1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Nomadik RNG support
4 * Copyright 2009 Alessandro Rubini
5 */
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
nmk_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)16 static 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 read
23 * 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 */
30 static struct hwrng nmk_rng = {
31 .name = "nomadik",
32 .read = nmk_rng_read,
33 };
34
nmk_rng_probe(struct amba_device * dev,const struct amba_id * id)35 static 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
59 out_release:
60 amba_release_regions(dev);
61 return ret;
62 }
63
nmk_rng_remove(struct amba_device * dev)64 static void nmk_rng_remove(struct amba_device *dev)
65 {
66 amba_release_regions(dev);
67 }
68
69 static 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
77 MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
78
79 static struct amba_driver nmk_rng_driver = {
80 .drv = {
81 .owner = THIS_MODULE,
82 .name = "rng",
83 },
84 .probe = nmk_rng_probe,
85 .remove = nmk_rng_remove,
86 .id_table = nmk_rng_ids,
87 };
88
89 module_amba_driver(nmk_rng_driver);
90
91 MODULE_LICENSE("GPL");
92