drivers/char/hw_random/hisi-rng.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2016 HiSilicon Co., Ltd.
   4  */
   5
   6 #include <linux/err.h>
   7 #include <linux/kernel.h>
   8 #include <linux/hw_random.h>
   9 #include <linux/io.h>
  10 #include <linux/module.h>
  11 #include <linux/of.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/random.h>
  14
  15 #define RNG_SEED        0x0
  16 #define RNG_CTRL        0x4
  17   #define RNG_SEED_SEL  BIT(2)
  18   #define RNG_RING_EN   BIT(1)
  19   #define RNG_EN        BIT(0)
  20 #define RNG_RAN_NUM     0x10
  21 #define RNG_PHY_SEED    0x14
  22
  23 #define to_hisi_rng(p)  container_of(p, struct hisi_rng, rng)
  24
  25 static int seed_sel;
  26 module_param(seed_sel, int, S_IRUGO);
  27 MODULE_PARM_DESC(seed_sel, "Auto reload seed. 0, use LFSR(default); 1, use ring oscillator.");
  28
  29 struct hisi_rng {
  30         void __iomem *base;
  31         struct hwrng rng;
  32 };
  33
  34 static int hisi_rng_init(struct hwrng *rng)
  35 {
  36         struct hisi_rng *hrng = to_hisi_rng(rng);
  37         int val = RNG_EN;
  38         u32 seed;
  39
  40         /* get a random number as initial seed */
  41         get_random_bytes(&seed, sizeof(seed));
  42
  43         writel_relaxed(seed, hrng->base + RNG_SEED);
  44
  45         /**
  46          * The seed is reload periodically, there are two choice
  47          * of seeds, default seed using the value from LFSR, or
  48          * will use seed generated by ring oscillator.
  49          */
  50         if (seed_sel == 1)
  51                 val |= RNG_RING_EN | RNG_SEED_SEL;
  52
  53         writel_relaxed(val, hrng->base + RNG_CTRL);
  54         return 0;
  55 }
  56
  57 static void hisi_rng_cleanup(struct hwrng *rng)
  58 {
  59         struct hisi_rng *hrng = to_hisi_rng(rng);
  60
  61         writel_relaxed(0, hrng->base + RNG_CTRL);
  62 }
  63
  64 static int hisi_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  65 {
  66         struct hisi_rng *hrng = to_hisi_rng(rng);
  67         u32 *data = buf;
  68
  69         *data = readl_relaxed(hrng->base + RNG_RAN_NUM);
  70         return 4;
  71 }
  72
  73 static int hisi_rng_probe(struct platform_device *pdev)
  74 {
  75         struct hisi_rng *rng;
  76         int ret;
  77
  78         rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
  79         if (!rng)
  80                 return -ENOMEM;
  81
  82         platform_set_drvdata(pdev, rng);
  83
  84         rng->base = devm_platform_ioremap_resource(pdev, 0);
  85         if (IS_ERR(rng->base))
  86                 return PTR_ERR(rng->base);
  87
  88         rng->rng.name = pdev->name;
  89         rng->rng.init = hisi_rng_init;
  90         rng->rng.cleanup = hisi_rng_cleanup;
  91         rng->rng.read = hisi_rng_read;
  92
  93         ret = devm_hwrng_register(&pdev->dev, &rng->rng);
  94         if (ret) {
  95                 dev_err(&pdev->dev, "failed to register hwrng\n");
  96                 return ret;
  97         }
  98
  99         return 0;
 100 }
 101
 102 static const struct of_device_id hisi_rng_dt_ids[] __maybe_unused = {
 103         { .compatible = "hisilicon,hip04-rng" },
 104         { .compatible = "hisilicon,hip05-rng" },
 105         { }
 106 };
 107 MODULE_DEVICE_TABLE(of, hisi_rng_dt_ids);
 108
 109 static struct platform_driver hisi_rng_driver = {
 110         .probe          = hisi_rng_probe,
 111         .driver         = {
 112                 .name   = "hisi-rng",
 113                 .of_match_table = of_match_ptr(hisi_rng_dt_ids),
 114         },
 115 };
 116
 117 module_platform_driver(hisi_rng_driver);
 118
 119 MODULE_LICENSE("GPL");
 120 MODULE_AUTHOR("Kefeng Wang <wangkefeng.wang@huawei>");
 121 MODULE_DESCRIPTION("Hisilicon random number generator driver");