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/of.h> 27 #include <linux/hw_random.h> 28 #include <linux/io.h> 29 #include <linux/slab.h> 30 #include <linux/timeriomem-rng.h> 31 #include <linux/jiffies.h> 32 #include <linux/sched.h> 33 #include <linux/timer.h> 34 #include <linux/completion.h> 35 36 struct timeriomem_rng_private_data { 37 void __iomem *io_base; 38 unsigned int expires; 39 unsigned int period; 40 unsigned int present:1; 41 42 struct timer_list timer; 43 struct completion completion; 44 45 struct hwrng timeriomem_rng_ops; 46 }; 47 48 #define to_rng_priv(rng) \ 49 ((struct timeriomem_rng_private_data *)rng->priv) 50 51 /* 52 * have data return 1, however return 0 if we have nothing 53 */ 54 static int timeriomem_rng_data_present(struct hwrng *rng, int wait) 55 { 56 struct timeriomem_rng_private_data *priv = to_rng_priv(rng); 57 58 if (!wait || priv->present) 59 return priv->present; 60 61 wait_for_completion(&priv->completion); 62 63 return 1; 64 } 65 66 static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data) 67 { 68 struct timeriomem_rng_private_data *priv = to_rng_priv(rng); 69 unsigned long cur; 70 s32 delay; 71 72 *data = readl(priv->io_base); 73 74 cur = jiffies; 75 76 delay = cur - priv->expires; 77 delay = priv->period - (delay % priv->period); 78 79 priv->expires = cur + delay; 80 priv->present = 0; 81 82 reinit_completion(&priv->completion); 83 mod_timer(&priv->timer, priv->expires); 84 85 return 4; 86 } 87 88 static void timeriomem_rng_trigger(unsigned long data) 89 { 90 struct timeriomem_rng_private_data *priv 91 = (struct timeriomem_rng_private_data *)data; 92 93 priv->present = 1; 94 complete(&priv->completion); 95 } 96 97 static int timeriomem_rng_probe(struct platform_device *pdev) 98 { 99 struct timeriomem_rng_data *pdata = pdev->dev.platform_data; 100 struct timeriomem_rng_private_data *priv; 101 struct resource *res; 102 int err = 0; 103 int period; 104 105 if (!pdev->dev.of_node && !pdata) { 106 dev_err(&pdev->dev, "timeriomem_rng_data is missing\n"); 107 return -EINVAL; 108 } 109 110 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 111 if (!res) 112 return -ENXIO; 113 114 if (res->start % 4 != 0 || resource_size(res) != 4) { 115 dev_err(&pdev->dev, 116 "address must be four bytes wide and aligned\n"); 117 return -EINVAL; 118 } 119 120 /* Allocate memory for the device structure (and zero it) */ 121 priv = devm_kzalloc(&pdev->dev, 122 sizeof(struct timeriomem_rng_private_data), GFP_KERNEL); 123 if (!priv) 124 return -ENOMEM; 125 126 platform_set_drvdata(pdev, priv); 127 128 if (pdev->dev.of_node) { 129 int i; 130 131 if (!of_property_read_u32(pdev->dev.of_node, 132 "period", &i)) 133 period = i; 134 else { 135 dev_err(&pdev->dev, "missing period\n"); 136 return -EINVAL; 137 } 138 } else { 139 period = pdata->period; 140 } 141 142 priv->period = usecs_to_jiffies(period); 143 if (priv->period < 1) { 144 dev_err(&pdev->dev, "period is less than one jiffy\n"); 145 return -EINVAL; 146 } 147 148 priv->expires = jiffies; 149 priv->present = 1; 150 151 init_completion(&priv->completion); 152 complete(&priv->completion); 153 154 setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv); 155 156 priv->timeriomem_rng_ops.name = dev_name(&pdev->dev); 157 priv->timeriomem_rng_ops.data_present = timeriomem_rng_data_present; 158 priv->timeriomem_rng_ops.data_read = timeriomem_rng_data_read; 159 priv->timeriomem_rng_ops.priv = (unsigned long)priv; 160 161 priv->io_base = devm_ioremap_resource(&pdev->dev, res); 162 if (IS_ERR(priv->io_base)) { 163 err = PTR_ERR(priv->io_base); 164 goto out_timer; 165 } 166 167 err = hwrng_register(&priv->timeriomem_rng_ops); 168 if (err) { 169 dev_err(&pdev->dev, "problem registering\n"); 170 goto out_timer; 171 } 172 173 dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n", 174 priv->io_base, period); 175 176 return 0; 177 178 out_timer: 179 del_timer_sync(&priv->timer); 180 return err; 181 } 182 183 static int timeriomem_rng_remove(struct platform_device *pdev) 184 { 185 struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev); 186 187 hwrng_unregister(&priv->timeriomem_rng_ops); 188 189 del_timer_sync(&priv->timer); 190 191 return 0; 192 } 193 194 static const struct of_device_id timeriomem_rng_match[] = { 195 { .compatible = "timeriomem_rng" }, 196 {}, 197 }; 198 MODULE_DEVICE_TABLE(of, timeriomem_rng_match); 199 200 static struct platform_driver timeriomem_rng_driver = { 201 .driver = { 202 .name = "timeriomem_rng", 203 .owner = THIS_MODULE, 204 .of_match_table = timeriomem_rng_match, 205 }, 206 .probe = timeriomem_rng_probe, 207 .remove = timeriomem_rng_remove, 208 }; 209 210 module_platform_driver(timeriomem_rng_driver); 211 212 MODULE_LICENSE("GPL"); 213 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>"); 214 MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver"); 215