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 34 static struct timeriomem_rng_data *timeriomem_rng_data; 35 36 static void timeriomem_rng_trigger(unsigned long); 37 static 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 */ 42 static 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 55 static 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 78 static void timeriomem_rng_trigger(unsigned long dummy) 79 { 80 timeriomem_rng_data->present = 1; 81 complete(&timeriomem_rng_data->completion); 82 } 83 84 static 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 91 static 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, resource_size(res)); 104 if (!timeriomem_rng_data->address) 105 return -EIO; 106 107 if (timeriomem_rng_data->period != 0 108 && usecs_to_jiffies(timeriomem_rng_data->period) > 0) { 109 timeriomem_rng_timer.expires = jiffies; 110 111 timeriomem_rng_ops.priv = usecs_to_jiffies( 112 timeriomem_rng_data->period); 113 } 114 timeriomem_rng_data->present = 1; 115 116 ret = hwrng_register(&timeriomem_rng_ops); 117 if (ret) 118 goto failed; 119 120 dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n", 121 timeriomem_rng_data->address, 122 timeriomem_rng_data->period); 123 124 return 0; 125 126 failed: 127 dev_err(&pdev->dev, "problem registering\n"); 128 iounmap(timeriomem_rng_data->address); 129 130 return ret; 131 } 132 133 static int timeriomem_rng_remove(struct platform_device *pdev) 134 { 135 del_timer_sync(&timeriomem_rng_timer); 136 hwrng_unregister(&timeriomem_rng_ops); 137 138 iounmap(timeriomem_rng_data->address); 139 140 return 0; 141 } 142 143 static struct platform_driver timeriomem_rng_driver = { 144 .driver = { 145 .name = "timeriomem_rng", 146 .owner = THIS_MODULE, 147 }, 148 .probe = timeriomem_rng_probe, 149 .remove = __devexit_p(timeriomem_rng_remove), 150 }; 151 152 module_platform_driver(timeriomem_rng_driver); 153 154 MODULE_LICENSE("GPL"); 155 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>"); 156 MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver"); 157