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/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         reinit_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         init_completion(&nspi->req_completion);
 149
 150         return nspi;
 151 }
 152 EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);
 153
 154 static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
 155 {
 156         struct sk_buff *skb;
 157         unsigned char *hdr;
 158         u16 crc;
 159         int ret;
 160
 161         skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);
 162
 163         /* add the NCI SPI header to the start of the buffer */
 164         hdr = skb_push(skb, NCI_SPI_HDR_LEN);
 165         hdr[0] = NCI_SPI_DIRECT_WRITE;
 166         hdr[1] = NCI_SPI_CRC_ENABLED;
 167         hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
 168         hdr[3] = 0;
 169
 170         crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
 171         *skb_put(skb, 1) = crc >> 8;
 172         *skb_put(skb, 1) = crc & 0xFF;
 173
 174         ret = __nci_spi_send(nspi, skb, 0);
 175
 176         kfree_skb(skb);
 177
 178         return ret;
 179 }
 180
 181 static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
 182 {
 183         struct sk_buff *skb;
 184         struct spi_message m;
 185         unsigned char req[2], resp_hdr[2];
 186         struct spi_transfer tx, rx;
 187         unsigned short rx_len = 0;
 188         int ret;
 189
 190         spi_message_init(&m);
 191
 192         memset(&tx, 0, sizeof(struct spi_transfer));
 193         req[0] = NCI_SPI_DIRECT_READ;
 194         req[1] = nspi->acknowledge_mode;
 195         tx.tx_buf = req;
 196         tx.len = 2;
 197         tx.cs_change = 0;
 198         spi_message_add_tail(&tx, &m);
 199
 200         memset(&rx, 0, sizeof(struct spi_transfer));
 201         rx.rx_buf = resp_hdr;
 202         rx.len = 2;
 203         rx.cs_change = 1;
 204         spi_message_add_tail(&rx, &m);
 205
 206         ret = spi_sync(nspi->spi, &m);
 207         if (ret)
 208                 return NULL;
 209
 210         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
 211                 rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
 212                                 resp_hdr[1] + NCI_SPI_CRC_LEN;
 213         else
 214                 rx_len = (resp_hdr[0] << 8) | resp_hdr[1];
 215
 216         skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
 217         if (!skb)
 218                 return NULL;
 219
 220         spi_message_init(&m);
 221
 222         memset(&rx, 0, sizeof(struct spi_transfer));
 223         rx.rx_buf = skb_put(skb, rx_len);
 224         rx.len = rx_len;
 225         rx.cs_change = 0;
 226         rx.delay_usecs = nspi->xfer_udelay;
 227         spi_message_add_tail(&rx, &m);
 228
 229         ret = spi_sync(nspi->spi, &m);
 230         if (ret)
 231                 goto receive_error;
 232
 233         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
 234                 *skb_push(skb, 1) = resp_hdr[1];
 235                 *skb_push(skb, 1) = resp_hdr[0];
 236         }
 237
 238         return skb;
 239
 240 receive_error:
 241         kfree_skb(skb);
 242
 243         return NULL;
 244 }
 245
 246 static int nci_spi_check_crc(struct sk_buff *skb)
 247 {
 248         u16 crc_data = (skb->data[skb->len - 2] << 8) |
 249                         skb->data[skb->len - 1];
 250         int ret;
 251
 252         ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
 253                         == crc_data);
 254
 255         skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);
 256
 257         return ret;
 258 }
 259
 260 static u8 nci_spi_get_ack(struct sk_buff *skb)
 261 {
 262         u8 ret;
 263
 264         ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;
 265
 266         /* Remove NFCC part of the header: ACK, NACK and MSB payload len */
 267         skb_pull(skb, 2);
 268
 269         return ret;
 270 }
 271
 272 /**
 273  * nci_spi_read - read frame from NCI SPI drivers
 274  *
 275  * @nspi: The nci spi
 276  * Context: can sleep
 277  *
 278  * This call may only be used from a context that may sleep.  The sleep
 279  * is non-interruptible, and has no timeout.
 280  *
 281  * It returns an allocated skb containing the frame on success, or NULL.
 282  */
 283 struct sk_buff *nci_spi_read(struct nci_spi *nspi)
 284 {
 285         struct sk_buff *skb;
 286
 287         /* Retrieve frame from SPI */
 288         skb = __nci_spi_read(nspi);
 289         if (!skb)
 290                 goto done;
 291
 292         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
 293                 if (!nci_spi_check_crc(skb)) {
 294                         send_acknowledge(nspi, ACKNOWLEDGE_NACK);
 295                         goto done;
 296                 }
 297
 298                 /* In case of acknowledged mode: if ACK or NACK received,
 299                  * unblock completion of latest frame sent.
 300                  */
 301                 nspi->req_result = nci_spi_get_ack(skb);
 302                 if (nspi->req_result)
 303                         complete(&nspi->req_completion);
 304         }
 305
 306         /* If there is no payload (ACK/NACK only frame),
 307          * free the socket buffer
 308          */
 309         if (!skb->len) {
 310                 kfree_skb(skb);
 311                 skb = NULL;
 312                 goto done;
 313         }
 314
 315         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
 316                 send_acknowledge(nspi, ACKNOWLEDGE_ACK);
 317
 318 done:
 319
 320         return skb;
 321 }
 322 EXPORT_SYMBOL_GPL(nci_spi_read);