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
exynos_rng_readl(struct exynos_rng_dev * rng,u32 offset)87 static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset)
88 {
89 return readl_relaxed(rng->mem + offset);
90 }
91
exynos_rng_writel(struct exynos_rng_dev * rng,u32 val,u32 offset)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
exynos_rng_set_seed(struct exynos_rng_dev * rng,const u8 * seed,unsigned int slen)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 */
exynos_rng_get_random(struct exynos_rng_dev * rng,u8 * dst,unsigned int dlen,unsigned int * read)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 */
exynos_rng_reseed(struct exynos_rng_dev * rng)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, seed, sizeof(seed), &read))
185 return;
186
187 exynos_rng_set_seed(rng, seed, read);
188
189 /* Let others do some of their job. */
190 mutex_unlock(&rng->lock);
191 mutex_lock(&rng->lock);
192 }
193
exynos_rng_generate(struct crypto_rng * tfm,const u8 * src,unsigned int slen,u8 * dst,unsigned int dlen)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
207 mutex_lock(&rng->lock);
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);
218 mutex_unlock(&rng->lock);
219
220 clk_disable_unprepare(rng->clk);
221
222 return ret;
223 }
224
exynos_rng_seed(struct crypto_rng * tfm,const u8 * seed,unsigned int slen)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
236 mutex_lock(&rng->lock);
237 ret = exynos_rng_set_seed(ctx->rng, seed, slen);
238 mutex_unlock(&rng->lock);
239
240 clk_disable_unprepare(rng->clk);
241
242 return ret;
243 }
244
exynos_rng_kcapi_init(struct crypto_tfm * tfm)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
exynos_rng_probe(struct platform_device * pdev)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(&pdev->dev, sizeof(*rng), GFP_KERNEL);
277 if (!rng)
278 return -ENOMEM;
279
280 rng->type = (uintptr_t)of_device_get_match_data(&pdev->dev);
281
282 mutex_init(&rng->lock);
283
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
291 rng->mem = devm_platform_ioremap_resource(pdev, 0);
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
exynos_rng_remove(struct platform_device * pdev)309 static void exynos_rng_remove(struct platform_device *pdev)
310 {
311 crypto_unregister_rng(&exynos_rng_alg);
312
313 exynos_rng_dev = NULL;
314 }
315
exynos_rng_suspend(struct device * dev)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(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, rng->seed_save, sizeof(rng->seed_save),
334 &(rng->seed_save_len));
335
336 mutex_unlock(&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(rng->clk);
342
343 return 0;
344 }
345
exynos_rng_resume(struct device * dev)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(rng->clk);
356 if (ret)
357 return ret;
358
359 mutex_lock(&rng->lock);
360
361 ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len);
362
363 mutex_unlock(&rng->lock);
364
365 clk_disable_unprepare(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