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/iopoll.h>
  21 #include <linux/module.h>
  22 #include <linux/nvmem-provider.h>
  23 #include <linux/of.h>
  24 #include <linux/of_device.h>
  25 #include <linux/platform_device.h>
  26 #include <linux/slab.h>
  27 #include <linux/random.h>
  28
  29 /* Registers and special values for doing register-based SID readout on H3 */
  30 #define SUN8I_SID_PRCTL         0x40
  31 #define SUN8I_SID_RDKEY         0x60
  32
  33 #define SUN8I_SID_OFFSET_MASK   0x1FF
  34 #define SUN8I_SID_OFFSET_SHIFT  16
  35 #define SUN8I_SID_OP_LOCK       (0xAC << 8)
  36 #define SUN8I_SID_READ          BIT(1)
  37
  38 static struct nvmem_config econfig = {
  39         .name = "sunxi-sid",
  40         .read_only = true,
  41         .stride = 4,
  42         .word_size = 1,
  43 };
  44
  45 struct sunxi_sid_cfg {
  46         u32     value_offset;
  47         u32     size;
  48         bool    need_register_readout;
  49 };
  50
  51 struct sunxi_sid {
  52         void __iomem            *base;
  53         u32                     value_offset;
  54 };
  55
  56 /* We read the entire key, due to a 32 bit read alignment requirement. Since we
  57  * want to return the requested byte, this results in somewhat slower code and
  58  * uses 4 times more reads as needed but keeps code simpler. Since the SID is
  59  * only very rarely probed, this is not really an issue.
  60  */
  61 static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid,
  62                               const unsigned int offset)
  63 {
  64         u32 sid_key;
  65
  66         sid_key = ioread32be(sid->base + round_down(offset, 4));
  67         sid_key >>= (offset % 4) * 8;
  68
  69         return sid_key; /* Only return the last byte */
  70 }
  71
  72 static int sunxi_sid_read(void *context, unsigned int offset,
  73                           void *val, size_t bytes)
  74 {
  75         struct sunxi_sid *sid = context;
  76         u8 *buf = val;
  77
  78         /* Offset the read operation to the real position of SID */
  79         offset += sid->value_offset;
  80
  81         while (bytes--)
  82                 *buf++ = sunxi_sid_read_byte(sid, offset++);
  83
  84         return 0;
  85 }
  86
  87 static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
  88                                       const unsigned int offset,
  89                                       u32 *out)
  90 {
  91         u32 reg_val;
  92         int ret;
  93
  94         /* Set word, lock access, and set read command */
  95         reg_val = (offset & SUN8I_SID_OFFSET_MASK)
  96                   << SUN8I_SID_OFFSET_SHIFT;
  97         reg_val |= SUN8I_SID_OP_LOCK | SUN8I_SID_READ;
  98         writel(reg_val, sid->base + SUN8I_SID_PRCTL);
  99
 100         ret = readl_poll_timeout(sid->base + SUN8I_SID_PRCTL, reg_val,
 101                                  !(reg_val & SUN8I_SID_READ), 100, 250000);
 102         if (ret)
 103                 return ret;
 104
 105         if (out)
 106                 *out = readl(sid->base + SUN8I_SID_RDKEY);
 107
 108         writel(0, sid->base + SUN8I_SID_PRCTL);
 109
 110         return 0;
 111 }
 112
 113 /*
 114  * On Allwinner H3, the value on the 0x200 offset of the SID controller seems
 115  * to be not reliable at all.
 116  * Read by the registers instead.
 117  */
 118 static int sun8i_sid_read_byte_by_reg(const struct sunxi_sid *sid,
 119                                       const unsigned int offset,
 120                                       u8 *out)
 121 {
 122         u32 word;
 123         int ret;
 124
 125         ret = sun8i_sid_register_readout(sid, offset & ~0x03, &word);
 126
 127         if (ret)
 128                 return ret;
 129
 130         *out = (word >> ((offset & 0x3) * 8)) & 0xff;
 131
 132         return 0;
 133 }
 134
 135 static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
 136                                  void *val, size_t bytes)
 137 {
 138         struct sunxi_sid *sid = context;
 139         u8 *buf = val;
 140         int ret;
 141
 142         while (bytes--) {
 143                 ret = sun8i_sid_read_byte_by_reg(sid, offset++, buf++);
 144                 if (ret)
 145                         return ret;
 146         }
 147
 148         return 0;
 149 }
 150
 151 static int sunxi_sid_probe(struct platform_device *pdev)
 152 {
 153         struct device *dev = &pdev->dev;
 154         struct resource *res;
 155         struct nvmem_device *nvmem;
 156         struct sunxi_sid *sid;
 157         int i, size;
 158         char *randomness;
 159         const struct sunxi_sid_cfg *cfg;
 160
 161         sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
 162         if (!sid)
 163                 return -ENOMEM;
 164
 165         cfg = of_device_get_match_data(dev);
 166         if (!cfg)
 167                 return -EINVAL;
 168         sid->value_offset = cfg->value_offset;
 169
 170         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 171         sid->base = devm_ioremap_resource(dev, res);
 172         if (IS_ERR(sid->base))
 173                 return PTR_ERR(sid->base);
 174
 175         size = cfg->size;
 176
 177         econfig.size = size;
 178         econfig.dev = dev;
 179         if (cfg->need_register_readout)
 180                 econfig.reg_read = sun8i_sid_read_by_reg;
 181         else
 182                 econfig.reg_read = sunxi_sid_read;
 183         econfig.priv = sid;
 184         nvmem = devm_nvmem_register(dev, &econfig);
 185         if (IS_ERR(nvmem))
 186                 return PTR_ERR(nvmem);
 187
 188         randomness = kzalloc(size, GFP_KERNEL);
 189         if (!randomness)
 190                 return -ENOMEM;
 191
 192         for (i = 0; i < size; i++)
 193                 econfig.reg_read(sid, i, &randomness[i], 1);
 194
 195         add_device_randomness(randomness, size);
 196         kfree(randomness);
 197
 198         platform_set_drvdata(pdev, nvmem);
 199
 200         return 0;
 201 }
 202
 203 static const struct sunxi_sid_cfg sun4i_a10_cfg = {
 204         .size = 0x10,
 205 };
 206
 207 static const struct sunxi_sid_cfg sun7i_a20_cfg = {
 208         .size = 0x200,
 209 };
 210
 211 static const struct sunxi_sid_cfg sun8i_h3_cfg = {
 212         .value_offset = 0x200,
 213         .size = 0x100,
 214         .need_register_readout = true,
 215 };
 216
 217 static const struct sunxi_sid_cfg sun50i_a64_cfg = {
 218         .value_offset = 0x200,
 219         .size = 0x100,
 220 };
 221
 222 static const struct of_device_id sunxi_sid_of_match[] = {
 223         { .compatible = "allwinner,sun4i-a10-sid", .data = &sun4i_a10_cfg },
 224         { .compatible = "allwinner,sun7i-a20-sid", .data = &sun7i_a20_cfg },
 225         { .compatible = "allwinner,sun8i-h3-sid", .data = &sun8i_h3_cfg },
 226         { .compatible = "allwinner,sun50i-a64-sid", .data = &sun50i_a64_cfg },
 227         {/* sentinel */},
 228 };
 229 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 230
 231 static struct platform_driver sunxi_sid_driver = {
 232         .probe = sunxi_sid_probe,
 233         .driver = {
 234                 .name = "eeprom-sunxi-sid",
 235                 .of_match_table = sunxi_sid_of_match,
 236         },
 237 };
 238 module_platform_driver(sunxi_sid_driver);
 239
 240 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 241 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 242 MODULE_LICENSE("GPL");