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| 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 | |
| 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 | |
| 48 | static void rng_io_end(void) |
| 49 | { |
| 50 | #ifndef CONFIG_64BIT |
| 51 | local_irq_enable(); |
| 52 | #endif |
| 53 | } |
| 54 | |
| 55 | static u64 read_rng(void __iomem *base, unsigned int offset) |
| 56 | { |
| 57 | return ____raw_readq(base + offset); |
| 58 | } |
| 59 | |
| 60 | static void write_rng(u64 val, void __iomem *base, unsigned int offset) |
| 61 | { |
| 62 | return ____raw_writeq(val, base + offset); |
| 63 | } |
| 64 | |
| 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 | |
| 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 | |
| 107 | static int __init tx4939_rng_probe(struct platform_device *dev) |
| 108 | { |
| 109 | struct tx4939_rng *rngdev; |
| 110 | struct resource *r; |
| 111 | int i; |
| 112 | |
| 113 | r = platform_get_resource(dev, IORESOURCE_MEM, 0); |
| 114 | if (!r) |
| 115 | return -EBUSY; |
| 116 | rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL); |
| 117 | if (!rngdev) |
| 118 | return -ENOMEM; |
| 119 | rngdev->base = devm_ioremap_resource(&dev->dev, r); |
| 120 | if (IS_ERR(rngdev->base)) |
| 121 | return PTR_ERR(rngdev->base); |
| 122 | |
| 123 | rngdev->rng.name = dev_name(&dev->dev); |
| 124 | rngdev->rng.data_present = tx4939_rng_data_present; |
| 125 | rngdev->rng.data_read = tx4939_rng_data_read; |
| 126 | |
| 127 | rng_io_start(); |
| 128 | /* Reset RNG */ |
| 129 | write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR); |
| 130 | write_rng(0, rngdev->base, TX4939_RNG_RCSR); |
| 131 | /* Start RNG */ |
| 132 | write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR); |
| 133 | rng_io_end(); |
| 134 | /* |
| 135 | * Drop first two results. From the datasheet: |
| 136 | * The quality of the random numbers generated immediately |
| 137 | * after reset can be insufficient. Therefore, do not use |
| 138 | * random numbers obtained from the first and second |
| 139 | * generations; use the ones from the third or subsequent |
| 140 | * generation. |
| 141 | */ |
| 142 | for (i = 0; i < 2; i++) { |
| 143 | rngdev->data_avail = 0; |
| 144 | if (!tx4939_rng_data_present(&rngdev->rng, 1)) |
| 145 | return -EIO; |
| 146 | } |
| 147 | |
| 148 | platform_set_drvdata(dev, rngdev); |
| 149 | return hwrng_register(&rngdev->rng); |
| 150 | } |
| 151 | |
| 152 | static int __exit tx4939_rng_remove(struct platform_device *dev) |
| 153 | { |
| 154 | struct tx4939_rng *rngdev = platform_get_drvdata(dev); |
| 155 | |
| 156 | hwrng_unregister(&rngdev->rng); |
| 157 | platform_set_drvdata(dev, NULL); |
| 158 | return 0; |
| 159 | } |
| 160 | |
| 161 | static struct platform_driver tx4939_rng_driver = { |
| 162 | .driver = { |
| 163 | .name = "tx4939-rng", |
| 164 | .owner = THIS_MODULE, |
| 165 | }, |
| 166 | .remove = tx4939_rng_remove, |
| 167 | }; |
| 168 | |
| 169 | static int __init tx4939rng_init(void) |
| 170 | { |
| 171 | return platform_driver_probe(&tx4939_rng_driver, tx4939_rng_probe); |
| 172 | } |
| 173 | |
| 174 | static void __exit tx4939rng_exit(void) |
| 175 | { |
| 176 | platform_driver_unregister(&tx4939_rng_driver); |
| 177 | } |
| 178 | |
| 179 | module_init(tx4939rng_init); |
| 180 | module_exit(tx4939rng_exit); |
| 181 | |
| 182 | MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939"); |
| 183 | MODULE_LICENSE("GPL"); |
| 184 |
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