1/*
  2 * Copyright (c) 2013 Oliver Schinagl <oliver@schinagl.nl>
  3 * http://www.linux-sunxi.org
  4 *
  5 * This program is free software; you can redistribute it and/or modify
  6 * it under the terms of the GNU General Public License as published by
  7 * the Free Software Foundation; either version 2 of the License, or
  8 * (at your option) any later version.
  9 *
 10 * This program is distributed in the hope that it will be useful,
 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13 * GNU General Public License for more details.
 14 *
 15 * This driver exposes the Allwinner security ID, efuses exported in byte-
 16 * sized chunks.
 17 */
 18
 19#include <linux/compiler.h>
 20#include <linux/device.h>
 21#include <linux/err.h>
 22#include <linux/export.h>
 23#include <linux/fs.h>
 24#include <linux/io.h>
 25#include <linux/kernel.h>
 26#include <linux/kobject.h>
 27#include <linux/module.h>
 28#include <linux/of_device.h>
 29#include <linux/platform_device.h>
 30#include <linux/random.h>
 31#include <linux/slab.h>
 32#include <linux/stat.h>
 33#include <linux/sysfs.h>
 34#include <linux/types.h>
 35
 36#define DRV_NAME "sunxi-sid"
 37
 38struct sunxi_sid_data {
 39	void __iomem *reg_base;
 40	unsigned int keysize;
 41};
 42
 43/* We read the entire key, due to a 32 bit read alignment requirement. Since we
 44 * want to return the requested byte, this results in somewhat slower code and
 45 * uses 4 times more reads as needed but keeps code simpler. Since the SID is
 46 * only very rarely probed, this is not really an issue.
 47 */
 48static u8 sunxi_sid_read_byte(const struct sunxi_sid_data *sid_data,
 49			      const unsigned int offset)
 50{
 51	u32 sid_key;
 52
 53	if (offset >= sid_data->keysize)
 54		return 0;
 55
 56	sid_key = ioread32be(sid_data->reg_base + round_down(offset, 4));
 57	sid_key >>= (offset % 4) * 8;
 58
 59	return sid_key; /* Only return the last byte */
 60}
 61
 62static ssize_t sid_read(struct file *fd, struct kobject *kobj,
 63			struct bin_attribute *attr, char *buf,
 64			loff_t pos, size_t size)
 65{
 66	struct platform_device *pdev;
 67	struct sunxi_sid_data *sid_data;
 68	int i;
 69
 70	pdev = to_platform_device(kobj_to_dev(kobj));
 71	sid_data = platform_get_drvdata(pdev);
 72
 73	if (pos < 0 || pos >= sid_data->keysize)
 74		return 0;
 75	if (size > sid_data->keysize - pos)
 76		size = sid_data->keysize - pos;
 77
 78	for (i = 0; i < size; i++)
 79		buf[i] = sunxi_sid_read_byte(sid_data, pos + i);
 80
 81	return i;
 82}
 83
 84static struct bin_attribute sid_bin_attr = {
 85	.attr = { .name = "eeprom", .mode = S_IRUGO, },
 86	.read = sid_read,
 87};
 88
 89static int sunxi_sid_remove(struct platform_device *pdev)
 90{
 91	device_remove_bin_file(&pdev->dev, &sid_bin_attr);
 92	dev_dbg(&pdev->dev, "driver unloaded\n");
 93
 94	return 0;
 95}
 96
 97static const struct of_device_id sunxi_sid_of_match[] = {
 98	{ .compatible = "allwinner,sun4i-a10-sid", .data = (void *)16},
 99	{ .compatible = "allwinner,sun7i-a20-sid", .data = (void *)512},
100	{/* sentinel */},
101};
102MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
103
104static int sunxi_sid_probe(struct platform_device *pdev)
105{
106	struct sunxi_sid_data *sid_data;
107	struct resource *res;
108	const struct of_device_id *of_dev_id;
109	u8 *entropy;
110	unsigned int i;
111
112	sid_data = devm_kzalloc(&pdev->dev, sizeof(struct sunxi_sid_data),
113				GFP_KERNEL);
114	if (!sid_data)
115		return -ENOMEM;
116
117	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
118	sid_data->reg_base = devm_ioremap_resource(&pdev->dev, res);
119	if (IS_ERR(sid_data->reg_base))
120		return PTR_ERR(sid_data->reg_base);
121
122	of_dev_id = of_match_device(sunxi_sid_of_match, &pdev->dev);
123	if (!of_dev_id)
124		return -ENODEV;
125	sid_data->keysize = (int)of_dev_id->data;
126
127	platform_set_drvdata(pdev, sid_data);
128
129	sid_bin_attr.size = sid_data->keysize;
130	if (device_create_bin_file(&pdev->dev, &sid_bin_attr))
131		return -ENODEV;
132
133	entropy = kzalloc(sizeof(u8) * sid_data->keysize, GFP_KERNEL);
134	for (i = 0; i < sid_data->keysize; i++)
135		entropy[i] = sunxi_sid_read_byte(sid_data, i);
136	add_device_randomness(entropy, sid_data->keysize);
137	kfree(entropy);
138
139	dev_dbg(&pdev->dev, "loaded\n");
140
141	return 0;
142}
143
144static struct platform_driver sunxi_sid_driver = {
145	.probe = sunxi_sid_probe,
146	.remove = sunxi_sid_remove,
147	.driver = {
148		.name = DRV_NAME,
149		.owner = THIS_MODULE,
150		.of_match_table = sunxi_sid_of_match,
151	},
152};
153module_platform_driver(sunxi_sid_driver);
154
155MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
156MODULE_DESCRIPTION("Allwinner sunxi security id driver");
157MODULE_LICENSE("GPL");