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         .owner = THIS_MODULE,
  44 };
  45
  46 struct sunxi_sid_cfg {
  47         u32     value_offset;
  48         u32     size;
  49         bool    need_register_readout;
  50 };
  51
  52 struct sunxi_sid {
  53         void __iomem            *base;
  54         u32                     value_offset;
  55 };
  56
  57 /* We read the entire key, due to a 32 bit read alignment requirement. Since we
  58  * want to return the requested byte, this results in somewhat slower code and
  59  * uses 4 times more reads as needed but keeps code simpler. Since the SID is
  60  * only very rarely probed, this is not really an issue.
  61  */
  62 static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid,
  63                               const unsigned int offset)
  64 {
  65         u32 sid_key;
  66
  67         sid_key = ioread32be(sid->base + round_down(offset, 4));
  68         sid_key >>= (offset % 4) * 8;
  69
  70         return sid_key; /* Only return the last byte */
  71 }
  72
  73 static int sunxi_sid_read(void *context, unsigned int offset,
  74                           void *val, size_t bytes)
  75 {
  76         struct sunxi_sid *sid = context;
  77         u8 *buf = val;
  78
  79         /* Offset the read operation to the real position of SID */
  80         offset += sid->value_offset;
  81
  82         while (bytes--)
  83                 *buf++ = sunxi_sid_read_byte(sid, offset++);
  84
  85         return 0;
  86 }
  87
  88 static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
  89                                       const unsigned int word)
  90 {
  91         u32 reg_val;
  92         int ret;
  93
  94         /* Set word, lock access, and set read command */
  95         reg_val = (word & 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         writel(0, sid->base + SUN8I_SID_PRCTL);
 106         return 0;
 107 }
 108
 109 static int sunxi_sid_probe(struct platform_device *pdev)
 110 {
 111         struct device *dev = &pdev->dev;
 112         struct resource *res;
 113         struct nvmem_device *nvmem;
 114         struct sunxi_sid *sid;
 115         int ret, i, size;
 116         char *randomness;
 117         const struct sunxi_sid_cfg *cfg;
 118
 119         sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
 120         if (!sid)
 121                 return -ENOMEM;
 122
 123         cfg = of_device_get_match_data(dev);
 124         if (!cfg)
 125                 return -EINVAL;
 126         sid->value_offset = cfg->value_offset;
 127
 128         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 129         sid->base = devm_ioremap_resource(dev, res);
 130         if (IS_ERR(sid->base))
 131                 return PTR_ERR(sid->base);
 132
 133         size = cfg->size;
 134
 135         if (cfg->need_register_readout) {
 136                 /*
 137                  * H3's SID controller have a bug that the value at 0x200
 138                  * offset is not the correct value when the hardware is reseted.
 139                  * However, after doing a register-based read operation, the
 140                  * value become right.
 141                  * Do a full read operation here, but ignore its value
 142                  * (as it's more fast to read by direct MMIO value than
 143                  * with registers)
 144                  */
 145                 for (i = 0; i < (size >> 2); i++) {
 146                         ret = sun8i_sid_register_readout(sid, i);
 147                         if (ret)
 148                                 return ret;
 149                 }
 150         }
 151
 152         econfig.size = size;
 153         econfig.dev = dev;
 154         econfig.reg_read = sunxi_sid_read;
 155         econfig.priv = sid;
 156         nvmem = nvmem_register(&econfig);
 157         if (IS_ERR(nvmem))
 158                 return PTR_ERR(nvmem);
 159
 160         randomness = kzalloc(sizeof(u8) * (size), GFP_KERNEL);
 161         if (!randomness) {
 162                 ret = -EINVAL;
 163                 goto err_unreg_nvmem;
 164         }
 165
 166         for (i = 0; i < size; i++)
 167                 randomness[i] = sunxi_sid_read_byte(sid, i);
 168
 169         add_device_randomness(randomness, size);
 170         kfree(randomness);
 171
 172         platform_set_drvdata(pdev, nvmem);
 173
 174         return 0;
 175
 176 err_unreg_nvmem:
 177         nvmem_unregister(nvmem);
 178         return ret;
 179 }
 180
 181 static int sunxi_sid_remove(struct platform_device *pdev)
 182 {
 183         struct nvmem_device *nvmem = platform_get_drvdata(pdev);
 184
 185         return nvmem_unregister(nvmem);
 186 }
 187
 188 static const struct sunxi_sid_cfg sun4i_a10_cfg = {
 189         .size = 0x10,
 190 };
 191
 192 static const struct sunxi_sid_cfg sun7i_a20_cfg = {
 193         .size = 0x200,
 194 };
 195
 196 static const struct sunxi_sid_cfg sun8i_h3_cfg = {
 197         .value_offset = 0x200,
 198         .size = 0x100,
 199         .need_register_readout = true,
 200 };
 201
 202 static const struct of_device_id sunxi_sid_of_match[] = {
 203         { .compatible = "allwinner,sun4i-a10-sid", .data = &sun4i_a10_cfg },
 204         { .compatible = "allwinner,sun7i-a20-sid", .data = &sun7i_a20_cfg },
 205         { .compatible = "allwinner,sun8i-h3-sid", .data = &sun8i_h3_cfg },
 206         {/* sentinel */},
 207 };
 208 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
 209
 210 static struct platform_driver sunxi_sid_driver = {
 211         .probe = sunxi_sid_probe,
 212         .remove = sunxi_sid_remove,
 213         .driver = {
 214                 .name = "eeprom-sunxi-sid",
 215                 .of_match_table = sunxi_sid_of_match,
 216         },
 217 };
 218 module_platform_driver(sunxi_sid_driver);
 219
 220 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
 221 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
 222 MODULE_LICENSE("GPL");