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         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(skb, 1) = crc >> 8;
  90                 *skb_put(skb, 1) = 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(skb, 1) = crc >> 8;
 176         *skb_put(skb, 1) = 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                 *skb_push(skb, 1) = resp_hdr[1];
 242                 *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");