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// SPDX-License-Identifier: GPL-2.0-only
/*
* PIC32 RNG driver
*
* Joshua Henderson <joshua.henderson@microchip.com>
* Copyright (C) 2016 Microchip Technology Inc. All rights reserved.
*/
#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/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#define RNGCON 0x04
#define TRNGEN BIT(8)
#define TRNGMOD BIT(11)
#define RNGSEED1 0x18
#define RNGSEED2 0x1C
#define RNGRCNT 0x20
#define RCNT_MASK 0x7F
struct pic32_rng {
void __iomem *base;
struct hwrng rng;
};
/*
* 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_init(struct hwrng *rng)
{
struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
/* enable TRNG in enhanced mode */
writel(TRNGEN | TRNGMOD, priv->base + RNGCON);
return 0;
}
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;
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 void pic32_rng_cleanup(struct hwrng *rng)
{
struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
writel(0, priv->base + RNGCON);
}
static int pic32_rng_probe(struct platform_device *pdev)
{
struct pic32_rng *priv;
struct clk *clk;
priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(priv->base))
return PTR_ERR(priv->base);
clk = devm_clk_get_enabled(&pdev->dev, NULL);
if (IS_ERR(clk))
return PTR_ERR(clk);
priv->rng.name = pdev->name;
priv->rng.init = pic32_rng_init;
priv->rng.read = pic32_rng_read;
priv->rng.cleanup = pic32_rng_cleanup;
return devm_hwrng_register(&pdev->dev, &priv->rng);
}
static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
{ .compatible = "microchip,pic32mzda-rng", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
static struct platform_driver pic32_rng_driver = {
.probe = pic32_rng_probe,
.driver = {
.name = "pic32-rng",
.of_match_table = 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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