drivers/char/hw_random/bcm2835-rng.c

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