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/*
* PIC32 RNG driver
*
* Joshua Henderson <joshua.henderson@microchip.com>
* Copyright (C) 2016 Microchip Technology Inc. All rights reserved.
*
* This program is free software; you can distribute it and/or modify it
* under the terms of the GNU General Public License (Version 2) as
* published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*/
#include <linux/clk.h>
#include <linux/clkdev.h>
#include <linux/err.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#define RNGCON 0x04
#define TRNGEN BIT(8)
#define PRNGEN BIT(9)
#define PRNGCONT BIT(10)
#define TRNGMOD BIT(11)
#define SEEDLOAD BIT(12)
#define RNGPOLY1 0x08
#define RNGPOLY2 0x0C
#define RNGNUMGEN1 0x10
#define RNGNUMGEN2 0x14
#define RNGSEED1 0x18
#define RNGSEED2 0x1C
#define RNGRCNT 0x20
#define RCNT_MASK 0x7F
struct pic32_rng {
void __iomem *base;
struct hwrng rng;
struct clk *clk;
};
/*
* The TRNG can generate up to 24Mbps. This is a timeout that should be safe
* enough given the instructions in the loop and that the TRNG may not always
* be at maximum rate.
*/
#define RNG_TIMEOUT 500
static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max,
bool wait)
{
struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
u64 *data = buf;
u32 t;
unsigned int timeout = RNG_TIMEOUT;
if (max < 8)
return 0;
do {
t = readl(priv->base + RNGRCNT) & RCNT_MASK;
if (t == 64) {
/* TRNG value comes through the seed registers */
*data = ((u64)readl(priv->base + RNGSEED2) << 32) +
readl(priv->base + RNGSEED1);
return 8;
}
} while (wait && --timeout);
return -EIO;
}
static int pic32_rng_probe(struct platform_device *pdev)
{
struct pic32_rng *priv;
struct resource *res;
u32 v;
int ret;
priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
priv->base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(priv->base))
return PTR_ERR(priv->base);
priv->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(priv->clk))
return PTR_ERR(priv->clk);
ret = clk_prepare_enable(priv->clk);
if (ret)
return ret;
/* enable TRNG in enhanced mode */
v = TRNGEN | TRNGMOD;
writel(v, priv->base + RNGCON);
priv->rng.name = pdev->name;
priv->rng.read = pic32_rng_read;
ret = hwrng_register(&priv->rng);
if (ret)
goto err_register;
platform_set_drvdata(pdev, priv);
return 0;
err_register:
clk_disable_unprepare(priv->clk);
return ret;
}
static int pic32_rng_remove(struct platform_device *pdev)
{
struct pic32_rng *rng = platform_get_drvdata(pdev);
hwrng_unregister(&rng->rng);
writel(0, rng->base + RNGCON);
clk_disable_unprepare(rng->clk);
return 0;
}
static const struct of_device_id pic32_rng_of_match[] = {
{ .compatible = "microchip,pic32mzda-rng", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
static struct platform_driver pic32_rng_driver = {
.probe = pic32_rng_probe,
.remove = pic32_rng_remove,
.driver = {
.name = "pic32-rng",
.of_match_table = of_match_ptr(pic32_rng_of_match),
},
};
module_platform_driver(pic32_rng_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
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