drivers/char/hw_random/bcm2835-rng.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2010-2012 Broadcom. All rights reserved.
   4  * Copyright (c) 2013 Lubomir Rintel
   5  */
   6
   7 #include <linux/hw_random.h>
   8 #include <linux/io.h>
   9 #include <linux/kernel.h>
  10 #include <linux/module.h>
  11 #include <linux/of_address.h>
  12 #include <linux/of_platform.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/printk.h>
  15 #include <linux/clk.h>
  16
  17 #define RNG_CTRL        0x0
  18 #define RNG_STATUS      0x4
  19 #define RNG_DATA        0x8
  20 #define RNG_INT_MASK    0x10
  21
  22 /* enable rng */
  23 #define RNG_RBGEN       0x1
  24
  25 /* the initial numbers generated are "less random" so will be discarded */
  26 #define RNG_WARMUP_COUNT 0x40000
  27
  28 #define RNG_INT_OFF     0x1
  29
  30 struct bcm2835_rng_priv {
  31         struct hwrng rng;
  32         void __iomem *base;
  33         bool mask_interrupts;
  34         struct clk *clk;
  35 };
  36
  37 static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
  38 {
  39         return container_of(rng, struct bcm2835_rng_priv, rng);
  40 }
  41
  42 static inline u32 rng_readl(struct bcm2835_rng_priv *priv, u32 offset)
  43 {
  44         /* MIPS chips strapped for BE will automagically configure the
  45          * peripheral registers for CPU-native byte order.
  46          */
  47         if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
  48                 return __raw_readl(priv->base + offset);
  49         else
  50                 return readl(priv->base + offset);
  51 }
  52
  53 static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val,
  54                               u32 offset)
  55 {
  56         if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
  57                 __raw_writel(val, priv->base + offset);
  58         else
  59                 writel(val, priv->base + offset);
  60 }
  61
  62 static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
  63                                bool wait)
  64 {
  65         struct bcm2835_rng_priv *priv = to_rng_priv(rng);
  66         u32 max_words = max / sizeof(u32);
  67         u32 num_words, count;
  68
  69         while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) {
  70                 if (!wait)
  71                         return 0;
  72                 cpu_relax();
  73         }
  74
  75         num_words = rng_readl(priv, RNG_STATUS) >> 24;
  76         if (num_words > max_words)
  77                 num_words = max_words;
  78
  79         for (count = 0; count < num_words; count++)
  80                 ((u32 *)buf)[count] = rng_readl(priv, RNG_DATA);
  81
  82         return num_words * sizeof(u32);
  83 }
  84
  85 static int bcm2835_rng_init(struct hwrng *rng)
  86 {
  87         struct bcm2835_rng_priv *priv = to_rng_priv(rng);
  88         int ret = 0;
  89         u32 val;
  90
  91         if (!IS_ERR(priv->clk)) {
  92                 ret = clk_prepare_enable(priv->clk);
  93                 if (ret)
  94                         return ret;
  95         }
  96
  97         if (priv->mask_interrupts) {
  98                 /* mask the interrupt */
  99                 val = rng_readl(priv, RNG_INT_MASK);
 100                 val |= RNG_INT_OFF;
 101                 rng_writel(priv, val, RNG_INT_MASK);
 102         }
 103
 104         /* set warm-up count & enable */
 105         rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS);
 106         rng_writel(priv, RNG_RBGEN, RNG_CTRL);
 107
 108         return ret;
 109 }
 110
 111 static void bcm2835_rng_cleanup(struct hwrng *rng)
 112 {
 113         struct bcm2835_rng_priv *priv = to_rng_priv(rng);
 114
 115         /* disable rng hardware */
 116         rng_writel(priv, 0, RNG_CTRL);
 117
 118         if (!IS_ERR(priv->clk))
 119                 clk_disable_unprepare(priv->clk);
 120 }
 121
 122 struct bcm2835_rng_of_data {
 123         bool mask_interrupts;
 124 };
 125
 126 static const struct bcm2835_rng_of_data nsp_rng_of_data = {
 127         .mask_interrupts = true,
 128 };
 129
 130 static const struct of_device_id bcm2835_rng_of_match[] = {
 131         { .compatible = "brcm,bcm2835-rng"},
 132         { .compatible = "brcm,bcm-nsp-rng", .data = &nsp_rng_of_data },
 133         { .compatible = "brcm,bcm5301x-rng", .data = &nsp_rng_of_data },
 134         { .compatible = "brcm,bcm6368-rng"},
 135         {},
 136 };
 137
 138 static int bcm2835_rng_probe(struct platform_device *pdev)
 139 {
 140         const struct bcm2835_rng_of_data *of_data;
 141         struct device *dev = &pdev->dev;
 142         struct device_node *np = dev->of_node;
 143         const struct of_device_id *rng_id;
 144         struct bcm2835_rng_priv *priv;
 145         struct resource *r;
 146         int err;
 147
 148         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 149         if (!priv)
 150                 return -ENOMEM;
 151
 152         platform_set_drvdata(pdev, priv);
 153
 154         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 155
 156         /* map peripheral */
 157         priv->base = devm_ioremap_resource(dev, r);
 158         if (IS_ERR(priv->base))
 159                 return PTR_ERR(priv->base);
 160
 161         /* Clock is optional on most platforms */
 162         priv->clk = devm_clk_get(dev, NULL);
 163         if (IS_ERR(priv->clk) && PTR_ERR(priv->clk) == -EPROBE_DEFER)
 164                 return -EPROBE_DEFER;
 165
 166         priv->rng.name = pdev->name;
 167         priv->rng.init = bcm2835_rng_init;
 168         priv->rng.read = bcm2835_rng_read;
 169         priv->rng.cleanup = bcm2835_rng_cleanup;
 170
 171         if (dev_of_node(dev)) {
 172                 rng_id = of_match_node(bcm2835_rng_of_match, np);
 173                 if (!rng_id)
 174                         return -EINVAL;
 175
 176                 /* Check for rng init function, execute it */
 177                 of_data = rng_id->data;
 178                 if (of_data)
 179                         priv->mask_interrupts = of_data->mask_interrupts;
 180         }
 181
 182         /* register driver */
 183         err = devm_hwrng_register(dev, &priv->rng);
 184         if (err)
 185                 dev_err(dev, "hwrng registration failed\n");
 186         else
 187                 dev_info(dev, "hwrng registered\n");
 188
 189         return err;
 190 }
 191
 192 MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
 193
 194 static struct platform_device_id bcm2835_rng_devtype[] = {
 195         { .name = "bcm2835-rng" },
 196         { .name = "bcm63xx-rng" },
 197         { /* sentinel */ }
 198 };
 199 MODULE_DEVICE_TABLE(platform, bcm2835_rng_devtype);
 200
 201 static struct platform_driver bcm2835_rng_driver = {
 202         .driver = {
 203                 .name = "bcm2835-rng",
 204                 .of_match_table = bcm2835_rng_of_match,
 205         },
 206         .probe          = bcm2835_rng_probe,
 207         .id_table       = bcm2835_rng_devtype,
 208 };
 209 module_platform_driver(bcm2835_rng_driver);
 210
 211 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
 212 MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
 213 MODULE_LICENSE("GPL v2");