xref: /openbmc/linux/drivers/nvmem/sunxi_sid.c (revision dfd4f649)
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 };
44 
45 struct sunxi_sid_cfg {
46 	u32	value_offset;
47 	u32	size;
48 	bool	need_register_readout;
49 };
50 
51 struct sunxi_sid {
52 	void __iomem		*base;
53 	u32			value_offset;
54 };
55 
56 /* We read the entire key, due to a 32 bit read alignment requirement. Since we
57  * want to return the requested byte, this results in somewhat slower code and
58  * uses 4 times more reads as needed but keeps code simpler. Since the SID is
59  * only very rarely probed, this is not really an issue.
60  */
61 static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid,
62 			      const unsigned int offset)
63 {
64 	u32 sid_key;
65 
66 	sid_key = ioread32be(sid->base + round_down(offset, 4));
67 	sid_key >>= (offset % 4) * 8;
68 
69 	return sid_key; /* Only return the last byte */
70 }
71 
72 static int sunxi_sid_read(void *context, unsigned int offset,
73 			  void *val, size_t bytes)
74 {
75 	struct sunxi_sid *sid = context;
76 	u8 *buf = val;
77 
78 	/* Offset the read operation to the real position of SID */
79 	offset += sid->value_offset;
80 
81 	while (bytes--)
82 		*buf++ = sunxi_sid_read_byte(sid, offset++);
83 
84 	return 0;
85 }
86 
87 static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
88 				      const unsigned int offset,
89 				      u32 *out)
90 {
91 	u32 reg_val;
92 	int ret;
93 
94 	/* Set word, lock access, and set read command */
95 	reg_val = (offset & 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 	if (out)
106 		*out = readl(sid->base + SUN8I_SID_RDKEY);
107 
108 	writel(0, sid->base + SUN8I_SID_PRCTL);
109 
110 	return 0;
111 }
112 
113 /*
114  * On Allwinner H3, the value on the 0x200 offset of the SID controller seems
115  * to be not reliable at all.
116  * Read by the registers instead.
117  */
118 static int sun8i_sid_read_byte_by_reg(const struct sunxi_sid *sid,
119 				      const unsigned int offset,
120 				      u8 *out)
121 {
122 	u32 word;
123 	int ret;
124 
125 	ret = sun8i_sid_register_readout(sid, offset & ~0x03, &word);
126 
127 	if (ret)
128 		return ret;
129 
130 	*out = (word >> ((offset & 0x3) * 8)) & 0xff;
131 
132 	return 0;
133 }
134 
135 static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
136 				 void *val, size_t bytes)
137 {
138 	struct sunxi_sid *sid = context;
139 	u8 *buf = val;
140 	int ret;
141 
142 	while (bytes--) {
143 		ret = sun8i_sid_read_byte_by_reg(sid, offset++, buf++);
144 		if (ret)
145 			return ret;
146 	}
147 
148 	return 0;
149 }
150 
151 static int sunxi_sid_probe(struct platform_device *pdev)
152 {
153 	struct device *dev = &pdev->dev;
154 	struct resource *res;
155 	struct nvmem_device *nvmem;
156 	struct sunxi_sid *sid;
157 	int i, size;
158 	char *randomness;
159 	const struct sunxi_sid_cfg *cfg;
160 
161 	sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
162 	if (!sid)
163 		return -ENOMEM;
164 
165 	cfg = of_device_get_match_data(dev);
166 	if (!cfg)
167 		return -EINVAL;
168 	sid->value_offset = cfg->value_offset;
169 
170 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
171 	sid->base = devm_ioremap_resource(dev, res);
172 	if (IS_ERR(sid->base))
173 		return PTR_ERR(sid->base);
174 
175 	size = cfg->size;
176 
177 	econfig.size = size;
178 	econfig.dev = dev;
179 	if (cfg->need_register_readout)
180 		econfig.reg_read = sun8i_sid_read_by_reg;
181 	else
182 		econfig.reg_read = sunxi_sid_read;
183 	econfig.priv = sid;
184 	nvmem = devm_nvmem_register(dev, &econfig);
185 	if (IS_ERR(nvmem))
186 		return PTR_ERR(nvmem);
187 
188 	randomness = kzalloc(size, GFP_KERNEL);
189 	if (!randomness)
190 		return -ENOMEM;
191 
192 	for (i = 0; i < size; i++)
193 		econfig.reg_read(sid, i, &randomness[i], 1);
194 
195 	add_device_randomness(randomness, size);
196 	kfree(randomness);
197 
198 	platform_set_drvdata(pdev, nvmem);
199 
200 	return 0;
201 }
202 
203 static const struct sunxi_sid_cfg sun4i_a10_cfg = {
204 	.size = 0x10,
205 };
206 
207 static const struct sunxi_sid_cfg sun7i_a20_cfg = {
208 	.size = 0x200,
209 };
210 
211 static const struct sunxi_sid_cfg sun8i_h3_cfg = {
212 	.value_offset = 0x200,
213 	.size = 0x100,
214 	.need_register_readout = true,
215 };
216 
217 static const struct sunxi_sid_cfg sun50i_a64_cfg = {
218 	.value_offset = 0x200,
219 	.size = 0x100,
220 };
221 
222 static const struct of_device_id sunxi_sid_of_match[] = {
223 	{ .compatible = "allwinner,sun4i-a10-sid", .data = &sun4i_a10_cfg },
224 	{ .compatible = "allwinner,sun7i-a20-sid", .data = &sun7i_a20_cfg },
225 	{ .compatible = "allwinner,sun8i-h3-sid", .data = &sun8i_h3_cfg },
226 	{ .compatible = "allwinner,sun50i-a64-sid", .data = &sun50i_a64_cfg },
227 	{/* sentinel */},
228 };
229 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
230 
231 static struct platform_driver sunxi_sid_driver = {
232 	.probe = sunxi_sid_probe,
233 	.driver = {
234 		.name = "eeprom-sunxi-sid",
235 		.of_match_table = sunxi_sid_of_match,
236 	},
237 };
238 module_platform_driver(sunxi_sid_driver);
239 
240 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
241 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
242 MODULE_LICENSE("GPL");
243