LXR linux/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
  32static 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
  42static 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
  65static struct hwrng bcm2835_rng_ops = {
  66        .name   = "bcm2835",
  67        .read   = bcm2835_rng_read,
  68};
  69
  70static 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
  77static 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                iounmap(rng_base);
  97                return -EINVAL;
  98        }
  99        /* Check for rng init function, execute it */
 100        rng_setup = rng_id->data;
 101        if (rng_setup)
 102                rng_setup(rng_base);
 103
 104        /* set warm-up count & enable */
 105        __raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
 106        __raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
 107
 108        /* register driver */
 109        err = hwrng_register(&bcm2835_rng_ops);
 110        if (err) {
 111                dev_err(dev, "hwrng registration failed\n");
 112                iounmap(rng_base);
 113        } else
 114                dev_info(dev, "hwrng registered\n");
 115
 116        return err;
 117}
 118
 119static int bcm2835_rng_remove(struct platform_device *pdev)
 120{
 121        void __iomem *rng_base = (void __iomem *)bcm2835_rng_ops.priv;
 122
 123        /* disable rng hardware */
 124        __raw_writel(0, rng_base + RNG_CTRL);
 125
 126        /* unregister driver */
 127        hwrng_unregister(&bcm2835_rng_ops);
 128        iounmap(rng_base);
 129
 130        return 0;
 131}
 132
 133MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
 134
 135static struct platform_driver bcm2835_rng_driver = {
 136        .driver = {
 137                .name = "bcm2835-rng",
 138                .of_match_table = bcm2835_rng_of_match,
 139        },
 140        .probe          = bcm2835_rng_probe,
 141        .remove         = bcm2835_rng_remove,
 142};
 143module_platform_driver(bcm2835_rng_driver);
 144
 145MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
 146MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
 147MODULE_LICENSE("GPL v2");
 148