drivers/char/hw_random/exynos-trng.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RNG driver for Exynos TRNGs
   4  *
   5  * Author: Łukasz Stelmach <l.stelmach@samsung.com>
   6  *
   7  * Copyright 2017 (c) Samsung Electronics Software, Inc.
   8  *
   9  * Based on the Exynos PRNG driver drivers/crypto/exynos-rng by
  10  * Krzysztof Kozłowski <krzk@kernel.org>
  11  */
  12
  13 #include <linux/clk.h>
  14 #include <linux/crypto.h>
  15 #include <linux/delay.h>
  16 #include <linux/err.h>
  17 #include <linux/hw_random.h>
  18 #include <linux/io.h>
  19 #include <linux/iopoll.h>
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/mod_devicetable.h>
  23 #include <linux/platform_device.h>
  24 #include <linux/pm_runtime.h>
  25
  26 #define EXYNOS_TRNG_CLKDIV         (0x0)
  27
  28 #define EXYNOS_TRNG_CTRL           (0x20)
  29 #define EXYNOS_TRNG_CTRL_RNGEN     BIT(31)
  30
  31 #define EXYNOS_TRNG_POST_CTRL      (0x30)
  32 #define EXYNOS_TRNG_ONLINE_CTRL    (0x40)
  33 #define EXYNOS_TRNG_ONLINE_STAT    (0x44)
  34 #define EXYNOS_TRNG_ONLINE_MAXCHI2 (0x48)
  35 #define EXYNOS_TRNG_FIFO_CTRL      (0x50)
  36 #define EXYNOS_TRNG_FIFO_0         (0x80)
  37 #define EXYNOS_TRNG_FIFO_1         (0x84)
  38 #define EXYNOS_TRNG_FIFO_2         (0x88)
  39 #define EXYNOS_TRNG_FIFO_3         (0x8c)
  40 #define EXYNOS_TRNG_FIFO_4         (0x90)
  41 #define EXYNOS_TRNG_FIFO_5         (0x94)
  42 #define EXYNOS_TRNG_FIFO_6         (0x98)
  43 #define EXYNOS_TRNG_FIFO_7         (0x9c)
  44 #define EXYNOS_TRNG_FIFO_LEN       (8)
  45 #define EXYNOS_TRNG_CLOCK_RATE     (500000)
  46
  47
  48 struct exynos_trng_dev {
  49         struct device    *dev;
  50         void __iomem     *mem;
  51         struct clk       *clk;
  52         struct hwrng rng;
  53 };
  54
  55 static int exynos_trng_do_read(struct hwrng *rng, void *data, size_t max,
  56                                bool wait)
  57 {
  58         struct exynos_trng_dev *trng;
  59         int val;
  60
  61         max = min_t(size_t, max, (EXYNOS_TRNG_FIFO_LEN * 4));
  62
  63         trng = (struct exynos_trng_dev *)rng->priv;
  64
  65         writel_relaxed(max * 8, trng->mem + EXYNOS_TRNG_FIFO_CTRL);
  66         val = readl_poll_timeout(trng->mem + EXYNOS_TRNG_FIFO_CTRL, val,
  67                                  val == 0, 200, 1000000);
  68         if (val < 0)
  69                 return val;
  70
  71         memcpy_fromio(data, trng->mem + EXYNOS_TRNG_FIFO_0, max);
  72
  73         return max;
  74 }
  75
  76 static int exynos_trng_init(struct hwrng *rng)
  77 {
  78         struct exynos_trng_dev *trng = (struct exynos_trng_dev *)rng->priv;
  79         unsigned long sss_rate;
  80         u32 val;
  81
  82         sss_rate = clk_get_rate(trng->clk);
  83
  84         /*
  85          * For most TRNG circuits the clock frequency of under 500 kHz
  86          * is safe.
  87          */
  88         val = sss_rate / (EXYNOS_TRNG_CLOCK_RATE * 2);
  89         if (val > 0x7fff) {
  90                 dev_err(trng->dev, "clock divider too large: %d", val);
  91                 return -ERANGE;
  92         }
  93         val = val << 1;
  94         writel_relaxed(val, trng->mem + EXYNOS_TRNG_CLKDIV);
  95
  96         /* Enable the generator. */
  97         val = EXYNOS_TRNG_CTRL_RNGEN;
  98         writel_relaxed(val, trng->mem + EXYNOS_TRNG_CTRL);
  99
 100         /*
 101          * Disable post-processing. /dev/hwrng is supposed to deliver
 102          * unprocessed data.
 103          */
 104         writel_relaxed(0, trng->mem + EXYNOS_TRNG_POST_CTRL);
 105
 106         return 0;
 107 }
 108
 109 static int exynos_trng_probe(struct platform_device *pdev)
 110 {
 111         struct exynos_trng_dev *trng;
 112         int ret = -ENOMEM;
 113
 114         trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
 115         if (!trng)
 116                 return ret;
 117
 118         trng->rng.name = devm_kstrdup(&pdev->dev, dev_name(&pdev->dev),
 119                                       GFP_KERNEL);
 120         if (!trng->rng.name)
 121                 return ret;
 122
 123         trng->rng.init = exynos_trng_init;
 124         trng->rng.read = exynos_trng_do_read;
 125         trng->rng.priv = (unsigned long) trng;
 126
 127         platform_set_drvdata(pdev, trng);
 128         trng->dev = &pdev->dev;
 129
 130         trng->mem = devm_platform_ioremap_resource(pdev, 0);
 131         if (IS_ERR(trng->mem))
 132                 return PTR_ERR(trng->mem);
 133
 134         pm_runtime_enable(&pdev->dev);
 135         ret = pm_runtime_get_sync(&pdev->dev);
 136         if (ret < 0) {
 137                 dev_err(&pdev->dev, "Could not get runtime PM.\n");
 138                 goto err_pm_get;
 139         }
 140
 141         trng->clk = devm_clk_get(&pdev->dev, "secss");
 142         if (IS_ERR(trng->clk)) {
 143                 ret = PTR_ERR(trng->clk);
 144                 dev_err(&pdev->dev, "Could not get clock.\n");
 145                 goto err_clock;
 146         }
 147
 148         ret = clk_prepare_enable(trng->clk);
 149         if (ret) {
 150                 dev_err(&pdev->dev, "Could not enable the clk.\n");
 151                 goto err_clock;
 152         }
 153
 154         ret = devm_hwrng_register(&pdev->dev, &trng->rng);
 155         if (ret) {
 156                 dev_err(&pdev->dev, "Could not register hwrng device.\n");
 157                 goto err_register;
 158         }
 159
 160         dev_info(&pdev->dev, "Exynos True Random Number Generator.\n");
 161
 162         return 0;
 163
 164 err_register:
 165         clk_disable_unprepare(trng->clk);
 166
 167 err_clock:
 168         pm_runtime_put_sync(&pdev->dev);
 169
 170 err_pm_get:
 171         pm_runtime_disable(&pdev->dev);
 172
 173         return ret;
 174 }
 175
 176 static int exynos_trng_remove(struct platform_device *pdev)
 177 {
 178         struct exynos_trng_dev *trng =  platform_get_drvdata(pdev);
 179
 180         clk_disable_unprepare(trng->clk);
 181
 182         pm_runtime_put_sync(&pdev->dev);
 183         pm_runtime_disable(&pdev->dev);
 184
 185         return 0;
 186 }
 187
 188 static int __maybe_unused exynos_trng_suspend(struct device *dev)
 189 {
 190         pm_runtime_put_sync(dev);
 191
 192         return 0;
 193 }
 194
 195 static int __maybe_unused exynos_trng_resume(struct device *dev)
 196 {
 197         int ret;
 198
 199         ret = pm_runtime_get_sync(dev);
 200         if (ret < 0) {
 201                 dev_err(dev, "Could not get runtime PM.\n");
 202                 pm_runtime_put_noidle(dev);
 203                 return ret;
 204         }
 205
 206         return 0;
 207 }
 208
 209 static SIMPLE_DEV_PM_OPS(exynos_trng_pm_ops, exynos_trng_suspend,
 210                          exynos_trng_resume);
 211
 212 static const struct of_device_id exynos_trng_dt_match[] = {
 213         {
 214                 .compatible = "samsung,exynos5250-trng",
 215         },
 216         { },
 217 };
 218 MODULE_DEVICE_TABLE(of, exynos_trng_dt_match);
 219
 220 static struct platform_driver exynos_trng_driver = {
 221         .driver = {
 222                 .name = "exynos-trng",
 223                 .pm = &exynos_trng_pm_ops,
 224                 .of_match_table = exynos_trng_dt_match,
 225         },
 226         .probe = exynos_trng_probe,
 227         .remove = exynos_trng_remove,
 228 };
 229
 230 module_platform_driver(exynos_trng_driver);
 231 MODULE_AUTHOR("Łukasz Stelmach");
 232 MODULE_DESCRIPTION("H/W TRNG driver for Exynos chips");
 233 MODULE_LICENSE("GPL v2");