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