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1 | /* |
2 | * RNG driver for TX4939 Random Number Generators (RNG) | |
3 | * | |
4 | * Copyright (C) 2009 Atsushi Nemoto <anemo@mba.ocn.ne.jp> | |
5 | * | |
6 | * This file is subject to the terms and conditions of the GNU General Public | |
7 | * License. See the file "COPYING" in the main directory of this archive | |
8 | * for more details. | |
9 | */ | |
10 | #include <linux/module.h> | |
11 | #include <linux/kernel.h> | |
12 | #include <linux/init.h> | |
13 | #include <linux/delay.h> | |
14 | #include <linux/io.h> | |
15 | #include <linux/platform_device.h> | |
16 | #include <linux/hw_random.h> | |
17 | ||
18 | #define TX4939_RNG_RCSR 0x00000000 | |
19 | #define TX4939_RNG_ROR(n) (0x00000018 + (n) * 8) | |
20 | ||
21 | #define TX4939_RNG_RCSR_INTE 0x00000008 | |
22 | #define TX4939_RNG_RCSR_RST 0x00000004 | |
23 | #define TX4939_RNG_RCSR_FIN 0x00000002 | |
24 | #define TX4939_RNG_RCSR_ST 0x00000001 | |
25 | ||
26 | struct tx4939_rng { | |
27 | struct hwrng rng; | |
28 | void __iomem *base; | |
29 | u64 databuf[3]; | |
30 | unsigned int data_avail; | |
31 | }; | |
32 | ||
33 | static void rng_io_start(void) | |
34 | { | |
35 | #ifndef CONFIG_64BIT | |
36 | /* | |
37 | * readq is reading a 64-bit register using a 64-bit load. On | |
38 | * a 32-bit kernel however interrupts or any other processor | |
39 | * exception would clobber the upper 32-bit of the processor | |
40 | * register so interrupts need to be disabled. | |
41 | */ | |
42 | local_irq_disable(); | |
43 | #endif | |
44 | } | |
45 | ||
46 | static void rng_io_end(void) | |
47 | { | |
48 | #ifndef CONFIG_64BIT | |
49 | local_irq_enable(); | |
50 | #endif | |
51 | } | |
52 | ||
53 | static u64 read_rng(void __iomem *base, unsigned int offset) | |
54 | { | |
55 | return ____raw_readq(base + offset); | |
56 | } | |
57 | ||
58 | static void write_rng(u64 val, void __iomem *base, unsigned int offset) | |
59 | { | |
60 | return ____raw_writeq(val, base + offset); | |
61 | } | |
62 | ||
63 | static int tx4939_rng_data_present(struct hwrng *rng, int wait) | |
64 | { | |
65 | struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); | |
66 | int i; | |
67 | ||
68 | if (rngdev->data_avail) | |
69 | return rngdev->data_avail; | |
70 | for (i = 0; i < 20; i++) { | |
71 | rng_io_start(); | |
72 | if (!(read_rng(rngdev->base, TX4939_RNG_RCSR) | |
73 | & TX4939_RNG_RCSR_ST)) { | |
74 | rngdev->databuf[0] = | |
75 | read_rng(rngdev->base, TX4939_RNG_ROR(0)); | |
76 | rngdev->databuf[1] = | |
77 | read_rng(rngdev->base, TX4939_RNG_ROR(1)); | |
78 | rngdev->databuf[2] = | |
79 | read_rng(rngdev->base, TX4939_RNG_ROR(2)); | |
80 | rngdev->data_avail = | |
81 | sizeof(rngdev->databuf) / sizeof(u32); | |
82 | /* Start RNG */ | |
83 | write_rng(TX4939_RNG_RCSR_ST, | |
84 | rngdev->base, TX4939_RNG_RCSR); | |
85 | wait = 0; | |
86 | } | |
87 | rng_io_end(); | |
88 | if (!wait) | |
89 | break; | |
90 | /* 90 bus clock cycles by default for generation */ | |
91 | ndelay(90 * 5); | |
92 | } | |
93 | return rngdev->data_avail; | |
94 | } | |
95 | ||
96 | static int tx4939_rng_data_read(struct hwrng *rng, u32 *buffer) | |
97 | { | |
98 | struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); | |
99 | ||
100 | rngdev->data_avail--; | |
101 | *buffer = *((u32 *)&rngdev->databuf + rngdev->data_avail); | |
102 | return sizeof(u32); | |
103 | } | |
104 | ||
105 | static int __init tx4939_rng_probe(struct platform_device *dev) | |
106 | { | |
107 | struct tx4939_rng *rngdev; | |
108 | struct resource *r; | |
109 | int i; | |
110 | ||
111 | r = platform_get_resource(dev, IORESOURCE_MEM, 0); | |
112 | if (!r) | |
113 | return -EBUSY; | |
114 | rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL); | |
115 | if (!rngdev) | |
116 | return -ENOMEM; | |
117 | if (!devm_request_mem_region(&dev->dev, r->start, resource_size(r), | |
118 | dev_name(&dev->dev))) | |
119 | return -EBUSY; | |
120 | rngdev->base = devm_ioremap(&dev->dev, r->start, resource_size(r)); | |
121 | if (!rngdev->base) | |
122 | return -EBUSY; | |
123 | ||
124 | rngdev->rng.name = dev_name(&dev->dev); | |
125 | rngdev->rng.data_present = tx4939_rng_data_present; | |
126 | rngdev->rng.data_read = tx4939_rng_data_read; | |
127 | ||
128 | rng_io_start(); | |
129 | /* Reset RNG */ | |
130 | write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR); | |
131 | write_rng(0, rngdev->base, TX4939_RNG_RCSR); | |
132 | /* Start RNG */ | |
133 | write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR); | |
134 | rng_io_end(); | |
135 | /* | |
136 | * Drop first two results. From the datasheet: | |
137 | * The quality of the random numbers generated immediately | |
138 | * after reset can be insufficient. Therefore, do not use | |
139 | * random numbers obtained from the first and second | |
140 | * generations; use the ones from the third or subsequent | |
141 | * generation. | |
142 | */ | |
143 | for (i = 0; i < 2; i++) { | |
144 | rngdev->data_avail = 0; | |
145 | if (!tx4939_rng_data_present(&rngdev->rng, 1)) | |
146 | return -EIO; | |
147 | } | |
148 | ||
149 | platform_set_drvdata(dev, rngdev); | |
150 | return hwrng_register(&rngdev->rng); | |
151 | } | |
152 | ||
153 | static int __exit tx4939_rng_remove(struct platform_device *dev) | |
154 | { | |
155 | struct tx4939_rng *rngdev = platform_get_drvdata(dev); | |
156 | ||
157 | hwrng_unregister(&rngdev->rng); | |
158 | platform_set_drvdata(dev, NULL); | |
159 | return 0; | |
160 | } | |
161 | ||
162 | static struct platform_driver tx4939_rng_driver = { | |
163 | .driver = { | |
164 | .name = "tx4939-rng", | |
165 | .owner = THIS_MODULE, | |
166 | }, | |
167 | .remove = tx4939_rng_remove, | |
168 | }; | |
169 | ||
170 | static int __init tx4939rng_init(void) | |
171 | { | |
172 | return platform_driver_probe(&tx4939_rng_driver, tx4939_rng_probe); | |
173 | } | |
174 | ||
175 | static void __exit tx4939rng_exit(void) | |
176 | { | |
177 | platform_driver_unregister(&tx4939_rng_driver); | |
178 | } | |
179 | ||
180 | module_init(tx4939rng_init); | |
181 | module_exit(tx4939rng_exit); | |
182 | ||
183 | MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939"); | |
184 | MODULE_LICENSE("GPL"); |