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 | |
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(addr: 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 | |
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->dev, NULL); |
42 | if (IS_ERR(ptr: rng_clk)) |
43 | return dev_err_probe(dev: &dev->dev, err: PTR_ERR(ptr: rng_clk), fmt: "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, offset: dev->res.start, |
50 | size: resource_size(res: &dev->res)); |
51 | if (!base) |
52 | goto out_release; |
53 | nmk_rng.priv = (unsigned long)base; |
54 | ret = devm_hwrng_register(dev: &dev->dev, rng: &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 | |
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_DESCRIPTION("ST-Ericsson Nomadik Random Number Generator" ); |
92 | MODULE_LICENSE("GPL" ); |
93 | |