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 27struct tx4939_rng { 28 struct hwrng rng; 29 void __iomem *base; 30 u64 databuf[3]; 31 unsigned int data_avail; 32}; 33 34static 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 47static void rng_io_end(void) 48{ 49#ifndef CONFIG_64BIT 50 local_irq_enable(); 51#endif 52} 53 54static u64 read_rng(void __iomem *base, unsigned int offset) 55{ 56 return ____raw_readq(base + offset); 57} 58 59static void write_rng(u64 val, void __iomem *base, unsigned int offset) 60{ 61 return ____raw_writeq(val, base + offset); 62} 63 64static 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 97static 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 106static 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 154static 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 163static struct platform_driver tx4939_rng_driver = { 164 .driver = { 165 .name = "tx4939-rng", 166 .owner = THIS_MODULE, 167 }, 168 .remove = tx4939_rng_remove, 169}; 170 171static int __init tx4939rng_init(void) 172{ 173 return platform_driver_probe(&tx4939_rng_driver, tx4939_rng_probe); 174} 175 176static void __exit tx4939rng_exit(void) 177{ 178 platform_driver_unregister(&tx4939_rng_driver); 179} 180 181module_init(tx4939rng_init); 182module_exit(tx4939rng_exit); 183 184MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939"); 185MODULE_LICENSE("GPL"); 186