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/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");