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