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 word)
  89 {
  90         u32 reg_val;
  91         int ret;
  92
  93         /* Set word, lock access, and set read command */
  94         reg_val = (word & SUN8I_SID_OFFSET_MASK)
  95                   << SUN8I_SID_OFFSET_SHIFT;
  96         reg_val |= SUN8I_SID_OP_LOCK | SUN8I_SID_READ;
  97         writel(reg_val, sid->base + SUN8I_SID_PRCTL);
  98
  99         ret = readl_poll_timeout(sid->base + SUN8I_SID_PRCTL, reg_val,
 100                                  !(reg_val & SUN8I_SID_READ), 100, 250000);
 101         if (ret)
 102                 return ret;
 103
 104         writel(0, sid->base + SUN8I_SID_PRCTL);
 105         return 0;
 106 }
 107
 108 static int sunxi_sid_probe(struct platform_device *pdev)
 109 {
 110         struct device *dev = &pdev->dev;
 111         struct resource *res;
 112         struct nvmem_device *nvmem;
 113         struct sunxi_sid *sid;
 114         int ret, i, size;
 115         char *randomness;
 116         const struct sunxi_sid_cfg *cfg;
 117
 118         sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
 119         if (!sid)
 120                 return -ENOMEM;
 121
 122         cfg = of_device_get_match_data(dev);
 123         if (!cfg)
 124                 return -EINVAL;
 125         sid->value_offset = cfg->value_offset;
 126
 127         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 128         sid->base = devm_ioremap_resource(dev, res);
 129         if (IS_ERR(sid->base))
 130                 return PTR_ERR(sid->base);
 131
 132         size = cfg->size;
 133
 134         if (cfg->need_register_readout) {
 135                 /*
 136                  * H3's SID controller have a bug that the value at 0x200
 137                  * offset is not the correct value when the hardware is reseted.
 138                  * However, after doing a register-based read operation, the
 139                  * value become right.
 140                  * Do a full read operation here, but ignore its value
 141                  * (as it's more fast to read by direct MMIO value than
 142                  * with registers)
 143                  */
 144                 for (i = 0; i < (size >> 2); i++) {
 145                         ret = sun8i_sid_register_readout(sid, i);
 146                         if (ret)
 147                                 return ret;
 148                 }
 149         }
 150
 151         econfig.size = size;
 152         econfig.dev = dev;
 153         econfig.reg_read = sunxi_sid_read;
 154         econfig.priv = sid;
 155         nvmem = nvmem_register(&econfig);
 156         if (IS_ERR(nvmem))
 157                 return PTR_ERR(nvmem);
 158
 159         randomness = kzalloc(sizeof(u8) * (size), GFP_KERNEL);
 160         if (!randomness) {
 161                 ret = -EINVAL;
 162                 goto err_unreg_nvmem;
 163         }
 164
 165         for (i = 0; i < size; i++)
 166                 randomness[i] = sunxi_sid_read_byte(sid, i);
 167
 168         add_device_randomness(randomness, size);
 169         kfree(randomness);
 170
 171         platform_set_drvdata(pdev, nvmem);
 172
 173         return 0;
 174
 175 err_unreg_nvmem:
 176         nvmem_unregister(nvmem);
 177         return ret;
 178 }
 179
 180 static int sunxi_sid_remove(struct platform_device *pdev)
 181 {
 182         struct nvmem_device *nvmem = platform_get_drvdata(pdev);
 183
 184         return nvmem_unregister(nvmem);
 185 }
 186
 187 static const struct sunxi_sid_cfg sun4i_a10_cfg = {
 188         .size = 0x10,
 189 };
 190
 191 static const struct sunxi_sid_cfg sun7i_a20_cfg = {
 192         .size = 0x200,
 193 };
 194
 195 static const struct sunxi_sid_cfg sun8i_h3_cfg = {
 196         .value_offset = 0x200,
 197         .size = 0x100,
 198         .need_register_readout = true,
 199 };
 200
 201 static const struct sunxi_sid_cfg sun50i_a64_cfg = {
 202         .value_offset = 0x200,
 203         .size = 0x100,
 204 };
 205
 206 static const struct of_device_id sunxi_sid_of_match[] = {
 207         { .compatible = "allwinner,sun4i-a10-sid", .data = &sun4i_a10_cfg },
 208         { .compatible = "allwinner,sun7i-a20-sid", .data = &sun7i_a20_cfg },
 209         { .compatible = "allwinner,sun8i-h3-sid", .data = &sun8i_h3_cfg },
 210         { .compatible = "allwinner,sun50i-a64-sid", .data = &sun50i_a64_cfg },
 211         {/* sentinel */},
 212 };
 213 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 214
 215 static struct platform_driver sunxi_sid_driver = {
 216         .probe = sunxi_sid_probe,
 217         .remove = sunxi_sid_remove,
 218         .driver = {
 219                 .name = "eeprom-sunxi-sid",
 220                 .of_match_table = sunxi_sid_of_match,
 221         },
 222 };
 223 module_platform_driver(sunxi_sid_driver);
 224
 225 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 226 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 227 MODULE_LICENSE("GPL");