net/nfc/nci/spi.c

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