drivers/char/hw_random/meson-rng.c

   1 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
   2 /*
   3  * Copyright (c) 2016 BayLibre, SAS.
   4  * Author: Neil Armstrong <narmstrong@baylibre.com>
   5  * Copyright (C) 2014 Amlogic, Inc.
   6  */
   7 #include <linux/err.h>
   8 #include <linux/module.h>
   9 #include <linux/io.h>
  10 #include <linux/platform_device.h>
  11 #include <linux/hw_random.h>
  12 #include <linux/slab.h>
  13 #include <linux/types.h>
  14 #include <linux/of.h>
  15 #include <linux/clk.h>
  16 #include <linux/iopoll.h>
  17
  18 #define RNG_DATA        0x00
  19 #define RNG_S4_DATA     0x08
  20 #define RNG_S4_CFG      0x00
  21
  22 #define RUN_BIT         BIT(0)
  23 #define SEED_READY_STS_BIT      BIT(31)
  24
  25 struct meson_rng_priv {
  26         int (*read)(struct hwrng *rng, void *buf, size_t max, bool wait);
  27 };
  28
  29 struct meson_rng_data {
  30         void __iomem *base;
  31         struct hwrng rng;
  32         struct device *dev;
  33 };
  34
  35 static int meson_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  36 {
  37         struct meson_rng_data *data =
  38                         container_of(rng, struct meson_rng_data, rng);
  39
  40         *(u32 *)buf = readl_relaxed(data->base + RNG_DATA);
  41
  42         return sizeof(u32);
  43 }
  44
  45 static int meson_rng_wait_status(void __iomem *cfg_addr, int bit)
  46 {
  47         u32 status = 0;
  48         int ret;
  49
  50         ret = readl_relaxed_poll_timeout_atomic(cfg_addr,
  51                                                 status, !(status & bit),
  52                                                 10, 10000);
  53         if (ret)
  54                 return -EBUSY;
  55
  56         return 0;
  57 }
  58
  59 static int meson_s4_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  60 {
  61         struct meson_rng_data *data =
  62                         container_of(rng, struct meson_rng_data, rng);
  63
  64         void __iomem *cfg_addr = data->base + RNG_S4_CFG;
  65         int err;
  66
  67         writel_relaxed(readl_relaxed(cfg_addr) | SEED_READY_STS_BIT, cfg_addr);
  68
  69         err = meson_rng_wait_status(cfg_addr, SEED_READY_STS_BIT);
  70         if (err) {
  71                 dev_err(data->dev, "Seed isn't ready, try again\n");
  72                 return err;
  73         }
  74
  75         err = meson_rng_wait_status(cfg_addr, RUN_BIT);
  76         if (err) {
  77                 dev_err(data->dev, "Can't get random number, try again\n");
  78                 return err;
  79         }
  80
  81         *(u32 *)buf = readl_relaxed(data->base + RNG_S4_DATA);
  82
  83         return sizeof(u32);
  84 }
  85
  86 static int meson_rng_probe(struct platform_device *pdev)
  87 {
  88         struct device *dev = &pdev->dev;
  89         struct meson_rng_data *data;
  90         struct clk *core_clk;
  91         const struct meson_rng_priv *priv;
  92
  93         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
  94         if (!data)
  95                 return -ENOMEM;
  96
  97         priv = device_get_match_data(&pdev->dev);
  98         if (!priv)
  99                 return -ENODEV;
 100
 101         data->base = devm_platform_ioremap_resource(pdev, 0);
 102         if (IS_ERR(data->base))
 103                 return PTR_ERR(data->base);
 104
 105         core_clk = devm_clk_get_optional_enabled(dev, "core");
 106         if (IS_ERR(core_clk))
 107                 return dev_err_probe(dev, PTR_ERR(core_clk),
 108                                      "Failed to get core clock\n");
 109
 110         data->rng.name = pdev->name;
 111         data->rng.read = priv->read;
 112
 113         data->dev = &pdev->dev;
 114
 115         return devm_hwrng_register(dev, &data->rng);
 116 }
 117
 118 static const struct meson_rng_priv meson_rng_priv = {
 119         .read = meson_rng_read,
 120 };
 121
 122 static const struct meson_rng_priv meson_rng_priv_s4 = {
 123         .read = meson_s4_rng_read,
 124 };
 125
 126 static const struct of_device_id meson_rng_of_match[] = {
 127         {
 128                 .compatible = "amlogic,meson-rng",
 129                 .data = (void *)&meson_rng_priv,
 130         },
 131         {
 132                 .compatible = "amlogic,meson-s4-rng",
 133                 .data = (void *)&meson_rng_priv_s4,
 134         },
 135         {},
 136 };
 137 MODULE_DEVICE_TABLE(of, meson_rng_of_match);
 138
 139 static struct platform_driver meson_rng_driver = {
 140         .probe  = meson_rng_probe,
 141         .driver = {
 142                 .name = "meson-rng",
 143                 .of_match_table = meson_rng_of_match,
 144         },
 145 };
 146
 147 module_platform_driver(meson_rng_driver);
 148
 149 MODULE_DESCRIPTION("Meson H/W Random Number Generator driver");
 150 MODULE_AUTHOR("Lawrence Mok <lawrence.mok@amlogic.com>");
 151 MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
 152 MODULE_LICENSE("Dual BSD/GPL");