drivers/nfc/microread/i2c.c

   1 /*
   2  * HCI based Driver for Inside Secure microread NFC Chip - i2c layer
   3  *
   4  * Copyright (C) 2013 Intel Corporation. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms and conditions of the GNU General Public License,
   8  * version 2, as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/module.h>
  22 #include <linux/i2c.h>
  23 #include <linux/delay.h>
  24 #include <linux/slab.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/gpio.h>
  27
  28 #include <linux/nfc.h>
  29 #include <net/nfc/hci.h>
  30 #include <net/nfc/llc.h>
  31
  32 #include "microread.h"
  33
  34 #define MICROREAD_I2C_DRIVER_NAME "microread"
  35
  36 #define MICROREAD_I2C_FRAME_HEADROOM 1
  37 #define MICROREAD_I2C_FRAME_TAILROOM 1
  38
  39 /* framing in HCI mode */
  40 #define MICROREAD_I2C_LLC_LEN           1
  41 #define MICROREAD_I2C_LLC_CRC           1
  42 #define MICROREAD_I2C_LLC_LEN_CRC       (MICROREAD_I2C_LLC_LEN + \
  43                                         MICROREAD_I2C_LLC_CRC)
  44 #define MICROREAD_I2C_LLC_MIN_SIZE      (1 + MICROREAD_I2C_LLC_LEN_CRC)
  45 #define MICROREAD_I2C_LLC_MAX_PAYLOAD   29
  46 #define MICROREAD_I2C_LLC_MAX_SIZE      (MICROREAD_I2C_LLC_LEN_CRC + 1 + \
  47                                         MICROREAD_I2C_LLC_MAX_PAYLOAD)
  48
  49 struct microread_i2c_phy {
  50         struct i2c_client *i2c_dev;
  51         struct nfc_hci_dev *hdev;
  52
  53         int hard_fault;         /*
  54                                  * < 0 if hardware error occured (e.g. i2c err)
  55                                  * and prevents normal operation.
  56                                  */
  57 };
  58
  59 #define I2C_DUMP_SKB(info, skb)                                 \
  60 do {                                                            \
  61         pr_debug("%s:\n", info);                                \
  62         print_hex_dump(KERN_DEBUG, "i2c: ", DUMP_PREFIX_OFFSET, \
  63                        16, 1, (skb)->data, (skb)->len, 0);      \
  64 } while (0)
  65
  66 static void microread_i2c_add_len_crc(struct sk_buff *skb)
  67 {
  68         int i;
  69         u8 crc = 0;
  70         int len;
  71
  72         len = skb->len;
  73         *(u8 *)skb_push(skb, 1) = len;
  74
  75         for (i = 0; i < skb->len; i++)
  76                 crc = crc ^ skb->data[i];
  77
  78         skb_put_u8(skb, crc);
  79 }
  80
  81 static void microread_i2c_remove_len_crc(struct sk_buff *skb)
  82 {
  83         skb_pull(skb, MICROREAD_I2C_FRAME_HEADROOM);
  84         skb_trim(skb, MICROREAD_I2C_FRAME_TAILROOM);
  85 }
  86
  87 static int check_crc(struct sk_buff *skb)
  88 {
  89         int i;
  90         u8 crc = 0;
  91
  92         for (i = 0; i < skb->len - 1; i++)
  93                 crc = crc ^ skb->data[i];
  94
  95         if (crc != skb->data[skb->len-1]) {
  96                 pr_err("CRC error 0x%x != 0x%x\n", crc, skb->data[skb->len-1]);
  97                 pr_info("%s: BAD CRC\n", __func__);
  98                 return -EPERM;
  99         }
 100
 101         return 0;
 102 }
 103
 104 static int microread_i2c_enable(void *phy_id)
 105 {
 106         return 0;
 107 }
 108
 109 static void microread_i2c_disable(void *phy_id)
 110 {
 111         return;
 112 }
 113
 114 static int microread_i2c_write(void *phy_id, struct sk_buff *skb)
 115 {
 116         int r;
 117         struct microread_i2c_phy *phy = phy_id;
 118         struct i2c_client *client = phy->i2c_dev;
 119
 120         if (phy->hard_fault != 0)
 121                 return phy->hard_fault;
 122
 123         usleep_range(3000, 6000);
 124
 125         microread_i2c_add_len_crc(skb);
 126
 127         I2C_DUMP_SKB("i2c frame written", skb);
 128
 129         r = i2c_master_send(client, skb->data, skb->len);
 130
 131         if (r == -EREMOTEIO) {  /* Retry, chip was in standby */
 132                 usleep_range(6000, 10000);
 133                 r = i2c_master_send(client, skb->data, skb->len);
 134         }
 135
 136         if (r >= 0) {
 137                 if (r != skb->len)
 138                         r = -EREMOTEIO;
 139                 else
 140                         r = 0;
 141         }
 142
 143         microread_i2c_remove_len_crc(skb);
 144
 145         return r;
 146 }
 147
 148
 149 static int microread_i2c_read(struct microread_i2c_phy *phy,
 150                               struct sk_buff **skb)
 151 {
 152         int r;
 153         u8 len;
 154         u8 tmp[MICROREAD_I2C_LLC_MAX_SIZE - 1];
 155         struct i2c_client *client = phy->i2c_dev;
 156
 157         r = i2c_master_recv(client, &len, 1);
 158         if (r != 1) {
 159                 nfc_err(&client->dev, "cannot read len byte\n");
 160                 return -EREMOTEIO;
 161         }
 162
 163         if ((len < MICROREAD_I2C_LLC_MIN_SIZE) ||
 164             (len > MICROREAD_I2C_LLC_MAX_SIZE)) {
 165                 nfc_err(&client->dev, "invalid len byte\n");
 166                 r = -EBADMSG;
 167                 goto flush;
 168         }
 169
 170         *skb = alloc_skb(1 + len, GFP_KERNEL);
 171         if (*skb == NULL) {
 172                 r = -ENOMEM;
 173                 goto flush;
 174         }
 175
 176         skb_put_u8(*skb, len);
 177
 178         r = i2c_master_recv(client, skb_put(*skb, len), len);
 179         if (r != len) {
 180                 kfree_skb(*skb);
 181                 return -EREMOTEIO;
 182         }
 183
 184         I2C_DUMP_SKB("cc frame read", *skb);
 185
 186         r = check_crc(*skb);
 187         if (r != 0) {
 188                 kfree_skb(*skb);
 189                 r = -EBADMSG;
 190                 goto flush;
 191         }
 192
 193         skb_pull(*skb, 1);
 194         skb_trim(*skb, (*skb)->len - MICROREAD_I2C_FRAME_TAILROOM);
 195
 196         usleep_range(3000, 6000);
 197
 198         return 0;
 199
 200 flush:
 201         if (i2c_master_recv(client, tmp, sizeof(tmp)) < 0)
 202                 r = -EREMOTEIO;
 203
 204         usleep_range(3000, 6000);
 205
 206         return r;
 207 }
 208
 209 static irqreturn_t microread_i2c_irq_thread_fn(int irq, void *phy_id)
 210 {
 211         struct microread_i2c_phy *phy = phy_id;
 212         struct sk_buff *skb = NULL;
 213         int r;
 214
 215         if (!phy || irq != phy->i2c_dev->irq) {
 216                 WARN_ON_ONCE(1);
 217                 return IRQ_NONE;
 218         }
 219
 220         if (phy->hard_fault != 0)
 221                 return IRQ_HANDLED;
 222
 223         r = microread_i2c_read(phy, &skb);
 224         if (r == -EREMOTEIO) {
 225                 phy->hard_fault = r;
 226
 227                 nfc_hci_recv_frame(phy->hdev, NULL);
 228
 229                 return IRQ_HANDLED;
 230         } else if ((r == -ENOMEM) || (r == -EBADMSG)) {
 231                 return IRQ_HANDLED;
 232         }
 233
 234         nfc_hci_recv_frame(phy->hdev, skb);
 235
 236         return IRQ_HANDLED;
 237 }
 238
 239 static struct nfc_phy_ops i2c_phy_ops = {
 240         .write = microread_i2c_write,
 241         .enable = microread_i2c_enable,
 242         .disable = microread_i2c_disable,
 243 };
 244
 245 static int microread_i2c_probe(struct i2c_client *client,
 246                                const struct i2c_device_id *id)
 247 {
 248         struct microread_i2c_phy *phy;
 249         int r;
 250
 251         dev_dbg(&client->dev, "client %p\n", client);
 252
 253         phy = devm_kzalloc(&client->dev, sizeof(struct microread_i2c_phy),
 254                            GFP_KERNEL);
 255         if (!phy)
 256                 return -ENOMEM;
 257
 258         i2c_set_clientdata(client, phy);
 259         phy->i2c_dev = client;
 260
 261         r = request_threaded_irq(client->irq, NULL, microread_i2c_irq_thread_fn,
 262                                  IRQF_TRIGGER_RISING | IRQF_ONESHOT,
 263                                  MICROREAD_I2C_DRIVER_NAME, phy);
 264         if (r) {
 265                 nfc_err(&client->dev, "Unable to register IRQ handler\n");
 266                 return r;
 267         }
 268
 269         r = microread_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
 270                             MICROREAD_I2C_FRAME_HEADROOM,
 271                             MICROREAD_I2C_FRAME_TAILROOM,
 272                             MICROREAD_I2C_LLC_MAX_PAYLOAD, &phy->hdev);
 273         if (r < 0)
 274                 goto err_irq;
 275
 276         nfc_info(&client->dev, "Probed\n");
 277
 278         return 0;
 279
 280 err_irq:
 281         free_irq(client->irq, phy);
 282
 283         return r;
 284 }
 285
 286 static int microread_i2c_remove(struct i2c_client *client)
 287 {
 288         struct microread_i2c_phy *phy = i2c_get_clientdata(client);
 289
 290         microread_remove(phy->hdev);
 291
 292         free_irq(client->irq, phy);
 293
 294         return 0;
 295 }
 296
 297 static const struct i2c_device_id microread_i2c_id[] = {
 298         { MICROREAD_I2C_DRIVER_NAME, 0},
 299         { }
 300 };
 301 MODULE_DEVICE_TABLE(i2c, microread_i2c_id);
 302
 303 static struct i2c_driver microread_i2c_driver = {
 304         .driver = {
 305                 .name = MICROREAD_I2C_DRIVER_NAME,
 306         },
 307         .probe          = microread_i2c_probe,
 308         .remove         = microread_i2c_remove,
 309         .id_table       = microread_i2c_id,
 310 };
 311
 312 module_i2c_driver(microread_i2c_driver);
 313
 314 MODULE_LICENSE("GPL");
 315 MODULE_DESCRIPTION(DRIVER_DESC);