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 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_config_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 = CONFIGURATION_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_config_cmd); 72 73 int atmel_i2c_init_read_otp_cmd(struct atmel_i2c_cmd *cmd, u16 addr) 74 { 75 if (addr >= OTP_ZONE_SIZE / 4) 76 return -EINVAL; 77 78 cmd->word_addr = COMMAND; 79 cmd->opcode = OPCODE_READ; 80 /* 81 * Read the word from OTP zone that may contain e.g. serial 82 * numbers or similar if persistently pre-initialized and locked 83 */ 84 cmd->param1 = OTP_ZONE; 85 cmd->param2 = cpu_to_le16(addr); 86 cmd->count = READ_COUNT; 87 88 atmel_i2c_checksum(cmd); 89 90 cmd->msecs = MAX_EXEC_TIME_READ; 91 cmd->rxsize = READ_RSP_SIZE; 92 93 return 0; 94 } 95 EXPORT_SYMBOL(atmel_i2c_init_read_otp_cmd); 96 97 void atmel_i2c_init_random_cmd(struct atmel_i2c_cmd *cmd) 98 { 99 cmd->word_addr = COMMAND; 100 cmd->opcode = OPCODE_RANDOM; 101 cmd->param1 = 0; 102 cmd->param2 = 0; 103 cmd->count = RANDOM_COUNT; 104 105 atmel_i2c_checksum(cmd); 106 107 cmd->msecs = MAX_EXEC_TIME_RANDOM; 108 cmd->rxsize = RANDOM_RSP_SIZE; 109 } 110 EXPORT_SYMBOL(atmel_i2c_init_random_cmd); 111 112 void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid) 113 { 114 cmd->word_addr = COMMAND; 115 cmd->count = GENKEY_COUNT; 116 cmd->opcode = OPCODE_GENKEY; 117 cmd->param1 = GENKEY_MODE_PRIVATE; 118 /* a random private key will be generated and stored in slot keyID */ 119 cmd->param2 = cpu_to_le16(keyid); 120 121 atmel_i2c_checksum(cmd); 122 123 cmd->msecs = MAX_EXEC_TIME_GENKEY; 124 cmd->rxsize = GENKEY_RSP_SIZE; 125 } 126 EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd); 127 128 int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd, 129 struct scatterlist *pubkey) 130 { 131 size_t copied; 132 133 cmd->word_addr = COMMAND; 134 cmd->count = ECDH_COUNT; 135 cmd->opcode = OPCODE_ECDH; 136 cmd->param1 = ECDH_PREFIX_MODE; 137 /* private key slot */ 138 cmd->param2 = cpu_to_le16(DATA_SLOT_2); 139 140 /* 141 * The device only supports P-256. Its public key is encoded as 142 * two 32-byte coordinates. 143 */ 144 copied = sg_copy_to_buffer(pubkey, 145 sg_nents_for_len(pubkey, 146 ATMEL_ECC_PUBKEY_SIZE), 147 cmd->data, ATMEL_ECC_PUBKEY_SIZE); 148 if (copied != ATMEL_ECC_PUBKEY_SIZE) 149 return -EINVAL; 150 151 atmel_i2c_checksum(cmd); 152 153 cmd->msecs = MAX_EXEC_TIME_ECDH; 154 cmd->rxsize = ECDH_RSP_SIZE; 155 156 return 0; 157 } 158 EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd); 159 160 /* 161 * After wake and after execution of a command, there will be error, status, or 162 * result bytes in the device's output register that can be retrieved by the 163 * system. When the length of that group is four bytes, the codes returned are 164 * detailed in error_list. 165 */ 166 static int atmel_i2c_status(struct device *dev, u8 *status) 167 { 168 size_t err_list_len = ARRAY_SIZE(error_list); 169 int i; 170 u8 err_id = status[1]; 171 172 if (*status != STATUS_SIZE) 173 return 0; 174 175 if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR) 176 return 0; 177 178 for (i = 0; i < err_list_len; i++) 179 if (error_list[i].value == err_id) 180 break; 181 182 /* if err_id is not in the error_list then ignore it */ 183 if (i != err_list_len) { 184 dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text); 185 return err_id; 186 } 187 188 return 0; 189 } 190 191 static int atmel_i2c_wakeup(struct i2c_client *client) 192 { 193 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); 194 u8 status[STATUS_RSP_SIZE]; 195 int ret; 196 197 /* 198 * The device ignores any levels or transitions on the SCL pin when the 199 * device is idle, asleep or during waking up. Don't check for error 200 * when waking up the device. 201 */ 202 i2c_transfer_buffer_flags(client, i2c_priv->wake_token, 203 i2c_priv->wake_token_sz, I2C_M_IGNORE_NAK); 204 205 /* 206 * Wait to wake the device. Typical execution times for ecdh and genkey 207 * are around tens of milliseconds. Delta is chosen to 50 microseconds. 208 */ 209 usleep_range(TWHI_MIN, TWHI_MAX); 210 211 ret = i2c_master_recv(client, status, STATUS_SIZE); 212 if (ret < 0) 213 return ret; 214 215 return atmel_i2c_status(&client->dev, status); 216 } 217 218 static int atmel_i2c_sleep(struct i2c_client *client) 219 { 220 u8 sleep = SLEEP_TOKEN; 221 222 return i2c_master_send(client, &sleep, 1); 223 } 224 225 /* 226 * atmel_i2c_send_receive() - send a command to the device and receive its 227 * response. 228 * @client: i2c client device 229 * @cmd : structure used to communicate with the device 230 * 231 * After the device receives a Wake token, a watchdog counter starts within the 232 * device. After the watchdog timer expires, the device enters sleep mode 233 * regardless of whether some I/O transmission or command execution is in 234 * progress. If a command is attempted when insufficient time remains prior to 235 * watchdog timer execution, the device will return the watchdog timeout error 236 * code without attempting to execute the command. There is no way to reset the 237 * counter other than to put the device into sleep or idle mode and then 238 * wake it up again. 239 */ 240 int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd) 241 { 242 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); 243 int ret; 244 245 mutex_lock(&i2c_priv->lock); 246 247 ret = atmel_i2c_wakeup(client); 248 if (ret) 249 goto err; 250 251 /* send the command */ 252 ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE); 253 if (ret < 0) 254 goto err; 255 256 /* delay the appropriate amount of time for command to execute */ 257 msleep(cmd->msecs); 258 259 /* receive the response */ 260 ret = i2c_master_recv(client, cmd->data, cmd->rxsize); 261 if (ret < 0) 262 goto err; 263 264 /* put the device into low-power mode */ 265 ret = atmel_i2c_sleep(client); 266 if (ret < 0) 267 goto err; 268 269 mutex_unlock(&i2c_priv->lock); 270 return atmel_i2c_status(&client->dev, cmd->data); 271 err: 272 mutex_unlock(&i2c_priv->lock); 273 return ret; 274 } 275 EXPORT_SYMBOL(atmel_i2c_send_receive); 276 277 static void atmel_i2c_work_handler(struct work_struct *work) 278 { 279 struct atmel_i2c_work_data *work_data = 280 container_of(work, struct atmel_i2c_work_data, work); 281 struct atmel_i2c_cmd *cmd = &work_data->cmd; 282 struct i2c_client *client = work_data->client; 283 int status; 284 285 status = atmel_i2c_send_receive(client, cmd); 286 work_data->cbk(work_data, work_data->areq, status); 287 } 288 289 static struct workqueue_struct *atmel_wq; 290 291 void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data, 292 void (*cbk)(struct atmel_i2c_work_data *work_data, 293 void *areq, int status), 294 void *areq) 295 { 296 work_data->cbk = cbk; 297 work_data->areq = areq; 298 299 INIT_WORK(&work_data->work, atmel_i2c_work_handler); 300 queue_work(atmel_wq, &work_data->work); 301 } 302 EXPORT_SYMBOL(atmel_i2c_enqueue); 303 304 void atmel_i2c_flush_queue(void) 305 { 306 flush_workqueue(atmel_wq); 307 } 308 EXPORT_SYMBOL(atmel_i2c_flush_queue); 309 310 static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate) 311 { 312 u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC); 313 314 /* return the size of the wake_token in bytes */ 315 return DIV_ROUND_UP(no_of_bits, 8); 316 } 317 318 static int device_sanity_check(struct i2c_client *client) 319 { 320 struct atmel_i2c_cmd *cmd; 321 int ret; 322 323 cmd = kmalloc_obj(*cmd); 324 if (!cmd) 325 return -ENOMEM; 326 327 atmel_i2c_init_read_config_cmd(cmd); 328 329 ret = atmel_i2c_send_receive(client, cmd); 330 if (ret) 331 goto free_cmd; 332 333 /* 334 * It is vital that the Configuration, Data and OTP zones be locked 335 * prior to release into the field of the system containing the device. 336 * Failure to lock these zones may permit modification of any secret 337 * keys and may lead to other security problems. 338 */ 339 if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) { 340 dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n"); 341 ret = -ENOTSUPP; 342 } 343 344 /* fall through */ 345 free_cmd: 346 kfree(cmd); 347 return ret; 348 } 349 350 int atmel_i2c_probe(struct i2c_client *client) 351 { 352 struct atmel_i2c_client_priv *i2c_priv; 353 struct device *dev = &client->dev; 354 int ret; 355 u32 bus_clk_rate; 356 357 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { 358 dev_err(dev, "I2C_FUNC_I2C not supported\n"); 359 return -ENODEV; 360 } 361 362 bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev); 363 if (!bus_clk_rate) { 364 ret = device_property_read_u32(&client->adapter->dev, 365 "clock-frequency", &bus_clk_rate); 366 if (ret) { 367 dev_err(dev, "failed to read clock-frequency property\n"); 368 return ret; 369 } 370 } 371 372 if (bus_clk_rate > I2C_MAX_FAST_MODE_PLUS_FREQ) { 373 dev_err(dev, "%u exceeds maximum supported clock frequency (1MHz)\n", 374 bus_clk_rate); 375 return -EINVAL; 376 } 377 378 i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL); 379 if (!i2c_priv) 380 return -ENOMEM; 381 382 i2c_priv->client = client; 383 mutex_init(&i2c_priv->lock); 384 385 /* 386 * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate - 387 * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz 388 * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE. 389 */ 390 i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate); 391 392 memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token)); 393 394 atomic_set(&i2c_priv->tfm_count, 0); 395 396 i2c_set_clientdata(client, i2c_priv); 397 398 return device_sanity_check(client); 399 } 400 EXPORT_SYMBOL(atmel_i2c_probe); 401 402 static int __init atmel_i2c_init(void) 403 { 404 atmel_wq = alloc_workqueue("atmel_wq", WQ_PERCPU, 0); 405 return atmel_wq ? 0 : -ENOMEM; 406 } 407 408 static void __exit atmel_i2c_exit(void) 409 { 410 destroy_workqueue(atmel_wq); 411 } 412 413 module_init(atmel_i2c_init); 414 module_exit(atmel_i2c_exit); 415 416 MODULE_AUTHOR("Tudor Ambarus"); 417 MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver"); 418 MODULE_LICENSE("GPL v2"); 419