1/* 2 * drivers/char/hw_random/timeriomem-rng.c 3 * 4 * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk> 5 * 6 * Derived from drivers/char/hw_random/omap-rng.c 7 * Copyright 2005 (c) MontaVista Software, Inc. 8 * Author: Deepak Saxena <dsaxena@plexity.net> 9 * 10 * This program is free software; you can redistribute it and/or modify 11 * it under the terms of the GNU General Public License version 2 as 12 * published by the Free Software Foundation. 13 * 14 * Overview: 15 * This driver is useful for platforms that have an IO range that provides 16 * periodic random data from a single IO memory address. All the platform 17 * has to do is provide the address and 'wait time' that new data becomes 18 * available. 19 * 20 * TODO: add support for reading sizes other than 32bits and masking 21 */ 22 23#include <linux/module.h> 24#include <linux/kernel.h> 25#include <linux/platform_device.h> 26#include <linux/hw_random.h> 27#include <linux/io.h> 28#include <linux/timeriomem-rng.h> 29#include <linux/jiffies.h> 30#include <linux/sched.h> 31#include <linux/timer.h> 32#include <linux/completion.h> 33 34static struct timeriomem_rng_data *timeriomem_rng_data; 35 36static void timeriomem_rng_trigger(unsigned long); 37static DEFINE_TIMER(timeriomem_rng_timer, timeriomem_rng_trigger, 0, 0); 38 39/* 40 * have data return 1, however return 0 if we have nothing 41 */ 42static int timeriomem_rng_data_present(struct hwrng *rng, int wait) 43{ 44 if (rng->priv == 0) 45 return 1; 46 47 if (!wait || timeriomem_rng_data->present) 48 return timeriomem_rng_data->present; 49 50 wait_for_completion(&timeriomem_rng_data->completion); 51 52 return 1; 53} 54 55static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data) 56{ 57 unsigned long cur; 58 s32 delay; 59 60 *data = readl(timeriomem_rng_data->address); 61 62 if (rng->priv != 0) { 63 cur = jiffies; 64 65 delay = cur - timeriomem_rng_timer.expires; 66 delay = rng->priv - (delay % rng->priv); 67 68 timeriomem_rng_timer.expires = cur + delay; 69 timeriomem_rng_data->present = 0; 70 71 init_completion(&timeriomem_rng_data->completion); 72 add_timer(&timeriomem_rng_timer); 73 } 74 75 return 4; 76} 77 78static void timeriomem_rng_trigger(unsigned long dummy) 79{ 80 timeriomem_rng_data->present = 1; 81 complete(&timeriomem_rng_data->completion); 82} 83 84static struct hwrng timeriomem_rng_ops = { 85 .name = "timeriomem", 86 .data_present = timeriomem_rng_data_present, 87 .data_read = timeriomem_rng_data_read, 88 .priv = 0, 89}; 90 91static int __devinit timeriomem_rng_probe(struct platform_device *pdev) 92{ 93 struct resource *res; 94 int ret; 95 96 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 97 98 if (!res) 99 return -ENOENT; 100 101 timeriomem_rng_data = pdev->dev.platform_data; 102 103 timeriomem_rng_data->address = ioremap(res->start, 104 res->end - res->start + 1); 105 if (!timeriomem_rng_data->address) 106 return -EIO; 107 108 if (timeriomem_rng_data->period != 0 109 && usecs_to_jiffies(timeriomem_rng_data->period) > 0) { 110 timeriomem_rng_timer.expires = jiffies; 111 112 timeriomem_rng_ops.priv = usecs_to_jiffies( 113 timeriomem_rng_data->period); 114 } 115 timeriomem_rng_data->present = 1; 116 117 ret = hwrng_register(&timeriomem_rng_ops); 118 if (ret) 119 goto failed; 120 121 dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n", 122 timeriomem_rng_data->address, 123 timeriomem_rng_data->period); 124 125 return 0; 126 127failed: 128 dev_err(&pdev->dev, "problem registering\n"); 129 iounmap(timeriomem_rng_data->address); 130 131 return ret; 132} 133 134static int __devexit timeriomem_rng_remove(struct platform_device *pdev) 135{ 136 del_timer_sync(&timeriomem_rng_timer); 137 hwrng_unregister(&timeriomem_rng_ops); 138 139 iounmap(timeriomem_rng_data->address); 140 141 return 0; 142} 143 144static struct platform_driver timeriomem_rng_driver = { 145 .driver = { 146 .name = "timeriomem_rng", 147 .owner = THIS_MODULE, 148 }, 149 .probe = timeriomem_rng_probe, 150 .remove = __devexit_p(timeriomem_rng_remove), 151}; 152 153static int __init timeriomem_rng_init(void) 154{ 155 return platform_driver_register(&timeriomem_rng_driver); 156} 157 158static void __exit timeriomem_rng_exit(void) 159{ 160 platform_driver_unregister(&timeriomem_rng_driver); 161} 162 163module_init(timeriomem_rng_init); 164module_exit(timeriomem_rng_exit); 165 166MODULE_LICENSE("GPL"); 167MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>"); 168MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver"); 169