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// 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");