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/module.h> 22 23 #include <linux/export.h> 24 #include <linux/spi/spi.h> 25 #include <linux/crc-ccitt.h> 26 #include <net/nfc/nci_core.h> 27 28 #define NCI_SPI_ACK_SHIFT 6 29 #define NCI_SPI_MSB_PAYLOAD_MASK 0x3F 30 31 #define NCI_SPI_SEND_TIMEOUT (NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \ 32 NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT) 33 34 #define NCI_SPI_DIRECT_WRITE 0x01 35 #define NCI_SPI_DIRECT_READ 0x02 36 37 #define ACKNOWLEDGE_NONE 0 38 #define ACKNOWLEDGE_ACK 1 39 #define ACKNOWLEDGE_NACK 2 40 41 #define CRC_INIT 0xFFFF 42 43 static int __nci_spi_send(struct nci_spi *nspi, struct sk_buff *skb, 44 int cs_change) 45 { 46 struct spi_message m; 47 struct spi_transfer t; 48 49 memset(&t, 0, sizeof(struct spi_transfer)); 50 /* a NULL skb means we just want the SPI chip select line to raise */ 51 if (skb) { 52 t.tx_buf = skb->data; 53 t.len = skb->len; 54 } else { 55 /* still set tx_buf non NULL to make the driver happy */ 56 t.tx_buf = &t; 57 t.len = 0; 58 } 59 t.cs_change = cs_change; 60 t.delay_usecs = nspi->xfer_udelay; 61 t.speed_hz = nspi->xfer_speed_hz; 62 63 spi_message_init(&m); 64 spi_message_add_tail(&t, &m); 65 66 return spi_sync(nspi->spi, &m); 67 } 68 69 int nci_spi_send(struct nci_spi *nspi, 70 struct completion *write_handshake_completion, 71 struct sk_buff *skb) 72 { 73 unsigned int payload_len = skb->len; 74 unsigned char *hdr; 75 int ret; 76 long completion_rc; 77 78 /* add the NCI SPI header to the start of the buffer */ 79 hdr = skb_push(skb, NCI_SPI_HDR_LEN); 80 hdr[0] = NCI_SPI_DIRECT_WRITE; 81 hdr[1] = nspi->acknowledge_mode; 82 hdr[2] = payload_len >> 8; 83 hdr[3] = payload_len & 0xFF; 84 85 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) { 86 u16 crc; 87 88 crc = crc_ccitt(CRC_INIT, skb->data, skb->len); 89 skb_put_u8(skb, crc >> 8); 90 skb_put_u8(skb, crc & 0xFF); 91 } 92 93 if (write_handshake_completion) { 94 /* Trick SPI driver to raise chip select */ 95 ret = __nci_spi_send(nspi, NULL, 1); 96 if (ret) 97 goto done; 98 99 /* wait for NFC chip hardware handshake to complete */ 100 if (wait_for_completion_timeout(write_handshake_completion, 101 msecs_to_jiffies(1000)) == 0) { 102 ret = -ETIME; 103 goto done; 104 } 105 } 106 107 ret = __nci_spi_send(nspi, skb, 0); 108 if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED) 109 goto done; 110 111 reinit_completion(&nspi->req_completion); 112 completion_rc = wait_for_completion_interruptible_timeout( 113 &nspi->req_completion, 114 NCI_SPI_SEND_TIMEOUT); 115 116 if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK) 117 ret = -EIO; 118 119 done: 120 kfree_skb(skb); 121 122 return ret; 123 } 124 EXPORT_SYMBOL_GPL(nci_spi_send); 125 126 /* ---- Interface to NCI SPI drivers ---- */ 127 128 /** 129 * nci_spi_allocate_spi - allocate a new nci spi 130 * 131 * @spi: SPI device 132 * @acknowledge_mode: Acknowledge mode used by the NFC device 133 * @delay: delay between transactions in us 134 * @ndev: nci dev to send incoming nci frames to 135 */ 136 struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi, 137 u8 acknowledge_mode, unsigned int delay, 138 struct nci_dev *ndev) 139 { 140 struct nci_spi *nspi; 141 142 nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL); 143 if (!nspi) 144 return NULL; 145 146 nspi->acknowledge_mode = acknowledge_mode; 147 nspi->xfer_udelay = delay; 148 /* Use controller max SPI speed by default */ 149 nspi->xfer_speed_hz = 0; 150 nspi->spi = spi; 151 nspi->ndev = ndev; 152 init_completion(&nspi->req_completion); 153 154 return nspi; 155 } 156 EXPORT_SYMBOL_GPL(nci_spi_allocate_spi); 157 158 static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge) 159 { 160 struct sk_buff *skb; 161 unsigned char *hdr; 162 u16 crc; 163 int ret; 164 165 skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL); 166 167 /* add the NCI SPI header to the start of the buffer */ 168 hdr = skb_push(skb, NCI_SPI_HDR_LEN); 169 hdr[0] = NCI_SPI_DIRECT_WRITE; 170 hdr[1] = NCI_SPI_CRC_ENABLED; 171 hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT; 172 hdr[3] = 0; 173 174 crc = crc_ccitt(CRC_INIT, skb->data, skb->len); 175 skb_put_u8(skb, crc >> 8); 176 skb_put_u8(skb, crc & 0xFF); 177 178 ret = __nci_spi_send(nspi, skb, 0); 179 180 kfree_skb(skb); 181 182 return ret; 183 } 184 185 static struct sk_buff *__nci_spi_read(struct nci_spi *nspi) 186 { 187 struct sk_buff *skb; 188 struct spi_message m; 189 unsigned char req[2], resp_hdr[2]; 190 struct spi_transfer tx, rx; 191 unsigned short rx_len = 0; 192 int ret; 193 194 spi_message_init(&m); 195 196 memset(&tx, 0, sizeof(struct spi_transfer)); 197 req[0] = NCI_SPI_DIRECT_READ; 198 req[1] = nspi->acknowledge_mode; 199 tx.tx_buf = req; 200 tx.len = 2; 201 tx.cs_change = 0; 202 tx.speed_hz = nspi->xfer_speed_hz; 203 spi_message_add_tail(&tx, &m); 204 205 memset(&rx, 0, sizeof(struct spi_transfer)); 206 rx.rx_buf = resp_hdr; 207 rx.len = 2; 208 rx.cs_change = 1; 209 rx.speed_hz = nspi->xfer_speed_hz; 210 spi_message_add_tail(&rx, &m); 211 212 ret = spi_sync(nspi->spi, &m); 213 if (ret) 214 return NULL; 215 216 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) 217 rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) + 218 resp_hdr[1] + NCI_SPI_CRC_LEN; 219 else 220 rx_len = (resp_hdr[0] << 8) | resp_hdr[1]; 221 222 skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL); 223 if (!skb) 224 return NULL; 225 226 spi_message_init(&m); 227 228 memset(&rx, 0, sizeof(struct spi_transfer)); 229 rx.rx_buf = skb_put(skb, rx_len); 230 rx.len = rx_len; 231 rx.cs_change = 0; 232 rx.delay_usecs = nspi->xfer_udelay; 233 rx.speed_hz = nspi->xfer_speed_hz; 234 spi_message_add_tail(&rx, &m); 235 236 ret = spi_sync(nspi->spi, &m); 237 if (ret) 238 goto receive_error; 239 240 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) { 241 *(u8 *)skb_push(skb, 1) = resp_hdr[1]; 242 *(u8 *)skb_push(skb, 1) = resp_hdr[0]; 243 } 244 245 return skb; 246 247 receive_error: 248 kfree_skb(skb); 249 250 return NULL; 251 } 252 253 static int nci_spi_check_crc(struct sk_buff *skb) 254 { 255 u16 crc_data = (skb->data[skb->len - 2] << 8) | 256 skb->data[skb->len - 1]; 257 int ret; 258 259 ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN) 260 == crc_data); 261 262 skb_trim(skb, skb->len - NCI_SPI_CRC_LEN); 263 264 return ret; 265 } 266 267 static u8 nci_spi_get_ack(struct sk_buff *skb) 268 { 269 u8 ret; 270 271 ret = skb->data[0] >> NCI_SPI_ACK_SHIFT; 272 273 /* Remove NFCC part of the header: ACK, NACK and MSB payload len */ 274 skb_pull(skb, 2); 275 276 return ret; 277 } 278 279 /** 280 * nci_spi_read - read frame from NCI SPI drivers 281 * 282 * @nspi: The nci spi 283 * Context: can sleep 284 * 285 * This call may only be used from a context that may sleep. The sleep 286 * is non-interruptible, and has no timeout. 287 * 288 * It returns an allocated skb containing the frame on success, or NULL. 289 */ 290 struct sk_buff *nci_spi_read(struct nci_spi *nspi) 291 { 292 struct sk_buff *skb; 293 294 /* Retrieve frame from SPI */ 295 skb = __nci_spi_read(nspi); 296 if (!skb) 297 goto done; 298 299 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) { 300 if (!nci_spi_check_crc(skb)) { 301 send_acknowledge(nspi, ACKNOWLEDGE_NACK); 302 goto done; 303 } 304 305 /* In case of acknowledged mode: if ACK or NACK received, 306 * unblock completion of latest frame sent. 307 */ 308 nspi->req_result = nci_spi_get_ack(skb); 309 if (nspi->req_result) 310 complete(&nspi->req_completion); 311 } 312 313 /* If there is no payload (ACK/NACK only frame), 314 * free the socket buffer 315 */ 316 if (!skb->len) { 317 kfree_skb(skb); 318 skb = NULL; 319 goto done; 320 } 321 322 if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) 323 send_acknowledge(nspi, ACKNOWLEDGE_ACK); 324 325 done: 326 327 return skb; 328 } 329 EXPORT_SYMBOL_GPL(nci_spi_read); 330 331 MODULE_LICENSE("GPL"); 332