diff options
Diffstat (limited to '')
-rw-r--r-- | drivers/crypto/exynos-rng.c | 403 |
1 files changed, 403 insertions, 0 deletions
diff --git a/drivers/crypto/exynos-rng.c b/drivers/crypto/exynos-rng.c new file mode 100644 index 000000000..2cfabb99c --- /dev/null +++ b/drivers/crypto/exynos-rng.c @@ -0,0 +1,403 @@ +// 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; + struct resource *res; + 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); + } + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + rng->mem = devm_ioremap_resource(&pdev->dev, res); + 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"); |