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