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// SPDX-License-Identifier: GPL-2.0
/*
* RNG driver for Exynos TRNGs
*
* Author: Łukasz Stelmach <l.stelmach@samsung.com>
*
* Copyright 2017 (c) Samsung Electronics Software, Inc.
*
* Based on the Exynos PRNG driver drivers/crypto/exynos-rng by
* Krzysztof Kozłowski <krzk@kernel.org>
*/
#include <linux/clk.h>
#include <linux/crypto.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#define EXYNOS_TRNG_CLKDIV (0x0)
#define EXYNOS_TRNG_CTRL (0x20)
#define EXYNOS_TRNG_CTRL_RNGEN BIT(31)
#define EXYNOS_TRNG_POST_CTRL (0x30)
#define EXYNOS_TRNG_ONLINE_CTRL (0x40)
#define EXYNOS_TRNG_ONLINE_STAT (0x44)
#define EXYNOS_TRNG_ONLINE_MAXCHI2 (0x48)
#define EXYNOS_TRNG_FIFO_CTRL (0x50)
#define EXYNOS_TRNG_FIFO_0 (0x80)
#define EXYNOS_TRNG_FIFO_1 (0x84)
#define EXYNOS_TRNG_FIFO_2 (0x88)
#define EXYNOS_TRNG_FIFO_3 (0x8c)
#define EXYNOS_TRNG_FIFO_4 (0x90)
#define EXYNOS_TRNG_FIFO_5 (0x94)
#define EXYNOS_TRNG_FIFO_6 (0x98)
#define EXYNOS_TRNG_FIFO_7 (0x9c)
#define EXYNOS_TRNG_FIFO_LEN (8)
#define EXYNOS_TRNG_CLOCK_RATE (500000)
struct exynos_trng_dev {
struct device *dev;
void __iomem *mem;
struct clk *clk;
struct hwrng rng;
};
static int exynos_trng_do_read(struct hwrng *rng, void *data, size_t max,
bool wait)
{
struct exynos_trng_dev *trng;
int val;
max = min_t(size_t, max, (EXYNOS_TRNG_FIFO_LEN * 4));
trng = (struct exynos_trng_dev *)rng->priv;
writel_relaxed(max * 8, trng->mem + EXYNOS_TRNG_FIFO_CTRL);
val = readl_poll_timeout(trng->mem + EXYNOS_TRNG_FIFO_CTRL, val,
val == 0, 200, 1000000);
if (val < 0)
return val;
memcpy_fromio(data, trng->mem + EXYNOS_TRNG_FIFO_0, max);
return max;
}
static int exynos_trng_init(struct hwrng *rng)
{
struct exynos_trng_dev *trng = (struct exynos_trng_dev *)rng->priv;
unsigned long sss_rate;
u32 val;
sss_rate = clk_get_rate(trng->clk);
/*
* For most TRNG circuits the clock frequency of under 500 kHz
* is safe.
*/
val = sss_rate / (EXYNOS_TRNG_CLOCK_RATE * 2);
if (val > 0x7fff) {
dev_err(trng->dev, "clock divider too large: %d", val);
return -ERANGE;
}
val = val << 1;
writel_relaxed(val, trng->mem + EXYNOS_TRNG_CLKDIV);
/* Enable the generator. */
val = EXYNOS_TRNG_CTRL_RNGEN;
writel_relaxed(val, trng->mem + EXYNOS_TRNG_CTRL);
/*
* Disable post-processing. /dev/hwrng is supposed to deliver
* unprocessed data.
*/
writel_relaxed(0, trng->mem + EXYNOS_TRNG_POST_CTRL);
return 0;
}
static int exynos_trng_probe(struct platform_device *pdev)
{
struct exynos_trng_dev *trng;
struct resource *res;
int ret = -ENOMEM;
trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
if (!trng)
return ret;
trng->rng.name = devm_kstrdup(&pdev->dev, dev_name(&pdev->dev),
GFP_KERNEL);
if (!trng->rng.name)
return ret;
trng->rng.init = exynos_trng_init;
trng->rng.read = exynos_trng_do_read;
trng->rng.priv = (unsigned long) trng;
platform_set_drvdata(pdev, trng);
trng->dev = &pdev->dev;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
trng->mem = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(trng->mem))
return PTR_ERR(trng->mem);
pm_runtime_enable(&pdev->dev);
ret = pm_runtime_get_sync(&pdev->dev);
if (ret < 0) {
dev_err(&pdev->dev, "Could not get runtime PM.\n");
goto err_pm_get;
}
trng->clk = devm_clk_get(&pdev->dev, "secss");
if (IS_ERR(trng->clk)) {
ret = PTR_ERR(trng->clk);
dev_err(&pdev->dev, "Could not get clock.\n");
goto err_clock;
}
ret = clk_prepare_enable(trng->clk);
if (ret) {
dev_err(&pdev->dev, "Could not enable the clk.\n");
goto err_clock;
}
ret = hwrng_register(&trng->rng);
if (ret) {
dev_err(&pdev->dev, "Could not register hwrng device.\n");
goto err_register;
}
dev_info(&pdev->dev, "Exynos True Random Number Generator.\n");
return 0;
err_register:
clk_disable_unprepare(trng->clk);
err_clock:
pm_runtime_put_sync(&pdev->dev);
err_pm_get:
pm_runtime_disable(&pdev->dev);
return ret;
}
static int exynos_trng_remove(struct platform_device *pdev)
{
struct exynos_trng_dev *trng = platform_get_drvdata(pdev);
hwrng_unregister(&trng->rng);
clk_disable_unprepare(trng->clk);
pm_runtime_put_sync(&pdev->dev);
pm_runtime_disable(&pdev->dev);
return 0;
}
static int __maybe_unused exynos_trng_suspend(struct device *dev)
{
pm_runtime_put_sync(dev);
return 0;
}
static int __maybe_unused exynos_trng_resume(struct device *dev)
{
int ret;
ret = pm_runtime_get_sync(dev);
if (ret < 0) {
dev_err(dev, "Could not get runtime PM.\n");
pm_runtime_put_noidle(dev);
return ret;
}
return 0;
}
static SIMPLE_DEV_PM_OPS(exynos_trng_pm_ops, exynos_trng_suspend,
exynos_trng_resume);
static const struct of_device_id exynos_trng_dt_match[] = {
{
.compatible = "samsung,exynos5250-trng",
},
{ },
};
MODULE_DEVICE_TABLE(of, exynos_trng_dt_match);
static struct platform_driver exynos_trng_driver = {
.driver = {
.name = "exynos-trng",
.pm = &exynos_trng_pm_ops,
.of_match_table = exynos_trng_dt_match,
},
.probe = exynos_trng_probe,
.remove = exynos_trng_remove,
};
module_platform_driver(exynos_trng_driver);
MODULE_AUTHOR("Łukasz Stelmach");
MODULE_DESCRIPTION("H/W TRNG driver for Exynos chips");
MODULE_LICENSE("GPL v2");
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