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Atsushi Nemoto049a9472009-06-02 23:54:21 +09001/*
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 */
Thierry Redingc7c9e1c2013-01-21 11:08:59 +010010#include <linux/err.h>
Atsushi Nemoto049a9472009-06-02 23:54:21 +090011#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>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090018#include <linux/gfp.h>
Atsushi Nemoto049a9472009-06-02 23:54:21 +090019
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
Atsushi Nemoto049a9472009-06-02 23:54:21 +0900113 rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL);
114 if (!rngdev)
115 return -ENOMEM;
Julia Lawall9dc48032013-08-14 11:11:13 +0200116 r = platform_get_resource(dev, IORESOURCE_MEM, 0);
Thierry Redingc7c9e1c2013-01-21 11:08:59 +0100117 rngdev->base = devm_ioremap_resource(&dev->dev, r);
118 if (IS_ERR(rngdev->base))
119 return PTR_ERR(rngdev->base);
Atsushi Nemoto049a9472009-06-02 23:54:21 +0900120
121 rngdev->rng.name = dev_name(&dev->dev);
122 rngdev->rng.data_present = tx4939_rng_data_present;
123 rngdev->rng.data_read = tx4939_rng_data_read;
124
125 rng_io_start();
126 /* Reset RNG */
127 write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR);
128 write_rng(0, rngdev->base, TX4939_RNG_RCSR);
129 /* Start RNG */
130 write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR);
131 rng_io_end();
132 /*
133 * Drop first two results. From the datasheet:
134 * The quality of the random numbers generated immediately
135 * after reset can be insufficient. Therefore, do not use
136 * random numbers obtained from the first and second
137 * generations; use the ones from the third or subsequent
138 * generation.
139 */
140 for (i = 0; i < 2; i++) {
141 rngdev->data_avail = 0;
142 if (!tx4939_rng_data_present(&rngdev->rng, 1))
143 return -EIO;
144 }
145
146 platform_set_drvdata(dev, rngdev);
PrasannaKumar Muralidharan98a3c462016-08-28 14:19:12 +0530147 return devm_hwrng_register(&dev->dev, &rngdev->rng);
Atsushi Nemoto049a9472009-06-02 23:54:21 +0900148}
149
150static struct platform_driver tx4939_rng_driver = {
151 .driver = {
152 .name = "tx4939-rng",
Atsushi Nemoto049a9472009-06-02 23:54:21 +0900153 },
Atsushi Nemoto049a9472009-06-02 23:54:21 +0900154};
155
Fabio Porceddae7c21992013-03-14 18:09:33 +0100156module_platform_driver_probe(tx4939_rng_driver, tx4939_rng_probe);
Atsushi Nemoto049a9472009-06-02 23:54:21 +0900157
158MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939");
159MODULE_LICENSE("GPL");