1 /** 2 * Copyright (c) 2010-2012 Broadcom. All rights reserved. 3 * Copyright (c) 2013 Lubomir Rintel 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License ("GPL") 7 * version 2, as published by the Free Software Foundation. 8 */ 9 10 #include <linux/hw_random.h> 11 #include <linux/io.h> 12 #include <linux/kernel.h> 13 #include <linux/module.h> 14 #include <linux/of_address.h> 15 #include <linux/of_platform.h> 16 #include <linux/platform_device.h> 17 #include <linux/printk.h> 18 19 #define RNG_CTRL 0x0 20 #define RNG_STATUS 0x4 21 #define RNG_DATA 0x8 22 23 /* enable rng */ 24 #define RNG_RBGEN 0x1 25 26 /* the initial numbers generated are "less random" so will be discarded */ 27 #define RNG_WARMUP_COUNT 0x40000 28 29 static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max, 30 bool wait) 31 { 32 void __iomem *rng_base = (void __iomem *)rng->priv; 33 34 while ((__raw_readl(rng_base + RNG_STATUS) >> 24) == 0) { 35 if (!wait) 36 return 0; 37 cpu_relax(); 38 } 39 40 *(u32 *)buf = __raw_readl(rng_base + RNG_DATA); 41 return sizeof(u32); 42 } 43 44 static struct hwrng bcm2835_rng_ops = { 45 .name = "bcm2835", 46 .read = bcm2835_rng_read, 47 }; 48 49 static int bcm2835_rng_probe(struct platform_device *pdev) 50 { 51 struct device *dev = &pdev->dev; 52 struct device_node *np = dev->of_node; 53 void __iomem *rng_base; 54 int err; 55 56 /* map peripheral */ 57 rng_base = of_iomap(np, 0); 58 if (!rng_base) { 59 dev_err(dev, "failed to remap rng regs"); 60 return -ENODEV; 61 } 62 bcm2835_rng_ops.priv = (unsigned long)rng_base; 63 64 /* set warm-up count & enable */ 65 __raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS); 66 __raw_writel(RNG_RBGEN, rng_base + RNG_CTRL); 67 68 /* register driver */ 69 err = hwrng_register(&bcm2835_rng_ops); 70 if (err) { 71 dev_err(dev, "hwrng registration failed\n"); 72 iounmap(rng_base); 73 } else 74 dev_info(dev, "hwrng registered\n"); 75 76 return err; 77 } 78 79 static int bcm2835_rng_remove(struct platform_device *pdev) 80 { 81 void __iomem *rng_base = (void __iomem *)bcm2835_rng_ops.priv; 82 83 /* disable rng hardware */ 84 __raw_writel(0, rng_base + RNG_CTRL); 85 86 /* unregister driver */ 87 hwrng_unregister(&bcm2835_rng_ops); 88 iounmap(rng_base); 89 90 return 0; 91 } 92 93 static const struct of_device_id bcm2835_rng_of_match[] = { 94 { .compatible = "brcm,bcm2835-rng", }, 95 {}, 96 }; 97 MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match); 98 99 static struct platform_driver bcm2835_rng_driver = { 100 .driver = { 101 .name = "bcm2835-rng", 102 .of_match_table = bcm2835_rng_of_match, 103 }, 104 .probe = bcm2835_rng_probe, 105 .remove = bcm2835_rng_remove, 106 }; 107 module_platform_driver(bcm2835_rng_driver); 108 109 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>"); 110 MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver"); 111 MODULE_LICENSE("GPL v2"); 112