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1 | /* |
2 | * exynos-rng.c - Random Number Generator driver for the Exynos | |
3 | * | |
4 | * Copyright (c) 2017 Krzysztof Kozlowski <krzk@kernel.org> | |
5 | * | |
6 | * Loosely based on old driver from drivers/char/hw_random/exynos-rng.c: | |
7 | * Copyright (C) 2012 Samsung Electronics | |
8 | * Jonghwa Lee <jonghwa3.lee@samsung.com> | |
9 | * | |
10 | * This program is free software; you can redistribute it and/or modify | |
11 | * it under the terms of the GNU General Public License as published by | |
12 | * the Free Software Foundation; | |
13 | * | |
14 | * This program is distributed in the hope that it will be useful, | |
15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
17 | * GNU General Public License for more details. | |
18 | */ | |
19 | ||
20 | #include <linux/clk.h> | |
21 | #include <linux/crypto.h> | |
22 | #include <linux/err.h> | |
23 | #include <linux/io.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/platform_device.h> | |
26 | ||
27 | #include <crypto/internal/rng.h> | |
28 | ||
29 | #define EXYNOS_RNG_CONTROL 0x0 | |
30 | #define EXYNOS_RNG_STATUS 0x10 | |
31 | #define EXYNOS_RNG_SEED_BASE 0x140 | |
32 | #define EXYNOS_RNG_SEED(n) (EXYNOS_RNG_SEED_BASE + (n * 0x4)) | |
33 | #define EXYNOS_RNG_OUT_BASE 0x160 | |
34 | #define EXYNOS_RNG_OUT(n) (EXYNOS_RNG_OUT_BASE + (n * 0x4)) | |
35 | ||
36 | /* EXYNOS_RNG_CONTROL bit fields */ | |
37 | #define EXYNOS_RNG_CONTROL_START 0x18 | |
38 | /* EXYNOS_RNG_STATUS bit fields */ | |
39 | #define EXYNOS_RNG_STATUS_SEED_SETTING_DONE BIT(1) | |
40 | #define EXYNOS_RNG_STATUS_RNG_DONE BIT(5) | |
41 | ||
42 | /* Five seed and output registers, each 4 bytes */ | |
43 | #define EXYNOS_RNG_SEED_REGS 5 | |
44 | #define EXYNOS_RNG_SEED_SIZE (EXYNOS_RNG_SEED_REGS * 4) | |
45 | ||
46 | /* | |
47 | * Driver re-seeds itself with generated random numbers to increase | |
48 | * the randomness. | |
49 | * | |
50 | * Time for next re-seed in ms. | |
51 | */ | |
52 | #define EXYNOS_RNG_RESEED_TIME 100 | |
53 | /* | |
54 | * In polling mode, do not wait infinitely for the engine to finish the work. | |
55 | */ | |
56 | #define EXYNOS_RNG_WAIT_RETRIES 100 | |
57 | ||
58 | /* Context for crypto */ | |
59 | struct exynos_rng_ctx { | |
60 | struct exynos_rng_dev *rng; | |
61 | }; | |
62 | ||
63 | /* Device associated memory */ | |
64 | struct exynos_rng_dev { | |
65 | struct device *dev; | |
66 | void __iomem *mem; | |
67 | struct clk *clk; | |
68 | /* Generated numbers stored for seeding during resume */ | |
69 | u8 seed_save[EXYNOS_RNG_SEED_SIZE]; | |
70 | unsigned int seed_save_len; | |
71 | /* Time of last seeding in jiffies */ | |
72 | unsigned long last_seeding; | |
73 | }; | |
74 | ||
75 | static struct exynos_rng_dev *exynos_rng_dev; | |
76 | ||
77 | static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset) | |
78 | { | |
79 | return readl_relaxed(rng->mem + offset); | |
80 | } | |
81 | ||
82 | static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset) | |
83 | { | |
84 | writel_relaxed(val, rng->mem + offset); | |
85 | } | |
86 | ||
87 | static int exynos_rng_set_seed(struct exynos_rng_dev *rng, | |
88 | const u8 *seed, unsigned int slen) | |
89 | { | |
90 | u32 val; | |
91 | int i; | |
92 | ||
93 | /* Round seed length because loop iterates over full register size */ | |
94 | slen = ALIGN_DOWN(slen, 4); | |
95 | ||
96 | if (slen < EXYNOS_RNG_SEED_SIZE) | |
97 | return -EINVAL; | |
98 | ||
99 | for (i = 0; i < slen ; i += 4) { | |
100 | unsigned int seed_reg = (i / 4) % EXYNOS_RNG_SEED_REGS; | |
101 | ||
102 | val = seed[i] << 24; | |
103 | val |= seed[i + 1] << 16; | |
104 | val |= seed[i + 2] << 8; | |
105 | val |= seed[i + 3] << 0; | |
106 | ||
107 | exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(seed_reg)); | |
108 | } | |
109 | ||
110 | val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS); | |
111 | if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) { | |
112 | dev_warn(rng->dev, "Seed setting not finished\n"); | |
113 | return -EIO; | |
114 | } | |
115 | ||
116 | rng->last_seeding = jiffies; | |
117 | ||
118 | return 0; | |
119 | } | |
120 | ||
121 | /* | |
122 | * Read from output registers and put the data under 'dst' array, | |
123 | * up to dlen bytes. | |
124 | * | |
125 | * Returns number of bytes actually stored in 'dst' (dlen | |
126 | * or EXYNOS_RNG_SEED_SIZE). | |
127 | */ | |
128 | static unsigned int exynos_rng_copy_random(struct exynos_rng_dev *rng, | |
129 | u8 *dst, unsigned int dlen) | |
130 | { | |
131 | unsigned int cnt = 0; | |
132 | int i, j; | |
133 | u32 val; | |
134 | ||
135 | for (j = 0; j < EXYNOS_RNG_SEED_REGS; j++) { | |
136 | val = exynos_rng_readl(rng, EXYNOS_RNG_OUT(j)); | |
137 | ||
138 | for (i = 0; i < 4; i++) { | |
139 | dst[cnt] = val & 0xff; | |
140 | val >>= 8; | |
141 | if (++cnt >= dlen) | |
142 | return cnt; | |
143 | } | |
144 | } | |
145 | ||
146 | return cnt; | |
147 | } | |
148 | ||
149 | /* | |
150 | * Start the engine and poll for finish. Then read from output registers | |
151 | * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated | |
152 | * random data (EXYNOS_RNG_SEED_SIZE). | |
153 | * | |
154 | * On success: return 0 and store number of read bytes under 'read' address. | |
155 | * On error: return -ERRNO. | |
156 | */ | |
157 | static int exynos_rng_get_random(struct exynos_rng_dev *rng, | |
158 | u8 *dst, unsigned int dlen, | |
159 | unsigned int *read) | |
160 | { | |
161 | int retry = EXYNOS_RNG_WAIT_RETRIES; | |
162 | ||
163 | exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START, | |
164 | EXYNOS_RNG_CONTROL); | |
165 | ||
166 | while (!(exynos_rng_readl(rng, | |
167 | EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry) | |
168 | cpu_relax(); | |
169 | ||
170 | if (!retry) | |
171 | return -ETIMEDOUT; | |
172 | ||
173 | /* Clear status bit */ | |
174 | exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE, | |
175 | EXYNOS_RNG_STATUS); | |
176 | *read = exynos_rng_copy_random(rng, dst, dlen); | |
177 | ||
178 | return 0; | |
179 | } | |
180 | ||
181 | /* Re-seed itself from time to time */ | |
182 | static void exynos_rng_reseed(struct exynos_rng_dev *rng) | |
183 | { | |
184 | unsigned long next_seeding = rng->last_seeding + \ | |
185 | msecs_to_jiffies(EXYNOS_RNG_RESEED_TIME); | |
186 | unsigned long now = jiffies; | |
187 | unsigned int read = 0; | |
188 | u8 seed[EXYNOS_RNG_SEED_SIZE]; | |
189 | ||
190 | if (time_before(now, next_seeding)) | |
191 | return; | |
192 | ||
193 | if (exynos_rng_get_random(rng, seed, sizeof(seed), &read)) | |
194 | return; | |
195 | ||
196 | exynos_rng_set_seed(rng, seed, read); | |
197 | } | |
198 | ||
199 | static int exynos_rng_generate(struct crypto_rng *tfm, | |
200 | const u8 *src, unsigned int slen, | |
201 | u8 *dst, unsigned int dlen) | |
202 | { | |
203 | struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm); | |
204 | struct exynos_rng_dev *rng = ctx->rng; | |
205 | unsigned int read = 0; | |
206 | int ret; | |
207 | ||
208 | ret = clk_prepare_enable(rng->clk); | |
209 | if (ret) | |
210 | return ret; | |
211 | ||
212 | do { | |
213 | ret = exynos_rng_get_random(rng, dst, dlen, &read); | |
214 | if (ret) | |
215 | break; | |
216 | ||
217 | dlen -= read; | |
218 | dst += read; | |
219 | ||
220 | exynos_rng_reseed(rng); | |
221 | } while (dlen > 0); | |
222 | ||
223 | clk_disable_unprepare(rng->clk); | |
224 | ||
225 | return ret; | |
226 | } | |
227 | ||
228 | static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed, | |
229 | unsigned int slen) | |
230 | { | |
231 | struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm); | |
232 | struct exynos_rng_dev *rng = ctx->rng; | |
233 | int ret; | |
234 | ||
235 | ret = clk_prepare_enable(rng->clk); | |
236 | if (ret) | |
237 | return ret; | |
238 | ||
239 | ret = exynos_rng_set_seed(ctx->rng, seed, slen); | |
240 | ||
241 | clk_disable_unprepare(rng->clk); | |
242 | ||
243 | return ret; | |
244 | } | |
245 | ||
246 | static int exynos_rng_kcapi_init(struct crypto_tfm *tfm) | |
247 | { | |
248 | struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm); | |
249 | ||
250 | ctx->rng = exynos_rng_dev; | |
251 | ||
252 | return 0; | |
253 | } | |
254 | ||
255 | static struct rng_alg exynos_rng_alg = { | |
256 | .generate = exynos_rng_generate, | |
257 | .seed = exynos_rng_seed, | |
258 | .seedsize = EXYNOS_RNG_SEED_SIZE, | |
259 | .base = { | |
260 | .cra_name = "stdrng", | |
261 | .cra_driver_name = "exynos_rng", | |
262 | .cra_priority = 100, | |
263 | .cra_ctxsize = sizeof(struct exynos_rng_ctx), | |
264 | .cra_module = THIS_MODULE, | |
265 | .cra_init = exynos_rng_kcapi_init, | |
266 | } | |
267 | }; | |
268 | ||
269 | static int exynos_rng_probe(struct platform_device *pdev) | |
270 | { | |
271 | struct exynos_rng_dev *rng; | |
272 | struct resource *res; | |
273 | int ret; | |
274 | ||
275 | if (exynos_rng_dev) | |
276 | return -EEXIST; | |
277 | ||
278 | rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL); | |
279 | if (!rng) | |
280 | return -ENOMEM; | |
281 | ||
282 | rng->dev = &pdev->dev; | |
283 | rng->clk = devm_clk_get(&pdev->dev, "secss"); | |
284 | if (IS_ERR(rng->clk)) { | |
285 | dev_err(&pdev->dev, "Couldn't get clock.\n"); | |
286 | return PTR_ERR(rng->clk); | |
287 | } | |
288 | ||
289 | res = platform_get_resource(pdev, IORESOURCE_MEM, 0); | |
290 | rng->mem = devm_ioremap_resource(&pdev->dev, res); | |
291 | if (IS_ERR(rng->mem)) | |
292 | return PTR_ERR(rng->mem); | |
293 | ||
294 | platform_set_drvdata(pdev, rng); | |
295 | ||
296 | exynos_rng_dev = rng; | |
297 | ||
298 | ret = crypto_register_rng(&exynos_rng_alg); | |
299 | if (ret) { | |
300 | dev_err(&pdev->dev, | |
301 | "Couldn't register rng crypto alg: %d\n", ret); | |
302 | exynos_rng_dev = NULL; | |
303 | } | |
304 | ||
305 | return ret; | |
306 | } | |
307 | ||
308 | static int exynos_rng_remove(struct platform_device *pdev) | |
309 | { | |
310 | crypto_unregister_rng(&exynos_rng_alg); | |
311 | ||
312 | exynos_rng_dev = NULL; | |
313 | ||
314 | return 0; | |
315 | } | |
316 | ||
317 | static int __maybe_unused exynos_rng_suspend(struct device *dev) | |
318 | { | |
319 | struct platform_device *pdev = to_platform_device(dev); | |
320 | struct exynos_rng_dev *rng = platform_get_drvdata(pdev); | |
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 | ||
332 | /* Get new random numbers and store them for seeding on resume. */ | |
333 | exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save), | |
334 | &(rng->seed_save_len)); | |
335 | dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n", | |
336 | rng->seed_save_len); | |
337 | ||
338 | clk_disable_unprepare(rng->clk); | |
339 | ||
340 | return 0; | |
341 | } | |
342 | ||
343 | static int __maybe_unused exynos_rng_resume(struct device *dev) | |
344 | { | |
345 | struct platform_device *pdev = to_platform_device(dev); | |
346 | struct exynos_rng_dev *rng = platform_get_drvdata(pdev); | |
347 | int ret; | |
348 | ||
349 | /* Never seeded so nothing to do */ | |
350 | if (!rng->last_seeding) | |
351 | return 0; | |
352 | ||
353 | ret = clk_prepare_enable(rng->clk); | |
354 | if (ret) | |
355 | return ret; | |
356 | ||
357 | ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len); | |
358 | ||
359 | clk_disable_unprepare(rng->clk); | |
360 | ||
361 | return ret; | |
362 | } | |
363 | ||
364 | static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend, | |
365 | exynos_rng_resume); | |
366 | ||
367 | static const struct of_device_id exynos_rng_dt_match[] = { | |
368 | { | |
369 | .compatible = "samsung,exynos4-rng", | |
370 | }, | |
371 | { }, | |
372 | }; | |
373 | MODULE_DEVICE_TABLE(of, exynos_rng_dt_match); | |
374 | ||
375 | static struct platform_driver exynos_rng_driver = { | |
376 | .driver = { | |
377 | .name = "exynos-rng", | |
378 | .pm = &exynos_rng_pm_ops, | |
379 | .of_match_table = exynos_rng_dt_match, | |
380 | }, | |
381 | .probe = exynos_rng_probe, | |
382 | .remove = exynos_rng_remove, | |
383 | }; | |
384 | ||
385 | module_platform_driver(exynos_rng_driver); | |
386 | ||
387 | MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver"); | |
388 | MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>"); | |
389 | MODULE_LICENSE("GPL"); |