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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Nomadik RNG support4 * Copyright 2009 Alessandro Rubini5 */6 7#include <linux/kernel.h>8#include <linux/module.h>9#include <linux/device.h>10#include <linux/amba/bus.h>11#include <linux/hw_random.h>12#include <linux/io.h>13#include <linux/clk.h>14#include <linux/err.h>15 16static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)17{18 void __iomem *base = (void __iomem *)rng->priv;19 20 /*21 * The register is 32 bits and gives 16 random bits (low half).22 * A subsequent read will delay the core for 400ns, so we just read23 * once and accept the very unlikely very small delay, even if wait==0.24 */25 *(u16 *)data = __raw_readl(base + 8) & 0xffff;26 return 2;27}28 29/* we have at most one RNG per machine, granted */30static struct hwrng nmk_rng = {31 .name = "nomadik",32 .read = nmk_rng_read,33};34 35static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)36{37 struct clk *rng_clk;38 void __iomem *base;39 int ret;40 41 rng_clk = devm_clk_get_enabled(&dev->dev, NULL);42 if (IS_ERR(rng_clk))43 return dev_err_probe(&dev->dev, PTR_ERR(rng_clk), "could not get rng clock\n");44 45 ret = amba_request_regions(dev, dev->dev.init_name);46 if (ret)47 return ret;48 ret = -ENOMEM;49 base = devm_ioremap(&dev->dev, dev->res.start,50 resource_size(&dev->res));51 if (!base)52 goto out_release;53 nmk_rng.priv = (unsigned long)base;54 ret = devm_hwrng_register(&dev->dev, &nmk_rng);55 if (ret)56 goto out_release;57 return 0;58 59out_release:60 amba_release_regions(dev);61 return ret;62}63 64static void nmk_rng_remove(struct amba_device *dev)65{66 amba_release_regions(dev);67}68 69static const struct amba_id nmk_rng_ids[] = {70 {71 .id = 0x000805e1,72 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */73 },74 {0, 0},75};76 77MODULE_DEVICE_TABLE(amba, nmk_rng_ids);78 79static struct amba_driver nmk_rng_driver = {80 .drv = {81 .name = "rng",82 },83 .probe = nmk_rng_probe,84 .remove = nmk_rng_remove,85 .id_table = nmk_rng_ids,86};87 88module_amba_driver(nmk_rng_driver);89 90MODULE_DESCRIPTION("ST-Ericsson Nomadik Random Number Generator");91MODULE_LICENSE("GPL");92