drivers/crypto/exynos-rng.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * exynos-rng.c - Random Number Generator driver for the Exynos
0004  *
0005  * Copyright (c) 2017 Krzysztof Kozlowski <krzk@kernel.org>
0006  *
0007  * Loosely based on old driver from drivers/char/hw_random/exynos-rng.c:
0008  * Copyright (C) 2012 Samsung Electronics
0009  * Jonghwa Lee <jonghwa3.lee@samsung.com>
0010  */
0011
0012 #include <linux/clk.h>
0013 #include <linux/crypto.h>
0014 #include <linux/err.h>
0015 #include <linux/io.h>
0016 #include <linux/module.h>
0017 #include <linux/mutex.h>
0018 #include <linux/of_device.h>
0019 #include <linux/platform_device.h>
0020
0021 #include <crypto/internal/rng.h>
0022
0023 #define EXYNOS_RNG_CONTROL      0x0
0024 #define EXYNOS_RNG_STATUS       0x10
0025
0026 #define EXYNOS_RNG_SEED_CONF        0x14
0027 #define EXYNOS_RNG_GEN_PRNG         BIT(1)
0028
0029 #define EXYNOS_RNG_SEED_BASE        0x140
0030 #define EXYNOS_RNG_SEED(n)      (EXYNOS_RNG_SEED_BASE + (n * 0x4))
0031 #define EXYNOS_RNG_OUT_BASE     0x160
0032 #define EXYNOS_RNG_OUT(n)       (EXYNOS_RNG_OUT_BASE + (n * 0x4))
0033
0034 /* EXYNOS_RNG_CONTROL bit fields */
0035 #define EXYNOS_RNG_CONTROL_START    0x18
0036 /* EXYNOS_RNG_STATUS bit fields */
0037 #define EXYNOS_RNG_STATUS_SEED_SETTING_DONE BIT(1)
0038 #define EXYNOS_RNG_STATUS_RNG_DONE      BIT(5)
0039
0040 /* Five seed and output registers, each 4 bytes */
0041 #define EXYNOS_RNG_SEED_REGS        5
0042 #define EXYNOS_RNG_SEED_SIZE        (EXYNOS_RNG_SEED_REGS * 4)
0043
0044 enum exynos_prng_type {
0045     EXYNOS_PRNG_UNKNOWN = 0,
0046     EXYNOS_PRNG_EXYNOS4,
0047     EXYNOS_PRNG_EXYNOS5,
0048 };
0049
0050 /*
0051  * Driver re-seeds itself with generated random numbers to hinder
0052  * backtracking of the original seed.
0053  *
0054  * Time for next re-seed in ms.
0055  */
0056 #define EXYNOS_RNG_RESEED_TIME      1000
0057 #define EXYNOS_RNG_RESEED_BYTES     65536
0058
0059 /*
0060  * In polling mode, do not wait infinitely for the engine to finish the work.
0061  */
0062 #define EXYNOS_RNG_WAIT_RETRIES     100
0063
0064 /* Context for crypto */
0065 struct exynos_rng_ctx {
0066     struct exynos_rng_dev       *rng;
0067 };
0068
0069 /* Device associated memory */
0070 struct exynos_rng_dev {
0071     struct device           *dev;
0072     enum exynos_prng_type       type;
0073     void __iomem            *mem;
0074     struct clk          *clk;
0075     struct mutex            lock;
0076     /* Generated numbers stored for seeding during resume */
0077     u8              seed_save[EXYNOS_RNG_SEED_SIZE];
0078     unsigned int            seed_save_len;
0079     /* Time of last seeding in jiffies */
0080     unsigned long           last_seeding;
0081     /* Bytes generated since last seeding */
0082     unsigned long           bytes_seeding;
0083 };
0084
0085 static struct exynos_rng_dev *exynos_rng_dev;
0086
0087 static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset)
0088 {
0089     return readl_relaxed(rng->mem + offset);
0090 }
0091
0092 static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset)
0093 {
0094     writel_relaxed(val, rng->mem + offset);
0095 }
0096
0097 static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
0098                    const u8 *seed, unsigned int slen)
0099 {
0100     u32 val;
0101     int i;
0102
0103     /* Round seed length because loop iterates over full register size */
0104     slen = ALIGN_DOWN(slen, 4);
0105
0106     if (slen < EXYNOS_RNG_SEED_SIZE)
0107         return -EINVAL;
0108
0109     for (i = 0; i < slen ; i += 4) {
0110         unsigned int seed_reg = (i / 4) % EXYNOS_RNG_SEED_REGS;
0111
0112         val = seed[i] << 24;
0113         val |= seed[i + 1] << 16;
0114         val |= seed[i + 2] << 8;
0115         val |= seed[i + 3] << 0;
0116
0117         exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(seed_reg));
0118     }
0119
0120     val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
0121     if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
0122         dev_warn(rng->dev, "Seed setting not finished\n");
0123         return -EIO;
0124     }
0125
0126     rng->last_seeding = jiffies;
0127     rng->bytes_seeding = 0;
0128
0129     return 0;
0130 }
0131
0132 /*
0133  * Start the engine and poll for finish.  Then read from output registers
0134  * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated
0135  * random data (EXYNOS_RNG_SEED_SIZE).
0136  *
0137  * On success: return 0 and store number of read bytes under 'read' address.
0138  * On error: return -ERRNO.
0139  */
0140 static int exynos_rng_get_random(struct exynos_rng_dev *rng,
0141                  u8 *dst, unsigned int dlen,
0142                  unsigned int *read)
0143 {
0144     int retry = EXYNOS_RNG_WAIT_RETRIES;
0145
0146     if (rng->type == EXYNOS_PRNG_EXYNOS4) {
0147         exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
0148                   EXYNOS_RNG_CONTROL);
0149     } else if (rng->type == EXYNOS_PRNG_EXYNOS5) {
0150         exynos_rng_writel(rng, EXYNOS_RNG_GEN_PRNG,
0151                   EXYNOS_RNG_SEED_CONF);
0152     }
0153
0154     while (!(exynos_rng_readl(rng,
0155             EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
0156         cpu_relax();
0157
0158     if (!retry)
0159         return -ETIMEDOUT;
0160
0161     /* Clear status bit */
0162     exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE,
0163               EXYNOS_RNG_STATUS);
0164     *read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE);
0165     memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read);
0166     rng->bytes_seeding += *read;
0167
0168     return 0;
0169 }
0170
0171 /* Re-seed itself from time to time */
0172 static void exynos_rng_reseed(struct exynos_rng_dev *rng)
0173 {
0174     unsigned long next_seeding = rng->last_seeding + \
0175                      msecs_to_jiffies(EXYNOS_RNG_RESEED_TIME);
0176     unsigned long now = jiffies;
0177     unsigned int read = 0;
0178     u8 seed[EXYNOS_RNG_SEED_SIZE];
0179
0180     if (time_before(now, next_seeding) &&
0181         rng->bytes_seeding < EXYNOS_RNG_RESEED_BYTES)
0182         return;
0183
0184     if (exynos_rng_get_random(rng, seed, sizeof(seed), &read))
0185         return;
0186
0187     exynos_rng_set_seed(rng, seed, read);
0188
0189     /* Let others do some of their job. */
0190     mutex_unlock(&rng->lock);
0191     mutex_lock(&rng->lock);
0192 }
0193
0194 static int exynos_rng_generate(struct crypto_rng *tfm,
0195                    const u8 *src, unsigned int slen,
0196                    u8 *dst, unsigned int dlen)
0197 {
0198     struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
0199     struct exynos_rng_dev *rng = ctx->rng;
0200     unsigned int read = 0;
0201     int ret;
0202
0203     ret = clk_prepare_enable(rng->clk);
0204     if (ret)
0205         return ret;
0206
0207     mutex_lock(&rng->lock);
0208     do {
0209         ret = exynos_rng_get_random(rng, dst, dlen, &read);
0210         if (ret)
0211             break;
0212
0213         dlen -= read;
0214         dst += read;
0215
0216         exynos_rng_reseed(rng);
0217     } while (dlen > 0);
0218     mutex_unlock(&rng->lock);
0219
0220     clk_disable_unprepare(rng->clk);
0221
0222     return ret;
0223 }
0224
0225 static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed,
0226                unsigned int slen)
0227 {
0228     struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
0229     struct exynos_rng_dev *rng = ctx->rng;
0230     int ret;
0231
0232     ret = clk_prepare_enable(rng->clk);
0233     if (ret)
0234         return ret;
0235
0236     mutex_lock(&rng->lock);
0237     ret = exynos_rng_set_seed(ctx->rng, seed, slen);
0238     mutex_unlock(&rng->lock);
0239
0240     clk_disable_unprepare(rng->clk);
0241
0242     return ret;
0243 }
0244
0245 static int exynos_rng_kcapi_init(struct crypto_tfm *tfm)
0246 {
0247     struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm);
0248
0249     ctx->rng = exynos_rng_dev;
0250
0251     return 0;
0252 }
0253
0254 static struct rng_alg exynos_rng_alg = {
0255     .generate       = exynos_rng_generate,
0256     .seed           = exynos_rng_seed,
0257     .seedsize       = EXYNOS_RNG_SEED_SIZE,
0258     .base           = {
0259         .cra_name       = "stdrng",
0260         .cra_driver_name    = "exynos_rng",
0261         .cra_priority       = 300,
0262         .cra_ctxsize        = sizeof(struct exynos_rng_ctx),
0263         .cra_module     = THIS_MODULE,
0264         .cra_init       = exynos_rng_kcapi_init,
0265     }
0266 };
0267
0268 static int exynos_rng_probe(struct platform_device *pdev)
0269 {
0270     struct exynos_rng_dev *rng;
0271     int ret;
0272
0273     if (exynos_rng_dev)
0274         return -EEXIST;
0275
0276     rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
0277     if (!rng)
0278         return -ENOMEM;
0279
0280     rng->type = (enum exynos_prng_type)of_device_get_match_data(&pdev->dev);
0281
0282     mutex_init(&rng->lock);
0283
0284     rng->dev = &pdev->dev;
0285     rng->clk = devm_clk_get(&pdev->dev, "secss");
0286     if (IS_ERR(rng->clk)) {
0287         dev_err(&pdev->dev, "Couldn't get clock.\n");
0288         return PTR_ERR(rng->clk);
0289     }
0290
0291     rng->mem = devm_platform_ioremap_resource(pdev, 0);
0292     if (IS_ERR(rng->mem))
0293         return PTR_ERR(rng->mem);
0294
0295     platform_set_drvdata(pdev, rng);
0296
0297     exynos_rng_dev = rng;
0298
0299     ret = crypto_register_rng(&exynos_rng_alg);
0300     if (ret) {
0301         dev_err(&pdev->dev,
0302             "Couldn't register rng crypto alg: %d\n", ret);
0303         exynos_rng_dev = NULL;
0304     }
0305
0306     return ret;
0307 }
0308
0309 static int exynos_rng_remove(struct platform_device *pdev)
0310 {
0311     crypto_unregister_rng(&exynos_rng_alg);
0312
0313     exynos_rng_dev = NULL;
0314
0315     return 0;
0316 }
0317
0318 static int __maybe_unused exynos_rng_suspend(struct device *dev)
0319 {
0320     struct exynos_rng_dev *rng = dev_get_drvdata(dev);
0321     int ret;
0322
0323     /* If we were never seeded then after resume it will be the same */
0324     if (!rng->last_seeding)
0325         return 0;
0326
0327     rng->seed_save_len = 0;
0328     ret = clk_prepare_enable(rng->clk);
0329     if (ret)
0330         return ret;
0331
0332     mutex_lock(&rng->lock);
0333
0334     /* Get new random numbers and store them for seeding on resume. */
0335     exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save),
0336                   &(rng->seed_save_len));
0337
0338     mutex_unlock(&rng->lock);
0339
0340     dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n",
0341         rng->seed_save_len);
0342
0343     clk_disable_unprepare(rng->clk);
0344
0345     return 0;
0346 }
0347
0348 static int __maybe_unused exynos_rng_resume(struct device *dev)
0349 {
0350     struct exynos_rng_dev *rng = dev_get_drvdata(dev);
0351     int ret;
0352
0353     /* Never seeded so nothing to do */
0354     if (!rng->last_seeding)
0355         return 0;
0356
0357     ret = clk_prepare_enable(rng->clk);
0358     if (ret)
0359         return ret;
0360
0361     mutex_lock(&rng->lock);
0362
0363     ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len);
0364
0365     mutex_unlock(&rng->lock);
0366
0367     clk_disable_unprepare(rng->clk);
0368
0369     return ret;
0370 }
0371
0372 static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend,
0373              exynos_rng_resume);
0374
0375 static const struct of_device_id exynos_rng_dt_match[] = {
0376     {
0377         .compatible = "samsung,exynos4-rng",
0378         .data = (const void *)EXYNOS_PRNG_EXYNOS4,
0379     }, {
0380         .compatible = "samsung,exynos5250-prng",
0381         .data = (const void *)EXYNOS_PRNG_EXYNOS5,
0382     },
0383     { },
0384 };
0385 MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);
0386
0387 static struct platform_driver exynos_rng_driver = {
0388     .driver     = {
0389         .name   = "exynos-rng",
0390         .pm = &exynos_rng_pm_ops,
0391         .of_match_table = exynos_rng_dt_match,
0392     },
0393     .probe      = exynos_rng_probe,
0394     .remove     = exynos_rng_remove,
0395 };
0396
0397 module_platform_driver(exynos_rng_driver);
0398
0399 MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver");
0400 MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>");
0401 MODULE_LICENSE("GPL v2");