1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-or-later
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Nomadik RNG support
4*4882a593Smuzhiyun * Copyright 2009 Alessandro Rubini
5*4882a593Smuzhiyun */
6*4882a593Smuzhiyun
7*4882a593Smuzhiyun #include <linux/kernel.h>
8*4882a593Smuzhiyun #include <linux/module.h>
9*4882a593Smuzhiyun #include <linux/device.h>
10*4882a593Smuzhiyun #include <linux/amba/bus.h>
11*4882a593Smuzhiyun #include <linux/hw_random.h>
12*4882a593Smuzhiyun #include <linux/io.h>
13*4882a593Smuzhiyun #include <linux/clk.h>
14*4882a593Smuzhiyun #include <linux/err.h>
15*4882a593Smuzhiyun
16*4882a593Smuzhiyun static struct clk *rng_clk;
17*4882a593Smuzhiyun
nmk_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)18*4882a593Smuzhiyun static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
19*4882a593Smuzhiyun {
20*4882a593Smuzhiyun void __iomem *base = (void __iomem *)rng->priv;
21*4882a593Smuzhiyun
22*4882a593Smuzhiyun /*
23*4882a593Smuzhiyun * The register is 32 bits and gives 16 random bits (low half).
24*4882a593Smuzhiyun * A subsequent read will delay the core for 400ns, so we just read
25*4882a593Smuzhiyun * once and accept the very unlikely very small delay, even if wait==0.
26*4882a593Smuzhiyun */
27*4882a593Smuzhiyun *(u16 *)data = __raw_readl(base + 8) & 0xffff;
28*4882a593Smuzhiyun return 2;
29*4882a593Smuzhiyun }
30*4882a593Smuzhiyun
31*4882a593Smuzhiyun /* we have at most one RNG per machine, granted */
32*4882a593Smuzhiyun static struct hwrng nmk_rng = {
33*4882a593Smuzhiyun .name = "nomadik",
34*4882a593Smuzhiyun .read = nmk_rng_read,
35*4882a593Smuzhiyun };
36*4882a593Smuzhiyun
nmk_rng_probe(struct amba_device * dev,const struct amba_id * id)37*4882a593Smuzhiyun static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
38*4882a593Smuzhiyun {
39*4882a593Smuzhiyun void __iomem *base;
40*4882a593Smuzhiyun int ret;
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun rng_clk = devm_clk_get(&dev->dev, NULL);
43*4882a593Smuzhiyun if (IS_ERR(rng_clk)) {
44*4882a593Smuzhiyun dev_err(&dev->dev, "could not get rng clock\n");
45*4882a593Smuzhiyun ret = PTR_ERR(rng_clk);
46*4882a593Smuzhiyun return ret;
47*4882a593Smuzhiyun }
48*4882a593Smuzhiyun
49*4882a593Smuzhiyun clk_prepare_enable(rng_clk);
50*4882a593Smuzhiyun
51*4882a593Smuzhiyun ret = amba_request_regions(dev, dev->dev.init_name);
52*4882a593Smuzhiyun if (ret)
53*4882a593Smuzhiyun goto out_clk;
54*4882a593Smuzhiyun ret = -ENOMEM;
55*4882a593Smuzhiyun base = devm_ioremap(&dev->dev, dev->res.start,
56*4882a593Smuzhiyun resource_size(&dev->res));
57*4882a593Smuzhiyun if (!base)
58*4882a593Smuzhiyun goto out_release;
59*4882a593Smuzhiyun nmk_rng.priv = (unsigned long)base;
60*4882a593Smuzhiyun ret = devm_hwrng_register(&dev->dev, &nmk_rng);
61*4882a593Smuzhiyun if (ret)
62*4882a593Smuzhiyun goto out_release;
63*4882a593Smuzhiyun return 0;
64*4882a593Smuzhiyun
65*4882a593Smuzhiyun out_release:
66*4882a593Smuzhiyun amba_release_regions(dev);
67*4882a593Smuzhiyun out_clk:
68*4882a593Smuzhiyun clk_disable_unprepare(rng_clk);
69*4882a593Smuzhiyun return ret;
70*4882a593Smuzhiyun }
71*4882a593Smuzhiyun
nmk_rng_remove(struct amba_device * dev)72*4882a593Smuzhiyun static void nmk_rng_remove(struct amba_device *dev)
73*4882a593Smuzhiyun {
74*4882a593Smuzhiyun amba_release_regions(dev);
75*4882a593Smuzhiyun clk_disable_unprepare(rng_clk);
76*4882a593Smuzhiyun }
77*4882a593Smuzhiyun
78*4882a593Smuzhiyun static const struct amba_id nmk_rng_ids[] = {
79*4882a593Smuzhiyun {
80*4882a593Smuzhiyun .id = 0x000805e1,
81*4882a593Smuzhiyun .mask = 0x000fffff, /* top bits are rev and cfg: accept all */
82*4882a593Smuzhiyun },
83*4882a593Smuzhiyun {0, 0},
84*4882a593Smuzhiyun };
85*4882a593Smuzhiyun
86*4882a593Smuzhiyun MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun static struct amba_driver nmk_rng_driver = {
89*4882a593Smuzhiyun .drv = {
90*4882a593Smuzhiyun .owner = THIS_MODULE,
91*4882a593Smuzhiyun .name = "rng",
92*4882a593Smuzhiyun },
93*4882a593Smuzhiyun .probe = nmk_rng_probe,
94*4882a593Smuzhiyun .remove = nmk_rng_remove,
95*4882a593Smuzhiyun .id_table = nmk_rng_ids,
96*4882a593Smuzhiyun };
97*4882a593Smuzhiyun
98*4882a593Smuzhiyun module_amba_driver(nmk_rng_driver);
99*4882a593Smuzhiyun
100*4882a593Smuzhiyun MODULE_LICENSE("GPL");
101