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 | |
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> |
17 | #include <linux/mutex.h> |
18 | #include <linux/of.h> |
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 |
25 | |
26 | #define EXYNOS_RNG_SEED_CONF 0x14 |
27 | #define EXYNOS_RNG_GEN_PRNG BIT(1) |
28 | |
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 | |
44 | enum exynos_prng_type { |
45 | EXYNOS_PRNG_UNKNOWN = 0, |
46 | EXYNOS_PRNG_EXYNOS4, |
47 | EXYNOS_PRNG_EXYNOS5, |
48 | }; |
49 | |
50 | /* |
51 | * Driver re-seeds itself with generated random numbers to hinder |
52 | * backtracking of the original seed. |
53 | * |
54 | * Time for next re-seed in ms. |
55 | */ |
56 | #define EXYNOS_RNG_RESEED_TIME 1000 |
57 | #define EXYNOS_RNG_RESEED_BYTES 65536 |
58 | |
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; |
72 | enum exynos_prng_type type; |
73 | void __iomem *mem; |
74 | struct clk *clk; |
75 | struct mutex lock; |
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; |
81 | /* Bytes generated since last seeding */ |
82 | unsigned long bytes_seeding; |
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; |
127 | rng->bytes_seeding = 0; |
128 | |
129 | return 0; |
130 | } |
131 | |
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 | |
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 | } |
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); |
164 | *read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE); |
165 | memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read); |
166 | rng->bytes_seeding += *read; |
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 | |
180 | if (time_before(now, next_seeding) && |
181 | rng->bytes_seeding < EXYNOS_RNG_RESEED_BYTES) |
182 | return; |
183 | |
184 | if (exynos_rng_get_random(rng, dst: seed, dlen: sizeof(seed), read: &read)) |
185 | return; |
186 | |
187 | exynos_rng_set_seed(rng, seed, slen: read); |
188 | |
189 | /* Let others do some of their job. */ |
190 | mutex_unlock(lock: &rng->lock); |
191 | mutex_lock(&rng->lock); |
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(clk: rng->clk); |
204 | if (ret) |
205 | return ret; |
206 | |
207 | mutex_lock(&rng->lock); |
208 | do { |
209 | ret = exynos_rng_get_random(rng, dst, dlen, read: &read); |
210 | if (ret) |
211 | break; |
212 | |
213 | dlen -= read; |
214 | dst += read; |
215 | |
216 | exynos_rng_reseed(rng); |
217 | } while (dlen > 0); |
218 | mutex_unlock(lock: &rng->lock); |
219 | |
220 | clk_disable_unprepare(clk: 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(clk: rng->clk); |
233 | if (ret) |
234 | return ret; |
235 | |
236 | mutex_lock(&rng->lock); |
237 | ret = exynos_rng_set_seed(rng: ctx->rng, seed, slen); |
238 | mutex_unlock(lock: &rng->lock); |
239 | |
240 | clk_disable_unprepare(clk: 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" , |
261 | .cra_priority = 300, |
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; |
271 | int ret; |
272 | |
273 | if (exynos_rng_dev) |
274 | return -EEXIST; |
275 | |
276 | rng = devm_kzalloc(dev: &pdev->dev, size: sizeof(*rng), GFP_KERNEL); |
277 | if (!rng) |
278 | return -ENOMEM; |
279 | |
280 | rng->type = (uintptr_t)of_device_get_match_data(dev: &pdev->dev); |
281 | |
282 | mutex_init(&rng->lock); |
283 | |
284 | rng->dev = &pdev->dev; |
285 | rng->clk = devm_clk_get(dev: &pdev->dev, id: "secss" ); |
286 | if (IS_ERR(ptr: rng->clk)) { |
287 | dev_err(&pdev->dev, "Couldn't get clock.\n" ); |
288 | return PTR_ERR(ptr: rng->clk); |
289 | } |
290 | |
291 | rng->mem = devm_platform_ioremap_resource(pdev, index: 0); |
292 | if (IS_ERR(ptr: rng->mem)) |
293 | return PTR_ERR(ptr: rng->mem); |
294 | |
295 | platform_set_drvdata(pdev, data: rng); |
296 | |
297 | exynos_rng_dev = rng; |
298 | |
299 | ret = crypto_register_rng(alg: &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 void exynos_rng_remove(struct platform_device *pdev) |
310 | { |
311 | crypto_unregister_rng(alg: &exynos_rng_alg); |
312 | |
313 | exynos_rng_dev = NULL; |
314 | } |
315 | |
316 | static int __maybe_unused exynos_rng_suspend(struct device *dev) |
317 | { |
318 | struct exynos_rng_dev *rng = dev_get_drvdata(dev); |
319 | int ret; |
320 | |
321 | /* If we were never seeded then after resume it will be the same */ |
322 | if (!rng->last_seeding) |
323 | return 0; |
324 | |
325 | rng->seed_save_len = 0; |
326 | ret = clk_prepare_enable(clk: rng->clk); |
327 | if (ret) |
328 | return ret; |
329 | |
330 | mutex_lock(&rng->lock); |
331 | |
332 | /* Get new random numbers and store them for seeding on resume. */ |
333 | exynos_rng_get_random(rng, dst: rng->seed_save, dlen: sizeof(rng->seed_save), |
334 | read: &(rng->seed_save_len)); |
335 | |
336 | mutex_unlock(lock: &rng->lock); |
337 | |
338 | dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n" , |
339 | rng->seed_save_len); |
340 | |
341 | clk_disable_unprepare(clk: rng->clk); |
342 | |
343 | return 0; |
344 | } |
345 | |
346 | static int __maybe_unused exynos_rng_resume(struct device *dev) |
347 | { |
348 | struct exynos_rng_dev *rng = dev_get_drvdata(dev); |
349 | int ret; |
350 | |
351 | /* Never seeded so nothing to do */ |
352 | if (!rng->last_seeding) |
353 | return 0; |
354 | |
355 | ret = clk_prepare_enable(clk: rng->clk); |
356 | if (ret) |
357 | return ret; |
358 | |
359 | mutex_lock(&rng->lock); |
360 | |
361 | ret = exynos_rng_set_seed(rng, seed: rng->seed_save, slen: rng->seed_save_len); |
362 | |
363 | mutex_unlock(lock: &rng->lock); |
364 | |
365 | clk_disable_unprepare(clk: rng->clk); |
366 | |
367 | return ret; |
368 | } |
369 | |
370 | static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend, |
371 | exynos_rng_resume); |
372 | |
373 | static const struct of_device_id exynos_rng_dt_match[] = { |
374 | { |
375 | .compatible = "samsung,exynos4-rng" , |
376 | .data = (const void *)EXYNOS_PRNG_EXYNOS4, |
377 | }, { |
378 | .compatible = "samsung,exynos5250-prng" , |
379 | .data = (const void *)EXYNOS_PRNG_EXYNOS5, |
380 | }, |
381 | { }, |
382 | }; |
383 | MODULE_DEVICE_TABLE(of, exynos_rng_dt_match); |
384 | |
385 | static struct platform_driver exynos_rng_driver = { |
386 | .driver = { |
387 | .name = "exynos-rng" , |
388 | .pm = &exynos_rng_pm_ops, |
389 | .of_match_table = exynos_rng_dt_match, |
390 | }, |
391 | .probe = exynos_rng_probe, |
392 | .remove_new = exynos_rng_remove, |
393 | }; |
394 | |
395 | module_platform_driver(exynos_rng_driver); |
396 | |
397 | MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver" ); |
398 | MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>" ); |
399 | MODULE_LICENSE("GPL v2" ); |
400 | |