target/linux/mediatek/files/drivers/char/hw_random/mtk-rng.c

   1 /*
   2  * Driver for Mediatek Hardware Random Number Generator
   3  *
   4  * Copyright (C) 2017 Sean Wang <sean.wang@mediatek.com>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of
   9  * the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  */
  16 #define MTK_RNG_DEV KBUILD_MODNAME
  17
  18 #include <linux/clk.h>
  19 #include <linux/delay.h>
  20 #include <linux/err.h>
  21 #include <linux/hw_random.h>
  22 #include <linux/io.h>
  23 #include <linux/iopoll.h>
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/of.h>
  27 #include <linux/platform_device.h>
  28
  29 #define USEC_POLL                       2
  30 #define TIMEOUT_POLL                    20
  31
  32 #define RNG_CTRL                        0x00
  33 #define RNG_EN                          BIT(0)
  34 #define RNG_READY                       BIT(31)
  35
  36 #define RNG_DATA                        0x08
  37
  38 #define to_mtk_rng(p)   container_of(p, struct mtk_rng, rng)
  39
  40 struct mtk_rng {
  41         void __iomem *base;
  42         struct clk *clk;
  43         struct hwrng rng;
  44 };
  45
  46 static int mtk_rng_init(struct hwrng *rng)
  47 {
  48         struct mtk_rng *priv = to_mtk_rng(rng);
  49         u32 val;
  50         int err;
  51
  52         err = clk_prepare_enable(priv->clk);
  53         if (err)
  54                 return err;
  55
  56         val = readl(priv->base + RNG_CTRL);
  57         val |= RNG_EN;
  58         writel(val, priv->base + RNG_CTRL);
  59
  60         return 0;
  61 }
  62
  63 static void mtk_rng_cleanup(struct hwrng *rng)
  64 {
  65         struct mtk_rng *priv = to_mtk_rng(rng);
  66         u32 val;
  67
  68         val = readl(priv->base + RNG_CTRL);
  69         val &= ~RNG_EN;
  70         writel(val, priv->base + RNG_CTRL);
  71
  72         clk_disable_unprepare(priv->clk);
  73 }
  74
  75 static bool mtk_rng_wait_ready(struct hwrng *rng, bool wait)
  76 {
  77         struct mtk_rng *priv = to_mtk_rng(rng);
  78         int ready;
  79
  80         ready = readl(priv->base + RNG_CTRL) & RNG_READY;
  81         if (!ready && wait)
  82                 readl_poll_timeout_atomic(priv->base + RNG_CTRL, ready,
  83                                           ready & RNG_READY, USEC_POLL,
  84                                           TIMEOUT_POLL);
  85         return !!ready;
  86 }
  87
  88 static int mtk_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  89 {
  90         struct mtk_rng *priv = to_mtk_rng(rng);
  91         int retval = 0;
  92
  93         while (max >= sizeof(u32)) {
  94                 if (!mtk_rng_wait_ready(rng, wait))
  95                         break;
  96
  97                 *(u32 *)buf = readl(priv->base + RNG_DATA);
  98                 retval += sizeof(u32);
  99                 buf += sizeof(u32);
 100                 max -= sizeof(u32);
 101         }
 102
 103         return retval || !wait ? retval : -EIO;
 104 }
 105
 106 static int mtk_rng_probe(struct platform_device *pdev)
 107 {
 108         struct resource *res;
 109         int ret;
 110         struct mtk_rng *priv;
 111
 112         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 113         if (!res) {
 114                 dev_err(&pdev->dev, "no iomem resource\n");
 115                 return -ENXIO;
 116         }
 117
 118         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 119         if (!priv)
 120                 return -ENOMEM;
 121
 122         priv->rng.name = pdev->name;
 123         priv->rng.init = mtk_rng_init;
 124         priv->rng.cleanup = mtk_rng_cleanup;
 125         priv->rng.read = mtk_rng_read;
 126
 127         priv->clk = devm_clk_get(&pdev->dev, "rng");
 128         if (IS_ERR(priv->clk)) {
 129                 ret = PTR_ERR(priv->clk);
 130                 dev_err(&pdev->dev, "no clock for device: %d\n", ret);
 131                 return ret;
 132         }
 133
 134         priv->base = devm_ioremap_resource(&pdev->dev, res);
 135         if (IS_ERR(priv->base))
 136                 return PTR_ERR(priv->base);
 137
 138         ret = devm_hwrng_register(&pdev->dev, &priv->rng);
 139         if (ret) {
 140                 dev_err(&pdev->dev, "failed to register rng device: %d\n",
 141                         ret);
 142                 return ret;
 143         }
 144
 145         dev_info(&pdev->dev, "registered RNG driver\n");
 146
 147         return 0;
 148 }
 149
 150 static const struct of_device_id mtk_rng_match[] = {
 151         { .compatible = "mediatek,mt7623-rng" },
 152         {},
 153 };
 154 MODULE_DEVICE_TABLE(of, mtk_rng_match);
 155
 156 static struct platform_driver mtk_rng_driver = {
 157         .probe          = mtk_rng_probe,
 158         .driver = {
 159                 .name = MTK_RNG_DEV,
 160                 .of_match_table = mtk_rng_match,
 161         },
 162 };
 163
 164 module_platform_driver(mtk_rng_driver);
 165
 166 MODULE_DESCRIPTION("Mediatek Random Number Generator Driver");
 167 MODULE_AUTHOR("Sean Wang <sean.wang@mediatek.com>");
 168 MODULE_LICENSE("GPL");