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/slab.h> 25 #include <linux/random.h> 26 27 static struct nvmem_config econfig = { 28 .name = "sunxi-sid", 29 .read_only = true, 30 .stride = 4, 31 .word_size = 1, 32 .owner = THIS_MODULE, 33 }; 34 35 struct sunxi_sid { 36 void __iomem *base; 37 }; 38 39 /* We read the entire key, due to a 32 bit read alignment requirement. Since we 40 * want to return the requested byte, this results in somewhat slower code and 41 * uses 4 times more reads as needed but keeps code simpler. Since the SID is 42 * only very rarely probed, this is not really an issue. 43 */ 44 static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid, 45 const unsigned int offset) 46 { 47 u32 sid_key; 48 49 sid_key = ioread32be(sid->base + round_down(offset, 4)); 50 sid_key >>= (offset % 4) * 8; 51 52 return sid_key; /* Only return the last byte */ 53 } 54 55 static int sunxi_sid_read(void *context, unsigned int offset, 56 void *val, size_t bytes) 57 { 58 struct sunxi_sid *sid = context; 59 u8 *buf = val; 60 61 while (bytes--) 62 *buf++ = sunxi_sid_read_byte(sid, offset++); 63 64 return 0; 65 } 66 67 static int sunxi_sid_probe(struct platform_device *pdev) 68 { 69 struct device *dev = &pdev->dev; 70 struct resource *res; 71 struct nvmem_device *nvmem; 72 struct sunxi_sid *sid; 73 int ret, i, size; 74 char *randomness; 75 76 sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL); 77 if (!sid) 78 return -ENOMEM; 79 80 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 81 sid->base = devm_ioremap_resource(dev, res); 82 if (IS_ERR(sid->base)) 83 return PTR_ERR(sid->base); 84 85 size = resource_size(res) - 1; 86 econfig.size = resource_size(res); 87 econfig.dev = dev; 88 econfig.reg_read = sunxi_sid_read; 89 econfig.priv = sid; 90 nvmem = nvmem_register(&econfig); 91 if (IS_ERR(nvmem)) 92 return PTR_ERR(nvmem); 93 94 randomness = kzalloc(sizeof(u8) * (size), GFP_KERNEL); 95 if (!randomness) { 96 ret = -EINVAL; 97 goto err_unreg_nvmem; 98 } 99 100 for (i = 0; i < size; i++) 101 randomness[i] = sunxi_sid_read_byte(sid, i); 102 103 add_device_randomness(randomness, size); 104 kfree(randomness); 105 106 platform_set_drvdata(pdev, nvmem); 107 108 return 0; 109 110 err_unreg_nvmem: 111 nvmem_unregister(nvmem); 112 return ret; 113 } 114 115 static int sunxi_sid_remove(struct platform_device *pdev) 116 { 117 struct nvmem_device *nvmem = platform_get_drvdata(pdev); 118 119 return nvmem_unregister(nvmem); 120 } 121 122 static const struct of_device_id sunxi_sid_of_match[] = { 123 { .compatible = "allwinner,sun4i-a10-sid" }, 124 { .compatible = "allwinner,sun7i-a20-sid" }, 125 {/* sentinel */}, 126 }; 127 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match); 128 129 static struct platform_driver sunxi_sid_driver = { 130 .probe = sunxi_sid_probe, 131 .remove = sunxi_sid_remove, 132 .driver = { 133 .name = "eeprom-sunxi-sid", 134 .of_match_table = sunxi_sid_of_match, 135 }, 136 }; 137 module_platform_driver(sunxi_sid_driver); 138 139 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>"); 140 MODULE_DESCRIPTION("Allwinner sunxi security id driver"); 141 MODULE_LICENSE("GPL"); 142