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 #include <linux/clk.h>
  19
  20 #define RNG_CTRL        0x0
  21 #define RNG_STATUS      0x4
  22 #define RNG_DATA        0x8
  23 #define RNG_INT_MASK    0x10
  24
  25 /* enable rng */
  26 #define RNG_RBGEN       0x1
  27
  28 /* the initial numbers generated are "less random" so will be discarded */
  29 #define RNG_WARMUP_COUNT 0x40000
  30
  31 #define RNG_INT_OFF     0x1
  32
  33 struct bcm2835_rng_priv {
  34         struct hwrng rng;
  35         void __iomem *base;
  36         bool mask_interrupts;
  37         struct clk *clk;
  38 };
  39
  40 static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
  41 {
  42         return container_of(rng, struct bcm2835_rng_priv, rng);
  43 }
  44
  45 static inline u32 rng_readl(struct bcm2835_rng_priv *priv, u32 offset)
  46 {
  47         /* MIPS chips strapped for BE will automagically configure the
  48          * peripheral registers for CPU-native byte order.
  49          */
  50         if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
  51                 return __raw_readl(priv->base + offset);
  52         else
  53                 return readl(priv->base + offset);
  54 }
  55
  56 static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val,
  57                               u32 offset)
  58 {
  59         if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
  60                 __raw_writel(val, priv->base + offset);
  61         else
  62                 writel(val, priv->base + offset);
  63 }
  64
  65 static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
  66                                bool wait)
  67 {
  68         struct bcm2835_rng_priv *priv = to_rng_priv(rng);
  69         u32 max_words = max / sizeof(u32);
  70         u32 num_words, count;
  71
  72         while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) {
  73                 if (!wait)
  74                         return 0;
  75                 cpu_relax();
  76         }
  77
  78         num_words = rng_readl(priv, RNG_STATUS) >> 24;
  79         if (num_words > max_words)
  80                 num_words = max_words;
  81
  82         for (count = 0; count < num_words; count++)
  83                 ((u32 *)buf)[count] = rng_readl(priv, RNG_DATA);
  84
  85         return num_words * sizeof(u32);
  86 }
  87
  88 static int bcm2835_rng_init(struct hwrng *rng)
  89 {
  90         struct bcm2835_rng_priv *priv = to_rng_priv(rng);
  91         int ret = 0;
  92         u32 val;
  93
  94         if (!IS_ERR(priv->clk)) {
  95                 ret = clk_prepare_enable(priv->clk);
  96                 if (ret)
  97                         return ret;
  98         }
  99
 100         if (priv->mask_interrupts) {
 101                 /* mask the interrupt */
 102                 val = rng_readl(priv, RNG_INT_MASK);
 103                 val |= RNG_INT_OFF;
 104                 rng_writel(priv, val, RNG_INT_MASK);
 105         }
 106
 107         /* set warm-up count & enable */
 108         rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS);
 109         rng_writel(priv, RNG_RBGEN, RNG_CTRL);
 110
 111         return ret;
 112 }
 113
 114 static void bcm2835_rng_cleanup(struct hwrng *rng)
 115 {
 116         struct bcm2835_rng_priv *priv = to_rng_priv(rng);
 117
 118         /* disable rng hardware */
 119         rng_writel(priv, 0, RNG_CTRL);
 120
 121         if (!IS_ERR(priv->clk))
 122                 clk_disable_unprepare(priv->clk);
 123 }
 124
 125 struct bcm2835_rng_of_data {
 126         bool mask_interrupts;
 127 };
 128
 129 static const struct bcm2835_rng_of_data nsp_rng_of_data = {
 130         .mask_interrupts = true,
 131 };
 132
 133 static const struct of_device_id bcm2835_rng_of_match[] = {
 134         { .compatible = "brcm,bcm2835-rng"},
 135         { .compatible = "brcm,bcm-nsp-rng", .data = &nsp_rng_of_data },
 136         { .compatible = "brcm,bcm5301x-rng", .data = &nsp_rng_of_data },
 137         { .compatible = "brcm,bcm6368-rng"},
 138         {},
 139 };
 140
 141 static int bcm2835_rng_probe(struct platform_device *pdev)
 142 {
 143         const struct bcm2835_rng_of_data *of_data;
 144         struct device *dev = &pdev->dev;
 145         struct device_node *np = dev->of_node;
 146         const struct of_device_id *rng_id;
 147         struct bcm2835_rng_priv *priv;
 148         struct resource *r;
 149         int err;
 150
 151         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 152         if (!priv)
 153                 return -ENOMEM;
 154
 155         platform_set_drvdata(pdev, priv);
 156
 157         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 158
 159         /* map peripheral */
 160         priv->base = devm_ioremap_resource(dev, r);
 161         if (IS_ERR(priv->base))
 162                 return PTR_ERR(priv->base);
 163
 164         /* Clock is optional on most platforms */
 165         priv->clk = devm_clk_get(dev, NULL);
 166         if (IS_ERR(priv->clk) && PTR_ERR(priv->clk) == -EPROBE_DEFER)
 167                 return -EPROBE_DEFER;
 168
 169         priv->rng.name = pdev->name;
 170         priv->rng.init = bcm2835_rng_init;
 171         priv->rng.read = bcm2835_rng_read;
 172         priv->rng.cleanup = bcm2835_rng_cleanup;
 173
 174         rng_id = of_match_node(bcm2835_rng_of_match, np);
 175         if (!rng_id)
 176                 return -EINVAL;
 177
 178         /* Check for rng init function, execute it */
 179         of_data = rng_id->data;
 180         if (of_data)
 181                 priv->mask_interrupts = of_data->mask_interrupts;
 182
 183         /* register driver */
 184         err = devm_hwrng_register(dev, &priv->rng);
 185         if (err)
 186                 dev_err(dev, "hwrng registration failed\n");
 187         else
 188                 dev_info(dev, "hwrng registered\n");
 189
 190         return err;
 191 }
 192
 193 MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
 194
 195 static struct platform_device_id bcm2835_rng_devtype[] = {
 196         { .name = "bcm2835-rng" },
 197         { .name = "bcm63xx-rng" },
 198         { /* sentinel */ }
 199 };
 200 MODULE_DEVICE_TABLE(platform, bcm2835_rng_devtype);
 201
 202 static struct platform_driver bcm2835_rng_driver = {
 203         .driver = {
 204                 .name = "bcm2835-rng",
 205                 .of_match_table = bcm2835_rng_of_match,
 206         },
 207         .probe          = bcm2835_rng_probe,
 208         .id_table       = bcm2835_rng_devtype,
 209 };
 210 module_platform_driver(bcm2835_rng_driver);
 211
 212 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
 213 MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
 214 MODULE_LICENSE("GPL v2");