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Linux/net/nfc/nci/spi.c

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  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, 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 
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 
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 
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 
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  */
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 

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