drivers/char/hw_random/hisi-rng.c

   1 /*
   2  * Copyright (C) 2016 HiSilicon Co., Ltd.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/err.h>
  10 #include <linux/kernel.h>
  11 #include <linux/hw_random.h>
  12 #include <linux/io.h>
  13 #include <linux/module.h>
  14 #include <linux/of.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/random.h>
  17
  18 #define RNG_SEED        0x0
  19 #define RNG_CTRL        0x4
  20   #define RNG_SEED_SEL  BIT(2)
  21   #define RNG_RING_EN   BIT(1)
  22   #define RNG_EN        BIT(0)
  23 #define RNG_RAN_NUM     0x10
  24 #define RNG_PHY_SEED    0x14
  25
  26 #define to_hisi_rng(p)  container_of(p, struct hisi_rng, rng)
  27
  28 static int seed_sel;
  29 module_param(seed_sel, int, S_IRUGO);
  30 MODULE_PARM_DESC(seed_sel, "Auto reload seed. 0, use LFSR(default); 1, use ring oscillator.");
  31
  32 struct hisi_rng {
  33         void __iomem *base;
  34         struct hwrng rng;
  35 };
  36
  37 static int hisi_rng_init(struct hwrng *rng)
  38 {
  39         struct hisi_rng *hrng = to_hisi_rng(rng);
  40         int val = RNG_EN;
  41         u32 seed;
  42
  43         /* get a random number as initial seed */
  44         get_random_bytes(&seed, sizeof(seed));
  45
  46         writel_relaxed(seed, hrng->base + RNG_SEED);
  47
  48         /**
  49          * The seed is reload periodically, there are two choice
  50          * of seeds, default seed using the value from LFSR, or
  51          * will use seed generated by ring oscillator.
  52          */
  53         if (seed_sel == 1)
  54                 val |= RNG_RING_EN | RNG_SEED_SEL;
  55
  56         writel_relaxed(val, hrng->base + RNG_CTRL);
  57         return 0;
  58 }
  59
  60 static void hisi_rng_cleanup(struct hwrng *rng)
  61 {
  62         struct hisi_rng *hrng = to_hisi_rng(rng);
  63
  64         writel_relaxed(0, hrng->base + RNG_CTRL);
  65 }
  66
  67 static int hisi_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  68 {
  69         struct hisi_rng *hrng = to_hisi_rng(rng);
  70         u32 *data = buf;
  71
  72         *data = readl_relaxed(hrng->base + RNG_RAN_NUM);
  73         return 4;
  74 }
  75
  76 static int hisi_rng_probe(struct platform_device *pdev)
  77 {
  78         struct hisi_rng *rng;
  79         struct resource *res;
  80         int ret;
  81
  82         rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
  83         if (!rng)
  84                 return -ENOMEM;
  85
  86         platform_set_drvdata(pdev, rng);
  87
  88         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  89         rng->base = devm_ioremap_resource(&pdev->dev, res);
  90         if (IS_ERR(rng->base))
  91                 return PTR_ERR(rng->base);
  92
  93         rng->rng.name = pdev->name;
  94         rng->rng.init = hisi_rng_init;
  95         rng->rng.cleanup = hisi_rng_cleanup;
  96         rng->rng.read = hisi_rng_read;
  97
  98         ret = devm_hwrng_register(&pdev->dev, &rng->rng);
  99         if (ret) {
 100                 dev_err(&pdev->dev, "failed to register hwrng\n");
 101                 return ret;
 102         }
 103
 104         return 0;
 105 }
 106
 107 static const struct of_device_id hisi_rng_dt_ids[] = {
 108         { .compatible = "hisilicon,hip04-rng" },
 109         { .compatible = "hisilicon,hip05-rng" },
 110         { }
 111 };
 112 MODULE_DEVICE_TABLE(of, hisi_rng_dt_ids);
 113
 114 static struct platform_driver hisi_rng_driver = {
 115         .probe          = hisi_rng_probe,
 116         .driver         = {
 117                 .name   = "hisi-rng",
 118                 .of_match_table = of_match_ptr(hisi_rng_dt_ids),
 119         },
 120 };
 121
 122 module_platform_driver(hisi_rng_driver);
 123
 124 MODULE_LICENSE("GPL");
 125 MODULE_AUTHOR("Kefeng Wang <wangkefeng.wang@huawei>");
 126 MODULE_DESCRIPTION("Hisilicon random number generator driver");