2 * RNG driver for TX4939 Random Number Generators (RNG)
4 * Copyright (C) 2009 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
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
10 #include <linux/module.h>
11 #include <linux/kernel.h>
12 #include <linux/init.h>
13 #include <linux/delay.h>
15 #include <linux/platform_device.h>
16 #include <linux/hw_random.h>
18 #define TX4939_RNG_RCSR 0x00000000
19 #define TX4939_RNG_ROR(n) (0x00000018 + (n) * 8)
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
30 unsigned int data_avail;
33 static void rng_io_start(void)
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.
46 static void rng_io_end(void)
53 static u64 read_rng(void __iomem *base, unsigned int offset)
55 return ____raw_readq(base + offset);
58 static void write_rng(u64 val, void __iomem *base, unsigned int offset)
60 return ____raw_writeq(val, base + offset);
63 static int tx4939_rng_data_present(struct hwrng *rng, int wait)
65 struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng);
68 if (rngdev->data_avail)
69 return rngdev->data_avail;
70 for (i = 0; i < 20; i++) {
72 if (!(read_rng(rngdev->base, TX4939_RNG_RCSR)
73 & TX4939_RNG_RCSR_ST)) {
75 read_rng(rngdev->base, TX4939_RNG_ROR(0));
77 read_rng(rngdev->base, TX4939_RNG_ROR(1));
79 read_rng(rngdev->base, TX4939_RNG_ROR(2));
81 sizeof(rngdev->databuf) / sizeof(u32);
83 write_rng(TX4939_RNG_RCSR_ST,
84 rngdev->base, TX4939_RNG_RCSR);
90 /* 90 bus clock cycles by default for generation */
93 return rngdev->data_avail;
96 static int tx4939_rng_data_read(struct hwrng *rng, u32 *buffer)
98 struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng);
100 rngdev->data_avail--;
101 *buffer = *((u32 *)&rngdev->databuf + rngdev->data_avail);
105 static int __init tx4939_rng_probe(struct platform_device *dev)
107 struct tx4939_rng *rngdev;
111 r = platform_get_resource(dev, IORESOURCE_MEM, 0);
114 rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL);
117 if (!devm_request_mem_region(&dev->dev, r->start, resource_size(r),
118 dev_name(&dev->dev)))
120 rngdev->base = devm_ioremap(&dev->dev, r->start, resource_size(r));
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;
130 write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR);
131 write_rng(0, rngdev->base, TX4939_RNG_RCSR);
133 write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR);
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
143 for (i = 0; i < 2; i++) {
144 rngdev->data_avail = 0;
145 if (!tx4939_rng_data_present(&rngdev->rng, 1))
149 platform_set_drvdata(dev, rngdev);
150 return hwrng_register(&rngdev->rng);
153 static int __exit tx4939_rng_remove(struct platform_device *dev)
155 struct tx4939_rng *rngdev = platform_get_drvdata(dev);
157 hwrng_unregister(&rngdev->rng);
158 platform_set_drvdata(dev, NULL);
162 static struct platform_driver tx4939_rng_driver = {
164 .name = "tx4939-rng",
165 .owner = THIS_MODULE,
167 .remove = tx4939_rng_remove,
170 static int __init tx4939rng_init(void)
172 return platform_driver_probe(&tx4939_rng_driver, tx4939_rng_probe);
175 static void __exit tx4939rng_exit(void)
177 platform_driver_unregister(&tx4939_rng_driver);
180 module_init(tx4939rng_init);
181 module_exit(tx4939rng_exit);
183 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939");
184 MODULE_LICENSE("GPL");