net/nfc/nci/spi.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2013  Intel Corporation. All rights reserved.
   4  */
   5
   6 #define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__
   7
   8 #include <linux/module.h>
   9
  10 #include <linux/export.h>
  11 #include <linux/spi/spi.h>
  12 #include <linux/crc-ccitt.h>
  13 #include <net/nfc/nci_core.h>
  14
  15 #define NCI_SPI_ACK_SHIFT               6
  16 #define NCI_SPI_MSB_PAYLOAD_MASK        0x3F
  17
  18 #define NCI_SPI_SEND_TIMEOUT    (NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
  19                                         NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)
  20
  21 #define NCI_SPI_DIRECT_WRITE    0x01
  22 #define NCI_SPI_DIRECT_READ     0x02
  23
  24 #define ACKNOWLEDGE_NONE        0
  25 #define ACKNOWLEDGE_ACK         1
  26 #define ACKNOWLEDGE_NACK        2
  27
  28 #define CRC_INIT                0xFFFF
  29
  30 static int __nci_spi_send(struct nci_spi *nspi, struct sk_buff *skb,
  31                           int cs_change)
  32 {
  33         struct spi_message m;
  34         struct spi_transfer t;
  35
  36         memset(&t, 0, sizeof(struct spi_transfer));
  37         /* a NULL skb means we just want the SPI chip select line to raise */
  38         if (skb) {
  39                 t.tx_buf = skb->data;
  40                 t.len = skb->len;
  41         } else {
  42                 /* still set tx_buf non NULL to make the driver happy */
  43                 t.tx_buf = &t;
  44                 t.len = 0;
  45         }
  46         t.cs_change = cs_change;
  47         t.delay.value = nspi->xfer_udelay;
  48         t.delay.unit = SPI_DELAY_UNIT_USECS;
  49         t.speed_hz = nspi->xfer_speed_hz;
  50
  51         spi_message_init(&m);
  52         spi_message_add_tail(&t, &m);
  53
  54         return spi_sync(nspi->spi, &m);
  55 }
  56
  57 int nci_spi_send(struct nci_spi *nspi,
  58                  struct completion *write_handshake_completion,
  59                  struct sk_buff *skb)
  60 {
  61         unsigned int payload_len = skb->len;
  62         unsigned char *hdr;
  63         int ret;
  64         long completion_rc;
  65
  66         /* add the NCI SPI header to the start of the buffer */
  67         hdr = skb_push(skb, NCI_SPI_HDR_LEN);
  68         hdr[0] = NCI_SPI_DIRECT_WRITE;
  69         hdr[1] = nspi->acknowledge_mode;
  70         hdr[2] = payload_len >> 8;
  71         hdr[3] = payload_len & 0xFF;
  72
  73         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
  74                 u16 crc;
  75
  76                 crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
  77                 skb_put_u8(skb, crc >> 8);
  78                 skb_put_u8(skb, crc & 0xFF);
  79         }
  80
  81         if (write_handshake_completion) {
  82                 /* Trick SPI driver to raise chip select */
  83                 ret = __nci_spi_send(nspi, NULL, 1);
  84                 if (ret)
  85                         goto done;
  86
  87                 /* wait for NFC chip hardware handshake to complete */
  88                 if (wait_for_completion_timeout(write_handshake_completion,
  89                                                 msecs_to_jiffies(1000)) == 0) {
  90                         ret = -ETIME;
  91                         goto done;
  92                 }
  93         }
  94
  95         ret = __nci_spi_send(nspi, skb, 0);
  96         if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
  97                 goto done;
  98
  99         reinit_completion(&nspi->req_completion);
 100         completion_rc = wait_for_completion_interruptible_timeout(
 101                                                         &nspi->req_completion,
 102                                                         NCI_SPI_SEND_TIMEOUT);
 103
 104         if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK)
 105                 ret = -EIO;
 106
 107 done:
 108         kfree_skb(skb);
 109
 110         return ret;
 111 }
 112 EXPORT_SYMBOL_GPL(nci_spi_send);
 113
 114 /* ---- Interface to NCI SPI drivers ---- */
 115
 116 /**
 117  * nci_spi_allocate_spi - allocate a new nci spi
 118  *
 119  * @spi: SPI device
 120  * @acknowledge_mode: Acknowledge mode used by the NFC device
 121  * @delay: delay between transactions in us
 122  * @ndev: nci dev to send incoming nci frames to
 123  */
 124 struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
 125                                      u8 acknowledge_mode, unsigned int delay,
 126                                      struct nci_dev *ndev)
 127 {
 128         struct nci_spi *nspi;
 129
 130         nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
 131         if (!nspi)
 132                 return NULL;
 133
 134         nspi->acknowledge_mode = acknowledge_mode;
 135         nspi->xfer_udelay = delay;
 136         /* Use controller max SPI speed by default */
 137         nspi->xfer_speed_hz = 0;
 138         nspi->spi = spi;
 139         nspi->ndev = ndev;
 140         init_completion(&nspi->req_completion);
 141
 142         return nspi;
 143 }
 144 EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);
 145
 146 static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
 147 {
 148         struct sk_buff *skb;
 149         unsigned char *hdr;
 150         u16 crc;
 151         int ret;
 152
 153         skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);
 154
 155         /* add the NCI SPI header to the start of the buffer */
 156         hdr = skb_push(skb, NCI_SPI_HDR_LEN);
 157         hdr[0] = NCI_SPI_DIRECT_WRITE;
 158         hdr[1] = NCI_SPI_CRC_ENABLED;
 159         hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
 160         hdr[3] = 0;
 161
 162         crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
 163         skb_put_u8(skb, crc >> 8);
 164         skb_put_u8(skb, crc & 0xFF);
 165
 166         ret = __nci_spi_send(nspi, skb, 0);
 167
 168         kfree_skb(skb);
 169
 170         return ret;
 171 }
 172
 173 static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
 174 {
 175         struct sk_buff *skb;
 176         struct spi_message m;
 177         unsigned char req[2], resp_hdr[2];
 178         struct spi_transfer tx, rx;
 179         unsigned short rx_len = 0;
 180         int ret;
 181
 182         spi_message_init(&m);
 183
 184         memset(&tx, 0, sizeof(struct spi_transfer));
 185         req[0] = NCI_SPI_DIRECT_READ;
 186         req[1] = nspi->acknowledge_mode;
 187         tx.tx_buf = req;
 188         tx.len = 2;
 189         tx.cs_change = 0;
 190         tx.speed_hz = nspi->xfer_speed_hz;
 191         spi_message_add_tail(&tx, &m);
 192
 193         memset(&rx, 0, sizeof(struct spi_transfer));
 194         rx.rx_buf = resp_hdr;
 195         rx.len = 2;
 196         rx.cs_change = 1;
 197         rx.speed_hz = nspi->xfer_speed_hz;
 198         spi_message_add_tail(&rx, &m);
 199
 200         ret = spi_sync(nspi->spi, &m);
 201         if (ret)
 202                 return NULL;
 203
 204         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
 205                 rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
 206                                 resp_hdr[1] + NCI_SPI_CRC_LEN;
 207         else
 208                 rx_len = (resp_hdr[0] << 8) | resp_hdr[1];
 209
 210         skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
 211         if (!skb)
 212                 return NULL;
 213
 214         spi_message_init(&m);
 215
 216         memset(&rx, 0, sizeof(struct spi_transfer));
 217         rx.rx_buf = skb_put(skb, rx_len);
 218         rx.len = rx_len;
 219         rx.cs_change = 0;
 220         rx.delay.value = nspi->xfer_udelay;
 221         rx.delay.unit = SPI_DELAY_UNIT_USECS;
 222         rx.speed_hz = nspi->xfer_speed_hz;
 223         spi_message_add_tail(&rx, &m);
 224
 225         ret = spi_sync(nspi->spi, &m);
 226         if (ret)
 227                 goto receive_error;
 228
 229         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
 230                 *(u8 *)skb_push(skb, 1) = resp_hdr[1];
 231                 *(u8 *)skb_push(skb, 1) = resp_hdr[0];
 232         }
 233
 234         return skb;
 235
 236 receive_error:
 237         kfree_skb(skb);
 238
 239         return NULL;
 240 }
 241
 242 static int nci_spi_check_crc(struct sk_buff *skb)
 243 {
 244         u16 crc_data = (skb->data[skb->len - 2] << 8) |
 245                         skb->data[skb->len - 1];
 246         int ret;
 247
 248         ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
 249                         == crc_data);
 250
 251         skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);
 252
 253         return ret;
 254 }
 255
 256 static u8 nci_spi_get_ack(struct sk_buff *skb)
 257 {
 258         u8 ret;
 259
 260         ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;
 261
 262         /* Remove NFCC part of the header: ACK, NACK and MSB payload len */
 263         skb_pull(skb, 2);
 264
 265         return ret;
 266 }
 267
 268 /**
 269  * nci_spi_read - read frame from NCI SPI drivers
 270  *
 271  * @nspi: The nci spi
 272  * Context: can sleep
 273  *
 274  * This call may only be used from a context that may sleep.  The sleep
 275  * is non-interruptible, and has no timeout.
 276  *
 277  * It returns an allocated skb containing the frame on success, or NULL.
 278  */
 279 struct sk_buff *nci_spi_read(struct nci_spi *nspi)
 280 {
 281         struct sk_buff *skb;
 282
 283         /* Retrieve frame from SPI */
 284         skb = __nci_spi_read(nspi);
 285         if (!skb)
 286                 goto done;
 287
 288         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
 289                 if (!nci_spi_check_crc(skb)) {
 290                         send_acknowledge(nspi, ACKNOWLEDGE_NACK);
 291                         goto done;
 292                 }
 293
 294                 /* In case of acknowledged mode: if ACK or NACK received,
 295                  * unblock completion of latest frame sent.
 296                  */
 297                 nspi->req_result = nci_spi_get_ack(skb);
 298                 if (nspi->req_result)
 299                         complete(&nspi->req_completion);
 300         }
 301
 302         /* If there is no payload (ACK/NACK only frame),
 303          * free the socket buffer
 304          */
 305         if (!skb->len) {
 306                 kfree_skb(skb);
 307                 skb = NULL;
 308                 goto done;
 309         }
 310
 311         if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
 312                 send_acknowledge(nspi, ACKNOWLEDGE_ACK);
 313
 314 done:
 315
 316         return skb;
 317 }
 318 EXPORT_SYMBOL_GPL(nci_spi_read);
 319
 320 MODULE_LICENSE("GPL");