Atsushi Nemoto | 049a947 | 2009-06-02 23:54:21 +0900 | [diff] [blame] | 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 | |
| 18 | #define TX4939_RNG_RCSR 0x00000000 |
| 19 | #define TX4939_RNG_ROR(n) (0x00000018 + (n) * 8) |
| 20 | |
| 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 |
| 25 | |
| 26 | struct tx4939_rng { |
| 27 | struct hwrng rng; |
| 28 | void __iomem *base; |
| 29 | u64 databuf[3]; |
| 30 | unsigned int data_avail; |
| 31 | }; |
| 32 | |
| 33 | static void rng_io_start(void) |
| 34 | { |
| 35 | #ifndef CONFIG_64BIT |
| 36 | /* |
| 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. |
| 41 | */ |
| 42 | local_irq_disable(); |
| 43 | #endif |
| 44 | } |
| 45 | |
| 46 | static void rng_io_end(void) |
| 47 | { |
| 48 | #ifndef CONFIG_64BIT |
| 49 | local_irq_enable(); |
| 50 | #endif |
| 51 | } |
| 52 | |
| 53 | static u64 read_rng(void __iomem *base, unsigned int offset) |
| 54 | { |
| 55 | return ____raw_readq(base + offset); |
| 56 | } |
| 57 | |
| 58 | static void write_rng(u64 val, void __iomem *base, unsigned int offset) |
| 59 | { |
| 60 | return ____raw_writeq(val, base + offset); |
| 61 | } |
| 62 | |
| 63 | static int tx4939_rng_data_present(struct hwrng *rng, int wait) |
| 64 | { |
| 65 | struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); |
| 66 | int i; |
| 67 | |
| 68 | if (rngdev->data_avail) |
| 69 | return rngdev->data_avail; |
| 70 | for (i = 0; i < 20; i++) { |
| 71 | rng_io_start(); |
| 72 | if (!(read_rng(rngdev->base, TX4939_RNG_RCSR) |
| 73 | & TX4939_RNG_RCSR_ST)) { |
| 74 | rngdev->databuf[0] = |
| 75 | read_rng(rngdev->base, TX4939_RNG_ROR(0)); |
| 76 | rngdev->databuf[1] = |
| 77 | read_rng(rngdev->base, TX4939_RNG_ROR(1)); |
| 78 | rngdev->databuf[2] = |
| 79 | read_rng(rngdev->base, TX4939_RNG_ROR(2)); |
| 80 | rngdev->data_avail = |
| 81 | sizeof(rngdev->databuf) / sizeof(u32); |
| 82 | /* Start RNG */ |
| 83 | write_rng(TX4939_RNG_RCSR_ST, |
| 84 | rngdev->base, TX4939_RNG_RCSR); |
| 85 | wait = 0; |
| 86 | } |
| 87 | rng_io_end(); |
| 88 | if (!wait) |
| 89 | break; |
| 90 | /* 90 bus clock cycles by default for generation */ |
| 91 | ndelay(90 * 5); |
| 92 | } |
| 93 | return rngdev->data_avail; |
| 94 | } |
| 95 | |
| 96 | static int tx4939_rng_data_read(struct hwrng *rng, u32 *buffer) |
| 97 | { |
| 98 | struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng); |
| 99 | |
| 100 | rngdev->data_avail--; |
| 101 | *buffer = *((u32 *)&rngdev->databuf + rngdev->data_avail); |
| 102 | return sizeof(u32); |
| 103 | } |
| 104 | |
| 105 | static int __init tx4939_rng_probe(struct platform_device *dev) |
| 106 | { |
| 107 | struct tx4939_rng *rngdev; |
| 108 | struct resource *r; |
| 109 | int i; |
| 110 | |
| 111 | r = platform_get_resource(dev, IORESOURCE_MEM, 0); |
| 112 | if (!r) |
| 113 | return -EBUSY; |
| 114 | rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL); |
| 115 | if (!rngdev) |
| 116 | return -ENOMEM; |
| 117 | if (!devm_request_mem_region(&dev->dev, r->start, resource_size(r), |
| 118 | dev_name(&dev->dev))) |
| 119 | return -EBUSY; |
| 120 | rngdev->base = devm_ioremap(&dev->dev, r->start, resource_size(r)); |
| 121 | if (!rngdev->base) |
| 122 | return -EBUSY; |
| 123 | |
| 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; |
| 127 | |
| 128 | rng_io_start(); |
| 129 | /* Reset RNG */ |
| 130 | write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR); |
| 131 | write_rng(0, rngdev->base, TX4939_RNG_RCSR); |
| 132 | /* Start RNG */ |
| 133 | write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR); |
| 134 | rng_io_end(); |
| 135 | /* |
| 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 |
| 141 | * generation. |
| 142 | */ |
| 143 | for (i = 0; i < 2; i++) { |
| 144 | rngdev->data_avail = 0; |
| 145 | if (!tx4939_rng_data_present(&rngdev->rng, 1)) |
| 146 | return -EIO; |
| 147 | } |
| 148 | |
| 149 | platform_set_drvdata(dev, rngdev); |
| 150 | return hwrng_register(&rngdev->rng); |
| 151 | } |
| 152 | |
| 153 | static int __exit tx4939_rng_remove(struct platform_device *dev) |
| 154 | { |
| 155 | struct tx4939_rng *rngdev = platform_get_drvdata(dev); |
| 156 | |
| 157 | hwrng_unregister(&rngdev->rng); |
| 158 | platform_set_drvdata(dev, NULL); |
| 159 | return 0; |
| 160 | } |
| 161 | |
| 162 | static struct platform_driver tx4939_rng_driver = { |
| 163 | .driver = { |
| 164 | .name = "tx4939-rng", |
| 165 | .owner = THIS_MODULE, |
| 166 | }, |
| 167 | .remove = tx4939_rng_remove, |
| 168 | }; |
| 169 | |
| 170 | static int __init tx4939rng_init(void) |
| 171 | { |
| 172 | return platform_driver_probe(&tx4939_rng_driver, tx4939_rng_probe); |
| 173 | } |
| 174 | |
| 175 | static void __exit tx4939rng_exit(void) |
| 176 | { |
| 177 | platform_driver_unregister(&tx4939_rng_driver); |
| 178 | } |
| 179 | |
| 180 | module_init(tx4939rng_init); |
| 181 | module_exit(tx4939rng_exit); |
| 182 | |
| 183 | MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939"); |
| 184 | MODULE_LICENSE("GPL"); |