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/regmap.h>
 25#include <linux/slab.h>
 26#include <linux/random.h>
 27
 28static struct nvmem_config econfig = {
 29	.name = "sunxi-sid",
 30	.read_only = true,
 31	.owner = THIS_MODULE,
 32};
 33
 34struct sunxi_sid {
 35	void __iomem		*base;
 36};
 37
 38/* We read the entire key, due to a 32 bit read alignment requirement. Since we
 39 * want to return the requested byte, this results in somewhat slower code and
 40 * uses 4 times more reads as needed but keeps code simpler. Since the SID is
 41 * only very rarely probed, this is not really an issue.
 42 */
 43static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid,
 44			      const unsigned int offset)
 45{
 46	u32 sid_key;
 47
 48	sid_key = ioread32be(sid->base + round_down(offset, 4));
 49	sid_key >>= (offset % 4) * 8;
 50
 51	return sid_key; /* Only return the last byte */
 52}
 53
 54static int sunxi_sid_read(void *context,
 55			  const void *reg, size_t reg_size,
 56			  void *val, size_t val_size)
 57{
 58	struct sunxi_sid *sid = context;
 59	unsigned int offset = *(u32 *)reg;
 60	u8 *buf = val;
 61
 62	while (val_size) {
 63		*buf++ = sunxi_sid_read_byte(sid, offset);
 64		val_size--;
 65		offset++;
 66	}
 67
 68	return 0;
 69}
 70
 71static int sunxi_sid_write(void *context, const void *data, size_t count)
 72{
 73	/* Unimplemented, dummy to keep regmap core happy */
 74	return 0;
 75}
 76
 77static struct regmap_bus sunxi_sid_bus = {
 78	.read = sunxi_sid_read,
 79	.write = sunxi_sid_write,
 80	.reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
 81	.val_format_endian_default = REGMAP_ENDIAN_NATIVE,
 82};
 83
 84static bool sunxi_sid_writeable_reg(struct device *dev, unsigned int reg)
 85{
 86	return false;
 87}
 88
 89static struct regmap_config sunxi_sid_regmap_config = {
 90	.reg_bits = 32,
 91	.val_bits = 8,
 92	.reg_stride = 1,
 93	.writeable_reg = sunxi_sid_writeable_reg,
 94};
 95
 96static int sunxi_sid_probe(struct platform_device *pdev)
 97{
 98	struct device *dev = &pdev->dev;
 99	struct resource *res;
100	struct nvmem_device *nvmem;
101	struct regmap *regmap;
102	struct sunxi_sid *sid;
103	int ret, i, size;
104	char *randomness;
105
106	sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
107	if (!sid)
108		return -ENOMEM;
109
110	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
111	sid->base = devm_ioremap_resource(dev, res);
112	if (IS_ERR(sid->base))
113		return PTR_ERR(sid->base);
114
115	size = resource_size(res) - 1;
116	sunxi_sid_regmap_config.max_register = size;
117
118	regmap = devm_regmap_init(dev, &sunxi_sid_bus, sid,
119				  &sunxi_sid_regmap_config);
120	if (IS_ERR(regmap)) {
121		dev_err(dev, "regmap init failed\n");
122		return PTR_ERR(regmap);
123	}
124
125	econfig.dev = dev;
126	nvmem = nvmem_register(&econfig);
127	if (IS_ERR(nvmem))
128		return PTR_ERR(nvmem);
129
130	randomness = kzalloc(sizeof(u8) * (size), GFP_KERNEL);
131	if (!randomness) {
132		ret = -EINVAL;
133		goto err_unreg_nvmem;
134	}
135
136	for (i = 0; i < size; i++)
137		randomness[i] = sunxi_sid_read_byte(sid, i);
138
139	add_device_randomness(randomness, size);
140	kfree(randomness);
141
142	platform_set_drvdata(pdev, nvmem);
143
144	return 0;
145
146err_unreg_nvmem:
147	nvmem_unregister(nvmem);
148	return ret;
149}
150
151static int sunxi_sid_remove(struct platform_device *pdev)
152{
153	struct nvmem_device *nvmem = platform_get_drvdata(pdev);
154
155	return nvmem_unregister(nvmem);
156}
157
158static const struct of_device_id sunxi_sid_of_match[] = {
159	{ .compatible = "allwinner,sun4i-a10-sid" },
160	{ .compatible = "allwinner,sun7i-a20-sid" },
161	{/* sentinel */},
162};
163MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
164
165static struct platform_driver sunxi_sid_driver = {
166	.probe = sunxi_sid_probe,
167	.remove = sunxi_sid_remove,
168	.driver = {
169		.name = "eeprom-sunxi-sid",
170		.of_match_table = sunxi_sid_of_match,
171	},
172};
173module_platform_driver(sunxi_sid_driver);
174
175MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
176MODULE_DESCRIPTION("Allwinner sunxi security id driver");
177MODULE_LICENSE("GPL");