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/*
* Copyright (c) 2010-2011 Picochip Ltd., Jamie Iles
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* All enquiries to support@picochip.com
*/
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#define DATA_REG_OFFSET 0x0200
#define CSR_REG_OFFSET 0x0278
#define CSR_OUT_EMPTY_MASK (1 << 24)
#define CSR_FAULT_MASK (1 << 1)
#define TRNG_BLOCK_RESET_MASK (1 << 0)
#define TAI_REG_OFFSET 0x0380
/*
* The maximum amount of time in microseconds to spend waiting for data if the
* core wants us to wait. The TRNG should generate 32 bits every 320ns so a
* timeout of 20us seems reasonable. The TRNG does builtin tests of the data
* for randomness so we can't always assume there is data present.
*/
#define PICO_TRNG_TIMEOUT 20
static void __iomem *rng_base;
static struct clk *rng_clk;
static struct device *rng_dev;
static inline u32 picoxcell_trng_read_csr(void)
{
return __raw_readl(rng_base + CSR_REG_OFFSET);
}
static inline bool picoxcell_trng_is_empty(void)
{
return picoxcell_trng_read_csr() & CSR_OUT_EMPTY_MASK;
}
/*
* Take the random number generator out of reset and make sure the interrupts
* are masked. We shouldn't need to get large amounts of random bytes so just
* poll the status register. The hardware generates 32 bits every 320ns so we
* shouldn't have to wait long enough to warrant waiting for an IRQ.
*/
static void picoxcell_trng_start(void)
{
__raw_writel(0, rng_base + TAI_REG_OFFSET);
__raw_writel(0, rng_base + CSR_REG_OFFSET);
}
static void picoxcell_trng_reset(void)
{
__raw_writel(TRNG_BLOCK_RESET_MASK, rng_base + CSR_REG_OFFSET);
__raw_writel(TRNG_BLOCK_RESET_MASK, rng_base + TAI_REG_OFFSET);
picoxcell_trng_start();
}
/*
* Get some random data from the random number generator. The hw_random core
* layer provides us with locking.
*/
static int picoxcell_trng_read(struct hwrng *rng, void *buf, size_t max,
bool wait)
{
int i;
/* Wait for some data to become available. */
for (i = 0; i < PICO_TRNG_TIMEOUT && picoxcell_trng_is_empty(); ++i) {
if (!wait)
return 0;
udelay(1);
}
if (picoxcell_trng_read_csr() & CSR_FAULT_MASK) {
dev_err(rng_dev, "fault detected, resetting TRNG\n");
picoxcell_trng_reset();
return -EIO;
}
if (i == PICO_TRNG_TIMEOUT)
return 0;
*(u32 *)buf = __raw_readl(rng_base + DATA_REG_OFFSET);
return sizeof(u32);
}
static struct hwrng picoxcell_trng = {
.name = "picoxcell",
.read = picoxcell_trng_read,
};
static int picoxcell_trng_probe(struct platform_device *pdev)
{
int ret;
struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
rng_base = devm_ioremap_resource(&pdev->dev, mem);
if (IS_ERR(rng_base))
return PTR_ERR(rng_base);
rng_clk = clk_get(&pdev->dev, NULL);
if (IS_ERR(rng_clk)) {
dev_warn(&pdev->dev, "no clk\n");
return PTR_ERR(rng_clk);
}
ret = clk_enable(rng_clk);
if (ret) {
dev_warn(&pdev->dev, "unable to enable clk\n");
goto err_enable;
}
picoxcell_trng_start();
ret = hwrng_register(&picoxcell_trng);
if (ret)
goto err_register;
rng_dev = &pdev->dev;
dev_info(&pdev->dev, "pixoxcell random number generator active\n");
return 0;
err_register:
clk_disable(rng_clk);
err_enable:
clk_put(rng_clk);
return ret;
}
static int picoxcell_trng_remove(struct platform_device *pdev)
{
hwrng_unregister(&picoxcell_trng);
clk_disable(rng_clk);
clk_put(rng_clk);
return 0;
}
#ifdef CONFIG_PM
static int picoxcell_trng_suspend(struct device *dev)
{
clk_disable(rng_clk);
return 0;
}
static int picoxcell_trng_resume(struct device *dev)
{
return clk_enable(rng_clk);
}
static const struct dev_pm_ops picoxcell_trng_pm_ops = {
.suspend = picoxcell_trng_suspend,
.resume = picoxcell_trng_resume,
};
#endif /* CONFIG_PM */
static struct platform_driver picoxcell_trng_driver = {
.probe = picoxcell_trng_probe,
.remove = picoxcell_trng_remove,
.driver = {
.name = "picoxcell-trng",
.owner = THIS_MODULE,
#ifdef CONFIG_PM
.pm = &picoxcell_trng_pm_ops,
#endif /* CONFIG_PM */
},
};
module_platform_driver(picoxcell_trng_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jamie Iles");
MODULE_DESCRIPTION("Picochip picoXcell TRNG driver");
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