exynos-rng.c 9.2 KB

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  1. // SPDX-License-Identifier: GPL-2.0
  2. /*
  3. * exynos-rng.c - Random Number Generator driver for the Exynos
  4. *
  5. * Copyright (c) 2017 Krzysztof Kozlowski <krzk@kernel.org>
  6. *
  7. * Loosely based on old driver from drivers/char/hw_random/exynos-rng.c:
  8. * Copyright (C) 2012 Samsung Electronics
  9. * Jonghwa Lee <jonghwa3.lee@samsung.com>
  10. */
  11. #include <linux/clk.h>
  12. #include <linux/crypto.h>
  13. #include <linux/err.h>
  14. #include <linux/io.h>
  15. #include <linux/module.h>
  16. #include <linux/mutex.h>
  17. #include <linux/of_device.h>
  18. #include <linux/platform_device.h>
  19. #include <crypto/internal/rng.h>
  20. #define EXYNOS_RNG_CONTROL 0x0
  21. #define EXYNOS_RNG_STATUS 0x10
  22. #define EXYNOS_RNG_SEED_CONF 0x14
  23. #define EXYNOS_RNG_GEN_PRNG BIT(1)
  24. #define EXYNOS_RNG_SEED_BASE 0x140
  25. #define EXYNOS_RNG_SEED(n) (EXYNOS_RNG_SEED_BASE + (n * 0x4))
  26. #define EXYNOS_RNG_OUT_BASE 0x160
  27. #define EXYNOS_RNG_OUT(n) (EXYNOS_RNG_OUT_BASE + (n * 0x4))
  28. /* EXYNOS_RNG_CONTROL bit fields */
  29. #define EXYNOS_RNG_CONTROL_START 0x18
  30. /* EXYNOS_RNG_STATUS bit fields */
  31. #define EXYNOS_RNG_STATUS_SEED_SETTING_DONE BIT(1)
  32. #define EXYNOS_RNG_STATUS_RNG_DONE BIT(5)
  33. /* Five seed and output registers, each 4 bytes */
  34. #define EXYNOS_RNG_SEED_REGS 5
  35. #define EXYNOS_RNG_SEED_SIZE (EXYNOS_RNG_SEED_REGS * 4)
  36. enum exynos_prng_type {
  37. EXYNOS_PRNG_UNKNOWN = 0,
  38. EXYNOS_PRNG_EXYNOS4,
  39. EXYNOS_PRNG_EXYNOS5,
  40. };
  41. /*
  42. * Driver re-seeds itself with generated random numbers to hinder
  43. * backtracking of the original seed.
  44. *
  45. * Time for next re-seed in ms.
  46. */
  47. #define EXYNOS_RNG_RESEED_TIME 1000
  48. #define EXYNOS_RNG_RESEED_BYTES 65536
  49. /*
  50. * In polling mode, do not wait infinitely for the engine to finish the work.
  51. */
  52. #define EXYNOS_RNG_WAIT_RETRIES 100
  53. /* Context for crypto */
  54. struct exynos_rng_ctx {
  55. struct exynos_rng_dev *rng;
  56. };
  57. /* Device associated memory */
  58. struct exynos_rng_dev {
  59. struct device *dev;
  60. enum exynos_prng_type type;
  61. void __iomem *mem;
  62. struct clk *clk;
  63. struct mutex lock;
  64. /* Generated numbers stored for seeding during resume */
  65. u8 seed_save[EXYNOS_RNG_SEED_SIZE];
  66. unsigned int seed_save_len;
  67. /* Time of last seeding in jiffies */
  68. unsigned long last_seeding;
  69. /* Bytes generated since last seeding */
  70. unsigned long bytes_seeding;
  71. };
  72. static struct exynos_rng_dev *exynos_rng_dev;
  73. static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset)
  74. {
  75. return readl_relaxed(rng->mem + offset);
  76. }
  77. static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset)
  78. {
  79. writel_relaxed(val, rng->mem + offset);
  80. }
  81. static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
  82. const u8 *seed, unsigned int slen)
  83. {
  84. u32 val;
  85. int i;
  86. /* Round seed length because loop iterates over full register size */
  87. slen = ALIGN_DOWN(slen, 4);
  88. if (slen < EXYNOS_RNG_SEED_SIZE)
  89. return -EINVAL;
  90. for (i = 0; i < slen ; i += 4) {
  91. unsigned int seed_reg = (i / 4) % EXYNOS_RNG_SEED_REGS;
  92. val = seed[i] << 24;
  93. val |= seed[i + 1] << 16;
  94. val |= seed[i + 2] << 8;
  95. val |= seed[i + 3] << 0;
  96. exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(seed_reg));
  97. }
  98. val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
  99. if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
  100. dev_warn(rng->dev, "Seed setting not finished\n");
  101. return -EIO;
  102. }
  103. rng->last_seeding = jiffies;
  104. rng->bytes_seeding = 0;
  105. return 0;
  106. }
  107. /*
  108. * Start the engine and poll for finish. Then read from output registers
  109. * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated
  110. * random data (EXYNOS_RNG_SEED_SIZE).
  111. *
  112. * On success: return 0 and store number of read bytes under 'read' address.
  113. * On error: return -ERRNO.
  114. */
  115. static int exynos_rng_get_random(struct exynos_rng_dev *rng,
  116. u8 *dst, unsigned int dlen,
  117. unsigned int *read)
  118. {
  119. int retry = EXYNOS_RNG_WAIT_RETRIES;
  120. if (rng->type == EXYNOS_PRNG_EXYNOS4) {
  121. exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
  122. EXYNOS_RNG_CONTROL);
  123. } else if (rng->type == EXYNOS_PRNG_EXYNOS5) {
  124. exynos_rng_writel(rng, EXYNOS_RNG_GEN_PRNG,
  125. EXYNOS_RNG_SEED_CONF);
  126. }
  127. while (!(exynos_rng_readl(rng,
  128. EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
  129. cpu_relax();
  130. if (!retry)
  131. return -ETIMEDOUT;
  132. /* Clear status bit */
  133. exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE,
  134. EXYNOS_RNG_STATUS);
  135. *read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE);
  136. memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read);
  137. rng->bytes_seeding += *read;
  138. return 0;
  139. }
  140. /* Re-seed itself from time to time */
  141. static void exynos_rng_reseed(struct exynos_rng_dev *rng)
  142. {
  143. unsigned long next_seeding = rng->last_seeding + \
  144. msecs_to_jiffies(EXYNOS_RNG_RESEED_TIME);
  145. unsigned long now = jiffies;
  146. unsigned int read = 0;
  147. u8 seed[EXYNOS_RNG_SEED_SIZE];
  148. if (time_before(now, next_seeding) &&
  149. rng->bytes_seeding < EXYNOS_RNG_RESEED_BYTES)
  150. return;
  151. if (exynos_rng_get_random(rng, seed, sizeof(seed), &read))
  152. return;
  153. exynos_rng_set_seed(rng, seed, read);
  154. /* Let others do some of their job. */
  155. mutex_unlock(&rng->lock);
  156. mutex_lock(&rng->lock);
  157. }
  158. static int exynos_rng_generate(struct crypto_rng *tfm,
  159. const u8 *src, unsigned int slen,
  160. u8 *dst, unsigned int dlen)
  161. {
  162. struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
  163. struct exynos_rng_dev *rng = ctx->rng;
  164. unsigned int read = 0;
  165. int ret;
  166. ret = clk_prepare_enable(rng->clk);
  167. if (ret)
  168. return ret;
  169. mutex_lock(&rng->lock);
  170. do {
  171. ret = exynos_rng_get_random(rng, dst, dlen, &read);
  172. if (ret)
  173. break;
  174. dlen -= read;
  175. dst += read;
  176. exynos_rng_reseed(rng);
  177. } while (dlen > 0);
  178. mutex_unlock(&rng->lock);
  179. clk_disable_unprepare(rng->clk);
  180. return ret;
  181. }
  182. static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed,
  183. unsigned int slen)
  184. {
  185. struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
  186. struct exynos_rng_dev *rng = ctx->rng;
  187. int ret;
  188. ret = clk_prepare_enable(rng->clk);
  189. if (ret)
  190. return ret;
  191. mutex_lock(&rng->lock);
  192. ret = exynos_rng_set_seed(ctx->rng, seed, slen);
  193. mutex_unlock(&rng->lock);
  194. clk_disable_unprepare(rng->clk);
  195. return ret;
  196. }
  197. static int exynos_rng_kcapi_init(struct crypto_tfm *tfm)
  198. {
  199. struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm);
  200. ctx->rng = exynos_rng_dev;
  201. return 0;
  202. }
  203. static struct rng_alg exynos_rng_alg = {
  204. .generate = exynos_rng_generate,
  205. .seed = exynos_rng_seed,
  206. .seedsize = EXYNOS_RNG_SEED_SIZE,
  207. .base = {
  208. .cra_name = "stdrng",
  209. .cra_driver_name = "exynos_rng",
  210. .cra_priority = 300,
  211. .cra_ctxsize = sizeof(struct exynos_rng_ctx),
  212. .cra_module = THIS_MODULE,
  213. .cra_init = exynos_rng_kcapi_init,
  214. }
  215. };
  216. static int exynos_rng_probe(struct platform_device *pdev)
  217. {
  218. struct exynos_rng_dev *rng;
  219. int ret;
  220. if (exynos_rng_dev)
  221. return -EEXIST;
  222. rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
  223. if (!rng)
  224. return -ENOMEM;
  225. rng->type = (enum exynos_prng_type)of_device_get_match_data(&pdev->dev);
  226. mutex_init(&rng->lock);
  227. rng->dev = &pdev->dev;
  228. rng->clk = devm_clk_get(&pdev->dev, "secss");
  229. if (IS_ERR(rng->clk)) {
  230. dev_err(&pdev->dev, "Couldn't get clock.\n");
  231. return PTR_ERR(rng->clk);
  232. }
  233. rng->mem = devm_platform_ioremap_resource(pdev, 0);
  234. if (IS_ERR(rng->mem))
  235. return PTR_ERR(rng->mem);
  236. platform_set_drvdata(pdev, rng);
  237. exynos_rng_dev = rng;
  238. ret = crypto_register_rng(&exynos_rng_alg);
  239. if (ret) {
  240. dev_err(&pdev->dev,
  241. "Couldn't register rng crypto alg: %d\n", ret);
  242. exynos_rng_dev = NULL;
  243. }
  244. return ret;
  245. }
  246. static int exynos_rng_remove(struct platform_device *pdev)
  247. {
  248. crypto_unregister_rng(&exynos_rng_alg);
  249. exynos_rng_dev = NULL;
  250. return 0;
  251. }
  252. static int __maybe_unused exynos_rng_suspend(struct device *dev)
  253. {
  254. struct exynos_rng_dev *rng = dev_get_drvdata(dev);
  255. int ret;
  256. /* If we were never seeded then after resume it will be the same */
  257. if (!rng->last_seeding)
  258. return 0;
  259. rng->seed_save_len = 0;
  260. ret = clk_prepare_enable(rng->clk);
  261. if (ret)
  262. return ret;
  263. mutex_lock(&rng->lock);
  264. /* Get new random numbers and store them for seeding on resume. */
  265. exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save),
  266. &(rng->seed_save_len));
  267. mutex_unlock(&rng->lock);
  268. dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n",
  269. rng->seed_save_len);
  270. clk_disable_unprepare(rng->clk);
  271. return 0;
  272. }
  273. static int __maybe_unused exynos_rng_resume(struct device *dev)
  274. {
  275. struct exynos_rng_dev *rng = dev_get_drvdata(dev);
  276. int ret;
  277. /* Never seeded so nothing to do */
  278. if (!rng->last_seeding)
  279. return 0;
  280. ret = clk_prepare_enable(rng->clk);
  281. if (ret)
  282. return ret;
  283. mutex_lock(&rng->lock);
  284. ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len);
  285. mutex_unlock(&rng->lock);
  286. clk_disable_unprepare(rng->clk);
  287. return ret;
  288. }
  289. static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend,
  290. exynos_rng_resume);
  291. static const struct of_device_id exynos_rng_dt_match[] = {
  292. {
  293. .compatible = "samsung,exynos4-rng",
  294. .data = (const void *)EXYNOS_PRNG_EXYNOS4,
  295. }, {
  296. .compatible = "samsung,exynos5250-prng",
  297. .data = (const void *)EXYNOS_PRNG_EXYNOS5,
  298. },
  299. { },
  300. };
  301. MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);
  302. static struct platform_driver exynos_rng_driver = {
  303. .driver = {
  304. .name = "exynos-rng",
  305. .pm = &exynos_rng_pm_ops,
  306. .of_match_table = exynos_rng_dt_match,
  307. },
  308. .probe = exynos_rng_probe,
  309. .remove = exynos_rng_remove,
  310. };
  311. module_platform_driver(exynos_rng_driver);
  312. MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver");
  313. MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>");
  314. MODULE_LICENSE("GPL v2");