drivers/char/hw_random/meson-rng.c

   1 /*
   2  * This file is provided under a dual BSD/GPLv2 license.  When using or
   3  * redistributing this file, you may do so under either license.
   4  *
   5  * GPL LICENSE SUMMARY
   6  *
   7  * Copyright (c) 2016 BayLibre, SAS.
   8  * Author: Neil Armstrong <narmstrong@baylibre.com>
   9  * Copyright (C) 2014 Amlogic, Inc.
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of version 2 of the GNU General Public License as
  13  * published by the Free Software Foundation.
  14  *
  15  * This program is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  22  * The full GNU General Public License is included in this distribution
  23  * in the file called COPYING.
  24  *
  25  * BSD LICENSE
  26  *
  27  * Copyright (c) 2016 BayLibre, SAS.
  28  * Author: Neil Armstrong <narmstrong@baylibre.com>
  29  * Copyright (C) 2014 Amlogic, Inc.
  30  *
  31  * Redistribution and use in source and binary forms, with or without
  32  * modification, are permitted provided that the following conditions
  33  * are met:
  34  *
  35  *   * Redistributions of source code must retain the above copyright
  36  *     notice, this list of conditions and the following disclaimer.
  37  *   * Redistributions in binary form must reproduce the above copyright
  38  *     notice, this list of conditions and the following disclaimer in
  39  *     the documentation and/or other materials provided with the
  40  *     distribution.
  41  *   * Neither the name of Intel Corporation nor the names of its
  42  *     contributors may be used to endorse or promote products derived
  43  *     from this software without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  46  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  47  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  48  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  49  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  50  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  51  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  52  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  53  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  54  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  55  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  56  */
  57 #include <linux/err.h>
  58 #include <linux/module.h>
  59 #include <linux/io.h>
  60 #include <linux/platform_device.h>
  61 #include <linux/hw_random.h>
  62 #include <linux/slab.h>
  63 #include <linux/types.h>
  64 #include <linux/of.h>
  65 #include <linux/clk.h>
  66
  67 #define RNG_DATA 0x00
  68
  69 struct meson_rng_data {
  70         void __iomem *base;
  71         struct platform_device *pdev;
  72         struct hwrng rng;
  73         struct clk *core_clk;
  74 };
  75
  76 static int meson_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  77 {
  78         struct meson_rng_data *data =
  79                         container_of(rng, struct meson_rng_data, rng);
  80
  81         *(u32 *)buf = readl_relaxed(data->base + RNG_DATA);
  82
  83         return sizeof(u32);
  84 }
  85
  86 static void meson_rng_clk_disable(void *data)
  87 {
  88         clk_disable_unprepare(data);
  89 }
  90
  91 static int meson_rng_probe(struct platform_device *pdev)
  92 {
  93         struct device *dev = &pdev->dev;
  94         struct meson_rng_data *data;
  95         struct resource *res;
  96         int ret;
  97
  98         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
  99         if (!data)
 100                 return -ENOMEM;
 101
 102         data->pdev = pdev;
 103
 104         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 105         data->base = devm_ioremap_resource(dev, res);
 106         if (IS_ERR(data->base))
 107                 return PTR_ERR(data->base);
 108
 109         data->core_clk = devm_clk_get(dev, "core");
 110         if (IS_ERR(data->core_clk))
 111                 data->core_clk = NULL;
 112
 113         if (data->core_clk) {
 114                 ret = clk_prepare_enable(data->core_clk);
 115                 if (ret)
 116                         return ret;
 117                 ret = devm_add_action_or_reset(dev, meson_rng_clk_disable,
 118                                                data->core_clk);
 119                 if (ret)
 120                         return ret;
 121         }
 122
 123         data->rng.name = pdev->name;
 124         data->rng.read = meson_rng_read;
 125
 126         platform_set_drvdata(pdev, data);
 127
 128         return devm_hwrng_register(dev, &data->rng);
 129 }
 130
 131 static const struct of_device_id meson_rng_of_match[] = {
 132         { .compatible = "amlogic,meson-rng", },
 133         {},
 134 };
 135 MODULE_DEVICE_TABLE(of, meson_rng_of_match);
 136
 137 static struct platform_driver meson_rng_driver = {
 138         .probe  = meson_rng_probe,
 139         .driver = {
 140                 .name = "meson-rng",
 141                 .of_match_table = meson_rng_of_match,
 142         },
 143 };
 144
 145 module_platform_driver(meson_rng_driver);
 146
 147 MODULE_DESCRIPTION("Meson H/W Random Number Generator driver");
 148 MODULE_AUTHOR("Lawrence Mok <lawrence.mok@amlogic.com>");
 149 MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
 150 MODULE_LICENSE("Dual BSD/GPL");