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
30 static int __nci_spi_send(struct nci_spi *nspi, const 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
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 */
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
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 if (!skb)
155 return -ENOMEM;
156
157 /* add the NCI SPI header to the start of the buffer */
158 hdr = skb_push(skb, NCI_SPI_HDR_LEN);
159 hdr[0] = NCI_SPI_DIRECT_WRITE;
160 hdr[1] = NCI_SPI_CRC_ENABLED;
161 hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
162 hdr[3] = 0;
163
164 crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
165 skb_put_u8(skb, crc >> 8);
166 skb_put_u8(skb, crc & 0xFF);
167
168 ret = __nci_spi_send(nspi, skb, 0);
169
170 kfree_skb(skb);
171
172 return ret;
173 }
174
175 static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
176 {
177 struct sk_buff *skb;
178 struct spi_message m;
179 unsigned char req[2], resp_hdr[2];
180 struct spi_transfer tx, rx;
181 unsigned short rx_len = 0;
182 int ret;
183
184 spi_message_init(&m);
185
186 memset(&tx, 0, sizeof(struct spi_transfer));
187 req[0] = NCI_SPI_DIRECT_READ;
188 req[1] = nspi->acknowledge_mode;
189 tx.tx_buf = req;
190 tx.len = 2;
191 tx.cs_change = 0;
192 tx.speed_hz = nspi->xfer_speed_hz;
193 spi_message_add_tail(&tx, &m);
194
195 memset(&rx, 0, sizeof(struct spi_transfer));
196 rx.rx_buf = resp_hdr;
197 rx.len = 2;
198 rx.cs_change = 1;
199 rx.speed_hz = nspi->xfer_speed_hz;
200 spi_message_add_tail(&rx, &m);
201
202 ret = spi_sync(nspi->spi, &m);
203 if (ret)
204 return NULL;
205
206 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
207 rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
208 resp_hdr[1] + NCI_SPI_CRC_LEN;
209 else
210 rx_len = (resp_hdr[0] << 8) | resp_hdr[1];
211
212 skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
213 if (!skb)
214 return NULL;
215
216 spi_message_init(&m);
217
218 memset(&rx, 0, sizeof(struct spi_transfer));
219 rx.rx_buf = skb_put(skb, rx_len);
220 rx.len = rx_len;
221 rx.cs_change = 0;
222 rx.delay.value = nspi->xfer_udelay;
223 rx.delay.unit = SPI_DELAY_UNIT_USECS;
224 rx.speed_hz = nspi->xfer_speed_hz;
225 spi_message_add_tail(&rx, &m);
226
227 ret = spi_sync(nspi->spi, &m);
228 if (ret)
229 goto receive_error;
230
231 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
232 *(u8 *)skb_push(skb, 1) = resp_hdr[1];
233 *(u8 *)skb_push(skb, 1) = resp_hdr[0];
234 }
235
236 return skb;
237
238 receive_error:
239 kfree_skb(skb);
240
241 return NULL;
242 }
243
244 static int nci_spi_check_crc(struct sk_buff *skb)
245 {
246 u16 crc_data = (skb->data[skb->len - 2] << 8) |
247 skb->data[skb->len - 1];
248 int ret;
249
250 ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
251 == crc_data);
252
253 skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);
254
255 return ret;
256 }
257
258 static u8 nci_spi_get_ack(struct sk_buff *skb)
259 {
260 u8 ret;
261
262 ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;
263
264 /* Remove NFCC part of the header: ACK, NACK and MSB payload len */
265 skb_pull(skb, 2);
266
267 return ret;
268 }
269
270 /**
271 * nci_spi_read - read frame from NCI SPI drivers
272 *
273 * @nspi: The nci spi
274 * Context: can sleep
275 *
276 * This call may only be used from a context that may sleep. The sleep
277 * is non-interruptible, and has no timeout.
278 *
279 * It returns an allocated skb containing the frame on success, or NULL.
280 */
281 struct sk_buff *nci_spi_read(struct nci_spi *nspi)
282 {
283 struct sk_buff *skb;
284
285 /* Retrieve frame from SPI */
286 skb = __nci_spi_read(nspi);
287 if (!skb)
288 goto done;
289
290 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
291 if (!nci_spi_check_crc(skb)) {
292 send_acknowledge(nspi, ACKNOWLEDGE_NACK);
293 goto done;
294 }
295
296 /* In case of acknowledged mode: if ACK or NACK received,
297 * unblock completion of latest frame sent.
298 */
299 nspi->req_result = nci_spi_get_ack(skb);
300 if (nspi->req_result)
301 complete(&nspi->req_completion);
302 }
303
304 /* If there is no payload (ACK/NACK only frame),
305 * free the socket buffer
306 */
307 if (!skb->len) {
308 kfree_skb(skb);
309 skb = NULL;
310 goto done;
311 }
312
313 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
314 send_acknowledge(nspi, ACKNOWLEDGE_ACK);
315
316 done:
317
318 return skb;
319 }
320 EXPORT_SYMBOL_GPL(nci_spi_read);
321
322 MODULE_DESCRIPTION("NFC Controller Interface (NCI) SPI link layer");
323 MODULE_LICENSE("GPL");
324
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