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 #define RNG_INT_MASK    0x10
  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 #define RNG_INT_OFF     0x1
  31
  32 static void __init nsp_rng_init(void __iomem *base)
  33 {
  34         u32 val;
  35
  36         /* mask the interrupt */
  37         val = readl(base + RNG_INT_MASK);
  38         val |= RNG_INT_OFF;
  39         writel(val, base + RNG_INT_MASK);
  40 }
  41
  42 static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
  43                                bool wait)
  44 {
  45         void __iomem *rng_base = (void __iomem *)rng->priv;
  46         u32 max_words = max / sizeof(u32);
  47         u32 num_words, count;
  48
  49         while ((__raw_readl(rng_base + RNG_STATUS) >> 24) == 0) {
  50                 if (!wait)
  51                         return 0;
  52                 cpu_relax();
  53         }
  54
  55         num_words = readl(rng_base + RNG_STATUS) >> 24;
  56         if (num_words > max_words)
  57                 num_words = max_words;
  58
  59         for (count = 0; count < num_words; count++)
  60                 ((u32 *)buf)[count] = readl(rng_base + RNG_DATA);
  61
  62         return num_words * sizeof(u32);
  63 }
  64
  65 static struct hwrng bcm2835_rng_ops = {
  66         .name   = "bcm2835",
  67         .read   = bcm2835_rng_read,
  68 };
  69
  70 static const struct of_device_id bcm2835_rng_of_match[] = {
  71         { .compatible = "brcm,bcm2835-rng"},
  72         { .compatible = "brcm,bcm-nsp-rng", .data = nsp_rng_init},
  73         { .compatible = "brcm,bcm5301x-rng", .data = nsp_rng_init},
  74         {},
  75 };
  76
  77 static int bcm2835_rng_probe(struct platform_device *pdev)
  78 {
  79         struct device *dev = &pdev->dev;
  80         struct device_node *np = dev->of_node;
  81         void (*rng_setup)(void __iomem *base);
  82         const struct of_device_id *rng_id;
  83         void __iomem *rng_base;
  84         int err;
  85
  86         /* map peripheral */
  87         rng_base = of_iomap(np, 0);
  88         if (!rng_base) {
  89                 dev_err(dev, "failed to remap rng regs");
  90                 return -ENODEV;
  91         }
  92         bcm2835_rng_ops.priv = (unsigned long)rng_base;
  93
  94         rng_id = of_match_node(bcm2835_rng_of_match, np);
  95         if (!rng_id)
  96                 return -EINVAL;
  97
  98         /* Check for rng init function, execute it */
  99         rng_setup = rng_id->data;
 100         if (rng_setup)
 101                 rng_setup(rng_base);
 102
 103         /* set warm-up count & enable */
 104         __raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
 105         __raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
 106
 107         /* register driver */
 108         err = hwrng_register(&bcm2835_rng_ops);
 109         if (err) {
 110                 dev_err(dev, "hwrng registration failed\n");
 111                 iounmap(rng_base);
 112         } else
 113                 dev_info(dev, "hwrng registered\n");
 114
 115         return err;
 116 }
 117
 118 static int bcm2835_rng_remove(struct platform_device *pdev)
 119 {
 120         void __iomem *rng_base = (void __iomem *)bcm2835_rng_ops.priv;
 121
 122         /* disable rng hardware */
 123         __raw_writel(0, rng_base + RNG_CTRL);
 124
 125         /* unregister driver */
 126         hwrng_unregister(&bcm2835_rng_ops);
 127         iounmap(rng_base);
 128
 129         return 0;
 130 }
 131
 132 MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
 133
 134 static struct platform_driver bcm2835_rng_driver = {
 135         .driver = {
 136                 .name = "bcm2835-rng",
 137                 .of_match_table = bcm2835_rng_of_match,
 138         },
 139         .probe          = bcm2835_rng_probe,
 140         .remove         = bcm2835_rng_remove,
 141 };
 142 module_platform_driver(bcm2835_rng_driver);
 143
 144 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
 145 MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
 146 MODULE_LICENSE("GPL v2");