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
 27static 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
 35struct 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 */
 44static 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
 55static 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
 67static 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
110err_unreg_nvmem:
111	nvmem_unregister(nvmem);
112	return ret;
113}
114
115static 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
122static const struct of_device_id sunxi_sid_of_match[] = {
123	{ .compatible = "allwinner,sun4i-a10-sid" },
124	{ .compatible = "allwinner,sun7i-a20-sid" },
125	{/* sentinel */},
126};
127MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
128
129static 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};
137module_platform_driver(sunxi_sid_driver);
138
139MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
140MODULE_DESCRIPTION("Allwinner sunxi security id driver");
141MODULE_LICENSE("GPL");