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
  19
  20#include <linux/device.h>
  21#include <linux/io.h>
  22#include <linux/module.h>
  23#include <linux/nvmem-provider.h>
  24#include <linux/of.h>
  25#include <linux/platform_device.h>
  26#include <linux/regmap.h>
  27#include <linux/slab.h>
  28#include <linux/random.h>
  29
  30
  31static struct nvmem_config econfig = {
  32        .name = "sunxi-sid",
  33        .read_only = true,
  34        .owner = THIS_MODULE,
  35};
  36
  37struct sunxi_sid {
  38        void __iomem            *base;
  39};
  40
  41/* We read the entire key, due to a 32 bit read alignment requirement. Since we
  42 * want to return the requested byte, this results in somewhat slower code and
  43 * uses 4 times more reads as needed but keeps code simpler. Since the SID is
  44 * only very rarely probed, this is not really an issue.
  45 */
  46static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid,
  47                              const unsigned int offset)
  48{
  49        u32 sid_key;
  50
  51        sid_key = ioread32be(sid->base + round_down(offset, 4));
  52        sid_key >>= (offset % 4) * 8;
  53
  54        return sid_key; /* Only return the last byte */
  55}
  56
  57static int sunxi_sid_read(void *context,
  58                            const void *reg, size_t reg_size,
  59                            void *val, size_t val_size)
  60{
  61        struct sunxi_sid *sid = context;
  62        unsigned int offset = *(u32 *)reg;
  63        u8 *buf = val;
  64
  65        while (val_size) {
  66                *buf++ = sunxi_sid_read_byte(sid, offset);
  67                val_size--;
  68                offset++;
  69        }
  70
  71        return 0;
  72}
  73
  74static int sunxi_sid_write(void *context, const void *data, size_t count)
  75{
  76        /* Unimplemented, dummy to keep regmap core happy */
  77        return 0;
  78}
  79
  80static struct regmap_bus sunxi_sid_bus = {
  81        .read = sunxi_sid_read,
  82        .write = sunxi_sid_write,
  83        .reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
  84        .val_format_endian_default = REGMAP_ENDIAN_NATIVE,
  85};
  86
  87static bool sunxi_sid_writeable_reg(struct device *dev, unsigned int reg)
  88{
  89        return false;
  90}
  91
  92static struct regmap_config sunxi_sid_regmap_config = {
  93        .reg_bits = 32,
  94        .val_bits = 8,
  95        .reg_stride = 1,
  96        .writeable_reg = sunxi_sid_writeable_reg,
  97};
  98
  99static int sunxi_sid_probe(struct platform_device *pdev)
 100{
 101        struct device *dev = &pdev->dev;
 102        struct resource *res;
 103        struct nvmem_device *nvmem;
 104        struct regmap *regmap;
 105        struct sunxi_sid *sid;
 106        int ret, i, size;
 107        char *randomness;
 108
 109        sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
 110        if (!sid)
 111                return -ENOMEM;
 112
 113        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 114        sid->base = devm_ioremap_resource(dev, res);
 115        if (IS_ERR(sid->base))
 116                return PTR_ERR(sid->base);
 117
 118        size = resource_size(res) - 1;
 119        sunxi_sid_regmap_config.max_register = size;
 120
 121        regmap = devm_regmap_init(dev, &sunxi_sid_bus, sid,
 122                                  &sunxi_sid_regmap_config);
 123        if (IS_ERR(regmap)) {
 124                dev_err(dev, "regmap init failed\n");
 125                return PTR_ERR(regmap);
 126        }
 127
 128        econfig.dev = dev;
 129        nvmem = nvmem_register(&econfig);
 130        if (IS_ERR(nvmem))
 131                return PTR_ERR(nvmem);
 132
 133        randomness = kzalloc(sizeof(u8) * size, GFP_KERNEL);
 134        if (!randomness) {
 135                ret = -EINVAL;
 136                goto err_unreg_nvmem;
 137        }
 138
 139        for (i = 0; i < size; i++)
 140                randomness[i] = sunxi_sid_read_byte(sid, i);
 141
 142        add_device_randomness(randomness, size);
 143        kfree(randomness);
 144
 145        platform_set_drvdata(pdev, nvmem);
 146
 147        return 0;
 148
 149err_unreg_nvmem:
 150        nvmem_unregister(nvmem);
 151        return ret;
 152}
 153
 154static int sunxi_sid_remove(struct platform_device *pdev)
 155{
 156        struct nvmem_device *nvmem = platform_get_drvdata(pdev);
 157
 158        return nvmem_unregister(nvmem);
 159}
 160
 161static const struct of_device_id sunxi_sid_of_match[] = {
 162        { .compatible = "allwinner,sun4i-a10-sid" },
 163        { .compatible = "allwinner,sun7i-a20-sid" },
 164        {/* sentinel */},
 165};
 166MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 167
 168static struct platform_driver sunxi_sid_driver = {
 169        .probe = sunxi_sid_probe,
 170        .remove = sunxi_sid_remove,
 171        .driver = {
 172                .name = "eeprom-sunxi-sid",
 173                .of_match_table = sunxi_sid_of_match,
 174        },
 175};
 176module_platform_driver(sunxi_sid_driver);
 177
 178MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 179MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 180MODULE_LICENSE("GPL");
 181