media: tegra: enable a clock for VIP in APB MISC register
[linux-2.6.git] / drivers / char / hw_random / tx4939-rng.c
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 #include <linux/gfp.h>
18
19 #define TX4939_RNG_RCSR         0x00000000
20 #define TX4939_RNG_ROR(n)       (0x00000018 + (n) * 8)
21
22 #define TX4939_RNG_RCSR_INTE    0x00000008
23 #define TX4939_RNG_RCSR_RST     0x00000004
24 #define TX4939_RNG_RCSR_FIN     0x00000002
25 #define TX4939_RNG_RCSR_ST      0x00000001
26
27 struct tx4939_rng {
28         struct hwrng rng;
29         void __iomem *base;
30         u64 databuf[3];
31         unsigned int data_avail;
32 };
33
34 static void rng_io_start(void)
35 {
36 #ifndef CONFIG_64BIT
37         /*
38          * readq is reading a 64-bit register using a 64-bit load.  On
39          * a 32-bit kernel however interrupts or any other processor
40          * exception would clobber the upper 32-bit of the processor
41          * register so interrupts need to be disabled.
42          */
43         local_irq_disable();
44 #endif
45 }
46
47 static void rng_io_end(void)
48 {
49 #ifndef CONFIG_64BIT
50         local_irq_enable();
51 #endif
52 }
53
54 static u64 read_rng(void __iomem *base, unsigned int offset)
55 {
56         return ____raw_readq(base + offset);
57 }
58
59 static void write_rng(u64 val, void __iomem *base, unsigned int offset)
60 {
61         return ____raw_writeq(val, base + offset);
62 }
63
64 static int tx4939_rng_data_present(struct hwrng *rng, int wait)
65 {
66         struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng);
67         int i;
68
69         if (rngdev->data_avail)
70                 return rngdev->data_avail;
71         for (i = 0; i < 20; i++) {
72                 rng_io_start();
73                 if (!(read_rng(rngdev->base, TX4939_RNG_RCSR)
74                       & TX4939_RNG_RCSR_ST)) {
75                         rngdev->databuf[0] =
76                                 read_rng(rngdev->base, TX4939_RNG_ROR(0));
77                         rngdev->databuf[1] =
78                                 read_rng(rngdev->base, TX4939_RNG_ROR(1));
79                         rngdev->databuf[2] =
80                                 read_rng(rngdev->base, TX4939_RNG_ROR(2));
81                         rngdev->data_avail =
82                                 sizeof(rngdev->databuf) / sizeof(u32);
83                         /* Start RNG */
84                         write_rng(TX4939_RNG_RCSR_ST,
85                                   rngdev->base, TX4939_RNG_RCSR);
86                         wait = 0;
87                 }
88                 rng_io_end();
89                 if (!wait)
90                         break;
91                 /* 90 bus clock cycles by default for generation */
92                 ndelay(90 * 5);
93         }
94         return rngdev->data_avail;
95 }
96
97 static int tx4939_rng_data_read(struct hwrng *rng, u32 *buffer)
98 {
99         struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng);
100
101         rngdev->data_avail--;
102         *buffer = *((u32 *)&rngdev->databuf + rngdev->data_avail);
103         return sizeof(u32);
104 }
105
106 static int __init tx4939_rng_probe(struct platform_device *dev)
107 {
108         struct tx4939_rng *rngdev;
109         struct resource *r;
110         int i;
111
112         r = platform_get_resource(dev, IORESOURCE_MEM, 0);
113         if (!r)
114                 return -EBUSY;
115         rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL);
116         if (!rngdev)
117                 return -ENOMEM;
118         if (!devm_request_mem_region(&dev->dev, r->start, resource_size(r),
119                                      dev_name(&dev->dev)))
120                 return -EBUSY;
121         rngdev->base = devm_ioremap(&dev->dev, r->start, resource_size(r));
122         if (!rngdev->base)
123                 return -EBUSY;
124
125         rngdev->rng.name = dev_name(&dev->dev);
126         rngdev->rng.data_present = tx4939_rng_data_present;
127         rngdev->rng.data_read = tx4939_rng_data_read;
128
129         rng_io_start();
130         /* Reset RNG */
131         write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR);
132         write_rng(0, rngdev->base, TX4939_RNG_RCSR);
133         /* Start RNG */
134         write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR);
135         rng_io_end();
136         /*
137          * Drop first two results.  From the datasheet:
138          * The quality of the random numbers generated immediately
139          * after reset can be insufficient.  Therefore, do not use
140          * random numbers obtained from the first and second
141          * generations; use the ones from the third or subsequent
142          * generation.
143          */
144         for (i = 0; i < 2; i++) {
145                 rngdev->data_avail = 0;
146                 if (!tx4939_rng_data_present(&rngdev->rng, 1))
147                         return -EIO;
148         }
149
150         platform_set_drvdata(dev, rngdev);
151         return hwrng_register(&rngdev->rng);
152 }
153
154 static int __exit tx4939_rng_remove(struct platform_device *dev)
155 {
156         struct tx4939_rng *rngdev = platform_get_drvdata(dev);
157
158         hwrng_unregister(&rngdev->rng);
159         platform_set_drvdata(dev, NULL);
160         return 0;
161 }
162
163 static struct platform_driver tx4939_rng_driver = {
164         .driver         = {
165                 .name   = "tx4939-rng",
166                 .owner  = THIS_MODULE,
167         },
168         .remove = tx4939_rng_remove,
169 };
170
171 static int __init tx4939rng_init(void)
172 {
173         return platform_driver_probe(&tx4939_rng_driver, tx4939_rng_probe);
174 }
175
176 static void __exit tx4939rng_exit(void)
177 {
178         platform_driver_unregister(&tx4939_rng_driver);
179 }
180
181 module_init(tx4939rng_init);
182 module_exit(tx4939rng_exit);
183
184 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939");
185 MODULE_LICENSE("GPL");