LXR linux/drivers/nvmem/sunxi

   1/*
   2 * Allwinner sunXi SoCs Security ID support.
   3 *
   4 * Copyright (c) 2013 Oliver Schinagl <oliver@schinagl.nl>
   5 * Copyright (C) 2014 Maxime Ripard <maxime.ripard@free-electrons.com>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License as published by
   9 * the Free Software Foundation; either version 2 of the License, or
  10 * (at your option) any later version.
  11 *
  12 * This program is distributed in the hope that it will be useful,
  13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 * GNU General Public License for more details.
  16 */
  17
  18#include <linux/device.h>
  19#include <linux/io.h>
  20#include <linux/module.h>
  21#include <linux/nvmem-provider.h>
  22#include <linux/of.h>
  23#include <linux/platform_device.h>
  24#include <linux/slab.h>
  25#include <linux/random.h>
  26
  27static struct nvmem_config econfig = {
  28        .name = "sunxi-sid",
  29        .read_only = true,
  30        .stride = 4,
  31        .word_size = 1,
  32        .owner = THIS_MODULE,
  33};
  34
  35struct sunxi_sid {
  36        void __iomem            *base;
  37};
  38
  39/* We read the entire key, due to a 32 bit read alignment requirement. Since we
  40 * want to return the requested byte, this results in somewhat slower code and
  41 * uses 4 times more reads as needed but keeps code simpler. Since the SID is
  42 * only very rarely probed, this is not really an issue.
  43 */
  44static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid,
  45                              const unsigned int offset)
  46{
  47        u32 sid_key;
  48
  49        sid_key = ioread32be(sid->base + round_down(offset, 4));
  50        sid_key >>= (offset % 4) * 8;
  51
  52        return sid_key; /* Only return the last byte */
  53}
  54
  55static int sunxi_sid_read(void *context, unsigned int offset,
  56                          void *val, size_t bytes)
  57{
  58        struct sunxi_sid *sid = context;
  59        u8 *buf = val;
  60
  61        while (bytes--)
  62                *buf++ = sunxi_sid_read_byte(sid, offset++);
  63
  64        return 0;
  65}
  66
  67static int sunxi_sid_probe(struct platform_device *pdev)
  68{
  69        struct device *dev = &pdev->dev;
  70        struct resource *res;
  71        struct nvmem_device *nvmem;
  72        struct sunxi_sid *sid;
  73        int ret, i, size;
  74        char *randomness;
  75
  76        sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
  77        if (!sid)
  78                return -ENOMEM;
  79
  80        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  81        sid->base = devm_ioremap_resource(dev, res);
  82        if (IS_ERR(sid->base))
  83                return PTR_ERR(sid->base);
  84
  85        size = resource_size(res) - 1;
  86        econfig.size = resource_size(res);
  87        econfig.dev = dev;
  88        econfig.reg_read = sunxi_sid_read;
  89        econfig.priv = sid;
  90        nvmem = nvmem_register(&econfig);
  91        if (IS_ERR(nvmem))
  92                return PTR_ERR(nvmem);
  93
  94        randomness = kzalloc(sizeof(u8) * (size), GFP_KERNEL);
  95        if (!randomness) {
  96                ret = -EINVAL;
  97                goto err_unreg_nvmem;
  98        }
  99
 100        for (i = 0; i < size; i++)
 101                randomness[i] = sunxi_sid_read_byte(sid, i);
 102
 103        add_device_randomness(randomness, size);
 104        kfree(randomness);
 105
 106        platform_set_drvdata(pdev, nvmem);
 107
 108        return 0;
 109
 110err_unreg_nvmem:
 111        nvmem_unregister(nvmem);
 112        return ret;
 113}
 114
 115static int sunxi_sid_remove(struct platform_device *pdev)
 116{
 117        struct nvmem_device *nvmem = platform_get_drvdata(pdev);
 118
 119        return nvmem_unregister(nvmem);
 120}
 121
 122static const struct of_device_id sunxi_sid_of_match[] = {
 123        { .compatible = "allwinner,sun4i-a10-sid" },
 124        { .compatible = "allwinner,sun7i-a20-sid" },
 125        {/* sentinel */},
 126};
 127MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 128
 129static struct platform_driver sunxi_sid_driver = {
 130        .probe = sunxi_sid_probe,
 131        .remove = sunxi_sid_remove,
 132        .driver = {
 133                .name = "eeprom-sunxi-sid",
 134                .of_match_table = sunxi_sid_of_match,
 135        },
 136};
 137module_platform_driver(sunxi_sid_driver);
 138
 139MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 140MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 141MODULE_LICENSE("GPL");
 142