root/drivers/crypto/atmel-i2c.c

DEFINITIONS

1. atmel_i2c_checksum
2. atmel_i2c_init_read_cmd
3. atmel_i2c_init_random_cmd
4. atmel_i2c_init_genkey_cmd
5. atmel_i2c_init_ecdh_cmd
6. atmel_i2c_status
7. atmel_i2c_wakeup
8. atmel_i2c_sleep
9. atmel_i2c_send_receive
10. atmel_i2c_work_handler
11. atmel_i2c_enqueue
12. atmel_i2c_wake_token_sz
13. device_sanity_check
14. atmel_i2c_probe

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Microchip / Atmel ECC (I2C) driver.
   4  *
   5  * Copyright (c) 2017, Microchip Technology Inc.
   6  * Author: Tudor Ambarus <tudor.ambarus@microchip.com>
   7  */
   8 
   9 #include <linux/bitrev.h>
  10 #include <linux/crc16.h>
  11 #include <linux/delay.h>
  12 #include <linux/device.h>
  13 #include <linux/err.h>
  14 #include <linux/errno.h>
  15 #include <linux/i2c.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19 #include <linux/scatterlist.h>
  20 #include <linux/slab.h>
  21 #include <linux/workqueue.h>
  22 #include "atmel-i2c.h"
  23 
  24 static const struct {
  25         u8 value;
  26         const char *error_text;
  27 } error_list[] = {
  28         { 0x01, "CheckMac or Verify miscompare" },
  29         { 0x03, "Parse Error" },
  30         { 0x05, "ECC Fault" },
  31         { 0x0F, "Execution Error" },
  32         { 0xEE, "Watchdog about to expire" },
  33         { 0xFF, "CRC or other communication error" },
  34 };
  35 
  36 /**
  37  * atmel_i2c_checksum() - Generate 16-bit CRC as required by ATMEL ECC.
  38  * CRC16 verification of the count, opcode, param1, param2 and data bytes.
  39  * The checksum is saved in little-endian format in the least significant
  40  * two bytes of the command. CRC polynomial is 0x8005 and the initial register
  41  * value should be zero.
  42  *
  43  * @cmd : structure used for communicating with the device.
  44  */
  45 static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd)
  46 {
  47         u8 *data = &cmd->count;
  48         size_t len = cmd->count - CRC_SIZE;
  49         __le16 *__crc16 = (__le16 *)(data + len);
  50 
  51         *__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len)));
  52 }
  53 
  54 void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd)
  55 {
  56         cmd->word_addr = COMMAND;
  57         cmd->opcode = OPCODE_READ;
  58         /*
  59          * Read the word from Configuration zone that contains the lock bytes
  60          * (UserExtra, Selector, LockValue, LockConfig).
  61          */
  62         cmd->param1 = CONFIG_ZONE;
  63         cmd->param2 = cpu_to_le16(DEVICE_LOCK_ADDR);
  64         cmd->count = READ_COUNT;
  65 
  66         atmel_i2c_checksum(cmd);
  67 
  68         cmd->msecs = MAX_EXEC_TIME_READ;
  69         cmd->rxsize = READ_RSP_SIZE;
  70 }
  71 EXPORT_SYMBOL(atmel_i2c_init_read_cmd);
  72 
  73 void atmel_i2c_init_random_cmd(struct atmel_i2c_cmd *cmd)
  74 {
  75         cmd->word_addr = COMMAND;
  76         cmd->opcode = OPCODE_RANDOM;
  77         cmd->param1 = 0;
  78         cmd->param2 = 0;
  79         cmd->count = RANDOM_COUNT;
  80 
  81         atmel_i2c_checksum(cmd);
  82 
  83         cmd->msecs = MAX_EXEC_TIME_RANDOM;
  84         cmd->rxsize = RANDOM_RSP_SIZE;
  85 }
  86 EXPORT_SYMBOL(atmel_i2c_init_random_cmd);
  87 
  88 void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid)
  89 {
  90         cmd->word_addr = COMMAND;
  91         cmd->count = GENKEY_COUNT;
  92         cmd->opcode = OPCODE_GENKEY;
  93         cmd->param1 = GENKEY_MODE_PRIVATE;
  94         /* a random private key will be generated and stored in slot keyID */
  95         cmd->param2 = cpu_to_le16(keyid);
  96 
  97         atmel_i2c_checksum(cmd);
  98 
  99         cmd->msecs = MAX_EXEC_TIME_GENKEY;
 100         cmd->rxsize = GENKEY_RSP_SIZE;
 101 }
 102 EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd);
 103 
 104 int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd,
 105                             struct scatterlist *pubkey)
 106 {
 107         size_t copied;
 108 
 109         cmd->word_addr = COMMAND;
 110         cmd->count = ECDH_COUNT;
 111         cmd->opcode = OPCODE_ECDH;
 112         cmd->param1 = ECDH_PREFIX_MODE;
 113         /* private key slot */
 114         cmd->param2 = cpu_to_le16(DATA_SLOT_2);
 115 
 116         /*
 117          * The device only supports NIST P256 ECC keys. The public key size will
 118          * always be the same. Use a macro for the key size to avoid unnecessary
 119          * computations.
 120          */
 121         copied = sg_copy_to_buffer(pubkey,
 122                                    sg_nents_for_len(pubkey,
 123                                                     ATMEL_ECC_PUBKEY_SIZE),
 124                                    cmd->data, ATMEL_ECC_PUBKEY_SIZE);
 125         if (copied != ATMEL_ECC_PUBKEY_SIZE)
 126                 return -EINVAL;
 127 
 128         atmel_i2c_checksum(cmd);
 129 
 130         cmd->msecs = MAX_EXEC_TIME_ECDH;
 131         cmd->rxsize = ECDH_RSP_SIZE;
 132 
 133         return 0;
 134 }
 135 EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd);
 136 
 137 /*
 138  * After wake and after execution of a command, there will be error, status, or
 139  * result bytes in the device's output register that can be retrieved by the
 140  * system. When the length of that group is four bytes, the codes returned are
 141  * detailed in error_list.
 142  */
 143 static int atmel_i2c_status(struct device *dev, u8 *status)
 144 {
 145         size_t err_list_len = ARRAY_SIZE(error_list);
 146         int i;
 147         u8 err_id = status[1];
 148 
 149         if (*status != STATUS_SIZE)
 150                 return 0;
 151 
 152         if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR)
 153                 return 0;
 154 
 155         for (i = 0; i < err_list_len; i++)
 156                 if (error_list[i].value == err_id)
 157                         break;
 158 
 159         /* if err_id is not in the error_list then ignore it */
 160         if (i != err_list_len) {
 161                 dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text);
 162                 return err_id;
 163         }
 164 
 165         return 0;
 166 }
 167 
 168 static int atmel_i2c_wakeup(struct i2c_client *client)
 169 {
 170         struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
 171         u8 status[STATUS_RSP_SIZE];
 172         int ret;
 173 
 174         /*
 175          * The device ignores any levels or transitions on the SCL pin when the
 176          * device is idle, asleep or during waking up. Don't check for error
 177          * when waking up the device.
 178          */
 179         i2c_master_send(client, i2c_priv->wake_token, i2c_priv->wake_token_sz);
 180 
 181         /*
 182          * Wait to wake the device. Typical execution times for ecdh and genkey
 183          * are around tens of milliseconds. Delta is chosen to 50 microseconds.
 184          */
 185         usleep_range(TWHI_MIN, TWHI_MAX);
 186 
 187         ret = i2c_master_recv(client, status, STATUS_SIZE);
 188         if (ret < 0)
 189                 return ret;
 190 
 191         return atmel_i2c_status(&client->dev, status);
 192 }
 193 
 194 static int atmel_i2c_sleep(struct i2c_client *client)
 195 {
 196         u8 sleep = SLEEP_TOKEN;
 197 
 198         return i2c_master_send(client, &sleep, 1);
 199 }
 200 
 201 /*
 202  * atmel_i2c_send_receive() - send a command to the device and receive its
 203  *                            response.
 204  * @client: i2c client device
 205  * @cmd   : structure used to communicate with the device
 206  *
 207  * After the device receives a Wake token, a watchdog counter starts within the
 208  * device. After the watchdog timer expires, the device enters sleep mode
 209  * regardless of whether some I/O transmission or command execution is in
 210  * progress. If a command is attempted when insufficient time remains prior to
 211  * watchdog timer execution, the device will return the watchdog timeout error
 212  * code without attempting to execute the command. There is no way to reset the
 213  * counter other than to put the device into sleep or idle mode and then
 214  * wake it up again.
 215  */
 216 int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd)
 217 {
 218         struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
 219         int ret;
 220 
 221         mutex_lock(&i2c_priv->lock);
 222 
 223         ret = atmel_i2c_wakeup(client);
 224         if (ret)
 225                 goto err;
 226 
 227         /* send the command */
 228         ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE);
 229         if (ret < 0)
 230                 goto err;
 231 
 232         /* delay the appropriate amount of time for command to execute */
 233         msleep(cmd->msecs);
 234 
 235         /* receive the response */
 236         ret = i2c_master_recv(client, cmd->data, cmd->rxsize);
 237         if (ret < 0)
 238                 goto err;
 239 
 240         /* put the device into low-power mode */
 241         ret = atmel_i2c_sleep(client);
 242         if (ret < 0)
 243                 goto err;
 244 
 245         mutex_unlock(&i2c_priv->lock);
 246         return atmel_i2c_status(&client->dev, cmd->data);
 247 err:
 248         mutex_unlock(&i2c_priv->lock);
 249         return ret;
 250 }
 251 EXPORT_SYMBOL(atmel_i2c_send_receive);
 252 
 253 static void atmel_i2c_work_handler(struct work_struct *work)
 254 {
 255         struct atmel_i2c_work_data *work_data =
 256                         container_of(work, struct atmel_i2c_work_data, work);
 257         struct atmel_i2c_cmd *cmd = &work_data->cmd;
 258         struct i2c_client *client = work_data->client;
 259         int status;
 260 
 261         status = atmel_i2c_send_receive(client, cmd);
 262         work_data->cbk(work_data, work_data->areq, status);
 263 }
 264 
 265 void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data,
 266                        void (*cbk)(struct atmel_i2c_work_data *work_data,
 267                                    void *areq, int status),
 268                        void *areq)
 269 {
 270         work_data->cbk = (void *)cbk;
 271         work_data->areq = areq;
 272 
 273         INIT_WORK(&work_data->work, atmel_i2c_work_handler);
 274         schedule_work(&work_data->work);
 275 }
 276 EXPORT_SYMBOL(atmel_i2c_enqueue);
 277 
 278 static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate)
 279 {
 280         u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC);
 281 
 282         /* return the size of the wake_token in bytes */
 283         return DIV_ROUND_UP(no_of_bits, 8);
 284 }
 285 
 286 static int device_sanity_check(struct i2c_client *client)
 287 {
 288         struct atmel_i2c_cmd *cmd;
 289         int ret;
 290 
 291         cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
 292         if (!cmd)
 293                 return -ENOMEM;
 294 
 295         atmel_i2c_init_read_cmd(cmd);
 296 
 297         ret = atmel_i2c_send_receive(client, cmd);
 298         if (ret)
 299                 goto free_cmd;
 300 
 301         /*
 302          * It is vital that the Configuration, Data and OTP zones be locked
 303          * prior to release into the field of the system containing the device.
 304          * Failure to lock these zones may permit modification of any secret
 305          * keys and may lead to other security problems.
 306          */
 307         if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) {
 308                 dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n");
 309                 ret = -ENOTSUPP;
 310         }
 311 
 312         /* fall through */
 313 free_cmd:
 314         kfree(cmd);
 315         return ret;
 316 }
 317 
 318 int atmel_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
 319 {
 320         struct atmel_i2c_client_priv *i2c_priv;
 321         struct device *dev = &client->dev;
 322         int ret;
 323         u32 bus_clk_rate;
 324 
 325         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 326                 dev_err(dev, "I2C_FUNC_I2C not supported\n");
 327                 return -ENODEV;
 328         }
 329 
 330         bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev);
 331         if (!bus_clk_rate) {
 332                 ret = device_property_read_u32(&client->adapter->dev,
 333                                                "clock-frequency", &bus_clk_rate);
 334                 if (ret) {
 335                         dev_err(dev, "failed to read clock-frequency property\n");
 336                         return ret;
 337                 }
 338         }
 339 
 340         if (bus_clk_rate > 1000000L) {
 341                 dev_err(dev, "%d exceeds maximum supported clock frequency (1MHz)\n",
 342                         bus_clk_rate);
 343                 return -EINVAL;
 344         }
 345 
 346         i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL);
 347         if (!i2c_priv)
 348                 return -ENOMEM;
 349 
 350         i2c_priv->client = client;
 351         mutex_init(&i2c_priv->lock);
 352 
 353         /*
 354          * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate -
 355          * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz
 356          * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE.
 357          */
 358         i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate);
 359 
 360         memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token));
 361 
 362         atomic_set(&i2c_priv->tfm_count, 0);
 363 
 364         i2c_set_clientdata(client, i2c_priv);
 365 
 366         ret = device_sanity_check(client);
 367         if (ret)
 368                 return ret;
 369 
 370         return 0;
 371 }
 372 EXPORT_SYMBOL(atmel_i2c_probe);
 373 
 374 MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
 375 MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
 376 MODULE_LICENSE("GPL v2");