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,const struct sk_buff * skb,int cs_change)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 
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