xref: /openbmc/linux/drivers/nvmem/sunxi_sid.c (revision 4da722ca)
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 	.owner = THIS_MODULE,
44 };
45 
46 struct sunxi_sid_cfg {
47 	u32	value_offset;
48 	u32	size;
49 	bool	need_register_readout;
50 };
51 
52 struct sunxi_sid {
53 	void __iomem		*base;
54 	u32			value_offset;
55 };
56 
57 /* We read the entire key, due to a 32 bit read alignment requirement. Since we
58  * want to return the requested byte, this results in somewhat slower code and
59  * uses 4 times more reads as needed but keeps code simpler. Since the SID is
60  * only very rarely probed, this is not really an issue.
61  */
62 static u8 sunxi_sid_read_byte(const struct sunxi_sid *sid,
63 			      const unsigned int offset)
64 {
65 	u32 sid_key;
66 
67 	sid_key = ioread32be(sid->base + round_down(offset, 4));
68 	sid_key >>= (offset % 4) * 8;
69 
70 	return sid_key; /* Only return the last byte */
71 }
72 
73 static int sunxi_sid_read(void *context, unsigned int offset,
74 			  void *val, size_t bytes)
75 {
76 	struct sunxi_sid *sid = context;
77 	u8 *buf = val;
78 
79 	/* Offset the read operation to the real position of SID */
80 	offset += sid->value_offset;
81 
82 	while (bytes--)
83 		*buf++ = sunxi_sid_read_byte(sid, offset++);
84 
85 	return 0;
86 }
87 
88 static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
89 				      const unsigned int word)
90 {
91 	u32 reg_val;
92 	int ret;
93 
94 	/* Set word, lock access, and set read command */
95 	reg_val = (word & 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 	writel(0, sid->base + SUN8I_SID_PRCTL);
106 	return 0;
107 }
108 
109 static int sunxi_sid_probe(struct platform_device *pdev)
110 {
111 	struct device *dev = &pdev->dev;
112 	struct resource *res;
113 	struct nvmem_device *nvmem;
114 	struct sunxi_sid *sid;
115 	int ret, i, size;
116 	char *randomness;
117 	const struct sunxi_sid_cfg *cfg;
118 
119 	sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
120 	if (!sid)
121 		return -ENOMEM;
122 
123 	cfg = of_device_get_match_data(dev);
124 	if (!cfg)
125 		return -EINVAL;
126 	sid->value_offset = cfg->value_offset;
127 
128 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
129 	sid->base = devm_ioremap_resource(dev, res);
130 	if (IS_ERR(sid->base))
131 		return PTR_ERR(sid->base);
132 
133 	size = cfg->size;
134 
135 	if (cfg->need_register_readout) {
136 		/*
137 		 * H3's SID controller have a bug that the value at 0x200
138 		 * offset is not the correct value when the hardware is reseted.
139 		 * However, after doing a register-based read operation, the
140 		 * value become right.
141 		 * Do a full read operation here, but ignore its value
142 		 * (as it's more fast to read by direct MMIO value than
143 		 * with registers)
144 		 */
145 		for (i = 0; i < (size >> 2); i++) {
146 			ret = sun8i_sid_register_readout(sid, i);
147 			if (ret)
148 				return ret;
149 		}
150 	}
151 
152 	econfig.size = size;
153 	econfig.dev = dev;
154 	econfig.reg_read = sunxi_sid_read;
155 	econfig.priv = sid;
156 	nvmem = nvmem_register(&econfig);
157 	if (IS_ERR(nvmem))
158 		return PTR_ERR(nvmem);
159 
160 	randomness = kzalloc(sizeof(u8) * (size), GFP_KERNEL);
161 	if (!randomness) {
162 		ret = -EINVAL;
163 		goto err_unreg_nvmem;
164 	}
165 
166 	for (i = 0; i < size; i++)
167 		randomness[i] = sunxi_sid_read_byte(sid, i);
168 
169 	add_device_randomness(randomness, size);
170 	kfree(randomness);
171 
172 	platform_set_drvdata(pdev, nvmem);
173 
174 	return 0;
175 
176 err_unreg_nvmem:
177 	nvmem_unregister(nvmem);
178 	return ret;
179 }
180 
181 static int sunxi_sid_remove(struct platform_device *pdev)
182 {
183 	struct nvmem_device *nvmem = platform_get_drvdata(pdev);
184 
185 	return nvmem_unregister(nvmem);
186 }
187 
188 static const struct sunxi_sid_cfg sun4i_a10_cfg = {
189 	.size = 0x10,
190 };
191 
192 static const struct sunxi_sid_cfg sun7i_a20_cfg = {
193 	.size = 0x200,
194 };
195 
196 static const struct sunxi_sid_cfg sun8i_h3_cfg = {
197 	.value_offset = 0x200,
198 	.size = 0x100,
199 	.need_register_readout = true,
200 };
201 
202 static const struct of_device_id sunxi_sid_of_match[] = {
203 	{ .compatible = "allwinner,sun4i-a10-sid", .data = &sun4i_a10_cfg },
204 	{ .compatible = "allwinner,sun7i-a20-sid", .data = &sun7i_a20_cfg },
205 	{ .compatible = "allwinner,sun8i-h3-sid", .data = &sun8i_h3_cfg },
206 	{/* sentinel */},
207 };
208 MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
209 
210 static struct platform_driver sunxi_sid_driver = {
211 	.probe = sunxi_sid_probe,
212 	.remove = sunxi_sid_remove,
213 	.driver = {
214 		.name = "eeprom-sunxi-sid",
215 		.of_match_table = sunxi_sid_of_match,
216 	},
217 };
218 module_platform_driver(sunxi_sid_driver);
219 
220 MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
221 MODULE_DESCRIPTION("Allwinner sunxi security id driver");
222 MODULE_LICENSE("GPL");
223