Commit | Line | Data |
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bc85b25e AR |
1 | /* |
2 | * Nomadik RNG support | |
3 | * Copyright 2009 Alessandro Rubini | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License as published by | |
7 | * the Free Software Foundation; either version 2 of the License, or | |
8 | * (at your option) any later version. | |
9 | */ | |
10 | ||
11 | #include <linux/kernel.h> | |
12 | #include <linux/module.h> | |
bc85b25e AR |
13 | #include <linux/device.h> |
14 | #include <linux/amba/bus.h> | |
15 | #include <linux/hw_random.h> | |
16 | #include <linux/io.h> | |
1944cc89 SK |
17 | #include <linux/clk.h> |
18 | #include <linux/err.h> | |
19 | ||
20 | static struct clk *rng_clk; | |
bc85b25e AR |
21 | |
22 | static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) | |
23 | { | |
24 | void __iomem *base = (void __iomem *)rng->priv; | |
25 | ||
26 | /* | |
27 | * The register is 32 bits and gives 16 random bits (low half). | |
28 | * A subsequent read will delay the core for 400ns, so we just read | |
29 | * once and accept the very unlikely very small delay, even if wait==0. | |
30 | */ | |
31 | *(u16 *)data = __raw_readl(base + 8) & 0xffff; | |
32 | return 2; | |
33 | } | |
34 | ||
35 | /* we have at most one RNG per machine, granted */ | |
36 | static struct hwrng nmk_rng = { | |
37 | .name = "nomadik", | |
38 | .read = nmk_rng_read, | |
39 | }; | |
40 | ||
aa25afad | 41 | static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id) |
bc85b25e AR |
42 | { |
43 | void __iomem *base; | |
44 | int ret; | |
45 | ||
1655c240 | 46 | rng_clk = devm_clk_get(&dev->dev, NULL); |
1944cc89 SK |
47 | if (IS_ERR(rng_clk)) { |
48 | dev_err(&dev->dev, "could not get rng clock\n"); | |
49 | ret = PTR_ERR(rng_clk); | |
50 | return ret; | |
51 | } | |
52 | ||
beca35d0 | 53 | clk_prepare_enable(rng_clk); |
1944cc89 | 54 | |
bc85b25e AR |
55 | ret = amba_request_regions(dev, dev->dev.init_name); |
56 | if (ret) | |
2725ae17 | 57 | goto out_clk; |
bc85b25e | 58 | ret = -ENOMEM; |
1655c240 JH |
59 | base = devm_ioremap(&dev->dev, dev->res.start, |
60 | resource_size(&dev->res)); | |
bc85b25e AR |
61 | if (!base) |
62 | goto out_release; | |
63 | nmk_rng.priv = (unsigned long)base; | |
64 | ret = hwrng_register(&nmk_rng); | |
65 | if (ret) | |
1655c240 | 66 | goto out_release; |
bc85b25e AR |
67 | return 0; |
68 | ||
bc85b25e AR |
69 | out_release: |
70 | amba_release_regions(dev); | |
2725ae17 | 71 | out_clk: |
1944cc89 | 72 | clk_disable(rng_clk); |
bc85b25e AR |
73 | return ret; |
74 | } | |
75 | ||
76 | static int nmk_rng_remove(struct amba_device *dev) | |
77 | { | |
bc85b25e | 78 | hwrng_unregister(&nmk_rng); |
bc85b25e | 79 | amba_release_regions(dev); |
1944cc89 | 80 | clk_disable(rng_clk); |
bc85b25e AR |
81 | return 0; |
82 | } | |
83 | ||
84 | static struct amba_id nmk_rng_ids[] = { | |
85 | { | |
86 | .id = 0x000805e1, | |
87 | .mask = 0x000fffff, /* top bits are rev and cfg: accept all */ | |
88 | }, | |
89 | {0, 0}, | |
90 | }; | |
91 | ||
4e3f3d53 DM |
92 | MODULE_DEVICE_TABLE(amba, nmk_rng_ids); |
93 | ||
bc85b25e AR |
94 | static struct amba_driver nmk_rng_driver = { |
95 | .drv = { | |
96 | .owner = THIS_MODULE, | |
97 | .name = "rng", | |
98 | }, | |
99 | .probe = nmk_rng_probe, | |
100 | .remove = nmk_rng_remove, | |
101 | .id_table = nmk_rng_ids, | |
102 | }; | |
103 | ||
9e5ed094 | 104 | module_amba_driver(nmk_rng_driver); |
bc85b25e AR |
105 | |
106 | MODULE_LICENSE("GPL"); |