atmel-i2c.c 9.9 KB

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