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         struct resource *res;
 113         int ret = -ENOMEM;
 114
 115         trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
 116         if (!trng)
 117                 return ret;
 118
 119         trng->rng.name = devm_kstrdup(&pdev->dev, dev_name(&pdev->dev),
 120                                       GFP_KERNEL);
 121         if (!trng->rng.name)
 122                 return ret;
 123
 124         trng->rng.init = exynos_trng_init;
 125         trng->rng.read = exynos_trng_do_read;
 126         trng->rng.priv = (unsigned long) trng;
 127
 128         platform_set_drvdata(pdev, trng);
 129         trng->dev = &pdev->dev;
 130
 131         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 132         trng->mem = devm_ioremap_resource(&pdev->dev, res);
 133         if (IS_ERR(trng->mem))
 134                 return PTR_ERR(trng->mem);
 135
 136         pm_runtime_enable(&pdev->dev);
 137         ret = pm_runtime_get_sync(&pdev->dev);
 138         if (ret < 0) {
 139                 dev_err(&pdev->dev, "Could not get runtime PM.\n");
 140                 goto err_pm_get;
 141         }
 142
 143         trng->clk = devm_clk_get(&pdev->dev, "secss");
 144         if (IS_ERR(trng->clk)) {
 145                 ret = PTR_ERR(trng->clk);
 146                 dev_err(&pdev->dev, "Could not get clock.\n");
 147                 goto err_clock;
 148         }
 149
 150         ret = clk_prepare_enable(trng->clk);
 151         if (ret) {
 152                 dev_err(&pdev->dev, "Could not enable the clk.\n");
 153                 goto err_clock;
 154         }
 155
 156         ret = hwrng_register(&trng->rng);
 157         if (ret) {
 158                 dev_err(&pdev->dev, "Could not register hwrng device.\n");
 159                 goto err_register;
 160         }
 161
 162         dev_info(&pdev->dev, "Exynos True Random Number Generator.\n");
 163
 164         return 0;
 165
 166 err_register:
 167         clk_disable_unprepare(trng->clk);
 168
 169 err_clock:
 170         pm_runtime_put_sync(&pdev->dev);
 171
 172 err_pm_get:
 173         pm_runtime_disable(&pdev->dev);
 174
 175         return ret;
 176 }
 177
 178 static int exynos_trng_remove(struct platform_device *pdev)
 179 {
 180         struct exynos_trng_dev *trng =  platform_get_drvdata(pdev);
 181
 182         hwrng_unregister(&trng->rng);
 183         clk_disable_unprepare(trng->clk);
 184
 185         pm_runtime_put_sync(&pdev->dev);
 186         pm_runtime_disable(&pdev->dev);
 187
 188         return 0;
 189 }
 190
 191 static int __maybe_unused exynos_trng_suspend(struct device *dev)
 192 {
 193         pm_runtime_put_sync(dev);
 194
 195         return 0;
 196 }
 197
 198 static int __maybe_unused exynos_trng_resume(struct device *dev)
 199 {
 200         int ret;
 201
 202         ret = pm_runtime_get_sync(dev);
 203         if (ret < 0) {
 204                 dev_err(dev, "Could not get runtime PM.\n");
 205                 pm_runtime_put_noidle(dev);
 206                 return ret;
 207         }
 208
 209         return 0;
 210 }
 211
 212 static SIMPLE_DEV_PM_OPS(exynos_trng_pm_ops, exynos_trng_suspend,
 213                          exynos_trng_resume);
 214
 215 static const struct of_device_id exynos_trng_dt_match[] = {
 216         {
 217                 .compatible = "samsung,exynos5250-trng",
 218         },
 219         { },
 220 };
 221 MODULE_DEVICE_TABLE(of, exynos_trng_dt_match);
 222
 223 static struct platform_driver exynos_trng_driver = {
 224         .driver = {
 225                 .name = "exynos-trng",
 226                 .pm = &exynos_trng_pm_ops,
 227                 .of_match_table = exynos_trng_dt_match,
 228         },
 229         .probe = exynos_trng_probe,
 230         .remove = exynos_trng_remove,
 231 };
 232
 233 module_platform_driver(exynos_trng_driver);
 234 MODULE_AUTHOR("Łukasz Stelmach");
 235 MODULE_DESCRIPTION("H/W TRNG driver for Exynos chips");
 236 MODULE_LICENSE("GPL v2");