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
  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
  31 static struct nvmem_config econfig = {
  32         .name = "sunxi-sid",
  33         .read_only = true,
  34         .owner = THIS_MODULE,
  35 };
  36
  37 struct 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  */
  46 static 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
  57 static 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
  74 static 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
  80 static 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
  87 static bool sunxi_sid_writeable_reg(struct device *dev, unsigned int reg)
  88 {
  89         return false;
  90 }
  91
  92 static 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
  99 static 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
 149 err_unreg_nvmem:
 150         nvmem_unregister(nvmem);
 151         return ret;
 152 }
 153
 154 static 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
 161 static const struct of_device_id sunxi_sid_of_match[] = {
 162         { .compatible = "allwinner,sun4i-a10-sid" },
 163         { .compatible = "allwinner,sun7i-a20-sid" },
 164         {/* sentinel */},
 165 };
 166 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 167
 168 static 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 };
 176 module_platform_driver(sunxi_sid_driver);
 177
 178 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 179 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 180 MODULE_LICENSE("GPL");