47 t.delay.value = nspi->xfer_udelay;
48 t.delay.unit = SPI_DELAY_UNIT_USECS;
49 t.speed_hz = nspi->xfer_speed_hz;
50
51 spi_message_init(&m);
52 spi_message_add_tail(&t, &m);
53
54 return spi_sync(nspi->spi, &m);
55 }
56
nci_spi_send(struct nci_spi * nspi,struct completion * write_handshake_completion,struct sk_buff * skb)57 int nci_spi_send(struct nci_spi *nspi,
58 struct completion *write_handshake_completion,
59 struct sk_buff *skb)
60 {
61 unsigned int payload_len = skb->len;
62 unsigned char *hdr;
63 int ret;
64 long completion_rc;
65
66 /* add the NCI SPI header to the start of the buffer */
67 hdr = skb_push(skb, NCI_SPI_HDR_LEN);
68 hdr[0] = NCI_SPI_DIRECT_WRITE;
69 hdr[1] = nspi->acknowledge_mode;
70 hdr[2] = payload_len >> 8;
71 hdr[3] = payload_len & 0xFF;
72
73 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
74 u16 crc;
75
76 crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
77 skb_put_u8(skb, crc >> 8);
78 skb_put_u8(skb, crc & 0xFF);
79 }
80
81 if (write_handshake_completion) {
82 /* Trick SPI driver to raise chip select */
83 ret = __nci_spi_send(nspi, NULL, 1);
84 if (ret)
85 goto done;
86
87 /* wait for NFC chip hardware handshake to complete */
88 if (wait_for_completion_timeout(write_handshake_completion,
89 msecs_to_jiffies(1000)) == 0) {
90 ret = -ETIME;
91 goto done;
92 }
93 }
94
95 ret = __nci_spi_send(nspi, skb, 0);
96 if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
97 goto done;
98
99 reinit_completion(&nspi->req_completion);
100 completion_rc = wait_for_completion_interruptible_timeout(
101 &nspi->req_completion,
102 NCI_SPI_SEND_TIMEOUT);
103
104 if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK)
105 ret = -EIO;
106
107 done:
108 kfree_skb(skb);
109
110 return ret;
111 }
112 EXPORT_SYMBOL_GPL(nci_spi_send);
113
114 /* ---- Interface to NCI SPI drivers ---- */
115
116 /**
117 * nci_spi_allocate_spi - allocate a new nci spi
118 *
119 * @spi: SPI device
120 * @acknowledge_mode: Acknowledge mode used by the NFC device
121 * @delay: delay between transactions in us
122 * @ndev: nci dev to send incoming nci frames to
123 */
nci_spi_allocate_spi(struct spi_device * spi,u8 acknowledge_mode,unsigned int delay,struct nci_dev * ndev)124 struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
125 u8 acknowledge_mode, unsigned int delay,
126 struct nci_dev *ndev)
127 {
128 struct nci_spi *nspi;
129
130 nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
131 if (!nspi)
132 return NULL;
133
134 nspi->acknowledge_mode = acknowledge_mode;
135 nspi->xfer_udelay = delay;
136 /* Use controller max SPI speed by default */
137 nspi->xfer_speed_hz = 0;
138 nspi->spi = spi;
139 nspi->ndev = ndev;
140 init_completion(&nspi->req_completion);
141
142 return nspi;
143 }
144 EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);
145
send_acknowledge(struct nci_spi * nspi,u8 acknowledge)146 static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
147 {
148 struct sk_buff *skb;
149 unsigned char *hdr;
150 u16 crc;
151 int ret;
152
153 skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);
154
155 /* add the NCI SPI header to the start of the buffer */
156 hdr = skb_push(skb, NCI_SPI_HDR_LEN);
157 hdr[0] = NCI_SPI_DIRECT_WRITE;
158 hdr[1] = NCI_SPI_CRC_ENABLED;
159 hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
160 hdr[3] = 0;
161
162 crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
163 skb_put_u8(skb, crc >> 8);
164 skb_put_u8(skb, crc & 0xFF);
165
166 ret = __nci_spi_send(nspi, skb, 0);
167
168 kfree_skb(skb);
169
170 return ret;
171 }
172
__nci_spi_read(struct nci_spi * nspi)173 static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
174 {
175 struct sk_buff *skb;
176 struct spi_message m;
177 unsigned char req[2], resp_hdr[2];
178 struct spi_transfer tx, rx;
179 unsigned short rx_len = 0;
180 int ret;
181
182 spi_message_init(&m);
183
184 memset(&tx, 0, sizeof(struct spi_transfer));
185 req[0] = NCI_SPI_DIRECT_READ;
186 req[1] = nspi->acknowledge_mode;
187 tx.tx_buf = req;
188 tx.len = 2;
189 tx.cs_change = 0;
190 tx.speed_hz = nspi->xfer_speed_hz;
191 spi_message_add_tail(&tx, &m);
192
193 memset(&rx, 0, sizeof(struct spi_transfer));
194 rx.rx_buf = resp_hdr;
195 rx.len = 2;
196 rx.cs_change = 1;
197 rx.speed_hz = nspi->xfer_speed_hz;
198 spi_message_add_tail(&rx, &m);
199
200 ret = spi_sync(nspi->spi, &m);
201 if (ret)
202 return NULL;
203
204 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
205 rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
206 resp_hdr[1] + NCI_SPI_CRC_LEN;
207 else
208 rx_len = (resp_hdr[0] << 8) | resp_hdr[1];
209
210 skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
211 if (!skb)
212 return NULL;
213
214 spi_message_init(&m);
215
216 memset(&rx, 0, sizeof(struct spi_transfer));
217 rx.rx_buf = skb_put(skb, rx_len);
218 rx.len = rx_len;
219 rx.cs_change = 0;
220 rx.delay.value = nspi->xfer_udelay;
221 rx.delay.unit = SPI_DELAY_UNIT_USECS;
222 rx.speed_hz = nspi->xfer_speed_hz;
223 spi_message_add_tail(&rx, &m);
224
225 ret = spi_sync(nspi->spi, &m);
226 if (ret)
227 goto receive_error;
228
229 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
230 *(u8 *)skb_push(skb, 1) = resp_hdr[1];
231 *(u8 *)skb_push(skb, 1) = resp_hdr[0];
232 }
233
234 return skb;
235
236 receive_error:
237 kfree_skb(skb);
238
239 return NULL;
240 }
241
nci_spi_check_crc(struct sk_buff * skb)242 static int nci_spi_check_crc(struct sk_buff *skb)
243 {
244 u16 crc_data = (skb->data[skb->len - 2] << 8) |
245 skb->data[skb->len - 1];
246 int ret;
247
248 ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
249 == crc_data);
250
251 skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);
252
253 return ret;
254 }
255
nci_spi_get_ack(struct sk_buff * skb)256 static u8 nci_spi_get_ack(struct sk_buff *skb)
257 {
258 u8 ret;
259
260 ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;
261
262 /* Remove NFCC part of the header: ACK, NACK and MSB payload len */
263 skb_pull(skb, 2);
264
265 return ret;
266 }
267
268 /**
269 * nci_spi_read - read frame from NCI SPI drivers
270 *
271 * @nspi: The nci spi
272 * Context: can sleep
273 *
274 * This call may only be used from a context that may sleep. The sleep
275 * is non-interruptible, and has no timeout.
276 *
277 * It returns an allocated skb containing the frame on success, or NULL.
278 */
nci_spi_read(struct nci_spi * nspi)279 struct sk_buff *nci_spi_read(struct nci_spi *nspi)
280 {
281 struct sk_buff *skb;
282
283 /* Retrieve frame from SPI */
284 skb = __nci_spi_read(nspi);
285 if (!skb)
286 goto done;
287
288 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
289 if (!nci_spi_check_crc(skb)) {
290 send_acknowledge(nspi, ACKNOWLEDGE_NACK);
291 goto done;
292 }
293
294 /* In case of acknowledged mode: if ACK or NACK received,
295 * unblock completion of latest frame sent.
296 */
297 nspi->req_result = nci_spi_get_ack(skb);
298 if (nspi->req_result)
299 complete(&nspi->req_completion);
300 }
301
302 /* If there is no payload (ACK/NACK only frame),
303 * free the socket buffer
304 */
305 if (!skb->len) {
306 kfree_skb(skb);
307 skb = NULL;
308 goto done;
309 }
310
311 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
312 send_acknowledge(nspi, ACKNOWLEDGE_ACK);
313
314 done:
315
316 return skb;
317 }
318 EXPORT_SYMBOL_GPL(nci_spi_read);
319
320 MODULE_LICENSE("GPL");
321
