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