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