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_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_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_transfer_buffer_flags(client, i2c_priv->wake_token, 180 i2c_priv->wake_token_sz, I2C_M_IGNORE_NAK); 181 182 /* 183 * Wait to wake the device. Typical execution times for ecdh and genkey 184 * are around tens of milliseconds. Delta is chosen to 50 microseconds. 185 */ 186 usleep_range(TWHI_MIN, TWHI_MAX); 187 188 ret = i2c_master_recv(client, status, STATUS_SIZE); 189 if (ret < 0) 190 return ret; 191 192 return atmel_i2c_status(&client->dev, status); 193 } 194 195 static int atmel_i2c_sleep(struct i2c_client *client) 196 { 197 u8 sleep = SLEEP_TOKEN; 198 199 return i2c_master_send(client, &sleep, 1); 200 } 201 202 /* 203 * atmel_i2c_send_receive() - send a command to the device and receive its 204 * response. 205 * @client: i2c client device 206 * @cmd : structure used to communicate with the device 207 * 208 * After the device receives a Wake token, a watchdog counter starts within the 209 * device. After the watchdog timer expires, the device enters sleep mode 210 * regardless of whether some I/O transmission or command execution is in 211 * progress. If a command is attempted when insufficient time remains prior to 212 * watchdog timer execution, the device will return the watchdog timeout error 213 * code without attempting to execute the command. There is no way to reset the 214 * counter other than to put the device into sleep or idle mode and then 215 * wake it up again. 216 */ 217 int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd) 218 { 219 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); 220 int ret; 221 222 mutex_lock(&i2c_priv->lock); 223 224 ret = atmel_i2c_wakeup(client); 225 if (ret) 226 goto err; 227 228 /* send the command */ 229 ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE); 230 if (ret < 0) 231 goto err; 232 233 /* delay the appropriate amount of time for command to execute */ 234 msleep(cmd->msecs); 235 236 /* receive the response */ 237 ret = i2c_master_recv(client, cmd->data, cmd->rxsize); 238 if (ret < 0) 239 goto err; 240 241 /* put the device into low-power mode */ 242 ret = atmel_i2c_sleep(client); 243 if (ret < 0) 244 goto err; 245 246 mutex_unlock(&i2c_priv->lock); 247 return atmel_i2c_status(&client->dev, cmd->data); 248 err: 249 mutex_unlock(&i2c_priv->lock); 250 return ret; 251 } 252 EXPORT_SYMBOL(atmel_i2c_send_receive); 253 254 static void atmel_i2c_work_handler(struct work_struct *work) 255 { 256 struct atmel_i2c_work_data *work_data = 257 container_of(work, struct atmel_i2c_work_data, work); 258 struct atmel_i2c_cmd *cmd = &work_data->cmd; 259 struct i2c_client *client = work_data->client; 260 int status; 261 262 status = atmel_i2c_send_receive(client, cmd); 263 work_data->cbk(work_data, work_data->areq, status); 264 } 265 266 static struct workqueue_struct *atmel_wq; 267 268 void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data, 269 void (*cbk)(struct atmel_i2c_work_data *work_data, 270 void *areq, int status), 271 void *areq) 272 { 273 work_data->cbk = (void *)cbk; 274 work_data->areq = areq; 275 276 INIT_WORK(&work_data->work, atmel_i2c_work_handler); 277 queue_work(atmel_wq, &work_data->work); 278 } 279 EXPORT_SYMBOL(atmel_i2c_enqueue); 280 281 void atmel_i2c_flush_queue(void) 282 { 283 flush_workqueue(atmel_wq); 284 } 285 EXPORT_SYMBOL(atmel_i2c_flush_queue); 286 287 static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate) 288 { 289 u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC); 290 291 /* return the size of the wake_token in bytes */ 292 return DIV_ROUND_UP(no_of_bits, 8); 293 } 294 295 static int device_sanity_check(struct i2c_client *client) 296 { 297 struct atmel_i2c_cmd *cmd; 298 int ret; 299 300 cmd = kmalloc(sizeof(*cmd), GFP_KERNEL); 301 if (!cmd) 302 return -ENOMEM; 303 304 atmel_i2c_init_read_cmd(cmd); 305 306 ret = atmel_i2c_send_receive(client, cmd); 307 if (ret) 308 goto free_cmd; 309 310 /* 311 * It is vital that the Configuration, Data and OTP zones be locked 312 * prior to release into the field of the system containing the device. 313 * Failure to lock these zones may permit modification of any secret 314 * keys and may lead to other security problems. 315 */ 316 if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) { 317 dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n"); 318 ret = -ENOTSUPP; 319 } 320 321 /* fall through */ 322 free_cmd: 323 kfree(cmd); 324 return ret; 325 } 326 327 int atmel_i2c_probe(struct i2c_client *client) 328 { 329 struct atmel_i2c_client_priv *i2c_priv; 330 struct device *dev = &client->dev; 331 int ret; 332 u32 bus_clk_rate; 333 334 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { 335 dev_err(dev, "I2C_FUNC_I2C not supported\n"); 336 return -ENODEV; 337 } 338 339 bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev); 340 if (!bus_clk_rate) { 341 ret = device_property_read_u32(&client->adapter->dev, 342 "clock-frequency", &bus_clk_rate); 343 if (ret) { 344 dev_err(dev, "failed to read clock-frequency property\n"); 345 return ret; 346 } 347 } 348 349 if (bus_clk_rate > 1000000L) { 350 dev_err(dev, "%u exceeds maximum supported clock frequency (1MHz)\n", 351 bus_clk_rate); 352 return -EINVAL; 353 } 354 355 i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL); 356 if (!i2c_priv) 357 return -ENOMEM; 358 359 i2c_priv->client = client; 360 mutex_init(&i2c_priv->lock); 361 362 /* 363 * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate - 364 * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz 365 * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE. 366 */ 367 i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate); 368 369 memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token)); 370 371 atomic_set(&i2c_priv->tfm_count, 0); 372 373 i2c_set_clientdata(client, i2c_priv); 374 375 return device_sanity_check(client); 376 } 377 EXPORT_SYMBOL(atmel_i2c_probe); 378 379 static int __init atmel_i2c_init(void) 380 { 381 atmel_wq = alloc_workqueue("atmel_wq", 0, 0); 382 return atmel_wq ? 0 : -ENOMEM; 383 } 384 385 static void __exit atmel_i2c_exit(void) 386 { 387 destroy_workqueue(atmel_wq); 388 } 389 390 module_init(atmel_i2c_init); 391 module_exit(atmel_i2c_exit); 392 393 MODULE_AUTHOR("Tudor Ambarus"); 394 MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver"); 395 MODULE_LICENSE("GPL v2"); 396