aboutsummaryrefslogtreecommitdiff
path: root/drivers/crypto/exynos-rng.c
blob: cbd8ca6e52ee49e6defec1f9bb1db1eb32f7b2fc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
// SPDX-License-Identifier: GPL-2.0
/*
 * exynos-rng.c - Random Number Generator driver for the Exynos
 *
 * Copyright (c) 2017 Krzysztof Kozlowski <krzk@kernel.org>
 *
 * Loosely based on old driver from drivers/char/hw_random/exynos-rng.c:
 * Copyright (C) 2012 Samsung Electronics
 * Jonghwa Lee <jonghwa3.lee@samsung.com>
 */

#include <linux/clk.h>
#include <linux/crypto.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>

#include <crypto/internal/rng.h>

#define EXYNOS_RNG_CONTROL		0x0
#define EXYNOS_RNG_STATUS		0x10

#define EXYNOS_RNG_SEED_CONF		0x14
#define EXYNOS_RNG_GEN_PRNG	        BIT(1)

#define EXYNOS_RNG_SEED_BASE		0x140
#define EXYNOS_RNG_SEED(n)		(EXYNOS_RNG_SEED_BASE + (n * 0x4))
#define EXYNOS_RNG_OUT_BASE		0x160
#define EXYNOS_RNG_OUT(n)		(EXYNOS_RNG_OUT_BASE + (n * 0x4))

/* EXYNOS_RNG_CONTROL bit fields */
#define EXYNOS_RNG_CONTROL_START	0x18
/* EXYNOS_RNG_STATUS bit fields */
#define EXYNOS_RNG_STATUS_SEED_SETTING_DONE	BIT(1)
#define EXYNOS_RNG_STATUS_RNG_DONE		BIT(5)

/* Five seed and output registers, each 4 bytes */
#define EXYNOS_RNG_SEED_REGS		5
#define EXYNOS_RNG_SEED_SIZE		(EXYNOS_RNG_SEED_REGS * 4)

enum exynos_prng_type {
	EXYNOS_PRNG_UNKNOWN = 0,
	EXYNOS_PRNG_EXYNOS4,
	EXYNOS_PRNG_EXYNOS5,
};

/*
 * Driver re-seeds itself with generated random numbers to hinder
 * backtracking of the original seed.
 *
 * Time for next re-seed in ms.
 */
#define EXYNOS_RNG_RESEED_TIME		1000
#define EXYNOS_RNG_RESEED_BYTES		65536

/*
 * In polling mode, do not wait infinitely for the engine to finish the work.
 */
#define EXYNOS_RNG_WAIT_RETRIES		100

/* Context for crypto */
struct exynos_rng_ctx {
	struct exynos_rng_dev		*rng;
};

/* Device associated memory */
struct exynos_rng_dev {
	struct device			*dev;
	enum exynos_prng_type		type;
	void __iomem			*mem;
	struct clk			*clk;
	struct mutex 			lock;
	/* Generated numbers stored for seeding during resume */
	u8				seed_save[EXYNOS_RNG_SEED_SIZE];
	unsigned int			seed_save_len;
	/* Time of last seeding in jiffies */
	unsigned long			last_seeding;
	/* Bytes generated since last seeding */
	unsigned long			bytes_seeding;
};

static struct exynos_rng_dev *exynos_rng_dev;

static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset)
{
	return readl_relaxed(rng->mem + offset);
}

static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset)
{
	writel_relaxed(val, rng->mem + offset);
}

static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
			       const u8 *seed, unsigned int slen)
{
	u32 val;
	int i;

	/* Round seed length because loop iterates over full register size */
	slen = ALIGN_DOWN(slen, 4);

	if (slen < EXYNOS_RNG_SEED_SIZE)
		return -EINVAL;

	for (i = 0; i < slen ; i += 4) {
		unsigned int seed_reg = (i / 4) % EXYNOS_RNG_SEED_REGS;

		val = seed[i] << 24;
		val |= seed[i + 1] << 16;
		val |= seed[i + 2] << 8;
		val |= seed[i + 3] << 0;

		exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(seed_reg));
	}

	val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
	if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
		dev_warn(rng->dev, "Seed setting not finished\n");
		return -EIO;
	}

	rng->last_seeding = jiffies;
	rng->bytes_seeding = 0;

	return 0;
}

/*
 * Start the engine and poll for finish.  Then read from output registers
 * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated
 * random data (EXYNOS_RNG_SEED_SIZE).
 *
 * On success: return 0 and store number of read bytes under 'read' address.
 * On error: return -ERRNO.
 */
static int exynos_rng_get_random(struct exynos_rng_dev *rng,
				 u8 *dst, unsigned int dlen,
				 unsigned int *read)
{
	int retry = EXYNOS_RNG_WAIT_RETRIES;

	if (rng->type == EXYNOS_PRNG_EXYNOS4) {
		exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
				  EXYNOS_RNG_CONTROL);
	} else if (rng->type == EXYNOS_PRNG_EXYNOS5) {
		exynos_rng_writel(rng, EXYNOS_RNG_GEN_PRNG,
				  EXYNOS_RNG_SEED_CONF);
	}

	while (!(exynos_rng_readl(rng,
			EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
		cpu_relax();

	if (!retry)
		return -ETIMEDOUT;

	/* Clear status bit */
	exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE,
			  EXYNOS_RNG_STATUS);
	*read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE);
	memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read);
	rng->bytes_seeding += *read;

	return 0;
}

/* Re-seed itself from time to time */
static void exynos_rng_reseed(struct exynos_rng_dev *rng)
{
	unsigned long next_seeding = rng->last_seeding + \
				     msecs_to_jiffies(EXYNOS_RNG_RESEED_TIME);
	unsigned long now = jiffies;
	unsigned int read = 0;
	u8 seed[EXYNOS_RNG_SEED_SIZE];

	if (time_before(now, next_seeding) &&
	    rng->bytes_seeding < EXYNOS_RNG_RESEED_BYTES)
		return;

	if (exynos_rng_get_random(rng, seed, sizeof(seed), &read))
		return;

	exynos_rng_set_seed(rng, seed, read);

	/* Let others do some of their job. */
	mutex_unlock(&rng->lock);
	mutex_lock(&rng->lock);
}

static int exynos_rng_generate(struct crypto_rng *tfm,
			       const u8 *src, unsigned int slen,
			       u8 *dst, unsigned int dlen)
{
	struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
	struct exynos_rng_dev *rng = ctx->rng;
	unsigned int read = 0;
	int ret;

	ret = clk_prepare_enable(rng->clk);
	if (ret)
		return ret;

	mutex_lock(&rng->lock);
	do {
		ret = exynos_rng_get_random(rng, dst, dlen, &read);
		if (ret)
			break;

		dlen -= read;
		dst += read;

		exynos_rng_reseed(rng);
	} while (dlen > 0);
	mutex_unlock(&rng->lock);

	clk_disable_unprepare(rng->clk);

	return ret;
}

static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed,
			   unsigned int slen)
{
	struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
	struct exynos_rng_dev *rng = ctx->rng;
	int ret;

	ret = clk_prepare_enable(rng->clk);
	if (ret)
		return ret;

	mutex_lock(&rng->lock);
	ret = exynos_rng_set_seed(ctx->rng, seed, slen);
	mutex_unlock(&rng->lock);

	clk_disable_unprepare(rng->clk);

	return ret;
}

static int exynos_rng_kcapi_init(struct crypto_tfm *tfm)
{
	struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm);

	ctx->rng = exynos_rng_dev;

	return 0;
}

static struct rng_alg exynos_rng_alg = {
	.generate		= exynos_rng_generate,
	.seed			= exynos_rng_seed,
	.seedsize		= EXYNOS_RNG_SEED_SIZE,
	.base			= {
		.cra_name		= "stdrng",
		.cra_driver_name	= "exynos_rng",
		.cra_priority		= 300,
		.cra_ctxsize		= sizeof(struct exynos_rng_ctx),
		.cra_module		= THIS_MODULE,
		.cra_init		= exynos_rng_kcapi_init,
	}
};

static int exynos_rng_probe(struct platform_device *pdev)
{
	struct exynos_rng_dev *rng;
	int ret;

	if (exynos_rng_dev)
		return -EEXIST;

	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
	if (!rng)
		return -ENOMEM;

	rng->type = (enum exynos_prng_type)of_device_get_match_data(&pdev->dev);

	mutex_init(&rng->lock);

	rng->dev = &pdev->dev;
	rng->clk = devm_clk_get(&pdev->dev, "secss");
	if (IS_ERR(rng->clk)) {
		dev_err(&pdev->dev, "Couldn't get clock.\n");
		return PTR_ERR(rng->clk);
	}

	rng->mem = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(rng->mem))
		return PTR_ERR(rng->mem);

	platform_set_drvdata(pdev, rng);

	exynos_rng_dev = rng;

	ret = crypto_register_rng(&exynos_rng_alg);
	if (ret) {
		dev_err(&pdev->dev,
			"Couldn't register rng crypto alg: %d\n", ret);
		exynos_rng_dev = NULL;
	}

	return ret;
}

static int exynos_rng_remove(struct platform_device *pdev)
{
	crypto_unregister_rng(&exynos_rng_alg);

	exynos_rng_dev = NULL;

	return 0;
}

static int __maybe_unused exynos_rng_suspend(struct device *dev)
{
	struct exynos_rng_dev *rng = dev_get_drvdata(dev);
	int ret;

	/* If we were never seeded then after resume it will be the same */
	if (!rng->last_seeding)
		return 0;

	rng->seed_save_len = 0;
	ret = clk_prepare_enable(rng->clk);
	if (ret)
		return ret;

	mutex_lock(&rng->lock);

	/* Get new random numbers and store them for seeding on resume. */
	exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save),
			      &(rng->seed_save_len));

	mutex_unlock(&rng->lock);

	dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n",
		rng->seed_save_len);

	clk_disable_unprepare(rng->clk);

	return 0;
}

static int __maybe_unused exynos_rng_resume(struct device *dev)
{
	struct exynos_rng_dev *rng = dev_get_drvdata(dev);
	int ret;

	/* Never seeded so nothing to do */
	if (!rng->last_seeding)
		return 0;

	ret = clk_prepare_enable(rng->clk);
	if (ret)
		return ret;

	mutex_lock(&rng->lock);

	ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len);

	mutex_unlock(&rng->lock);

	clk_disable_unprepare(rng->clk);

	return ret;
}

static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend,
			 exynos_rng_resume);

static const struct of_device_id exynos_rng_dt_match[] = {
	{
		.compatible = "samsung,exynos4-rng",
		.data = (const void *)EXYNOS_PRNG_EXYNOS4,
	}, {
		.compatible = "samsung,exynos5250-prng",
		.data = (const void *)EXYNOS_PRNG_EXYNOS5,
	},
	{ },
};
MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);

static struct platform_driver exynos_rng_driver = {
	.driver		= {
		.name	= "exynos-rng",
		.pm	= &exynos_rng_pm_ops,
		.of_match_table = exynos_rng_dt_match,
	},
	.probe		= exynos_rng_probe,
	.remove		= exynos_rng_remove,
};

module_platform_driver(exynos_rng_driver);

MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver");
MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>");
MODULE_LICENSE("GPL v2");