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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Nomadik RNG support
* Copyright 2009 Alessandro Rubini
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/amba/bus.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
static struct clk *rng_clk;
static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
{
void __iomem *base = (void __iomem *)rng->priv;
/*
* The register is 32 bits and gives 16 random bits (low half).
* A subsequent read will delay the core for 400ns, so we just read
* once and accept the very unlikely very small delay, even if wait==0.
*/
*(u16 *)data = __raw_readl(base + 8) & 0xffff;
return 2;
}
/* we have at most one RNG per machine, granted */
static struct hwrng nmk_rng = {
.name = "nomadik",
.read = nmk_rng_read,
};
static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
{
void __iomem *base;
int ret;
rng_clk = devm_clk_get(&dev->dev, NULL);
if (IS_ERR(rng_clk)) {
dev_err(&dev->dev, "could not get rng clock\n");
ret = PTR_ERR(rng_clk);
return ret;
}
clk_prepare_enable(rng_clk);
ret = amba_request_regions(dev, dev->dev.init_name);
if (ret)
goto out_clk;
ret = -ENOMEM;
base = devm_ioremap(&dev->dev, dev->res.start,
resource_size(&dev->res));
if (!base)
goto out_release;
nmk_rng.priv = (unsigned long)base;
ret = hwrng_register(&nmk_rng);
if (ret)
goto out_release;
return 0;
out_release:
amba_release_regions(dev);
out_clk:
clk_disable(rng_clk);
return ret;
}
static int nmk_rng_remove(struct amba_device *dev)
{
hwrng_unregister(&nmk_rng);
amba_release_regions(dev);
clk_disable(rng_clk);
return 0;
}
static struct amba_id nmk_rng_ids[] = {
{
.id = 0x000805e1,
.mask = 0x000fffff, /* top bits are rev and cfg: accept all */
},
{0, 0},
};
MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
static struct amba_driver nmk_rng_driver = {
.drv = {
.owner = THIS_MODULE,
.name = "rng",
},
.probe = nmk_rng_probe,
.remove = nmk_rng_remove,
.id_table = nmk_rng_ids,
};
module_amba_driver(nmk_rng_driver);
MODULE_LICENSE("GPL");
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