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
28 struct tx4939_rng {
29 struct hwrng rng;
30 void __iomem *base;
31 u64 databuf[3];
32 unsigned int data_avail;
33 };
34
rng_io_start(void)35 static 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
rng_io_end(void)48 static void rng_io_end(void)
49 {
50 #ifndef CONFIG_64BIT
51 local_irq_enable();
52 #endif
53 }
54
read_rng(void __iomem * base,unsigned int offset)55 static u64 read_rng(void __iomem *base, unsigned int offset)
56 {
57 return ____raw_readq(base + offset);
58 }
59
write_rng(u64 val,void __iomem * base,unsigned int offset)60 static void write_rng(u64 val, void __iomem *base, unsigned int offset)
61 {
62 return ____raw_writeq(val, base + offset);
63 }
64
tx4939_rng_data_present(struct hwrng * rng,int wait)65 static 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
tx4939_rng_data_read(struct hwrng * rng,u32 * buffer)98 static 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
tx4939_rng_probe(struct platform_device * dev)107 static int __init tx4939_rng_probe(struct platform_device *dev)
108 {
109 struct tx4939_rng *rngdev;
110 int i;
111
112 rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL);
113 if (!rngdev)
114 return -ENOMEM;
115 rngdev->base = devm_platform_ioremap_resource(dev, 0);
116 if (IS_ERR(rngdev->base))
117 return PTR_ERR(rngdev->base);
118
119 rngdev->rng.name = dev_name(&dev->dev);
120 rngdev->rng.data_present = tx4939_rng_data_present;
121 rngdev->rng.data_read = tx4939_rng_data_read;
122
123 rng_io_start();
124 /* Reset RNG */
125 write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR);
126 write_rng(0, rngdev->base, TX4939_RNG_RCSR);
127 /* Start RNG */
128 write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR);
129 rng_io_end();
130 /*
131 * Drop first two results. From the datasheet:
132 * The quality of the random numbers generated immediately
133 * after reset can be insufficient. Therefore, do not use
134 * random numbers obtained from the first and second
135 * generations; use the ones from the third or subsequent
136 * generation.
137 */
138 for (i = 0; i < 2; i++) {
139 rngdev->data_avail = 0;
140 if (!tx4939_rng_data_present(&rngdev->rng, 1))
141 return -EIO;
142 }
143
144 platform_set_drvdata(dev, rngdev);
145 return devm_hwrng_register(&dev->dev, &rngdev->rng);
146 }
147
148 static struct platform_driver tx4939_rng_driver = {
149 .driver = {
150 .name = "tx4939-rng",
151 },
152 };
153
154 module_platform_driver_probe(tx4939_rng_driver, tx4939_rng_probe);
155
156 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939");
157 MODULE_LICENSE("GPL");
158