drivers/nvmem/sunxi_sid.c

   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
  27 static 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
  35 struct 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  */
  44 static 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
  55 static 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
  67 static 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
 110 err_unreg_nvmem:
 111         nvmem_unregister(nvmem);
 112         return ret;
 113 }
 114
 115 static 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
 122 static const struct of_device_id sunxi_sid_of_match[] = {
 123         { .compatible = "allwinner,sun4i-a10-sid" },
 124         { .compatible = "allwinner,sun7i-a20-sid" },
 125         {/* sentinel */},
 126 };
 127 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 128
 129 static 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 };
 137 module_platform_driver(sunxi_sid_driver);
 138
 139 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 140 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 141 MODULE_LICENSE("GPL");