1 // SPDX-License-Identifier: GPL-2.0-or-later
4 * Copyright 2009 Alessandro Rubini
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>
13 #include <linux/clk.h>
14 #include <linux/err.h>
16 static struct clk *rng_clk;
18 static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
20 void __iomem *base = (void __iomem *)rng->priv;
23 * The register is 32 bits and gives 16 random bits (low half).
24 * A subsequent read will delay the core for 400ns, so we just read
25 * once and accept the very unlikely very small delay, even if wait==0.
27 *(u16 *)data = __raw_readl(base + 8) & 0xffff;
31 /* we have at most one RNG per machine, granted */
32 static struct hwrng nmk_rng = {
37 static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
42 rng_clk = devm_clk_get(&dev->dev, NULL);
43 if (IS_ERR(rng_clk)) {
44 dev_err(&dev->dev, "could not get rng clock\n");
45 ret = PTR_ERR(rng_clk);
49 clk_prepare_enable(rng_clk);
51 ret = amba_request_regions(dev, dev->dev.init_name);
55 base = devm_ioremap(&dev->dev, dev->res.start,
56 resource_size(&dev->res));
59 nmk_rng.priv = (unsigned long)base;
60 ret = devm_hwrng_register(&dev->dev, &nmk_rng);
66 amba_release_regions(dev);
68 clk_disable_unprepare(rng_clk);
72 static void nmk_rng_remove(struct amba_device *dev)
74 amba_release_regions(dev);
75 clk_disable_unprepare(rng_clk);
78 static const struct amba_id nmk_rng_ids[] = {
81 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */
86 MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
88 static struct amba_driver nmk_rng_driver = {
93 .probe = nmk_rng_probe,
94 .remove = nmk_rng_remove,
95 .id_table = nmk_rng_ids,
98 module_amba_driver(nmk_rng_driver);
100 MODULE_LICENSE("GPL");