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9f9cf046 | 1 | // SPDX-License-Identifier: GPL-2.0 |
c46ea13f KK |
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> | |
c46ea13f KK |
10 | */ |
11 | ||
12 | #include <linux/clk.h> | |
13 | #include <linux/crypto.h> | |
14 | #include <linux/err.h> | |
15 | #include <linux/io.h> | |
16 | #include <linux/module.h> | |
25cf7f06 | 17 | #include <linux/mutex.h> |
f76d38b2 | 18 | #include <linux/of_device.h> |
c46ea13f KK |
19 | #include <linux/platform_device.h> |
20 | ||
21 | #include <crypto/internal/rng.h> | |
22 | ||
23 | #define EXYNOS_RNG_CONTROL 0x0 | |
24 | #define EXYNOS_RNG_STATUS 0x10 | |
f76d38b2 ŁS |
25 | |
26 | #define EXYNOS_RNG_SEED_CONF 0x14 | |
27 | #define EXYNOS_RNG_GEN_PRNG BIT(1) | |
28 | ||
c46ea13f KK |
29 | #define EXYNOS_RNG_SEED_BASE 0x140 |
30 | #define EXYNOS_RNG_SEED(n) (EXYNOS_RNG_SEED_BASE + (n * 0x4)) | |
31 | #define EXYNOS_RNG_OUT_BASE 0x160 | |
32 | #define EXYNOS_RNG_OUT(n) (EXYNOS_RNG_OUT_BASE + (n * 0x4)) | |
33 | ||
34 | /* EXYNOS_RNG_CONTROL bit fields */ | |
35 | #define EXYNOS_RNG_CONTROL_START 0x18 | |
36 | /* EXYNOS_RNG_STATUS bit fields */ | |
37 | #define EXYNOS_RNG_STATUS_SEED_SETTING_DONE BIT(1) | |
38 | #define EXYNOS_RNG_STATUS_RNG_DONE BIT(5) | |
39 | ||
40 | /* Five seed and output registers, each 4 bytes */ | |
41 | #define EXYNOS_RNG_SEED_REGS 5 | |
42 | #define EXYNOS_RNG_SEED_SIZE (EXYNOS_RNG_SEED_REGS * 4) | |
43 | ||
f76d38b2 ŁS |
44 | enum exynos_prng_type { |
45 | EXYNOS_PRNG_UNKNOWN = 0, | |
46 | EXYNOS_PRNG_EXYNOS4, | |
47 | EXYNOS_PRNG_EXYNOS5, | |
48 | }; | |
49 | ||
c46ea13f | 50 | /* |
99c9acfe ŁS |
51 | * Driver re-seeds itself with generated random numbers to hinder |
52 | * backtracking of the original seed. | |
c46ea13f KK |
53 | * |
54 | * Time for next re-seed in ms. | |
55 | */ | |
99c9acfe ŁS |
56 | #define EXYNOS_RNG_RESEED_TIME 1000 |
57 | #define EXYNOS_RNG_RESEED_BYTES 65536 | |
58 | ||
c46ea13f KK |
59 | /* |
60 | * In polling mode, do not wait infinitely for the engine to finish the work. | |
61 | */ | |
62 | #define EXYNOS_RNG_WAIT_RETRIES 100 | |
63 | ||
64 | /* Context for crypto */ | |
65 | struct exynos_rng_ctx { | |
66 | struct exynos_rng_dev *rng; | |
67 | }; | |
68 | ||
69 | /* Device associated memory */ | |
70 | struct exynos_rng_dev { | |
71 | struct device *dev; | |
f76d38b2 | 72 | enum exynos_prng_type type; |
c46ea13f KK |
73 | void __iomem *mem; |
74 | struct clk *clk; | |
25cf7f06 | 75 | struct mutex lock; |
c46ea13f KK |
76 | /* Generated numbers stored for seeding during resume */ |
77 | u8 seed_save[EXYNOS_RNG_SEED_SIZE]; | |
78 | unsigned int seed_save_len; | |
79 | /* Time of last seeding in jiffies */ | |
80 | unsigned long last_seeding; | |
99c9acfe ŁS |
81 | /* Bytes generated since last seeding */ |
82 | unsigned long bytes_seeding; | |
c46ea13f KK |
83 | }; |
84 | ||
85 | static struct exynos_rng_dev *exynos_rng_dev; | |
86 | ||
87 | static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset) | |
88 | { | |
89 | return readl_relaxed(rng->mem + offset); | |
90 | } | |
91 | ||
92 | static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset) | |
93 | { | |
94 | writel_relaxed(val, rng->mem + offset); | |
95 | } | |
96 | ||
97 | static int exynos_rng_set_seed(struct exynos_rng_dev *rng, | |
98 | const u8 *seed, unsigned int slen) | |
99 | { | |
100 | u32 val; | |
101 | int i; | |
102 | ||
103 | /* Round seed length because loop iterates over full register size */ | |
104 | slen = ALIGN_DOWN(slen, 4); | |
105 | ||
106 | if (slen < EXYNOS_RNG_SEED_SIZE) | |
107 | return -EINVAL; | |
108 | ||
109 | for (i = 0; i < slen ; i += 4) { | |
110 | unsigned int seed_reg = (i / 4) % EXYNOS_RNG_SEED_REGS; | |
111 | ||
112 | val = seed[i] << 24; | |
113 | val |= seed[i + 1] << 16; | |
114 | val |= seed[i + 2] << 8; | |
115 | val |= seed[i + 3] << 0; | |
116 | ||
117 | exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(seed_reg)); | |
118 | } | |
119 | ||
120 | val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS); | |
121 | if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) { | |
122 | dev_warn(rng->dev, "Seed setting not finished\n"); | |
123 | return -EIO; | |
124 | } | |
125 | ||
126 | rng->last_seeding = jiffies; | |
99c9acfe | 127 | rng->bytes_seeding = 0; |
c46ea13f KK |
128 | |
129 | return 0; | |
130 | } | |
131 | ||
c46ea13f KK |
132 | /* |
133 | * Start the engine and poll for finish. Then read from output registers | |
134 | * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated | |
135 | * random data (EXYNOS_RNG_SEED_SIZE). | |
136 | * | |
137 | * On success: return 0 and store number of read bytes under 'read' address. | |
138 | * On error: return -ERRNO. | |
139 | */ | |
140 | static int exynos_rng_get_random(struct exynos_rng_dev *rng, | |
141 | u8 *dst, unsigned int dlen, | |
142 | unsigned int *read) | |
143 | { | |
144 | int retry = EXYNOS_RNG_WAIT_RETRIES; | |
145 | ||
f76d38b2 ŁS |
146 | if (rng->type == EXYNOS_PRNG_EXYNOS4) { |
147 | exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START, | |
148 | EXYNOS_RNG_CONTROL); | |
149 | } else if (rng->type == EXYNOS_PRNG_EXYNOS5) { | |
150 | exynos_rng_writel(rng, EXYNOS_RNG_GEN_PRNG, | |
151 | EXYNOS_RNG_SEED_CONF); | |
152 | } | |
c46ea13f KK |
153 | |
154 | while (!(exynos_rng_readl(rng, | |
155 | EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry) | |
156 | cpu_relax(); | |
157 | ||
158 | if (!retry) | |
159 | return -ETIMEDOUT; | |
160 | ||
161 | /* Clear status bit */ | |
162 | exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE, | |
163 | EXYNOS_RNG_STATUS); | |
3a5a5e5c ŁS |
164 | *read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE); |
165 | memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read); | |
99c9acfe | 166 | rng->bytes_seeding += *read; |
c46ea13f KK |
167 | |
168 | return 0; | |
169 | } | |
170 | ||
171 | /* Re-seed itself from time to time */ | |
172 | static void exynos_rng_reseed(struct exynos_rng_dev *rng) | |
173 | { | |
174 | unsigned long next_seeding = rng->last_seeding + \ | |
175 | msecs_to_jiffies(EXYNOS_RNG_RESEED_TIME); | |
176 | unsigned long now = jiffies; | |
177 | unsigned int read = 0; | |
178 | u8 seed[EXYNOS_RNG_SEED_SIZE]; | |
179 | ||
99c9acfe ŁS |
180 | if (time_before(now, next_seeding) && |
181 | rng->bytes_seeding < EXYNOS_RNG_RESEED_BYTES) | |
c46ea13f KK |
182 | return; |
183 | ||
184 | if (exynos_rng_get_random(rng, seed, sizeof(seed), &read)) | |
185 | return; | |
186 | ||
187 | exynos_rng_set_seed(rng, seed, read); | |
25cf7f06 ŁS |
188 | |
189 | /* Let others do some of their job. */ | |
190 | mutex_unlock(&rng->lock); | |
191 | mutex_lock(&rng->lock); | |
c46ea13f KK |
192 | } |
193 | ||
194 | static int exynos_rng_generate(struct crypto_rng *tfm, | |
195 | const u8 *src, unsigned int slen, | |
196 | u8 *dst, unsigned int dlen) | |
197 | { | |
198 | struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm); | |
199 | struct exynos_rng_dev *rng = ctx->rng; | |
200 | unsigned int read = 0; | |
201 | int ret; | |
202 | ||
203 | ret = clk_prepare_enable(rng->clk); | |
204 | if (ret) | |
205 | return ret; | |
206 | ||
25cf7f06 | 207 | mutex_lock(&rng->lock); |
c46ea13f KK |
208 | do { |
209 | ret = exynos_rng_get_random(rng, dst, dlen, &read); | |
210 | if (ret) | |
211 | break; | |
212 | ||
213 | dlen -= read; | |
214 | dst += read; | |
215 | ||
216 | exynos_rng_reseed(rng); | |
217 | } while (dlen > 0); | |
25cf7f06 | 218 | mutex_unlock(&rng->lock); |
c46ea13f KK |
219 | |
220 | clk_disable_unprepare(rng->clk); | |
221 | ||
222 | return ret; | |
223 | } | |
224 | ||
225 | static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed, | |
226 | unsigned int slen) | |
227 | { | |
228 | struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm); | |
229 | struct exynos_rng_dev *rng = ctx->rng; | |
230 | int ret; | |
231 | ||
232 | ret = clk_prepare_enable(rng->clk); | |
233 | if (ret) | |
234 | return ret; | |
235 | ||
25cf7f06 | 236 | mutex_lock(&rng->lock); |
c46ea13f | 237 | ret = exynos_rng_set_seed(ctx->rng, seed, slen); |
25cf7f06 | 238 | mutex_unlock(&rng->lock); |
c46ea13f KK |
239 | |
240 | clk_disable_unprepare(rng->clk); | |
241 | ||
242 | return ret; | |
243 | } | |
244 | ||
245 | static int exynos_rng_kcapi_init(struct crypto_tfm *tfm) | |
246 | { | |
247 | struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm); | |
248 | ||
249 | ctx->rng = exynos_rng_dev; | |
250 | ||
251 | return 0; | |
252 | } | |
253 | ||
254 | static struct rng_alg exynos_rng_alg = { | |
255 | .generate = exynos_rng_generate, | |
256 | .seed = exynos_rng_seed, | |
257 | .seedsize = EXYNOS_RNG_SEED_SIZE, | |
258 | .base = { | |
259 | .cra_name = "stdrng", | |
260 | .cra_driver_name = "exynos_rng", | |
3fc12642 | 261 | .cra_priority = 300, |
c46ea13f KK |
262 | .cra_ctxsize = sizeof(struct exynos_rng_ctx), |
263 | .cra_module = THIS_MODULE, | |
264 | .cra_init = exynos_rng_kcapi_init, | |
265 | } | |
266 | }; | |
267 | ||
268 | static int exynos_rng_probe(struct platform_device *pdev) | |
269 | { | |
270 | struct exynos_rng_dev *rng; | |
c46ea13f KK |
271 | int ret; |
272 | ||
273 | if (exynos_rng_dev) | |
274 | return -EEXIST; | |
275 | ||
276 | rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL); | |
277 | if (!rng) | |
278 | return -ENOMEM; | |
279 | ||
f76d38b2 ŁS |
280 | rng->type = (enum exynos_prng_type)of_device_get_match_data(&pdev->dev); |
281 | ||
25cf7f06 ŁS |
282 | mutex_init(&rng->lock); |
283 | ||
c46ea13f KK |
284 | rng->dev = &pdev->dev; |
285 | rng->clk = devm_clk_get(&pdev->dev, "secss"); | |
286 | if (IS_ERR(rng->clk)) { | |
287 | dev_err(&pdev->dev, "Couldn't get clock.\n"); | |
288 | return PTR_ERR(rng->clk); | |
289 | } | |
290 | ||
6d1c0186 | 291 | rng->mem = devm_platform_ioremap_resource(pdev, 0); |
c46ea13f KK |
292 | if (IS_ERR(rng->mem)) |
293 | return PTR_ERR(rng->mem); | |
294 | ||
295 | platform_set_drvdata(pdev, rng); | |
296 | ||
297 | exynos_rng_dev = rng; | |
298 | ||
299 | ret = crypto_register_rng(&exynos_rng_alg); | |
300 | if (ret) { | |
301 | dev_err(&pdev->dev, | |
302 | "Couldn't register rng crypto alg: %d\n", ret); | |
303 | exynos_rng_dev = NULL; | |
304 | } | |
305 | ||
306 | return ret; | |
307 | } | |
308 | ||
309 | static int exynos_rng_remove(struct platform_device *pdev) | |
310 | { | |
311 | crypto_unregister_rng(&exynos_rng_alg); | |
312 | ||
313 | exynos_rng_dev = NULL; | |
314 | ||
315 | return 0; | |
316 | } | |
317 | ||
318 | static int __maybe_unused exynos_rng_suspend(struct device *dev) | |
319 | { | |
8ce31dca | 320 | struct exynos_rng_dev *rng = dev_get_drvdata(dev); |
c46ea13f KK |
321 | int ret; |
322 | ||
323 | /* If we were never seeded then after resume it will be the same */ | |
324 | if (!rng->last_seeding) | |
325 | return 0; | |
326 | ||
327 | rng->seed_save_len = 0; | |
328 | ret = clk_prepare_enable(rng->clk); | |
329 | if (ret) | |
330 | return ret; | |
331 | ||
25cf7f06 ŁS |
332 | mutex_lock(&rng->lock); |
333 | ||
c46ea13f KK |
334 | /* Get new random numbers and store them for seeding on resume. */ |
335 | exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save), | |
336 | &(rng->seed_save_len)); | |
25cf7f06 ŁS |
337 | |
338 | mutex_unlock(&rng->lock); | |
339 | ||
c46ea13f KK |
340 | dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n", |
341 | rng->seed_save_len); | |
342 | ||
343 | clk_disable_unprepare(rng->clk); | |
344 | ||
345 | return 0; | |
346 | } | |
347 | ||
348 | static int __maybe_unused exynos_rng_resume(struct device *dev) | |
349 | { | |
8ce31dca | 350 | struct exynos_rng_dev *rng = dev_get_drvdata(dev); |
c46ea13f KK |
351 | int ret; |
352 | ||
353 | /* Never seeded so nothing to do */ | |
354 | if (!rng->last_seeding) | |
355 | return 0; | |
356 | ||
357 | ret = clk_prepare_enable(rng->clk); | |
358 | if (ret) | |
359 | return ret; | |
360 | ||
25cf7f06 ŁS |
361 | mutex_lock(&rng->lock); |
362 | ||
c46ea13f KK |
363 | ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len); |
364 | ||
25cf7f06 ŁS |
365 | mutex_unlock(&rng->lock); |
366 | ||
c46ea13f KK |
367 | clk_disable_unprepare(rng->clk); |
368 | ||
369 | return ret; | |
370 | } | |
371 | ||
372 | static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend, | |
373 | exynos_rng_resume); | |
374 | ||
375 | static const struct of_device_id exynos_rng_dt_match[] = { | |
376 | { | |
377 | .compatible = "samsung,exynos4-rng", | |
f76d38b2 ŁS |
378 | .data = (const void *)EXYNOS_PRNG_EXYNOS4, |
379 | }, { | |
380 | .compatible = "samsung,exynos5250-prng", | |
381 | .data = (const void *)EXYNOS_PRNG_EXYNOS5, | |
c46ea13f KK |
382 | }, |
383 | { }, | |
384 | }; | |
385 | MODULE_DEVICE_TABLE(of, exynos_rng_dt_match); | |
386 | ||
387 | static struct platform_driver exynos_rng_driver = { | |
388 | .driver = { | |
389 | .name = "exynos-rng", | |
390 | .pm = &exynos_rng_pm_ops, | |
391 | .of_match_table = exynos_rng_dt_match, | |
392 | }, | |
393 | .probe = exynos_rng_probe, | |
394 | .remove = exynos_rng_remove, | |
395 | }; | |
396 | ||
397 | module_platform_driver(exynos_rng_driver); | |
398 | ||
399 | MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver"); | |
400 | MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>"); | |
9f9cf046 | 401 | MODULE_LICENSE("GPL v2"); |