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
  17 #define RNG_DATA 0x00
  18
  19 struct meson_rng_data {
  20         void __iomem *base;
  21         struct platform_device *pdev;
  22         struct hwrng rng;
  23         struct clk *core_clk;
  24 };
  25
  26 static int meson_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  27 {
  28         struct meson_rng_data *data =
  29                         container_of(rng, struct meson_rng_data, rng);
  30
  31         *(u32 *)buf = readl_relaxed(data->base + RNG_DATA);
  32
  33         return sizeof(u32);
  34 }
  35
  36 static void meson_rng_clk_disable(void *data)
  37 {
  38         clk_disable_unprepare(data);
  39 }
  40
  41 static int meson_rng_probe(struct platform_device *pdev)
  42 {
  43         struct device *dev = &pdev->dev;
  44         struct meson_rng_data *data;
  45         int ret;
  46
  47         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
  48         if (!data)
  49                 return -ENOMEM;
  50
  51         data->pdev = pdev;
  52
  53         data->base = devm_platform_ioremap_resource(pdev, 0);
  54         if (IS_ERR(data->base))
  55                 return PTR_ERR(data->base);
  56
  57         data->core_clk = devm_clk_get(dev, "core");
  58         if (IS_ERR(data->core_clk))
  59                 data->core_clk = NULL;
  60
  61         if (data->core_clk) {
  62                 ret = clk_prepare_enable(data->core_clk);
  63                 if (ret)
  64                         return ret;
  65                 ret = devm_add_action_or_reset(dev, meson_rng_clk_disable,
  66                                                data->core_clk);
  67                 if (ret)
  68                         return ret;
  69         }
  70
  71         data->rng.name = pdev->name;
  72         data->rng.read = meson_rng_read;
  73
  74         platform_set_drvdata(pdev, data);
  75
  76         return devm_hwrng_register(dev, &data->rng);
  77 }
  78
  79 static const struct of_device_id meson_rng_of_match[] = {
  80         { .compatible = "amlogic,meson-rng", },
  81         {},
  82 };
  83 MODULE_DEVICE_TABLE(of, meson_rng_of_match);
  84
  85 static struct platform_driver meson_rng_driver = {
  86         .probe  = meson_rng_probe,
  87         .driver = {
  88                 .name = "meson-rng",
  89                 .of_match_table = meson_rng_of_match,
  90         },
  91 };
  92
  93 module_platform_driver(meson_rng_driver);
  94
  95 MODULE_DESCRIPTION("Meson H/W Random Number Generator driver");
  96 MODULE_AUTHOR("Lawrence Mok <lawrence.mok@amlogic.com>");
  97 MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
  98 MODULE_LICENSE("Dual BSD/GPL");